CA1146160A - Multiple coil heat exchanger - Google Patents
Multiple coil heat exchangerInfo
- Publication number
- CA1146160A CA1146160A CA000362221A CA362221A CA1146160A CA 1146160 A CA1146160 A CA 1146160A CA 000362221 A CA000362221 A CA 000362221A CA 362221 A CA362221 A CA 362221A CA 1146160 A CA1146160 A CA 1146160A
- Authority
- CA
- Canada
- Prior art keywords
- coil
- tube
- heat exchanger
- inner coil
- pitch
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D11/00—Bending not restricted to forms of material mentioned in only one of groups B21D5/00, B21D7/00, B21D9/00; Bending not provided for in groups B21D5/00 - B21D9/00; Twisting
- B21D11/06—Bending into helical or spiral form; Forming a succession of return bends, e.g. serpentine form
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D53/00—Making other particular articles
- B21D53/02—Making other particular articles heat exchangers or parts thereof, e.g. radiators, condensers fins, headers
- B21D53/06—Making other particular articles heat exchangers or parts thereof, e.g. radiators, condensers fins, headers of metal tubes
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
- F28D7/00—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall
- F28D7/08—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits being otherwise bent, e.g. in a serpentine or zig-zag
Abstract
MULTIPLE COIL HEAT EXCHANGER
ABSTRACT
A compact multiple coil heat exchanger having a high heat transfer density is provided to include at least an inner coil formed from a continuous tube into a plurality of contiguous turns about a common axis in a spiral arrangement and having a pitch in one direction and an outer coil formed from the con-tinuous tube into a plurality of overlapping turns concentrically about the inner coil in a spiral arrangement having an opposite pitch. Further, a coil-forming apparatus and continuous coil-forming method is directed to form a multiple coil heat exchanger from a continuous tube using a coil-forming die rotatably mounted on d support frame. The coil-forming die includes a continuous spiral thread constructed to receive and laterally support the continuous tube while fabricating the multiple coil heat exchanger according to the continuous coil-forming method of this invention.
The thread of the coil-forming die terminates at one end thereof at a coil-reversing plate having a first portion which spirals outward to a radial position above the thread and a second portion which axially extends towards the opposite end of the coil-forming die to form a one-piece multiple coil heat exchanger.
ABSTRACT
A compact multiple coil heat exchanger having a high heat transfer density is provided to include at least an inner coil formed from a continuous tube into a plurality of contiguous turns about a common axis in a spiral arrangement and having a pitch in one direction and an outer coil formed from the con-tinuous tube into a plurality of overlapping turns concentrically about the inner coil in a spiral arrangement having an opposite pitch. Further, a coil-forming apparatus and continuous coil-forming method is directed to form a multiple coil heat exchanger from a continuous tube using a coil-forming die rotatably mounted on d support frame. The coil-forming die includes a continuous spiral thread constructed to receive and laterally support the continuous tube while fabricating the multiple coil heat exchanger according to the continuous coil-forming method of this invention.
The thread of the coil-forming die terminates at one end thereof at a coil-reversing plate having a first portion which spirals outward to a radial position above the thread and a second portion which axially extends towards the opposite end of the coil-forming die to form a one-piece multiple coil heat exchanger.
Description
BACKGROUND OF THE INVENTION
This invention relates in general to a heat exchanger, and more particularly, to a compact multiple coil heat exchanger having an improved heat transfer density and adapted to ~e easily accessible for repairs and maintenance in a modern refri-geration system. ~ ;
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In modern refrigeration systems, the compactness of the systemis components results in the advantage of reducing the ~, ~
3~ 10 ~ overall refrigeration system size and ultimately the related manufacturing costs.~ In the design o a compact refr;geration system, each component must be separately designed to be as small as possible, yet fully functional to sati~y the refrigeration system;~requirements. One such component is a heat exchanger or condenser which is used to cool the hot compressed refrigerant gases during the operation of the refrigeration system. The heat exchanger design must ~e such that it occupies a minimum space~while~maintaining a~high;performance as measured ln BTU'sj hours/surface area.
In providlng a minimum of space in the refrigeration ~r system design for the heat exchanger, it is further required that the heat exchanger's configuration be such to facilitate its removal and/or installation as required for repairs or maintenance.
~ Heat exohangers incorporated in current refrigeration systems ;~ usually have their inlet and outlet disposed at opposite ends of ~ the heat exchanger. Thls restricted conflguration~requires a~
; ~ complicated arrangement o~f refrigerant and cooling connecting lines to~the~heat~exchanger,~ in~addition to~rendering the connections~relati~ely inaccessible for easy removal of the heat ~30~ exchanger.
~ ccord~nc31y, there is a need for a compact heat exchang~r whic}l occupi.es a minimum of space while rctainin~ a hi~h heat:
tr~nsfer density and is adapted fo.r easy insta~llation and connection to xe~rigerant cooling lines within the compact space provided in a modern refri~eration system.
SUM~ARY OF T~IE IN`VENTION
It is broadl~ an object of this invention to provide a multiple coil heat exchanger which fulfills one or more of the foxegoing req~tirements of modern refrigeratiorl systems. Sveci-~fically, it is within the contemplati.on of th.is invention to ~0 provide a heat exchanqer ~ormed from a continuous tu~e coiled about a common axis into inner and oute~ concentric overlapping coils having an inlet and outlet disposed in a co~mon plane at one end and a continuous trans:ition se~ment joining the inner and outer coils at the other end thereof.
~ A further ohject of this invention is to pro~ide a :' ~ multiple coil heat exchanger constructéd in a continuous coil-~` forming process by the uninterrupted. rotation of a coil~ol~ing die.
A still further object of this invention is to provide 20 a multiple coil heat ~xchanger which is compact and has a high heat transfer densi~y in relati.onship to its overall size.`
A stil:l further object of this invention is to provide a multiple coil heat exchallc3er that is constructed and arranc3ed ~` for eas~ instal].ation ~ithin a compact space provided in a modern re~rigerati.on system by havirlg at least its inlet and outlet extendill~ kanc3erntially from the inner and outer colls at one common end thereQf~
. A still fu7:the~ object of this invention is to :
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provide a coiled construction adapted to forln a multiple coil heat excharlger from a continuous length of tube by a continuous coil-forming method.
A slLill furthex object of this invention is to provide a coil-forminc3 apparatus constructed and arranged for fa~ricating from a continuous length of tube a heat exchanger adapted for easy installation within a modern refriyeration system ~hile retaining a high heat transfer density.
In accordance with one illustra~ive embodiment of this invention, there is provided a multiple coil heat exchanger formed from a continuous coiled tube. qlhe coiled ~ube is formed to include an inner coil having a plurality of contiguous turn~
coiled a~out a common axis in a spira~ arrangement having a pitch in one direction and an outer coil having a p]urality of contiyuo~s turns concentric about the inner coil along the common axis in a like spiral arrangement having a pitch in the opposite direction.
continuous transition segment formed from a~portion of the coiled tube continuously ioins the inner and outer coils at a : .
common end of the heat exchanger and having a first curved~
portion o~ increasing radius OL curvature to radially extend the tube r~la~ive to the inner coil and a s~cond curved portion for axially extending the tuhe over the inner coil in forminy the outer coil.
Further, there is provided a coil~forming apparatus for fabricating a continuous length of tube into a compact multiple coil heat exchanger. The coil-forming apparatus includes a sup~ort frame for rotatably mountirlg a coil-forming die about it~ axis and having a spiral-llke thread sized to recei,ve the tube commencing at one end of the coil-forming die and termin~tln~ at a coil-rever~ing plate ccnstructod at the ~.:
$~6~3 other end of the coil-Forminq die. The coi.l-reversincJ plate is constructecl at -the other end of the coi.l~fol~lT~ - die to mercJe with and be a continuation of the spiral~like thread o~ the coil~
formi.nc~ die. ~ first porti.on o~ the coil~réversing pl.ate spi.rals outwar,d to a radial posi.tion above the rad.ial extent o the spiral-like threads at the other end of tlle coil-formlng die ~nd a second portion of the coi.l~reversing plate axlally extends away ~: from the coil-reversing plate towards the one end of the coil-forming die.
Furthe.r, there is provided an improved method of fabri.cating the comDact rnultiple coil ~leat exchallger according to the illustrative embodiment of this invention. A continllous method of fabricatiny a multiple coil heat exchanger having a.high heat trans~er density is disclosed whi.ch is initially startcd by ,~ securing one free end of the tube at a coil-starting position.
In a continuo-ls and uni.nterrupted process, the desixed lenyth of tuhe is coiled in a spiral dirèction about an axis to form an , .inner coi' ha~i.ng adjacent turns extending in one direction awa~
from thé coil-starti.ng position. Further, bendlng the tube radially outward slightly past the radial extent of the lnner coi~
and axially towards the coil~start.i.ng position to form a tr~nsition segmerl,k and then continuously coiling the tube in a ' spi.ral direction about the i.nner coil in'the opposite directlon ' , ~o form the concentric outer coil having contiguous turns over-lapping the inner coil and extending toT~ard the coil-startincJ
position.
BP~IEF DESCRIPTIO~ OF TEI~ DR~.WIN~S
The above dessription as ~ell as further objects, ~ eatures and advant~es OL ~he Present invention ~ e .,.ore :
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fully underslood ~ reference to the fo'~lowinc~ detailed description of the pr~sently preferred, but noneth~l.esc; il.lus~rative m~iltiple coi.l heat exchan~er, coi.l-forminy apparatus and continuo-ls coil-forming me~thod in accordance with this inverl.tion when taken in conjunction with the accompanying clrawings, wherein:
FIG. 1 is a front elevational view of a multiple coil heat exchan~ex constructed according to this invention and em~odying concentric inner and outer coils havin~ inlet and outlet ends extending parallel to each other in a'co~on plane at one end of the heat exchanger to provide easy accessibility to the refrigeran-t and cooli.ng line connections for ready removal o~' the heat:
exchanger from a modern rerrigeration s~stem;
FIG. 2 ~s a side elevational view of a multiple coil h~at exchanger as viewed from the right of FIG. 1 iilustrating t~.e outex coil having a pit.ch i.n one direction anc~ -the inner coil having a pitc~.in t'he op~osite directi.on;
,. . , F}G. 3 is a, rear elevational view o~ the multip.le coil heat exchanger of FIG. 1 illustrating the continuous joining of the inner coil to the concentric outer coil b~ a co~tinuous transition seyment having a flrst portion which radially extends out~ard slicJhtl~ past tile inner coil and a second portion whicrl axially extends over the innel- coil towaras t:.he inlet and outlet ends o,~ the heat exchanger;
FIG. 4 is a side elevational vi.ew of a multip].e coil hea~ exchanger as viewed from the right of F~G. 1 havirlg a portion of the out:er coil removed to sho~ a substantial portion of i:he~outer coil rernoved to sho~ a substantial portion of the inner coil hav.ing a pitch in the opposite direction of the ou~er cc~i l; , " .
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YIG. 5 is a front elevational vie~ of a typical end cap : assembly for a concentric tube having a section removed to illustrate the construction and arranc~ement of~the end cap -to provide a separate inlet and outlet for a ~luid flowing within the inner tube and a fluid flowing within the annular region provided between the outer surface of the inner tube and the innex surface of the outer tube;
~ FIG. 6 is a front elevational view of a coil-formlng :~ . . apparatus constructed in accordance with this invention for forming a ~ultiple coil heat exchanger according to an illustrative embodiment of this invention and hatring an arcuate scale for determining the relative ~osition o~ the inlet and outlet wi-th respect to each ot~her at a common end of the multiple coil heat .. exchangex;
FIG. 7 is a si.de elevational view o~ the coil-forming apparatus as viewed from the le~t o~ FIG. 6 illustrating the , . . .
~ coil-forming die rotatably mounted on a supporting shaft :~ extending through an upstanding frame and having a spiral like .; thread t~rminating at a coil-reversing plate adjacent the u~-standing frame;
. FIG~ ~ is a partial section taken along lines 8-~ in : FIG. 7 illustrating the coil-reversing plate of the coil~forming di.e having a first portion which radially extends outwarcl past the raclial ext-.ent of the spiral~like thread of the coil-forming die ~ and a second portion which axially extends toward the front surfac~ of the coil-iorming die; and, FIGS. 9-.l4 are progressive side elevational views of the rotal~ing coil-formlng die :included within the coil-forming apparatus . .
~ of this in~enti.on for fabricating the multiple coil heat exchanger 6~
accordiny -to the continuous coil-fvrming metllc)d of this irvention and fuxther illustratiny the structural fea-tures and arrangelnent of the coil-reversing plate provided for fahric,lt.inc3 the transi.ion seyment of the mult~ple coil heat e~chanyer.
DETAILED DESCRIPTION OF THE PREF~RRED EM~ODIMENTS
. There will be described accordiny to one embodiment of this invent.i.on a compact multiple coil heat exc1lanc~er having a high heat transfer density pex unit volume as shown in the illustrative emhodiment of FIGS. 1 - 4. The multiple coil heat exchanger includes a sinyle coil.ed -tube formed into an inner ~ 10 coil of spiral-like turns about a con~on axis and an outer coil :~ of like.spiral-like turns overlapping the inner coil and con--tinuousl.y jolned to the inner coil by a continuous transition segment at one end thexeof. The ~ult:i.ple coil heat exchanger can . be fa~ricated from a single conti.nuolls tube as shown in ~IGo 1 or from a multiple concentric tube as shown in FIG. 5. ~1'he ~ultiple .~ : concentric tube can be constructed accordinJ to U. S. Patent ~o.
3,730,229, filed March 11, 1971, issued May 1, 1~3 and assigrled .o the same assignee of the present inven,ion. One unique fea~ure ~ of the multiple coil heat exchanger according to this invention - ~ is that both the i.nlet and out3.et ~see FIGS. 1 and 3) may be provided at one end o the heat exchanger and further if ~esi.redt extend parallel to one another in a co~non plane to provide ~ e~.sy access to the rnu1tiple coi]. heat exchanger when installed `. in a modern rerigeration system.
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~ The illustrative multi~le coil heat exchanger, accordiny ;, :t:o this ernbodiment of 'his ~nvention~i.s fabricated, by ~7ay o~ one example, USillg a mul.ti.ple coi7-1-orming apparatus having a coil-'. : .
~orrning die rotatably:~.ounted: thereon, as illustra ed in FIGS. 6 and :8. The coil-fcrmincJ die has a con~-inuous spiral thread sized ~: 30~ constructed to recei.ve the continuous tllbe and col~.mencin~
at one end of the coil-Eorming die and terminatin(3 at the other end at a coil-reversillcl plate. I'he coil-reversincJ plate - merges wi.th and is a continuation of the spiral-like t.hread of the coll-forming die. The coil-reversing plate.include, a first circum~erential segment ~hich includes a ramp to xadially extend the continuous tube outward past the radially extent o the inner tube and a second circ~.m~Eerential segment fox axially extending the con-tinuous tube over the last turn o- the inner coil.
The multiple coil heat exchanger is fabricated using ~' the coil-forming apparatws of this invention and a continuous coil-forming me~hod, as described with reference to FIGS.
9 - 14. It is to be unclerstood that the multiple coil heat ~, exchanger, according to this invention, may be fabricated on other coil~forming apparatus other than the illustratec1 coil-forming apparatus of thls invention and according to a method:which further departs from the continuous coil form:ing method which will be described.
' Referri.ng speci~ically to the drawings, there is shown in ~;'IGS. 1 - 4, a multiple coil heat exchanger constructed ` according to this i.nvention, generall.y desicJnated by reference ; numeral 100. The heat exchanger 100 is formed from a continuous tube 102 spirally coiled about; a co~non axis 104 as shoi~n in FIGS. 2 and 4 to form lnner and ou-ter concentric overlapping ' ' coils 106, 108.
The inner coil 306 includes a plurality of conti~uous turns of substant;.ally,e~ual radius coiled abowt and spacecl along the com~.on axis 104 in a spiral arrdrlgement. The `':'~ , ~ .
outer coil 108 is likewisc-~ formed in a spiral arrangement from the tube 102 of a pl~lrality o~ continuo-ls turns of substantially equ~l radius coiled concentrica~ily about and substantially coextensive with the inner coil 106. The outer coil 108 is spaced along the common axis 104 in the : opposite direction of the inner coil 106.
As shown in FIG. 3, the inner:and outer coils 106, 108 are joined unin~erruptecl by a continuous transition se~ment 110 at the far end of the heat exchancJer 100. The transition ~ 10 segment 110 forms a portion of the last turn of the inner : coil 106 and a portion of t.he ~irst turn of the outer coil 108.
: ~ ~irst curved portion 112 of the transition segment 110 is oE
. increasing .raclius of curvature to radially extend the tube 102 . slightly past the radial extent of the-inner coil 106 r The second curved portion 114 is continuous with the firs-t curved .
portion 112 and extends the tube 102 from its incxeased radius o curvature axially over the last turn of the inner coil 106 to form the outer coil 108.
As shown in ~IGS. 1 and 3, the outer coil 108 includes a straight inlet segment 116 adaptea to ingress a heat transfer fluid and the .inner coil 106 includes a stralght outlet SeCJment 118 adapted to egress the heat trans:Eer .fluid. Both the inlet and outlet segments 116, 113 extend tangentially from the respective inner and outer coils 106, 108 and substanti.ally parallel to each other at the rear end of the heat exchanger 100 in a common plane that is transverse to the common axis lC4.
As illustrated~ the lnl.et and outlet segments 116, 11~ terminate within the common plane at substantially the same extended location. As will be further described wlth reference to the ~;' :
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continuous method of fabricatin~ the heat exchallger 100 according to this invention, the inlet and outlet segmeIlts 116, 118 may extend in other than parallel relationship to each other.
As shown in FIG. 2, the turns of the outer coil 108 are right handed turns having a pitch angle l for~ed between a plane transverse to the coI~on axis 104 and a plane including : a turn o~ the outer coil 108. As shown in FIG. 4, ~he turns of the inner coil 10~ are left handed turns having an dpposite pitch angle B2 ~ormed hetween a plane transverse the common axis 104 and 10 a plane including a turn of the inner coil 106. The pltch angles ~1 and ~2 are usually selected to be small ~o provide for the co~pact construct;.on of the turns of the inner and owter coils 106, 108, but sufficiently large to enable the turns of the ~
.inne~ and ouker coils 106, 108 to be formed contiguous and over-lapping without excessive deformation o~ the tuhe 102 during ~he continuous coil~forming method according to this inventi.on.
The relati~e size of the pitch angles 91 and ~2 are ~: ge;lerally a function of the diamete.r of the inner and outer coils 106, 108 alld of the ~iarr~eter of the tube 102. Gene.rally, small pitch an~les ~1~ 2 are permitted by includlng a relatively large diameter for the inner and outer coils 106, 10~, or a relatively small diarneter for.the tube 102. In one illus~rative embodiment of the multiple coil heat exchange~r 100, the pitch .` anyles ~1 9~ were selected t.o be in the range of approximately 4 ~20.and approximately equal to each other~
; As thus described, the mu].tiple coil heat exchanger 100 according to ~this invention, is constructed of a surficient number-of turns o the tube 102 -c.o provide a compact heat exchanger .1~ , - .
~` having a hlgh heat transfer densl;ty to meet the mlnimum si~e requirements and per.~ormance cîiteria o. modersl re~rigQrat sysk_ms.
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~ ~ , The multip].e coil heat e~changer 100 may be abricatrd from a sing].e continuous tube 102 as shown in FIGS. 1 to ~ or from a multiple concentric tube 120 as shown in FIG. 5. The , i.ncorporation of a multiple concen-~ric tube 120 in the multiple coil heat exchanger 100 of this invention results ; in a heat exchanger 100 haviny increased heat transfer area ~ ' to provide overal]. higher effi-ciency of the heat exchanger .
,. 100. The concentric l,ube 120 i.s illustrated to include a :~ : . conti~uous inner corregated tube 122 coneentric with a , ..10 , continuous non~corregated outer tube 1~4~ Heat is exchanged ~:, between a heat transfer fluid flowing within the inner tube 122 and a heat transfer flui.d flowin~ i.n the annular reg;.on 12~ provided between the outer surface of the inner tube 122 . . ana the inner.surface of the outer tube 124. The construction of one multiple concentric tube for fabricating a multlple coil ~eat exchanger acaordiny to this invention is desc.ribed i.n the '~ aforementioned patent assigned to the same assignee as the ' p.resent inventlon.
:. An end cap assembly 128 which is illustrated as heing ~ ~ecured over the opening 130 located at each terminal end of the ,, ou~er kube .l24 conv~lliently provides an inlet and outlet to r,he .
inner tube 122 and the annular resion 126. The i.nner tube 122 extends through the top portion 132 of the end cap ass~r~ly 128 to provide inlet/outlet port 134 for the inner tube 122.
~, short tube,se~ment 136 extending through a side portion of the end cap assembly 128 to provi.de an inlet/outlet p'ort 138 for the annular rcgion 126.
As shown in ~IGS. 6 and 7, a coil-forming appara-tus 140 accordi.n~ to this;irvention, is ill~s~rated for fabricatin~ a multi.p~e coil:heat exchanger 100 as prev.iously ~escribed.
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In general, the coil-formillg apparatlls 140 includes a base plate 142 and an ups1-anding franie 14~ throuc3h which a hori~ontal supporting shaft 1~6 extencls which is rotatably mounted b~
appropriate bearings (not shown) on the frame 144; Attached to the supporting shaft 146 ls a coil-formlng die 148 rotatably mounted for ro~ation about the central axis 150 by suitable drive means (not shown), such as an electric motor. The coil~orminy die 148 is adapted for rotation in either a coil-forming direction as indicated by arrow 152 or a coil-releasing direction as indicated by the arrow 154 by the drive means. The coil-forming die has a continuous spiral , , like thread 178 cornmencing at one end o~ the die and terminating `~ - at a coil-reversing plate 180 located adjacent the upstanding ~rame l44 at the other end'of the coil-forming die.
As shown in FIG. 7, the coi,l-forming die 1~8 includes , a continuous spiraling left handed thread 178'commencing at the front surface 158 and terminating at a progressive c~irc~nferentially extendiny coil reversing plate 180 at the rear portion of the coil-forming die adjacent the upstanding 20 fxarne 144. The thread l78 is constructed to include a root 184 and adjacent thread side walls 186~ The thread side walls 186 and root 184 are cons,tructed and arranged to , partially circumscribe tube 102. The circumscribing of the tube 102 provides lateral circumferential support for the ~; tube 102 during the coi7-fo~ming operation, thereby preventing the tube 102 rom flattening. The pitch angle ~2 of the inner coil 106 is determined by the corresponding pitch angle of the thread 178. In one illus-trative embodiment of ~ the multiple coil heat exchanger according to this in~ention, ;~ 30 the root 184 and the thread side wâlls 18~ circumscr~be the ~ ube 102 slightly a~o~e the center a~is oE the tuhe 102.
The coil-reversillg plate lS0, as S}lOWn generall~ i n FIGS. 7 and 8, is constructed of a ci.rcular wedJe shaped disc 1~8 positioned a~out a celltral axis 150 at: he rear pOrtiOIl of : the coil-forming die 148. The disc 188 inc'ludes a circular planar wedginy surface 190 which supports a coaxial, radially extendi.ng ramp 192 of varying width. The construction of the , coil--reversing plate 180 is best shown with reference to FIG~ 9 and 11. r~he coil-reversing plate 180 is generally divided .into , , two continuous 180 circumferential seyments designated ~BC and ~ 10 CD~. The first circumferential segment ABC is shot~n in FIG. 9.
The root 1~4 and side wall 186 of the last thread at the rear porti.on of the co~ formincJ d.ie 148 merges radial.ly with the ramp 192. The ramp 192 of the first eircumferential segment ABC is constructed of uniform width to acco~modate the diameter of the tube ].02.
The ramp 192 is bound on the right side by the wedging surface 190 which provides a supporti.ng wall for the tube 102.
The ramp 192 and wedging surface 190 within ~he first circumfexentlal se~ment ABC provide a pseudo--thread for the tu~e 102 havinc; a ~0 pitch angle substantially equal to the pitch angle ~2 of the inner coi,l 106. The ramp 192 starts with a diameter equal to the i.nside diameter of the inrler coil 102 at A. As the ramp 192 circumfe.rentially proyresses t.:hrough the first circumferentlal segment ~BC, the ramp 192 continuously and,gradually extenàs radial.ty outward from the central axis 150 until t~e diameter ' of the ramp 192 is sliglltly greater than the inside diamPter o~ the outer aoiJ 1.08 at C.
The second circumferential se3ment CDA or the coil-reversing plate i80 is shown in FIG. 11. The ramo 192 through the second circ~mferential segment C~ is constr~cted to retain .its radial extcnded position from the common axis lS0 correspolldiny ; to slightly greater than the i.nside diameter of the outer coil : 108~ The rarnp 192 gra.dually decreases in ~rid~l frorn its ; initial width corresponding to the diameter of tube 102 at C
until the width of the ramp 192 vanishes upon mergin~ with the ~edging surface 190 at A. The ramL~ 192 wi.thin the second circumferential segment CDA is likewise bound on the ri.~ht side by the wedgin~ surface 190 which provides a supporting wall'for ~;~ the: tube 102. The ramp 192 and the wedc3ing surFace 190 throucJh 10: the second circumferentlal segrnent CDA provide a pseudo-thread .~ or the tube 102 having a pi.tch angle substantially equal to the pitch angle ~1 of the outer coil 108.
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A~ adjusta~l~e clamp 156 is mounted to the front ~surface 158 of the coil~forming die 148. The adjustable clamp 156 includes a hook porti.on 160 to engage the free end 162 of ~ .
. the tube 10~ to secure the free:~end 160 to the coil-~orming die : 148 du~ing the oontinuous coil-forming operation. The upstanding ; : ~ frame~144 has trans~ersely mounted thereto an adjustable ro].ler : l ' .
support assembly I64 by a horizonta1 ~-shaped bracket lG6 :through which a rod 1.68 extends parallel there~7ith. A roller support 170 having a radi~lly extending lip portion 172 at each ~, .
~' end thexeof is slidably mourlted on the rod lG8 for movement parallel to the central axis 1.50 for continuous support of the ~, tube 102 as it is coiled upon the coil-forming die 148 in ~, accordance with the coil-forming method o~ this i~vention.
., Attached to the uppex portion of the upstanding ~rame 144 i.s an axcuate scale 174 partially circumserihincJ the coil forming die 14a~. ~rrhe~scal.e 17~ i.ncludes a plurality o~ scale marks 176 which are:used durlng ~the fabrication OL the multiple.
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'.~ ;30 o~ heat eYchanger 100 to locate the pxecise ~ositi.on of the ~., : .
' inlet and outlet seyments 116, 118 relative to each.ot]ler as will be described hereina~t-er.
The operation of the coil-forminy a~`~aratus 140 will be bect understood by nex-t descri~ing the continuous coil-formi.ncJ method of this invention for fabrlcatinc3 a compact multiple coil heat exchanger 100 having a high heat transfer density using such apparatus 140. Initially referring to FIG. 6, a length of continuous tube 102 is positioned between lip portions 172 of the roller support 170 while the free end 162 ls firmly secured within the fi.rst thread oE the coi.l-forming die 148 at a coil-starting position by the hook ~, portion 160 o~ the adjustable clamp 156. The free end 162 : j .
. extends sufficiently b'eyond the adjustable clamp 156 to provide the outlet segment 118 of the inner coil 106. The initial rotational position of the coil-forming die 148 is ;- observed with reference to the scale marks~ 176 of the arcuate . scale 174. The precise position of the inlet and outlet ~; segments 11~, llR relati~e to each other can be readi:ly : determined by terminating the continuous pil-fo.~ming operation when the final rotational position of the ccil-forming die 1~8 is at the appropriate selected scale maxk 176 of the . arcuate scale 174.
Next, referring to FIGS. 9 through l~s ~ the coilinc3 of the t~e 102 about the coil-forming die 148 in fabricating the inner coil 106, the transitiorl segment 110 and the outer coil 108 of the heat exchanger 100 is progressively shown.
Referring specifically to FI~. 9, the tuhe 102 having been : secured within the first thread of the coil-forming die 1~s8 by hook portion 16b is rotated about the central axis 150 in the direction of the arrow 194. As the coil-forming die 1s8 is continuowsly :rotated, ~he tube 102 is spirally coiled within the thread 178 formincJ two conti~uous turns of the inner coil 106 of equal radi.us and having a pi~ch angle 2 :The tube 102 is llOW positioned at the start of the coil-reversing plate 180 where the last thread of the coil-forming die 148 meryes with the ramp 192 at the flrst circumferential segment ABC.
The transit;.on segment 110 of the heat exchanger LOO
:,is f~bri.cated by the coil-reversing plate 180 by continuously 10. `rotating the coil-fo.rming die 1~8 through 360 as sbown in FIG. 10 throu~h FIG. 13~ ReferrincJ to FIG. 10, as the coil-forming die ~8 is rotated in the directi.on of arrow 19~, the ramp 192 in '.'the ~irst circumferenttial segment ABC gradually increases the ~~raclius of curvature of the tube 102 relative to the.last turn .,,~19~ ol the inner coil 106. As shown in FIG. 11, the rotation of lthe coil-reversing plate 180 through the fixst 180, con-. i . .
tinuously and gradually extends radially outward the tube 102 fro'm the center axis 150 until the radial exter.ded position or the be 102 is slightly greater than the inside diameter of the outer coil 108 at C to prevent possible binding bet~een the inner and outer coils 106, 108. The engagement of the tube 102 by the .1 , I ~irst circl~mferential 5ec,~ment ABC of the coil-reversing plate,180 :~ ~orins the first c~rv~d portion 112 of the transition seg~ent ., .
,1 110 to having a pitch angle sLIbstantially equal to the pitch '1 angle 2 of the inner coil 106.
~''l The second curved portion 114 of the tr~nsition .':1 .
'I seg~ent 110 is fabrlcated by -the second ci.rcumferentia~
segment C~A of the coil reversing pla~e 180 ~y the continuecl : : .
`, rotation ol. tne coil-rever~-;ing plate 18a through a second 180~
. :
-.~,'~ 30 as~shown in FIC7S. 11 throuc3h 13. Referring to FI~.'ll, the : tube I02 is now positioned at C corresponding ~o the start of the second circum~.erential segment CDA of the coil reversing ,:' : : .
~ 6~6~
plate 180. As heretofore described, the ramp 192 and wedyiny surface 190 provide a pseudo-thread for the tube 102 llaviny a pitch anyle substantially equal to the pitch angle ~1 of the outer coil 108.
As shown in FIGS. 1~ and 13, the second curved portion 114 of the transition segment 110 is fabricated b~
rotating the coil-forming die 1~8 in the direction of the arrow 194 through a seconcl 180. As the tube 102 is enyayed . by the second circumferential segment C~A through the second . 10 180~ of rotation of the coil forming die 1~8, the pitch:
.~ , `~ angle of the tube 102 is changed from the pitch angle 32 of the ~,. . .
inner coil lG6 to the pitch angle ~l of the outer coil 108.
The combined effect of the decreasincJ width of the xamp 192 i.n I the seconc~ circumferential segment CDA and the changing of .~ the pitch angle ~2 of the tube 102 to the pitch angle ~l of .` the outer co.il 108, causes the tube 102 to be progressi.veiy an.d .~ . axially extended over the las-t turn 196 of the inner coil 106 ~: ` as shown in FIGS. 12 and 13. The tube 102 having been axially extended over the last tuxn 196 over the inner coil 106 now corrcsponds to a portion of the first turn of the outer coil 108 having a pitch angle ~1 As shown in FIG. 14, the outer coi.l 10~ is formed fro~
the tub~ 102 by urther rotatin~ the coil--forming die 14~ in the . direction of th~ arrow 19~. As the coil-forming die 148 is ~: rotated, the tube 102 is coiled about the inner coil 106 to form . a plurality of conti.guous turns of equal radius coiled con-centrica].ly ahout~alld substantially coexteIIsive ~aith the inner :coil 106 in:a spiral.arranyement. The coil-forming operation is : .
termlnated when the rotational position of the coil-~forming die 30 148 corresponds to the selected scale~mark :176 or the arcuate `
scale 174 such that the inlet and outlet s~cJr.lents 116, 118 are located at -their desired respective locations. The comple~ed multiple c~il heat e~chancJer 100 is removed from the coil-fo-c~ ng die 148 by rotatin~ the coil~formin~ die in t~le coi.l-releasing directior~ 154 as sho~n in E'IG. 6 t~rhile -estraining the completed heat e~changer 100 from rotation.
The ramp 192 of the coil-reversing plate l80 ~ithin the first circumferential segment ABC has been described as gradually extending radially outward until the diameter of the ramp lg2 is slightly greater than the inside diameter of the ;
1~ outer coil 108. The radially extending portion of the ramp 192 can be constructed to circumscribe a greater or lesser ~, portion of the coil-reversing plate 180 than 180 to provicle the first circum~erential segment ABC. Whe~ the radially ~ .
ext:endin.g outwaxd portion of the ramp 192 circumscribes greater than 180 o~ the. coi]-reversing plate 180, the circumferential segment ABC provides a more:gradual radial bending of the ~irst curved portion 112 of the transition segment 110 to provide easy removal of the heat exchanger 100 from the coil-orming die 148.
20 The. second circumferential secJmerlt CDA o~ the coil-reversiny plate 180 has been described to progressively axial.ly extend the tube 102 over the last turn 196 of the inner coil 106 as shown in FIGS. l? and 13. The second circlunferential segment CD~ of the coil-reversing plate 180 may also be constructed to circumscribe greater or less than 180 o~ the coil-reversing plate 180. Changing the extent of the second circum~erential segment CDA only requires that there be no undue inter~erence wi.th the last turn 196 of the inner coil 106 as i ~ . . .
the second circumferential slegment CDA axially extends the tube 30 102 over the last turn 196. By axial.ly extendlng the tube 102 ~4~
over the inner coil 106 when the transition segment 110 has been e~tended radially ouh~arcl to sli.glltlv qreat~r than thc~ outside diameter of the inner coi.l 106, tll~ outer coi~ 10~ rnay be iabricatecl Wit}lOut exertillg unclue compressive forces on the inner coil 106 which would otherwise tend to fu1-ther flatten the inner coil 106 as well as inhibit the removing of the heat exchanger 100 from the coil-forming die 14~ upon completion.
With the coil-formina ~pp~ratus as thus descri~e~' ~ccordIng -ko this invention, a multiple coil`heat ex~hanc~er can ~e iormed into a compact configuration oi minimum si~e whi.l.e having a hi~h heat transfer density as measured in BTI~'s/
hour/surface area. The heat transier capacity of the multiple coil heat exchanc3er m~y be iurther lncreased with a n~inimum increase in size by coiling on an additional layer ,of coi.ls concentrical.ly about the outer coil 108. This can be achieved by attaching to the front surface 158 of the coil-form~ng die 148, after the inner coil 106 has beeII,start2d, an additional coi'1-xe~ersing plate of the t~pe previously ~escri.bed. The coi1-reversing plate radially extends the outer coil 108 to a , raflially extendec~ positlon sllghtly c~reater than the outside ' di.ameter of the outer coil 108 and axially extencls tube 102 ~' over the outer coil 108 to fo.rm a concentric and coextensiye , :~ thi`rd coil while cont.inu.ing the rotation of the coi.l-forming ~, die 14~.
' The pitch diameter of the coil~formin~3 die 148 required for coiling 'a tu~e into a multi.ple coil heat ~' exchanger 100 requires taking several factors into consideration.
For example, one ~actor is the minim~n bending ra~ius for the ~ube 102 ~rhich general~ hould ~e;~larger thall so.ne multiPle ~30 of the diameter of the tube 102~ tQ avoid damage to the t-~e, SUCIl as e~cessive tube disiortion arlcl cracks. ~ second consi.dera-ti.on is that as the diameter of the coi.l is decrecls~!d, there is a corresponding reduction in the len~th of the multip:le coil heat exchanger 100 that can he formed from a pre-determined length of tube 102 ~or a specified number of ~urns.
In one embodiment, a coil~forming die 148 for forming a concentric heat exchan~er 100 from a tube 102 ha~ing a 1 1/2 inch outer diameter has a pitch diameter of about 9 3/4 inches.
~he extent that thread sidewalls 186 circumscri~e ~ 10 the tube 102 is a function of the amount of positive lateral -~ support needed to prevent flattening of the t~e 102. For ., ~
example, for a 1 1/2 inch outer diameter tube 102, a circumscribing of the tube 102 by capproximately 1/16 of an inch above the center line of the tube 102 is usually found sufficien~O ~en i the pi~ch diameter and the extent of positive lateral support are selected as in the aforementioned examples, the inner coil 106 can be coiled with a sufficiently large bending radius to avoid excessi~t2 distortion or flattening. The coil forming ~ ~le 148 can be made from steel with a numerically con~ro31ed machining tool or from an aluminum sand casti.ng through use of a wooden pattern and a suitable sand mold.
In a multiple coil~-forming apparatus according to .
this invent;.on, a multiple coi.l concentric heat exchanger can be fabricated from both a thin wall, about 0.0~8 inches~
:, .
and a heavy wall, about 0.065 ~ 0.109 inches, tube 102.
In modern refrigeration s~stems~ a typical diameter for a tube 102 used to fabricate a rnultiple coil heat exchanser 100 may be in the order of 1 1/2 inches, though different sizes can be accommodated acco~-ding to the ooil-~orming apparatus and 0 ~ continuous coil-form.ng method of this irlventi.on.
, , The contiIluous outer tube 124 of a multiple concentric tube 120 is pre-ferably Eormed of carbon steel which, after all mechanical workiny, is ~ully annealed and lea}~ tested for `~ cracks and faulty welds. The coil-forming die 148 descIibed herein is shown as cylindrical havin~ a uniform diameter although other shapes may be employed dependiny upon the desired configuration of the mulkiple coil heat exchanger 100. For example, the inner and outer coils can be fabricated in the shape of a cone having decreasin~ diameters along their length. With a different shaped coil~forming die, howeverj a collapsing die may be necessary to xelease the completed multlple co~l heat exchanger ~; lO0 therefrom.
~; In a heat eXchanyer in accordance with this inveIltion, a high density heat exchange capacity is obtained. The heat exchanger is made of a heat exchange tube which has been ,i bent into a co1l~d structure formed of an inner coil composed of a plurality of li~e-sized turns and an outer coil also composed of a plurality of like-sized turns, but closely wrapped about the inner coil. The inner and outer coils are joined by a contiguous transition seyment, whih, starting at one end of the inner coil, is radially extended relative to the inner coil and axially wedged over th~ inner coll to commence the second outer coil.
The term "coil" as used hereln means a plurality of ` turns or loops of a heat exchanye tube around an axis where the turns are spaced along the axis and axe yenerally of the same size. A mult;ple coil structure thus means at least a pair or ,-' : : , :
such coils, one wrapped over the other, w~th each coil formed of generally l1~e-sized turns.
' : ~
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A heat exchanger in accordance with this .iIIvelltion is :Eormed by ~AJrappl.ng a loncJituclinal h~at e~chanye tube over a di~
provi.deci wi.th a screw -thread si.~ed to at least parti.all.y circumferentially suppol-t the tube. The die is mounted for rotat~on about an axis so that upon die rotation ~he hea~
exchanye tube is wound up on the thread of the die to form flrst an inner coil.
' At an axial end of the die is a circumferentia~ coil reversing surface in alignment with the' die thread. This sur.ac~
has a first portlon which spirals outwardly so that the h~at exchange tube is radially bent above the turns of the inner col~.
The coil-reverslng surface has a seco'nd portion which axially ramps towards the other axial end of the die to direct the previously raclially outwardl~ bent heat e.{change tube over the inner aoil and thus commence a second or outer coil.
With an apparatus in accorda'nce with this invention~
a heat exchanger in accordance with this invention can be formed and completed iIl a sinqle step of continuous rotabion of the die .in one direction. The multi.ple coil struc:ture is compact and yields a high density of heat exchancJe capacity. The process for making a heat exchanger in accordance with the invention aclvantageously reduces mechanical working of the heat exchange tube so that a more consistent qu~lit~, such as more uniform diameter of the bent tube, in a shorter time is obtained.
The invention herein has been clescribed with reference to particular ernbodiments, it is to be understood that these en~odimen~s are merely illustrative ~f the principles and application of this invention. Thus, it is to be unders~oocl .
, that numerous modifications rnay be maae in the illustrative embod~ments and other arranqements may be devised withc~ut departin~ from the spirit and scope Q~ this inventiorl.
This invention relates in general to a heat exchanger, and more particularly, to a compact multiple coil heat exchanger having an improved heat transfer density and adapted to ~e easily accessible for repairs and maintenance in a modern refri-geration system. ~ ;
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In modern refrigeration systems, the compactness of the systemis components results in the advantage of reducing the ~, ~
3~ 10 ~ overall refrigeration system size and ultimately the related manufacturing costs.~ In the design o a compact refr;geration system, each component must be separately designed to be as small as possible, yet fully functional to sati~y the refrigeration system;~requirements. One such component is a heat exchanger or condenser which is used to cool the hot compressed refrigerant gases during the operation of the refrigeration system. The heat exchanger design must ~e such that it occupies a minimum space~while~maintaining a~high;performance as measured ln BTU'sj hours/surface area.
In providlng a minimum of space in the refrigeration ~r system design for the heat exchanger, it is further required that the heat exchanger's configuration be such to facilitate its removal and/or installation as required for repairs or maintenance.
~ Heat exohangers incorporated in current refrigeration systems ;~ usually have their inlet and outlet disposed at opposite ends of ~ the heat exchanger. Thls restricted conflguration~requires a~
; ~ complicated arrangement o~f refrigerant and cooling connecting lines to~the~heat~exchanger,~ in~addition to~rendering the connections~relati~ely inaccessible for easy removal of the heat ~30~ exchanger.
~ ccord~nc31y, there is a need for a compact heat exchang~r whic}l occupi.es a minimum of space while rctainin~ a hi~h heat:
tr~nsfer density and is adapted fo.r easy insta~llation and connection to xe~rigerant cooling lines within the compact space provided in a modern refri~eration system.
SUM~ARY OF T~IE IN`VENTION
It is broadl~ an object of this invention to provide a multiple coil heat exchanger which fulfills one or more of the foxegoing req~tirements of modern refrigeratiorl systems. Sveci-~fically, it is within the contemplati.on of th.is invention to ~0 provide a heat exchanqer ~ormed from a continuous tu~e coiled about a common axis into inner and oute~ concentric overlapping coils having an inlet and outlet disposed in a co~mon plane at one end and a continuous trans:ition se~ment joining the inner and outer coils at the other end thereof.
~ A further ohject of this invention is to pro~ide a :' ~ multiple coil heat exchanger constructéd in a continuous coil-~` forming process by the uninterrupted. rotation of a coil~ol~ing die.
A still further object of this invention is to provide 20 a multiple coil heat ~xchanger which is compact and has a high heat transfer densi~y in relati.onship to its overall size.`
A stil:l further object of this invention is to provide a multiple coil heat exchallc3er that is constructed and arranc3ed ~` for eas~ instal].ation ~ithin a compact space provided in a modern re~rigerati.on system by havirlg at least its inlet and outlet extendill~ kanc3erntially from the inner and outer colls at one common end thereQf~
. A still fu7:the~ object of this invention is to :
: ~
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provide a coiled construction adapted to forln a multiple coil heat excharlger from a continuous length of tube by a continuous coil-forming method.
A slLill furthex object of this invention is to provide a coil-forminc3 apparatus constructed and arranged for fa~ricating from a continuous length of tube a heat exchanger adapted for easy installation within a modern refriyeration system ~hile retaining a high heat transfer density.
In accordance with one illustra~ive embodiment of this invention, there is provided a multiple coil heat exchanger formed from a continuous coiled tube. qlhe coiled ~ube is formed to include an inner coil having a plurality of contiguous turn~
coiled a~out a common axis in a spira~ arrangement having a pitch in one direction and an outer coil having a p]urality of contiyuo~s turns concentric about the inner coil along the common axis in a like spiral arrangement having a pitch in the opposite direction.
continuous transition segment formed from a~portion of the coiled tube continuously ioins the inner and outer coils at a : .
common end of the heat exchanger and having a first curved~
portion o~ increasing radius OL curvature to radially extend the tube r~la~ive to the inner coil and a s~cond curved portion for axially extending the tuhe over the inner coil in forminy the outer coil.
Further, there is provided a coil~forming apparatus for fabricating a continuous length of tube into a compact multiple coil heat exchanger. The coil-forming apparatus includes a sup~ort frame for rotatably mountirlg a coil-forming die about it~ axis and having a spiral-llke thread sized to recei,ve the tube commencing at one end of the coil-forming die and termin~tln~ at a coil-rever~ing plate ccnstructod at the ~.:
$~6~3 other end of the coil-Forminq die. The coi.l-reversincJ plate is constructecl at -the other end of the coi.l~fol~lT~ - die to mercJe with and be a continuation of the spiral~like thread o~ the coil~
formi.nc~ die. ~ first porti.on o~ the coil~réversing pl.ate spi.rals outwar,d to a radial posi.tion above the rad.ial extent o the spiral-like threads at the other end of tlle coil-formlng die ~nd a second portion of the coi.l~reversing plate axlally extends away ~: from the coil-reversing plate towards the one end of the coil-forming die.
Furthe.r, there is provided an improved method of fabri.cating the comDact rnultiple coil ~leat exchallger according to the illustrative embodiment of this invention. A continllous method of fabricatiny a multiple coil heat exchanger having a.high heat trans~er density is disclosed whi.ch is initially startcd by ,~ securing one free end of the tube at a coil-starting position.
In a continuo-ls and uni.nterrupted process, the desixed lenyth of tuhe is coiled in a spiral dirèction about an axis to form an , .inner coi' ha~i.ng adjacent turns extending in one direction awa~
from thé coil-starti.ng position. Further, bendlng the tube radially outward slightly past the radial extent of the lnner coi~
and axially towards the coil~start.i.ng position to form a tr~nsition segmerl,k and then continuously coiling the tube in a ' spi.ral direction about the i.nner coil in'the opposite directlon ' , ~o form the concentric outer coil having contiguous turns over-lapping the inner coil and extending toT~ard the coil-startincJ
position.
BP~IEF DESCRIPTIO~ OF TEI~ DR~.WIN~S
The above dessription as ~ell as further objects, ~ eatures and advant~es OL ~he Present invention ~ e .,.ore :
~, , ~6~L6~
fully underslood ~ reference to the fo'~lowinc~ detailed description of the pr~sently preferred, but noneth~l.esc; il.lus~rative m~iltiple coi.l heat exchan~er, coi.l-forminy apparatus and continuo-ls coil-forming me~thod in accordance with this inverl.tion when taken in conjunction with the accompanying clrawings, wherein:
FIG. 1 is a front elevational view of a multiple coil heat exchan~ex constructed according to this invention and em~odying concentric inner and outer coils havin~ inlet and outlet ends extending parallel to each other in a'co~on plane at one end of the heat exchanger to provide easy accessibility to the refrigeran-t and cooli.ng line connections for ready removal o~' the heat:
exchanger from a modern rerrigeration s~stem;
FIG. 2 ~s a side elevational view of a multiple coil h~at exchanger as viewed from the right of FIG. 1 iilustrating t~.e outex coil having a pit.ch i.n one direction anc~ -the inner coil having a pitc~.in t'he op~osite directi.on;
,. . , F}G. 3 is a, rear elevational view o~ the multip.le coil heat exchanger of FIG. 1 illustrating the continuous joining of the inner coil to the concentric outer coil b~ a co~tinuous transition seyment having a flrst portion which radially extends out~ard slicJhtl~ past tile inner coil and a second portion whicrl axially extends over the innel- coil towaras t:.he inlet and outlet ends o,~ the heat exchanger;
FIG. 4 is a side elevational vi.ew of a multip].e coil hea~ exchanger as viewed from the right of F~G. 1 havirlg a portion of the out:er coil removed to sho~ a substantial portion of i:he~outer coil rernoved to sho~ a substantial portion of the inner coil hav.ing a pitch in the opposite direction of the ou~er cc~i l; , " .
~.~
~ : .
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YIG. 5 is a front elevational vie~ of a typical end cap : assembly for a concentric tube having a section removed to illustrate the construction and arranc~ement of~the end cap -to provide a separate inlet and outlet for a ~luid flowing within the inner tube and a fluid flowing within the annular region provided between the outer surface of the inner tube and the innex surface of the outer tube;
~ FIG. 6 is a front elevational view of a coil-formlng :~ . . apparatus constructed in accordance with this invention for forming a ~ultiple coil heat exchanger according to an illustrative embodiment of this invention and hatring an arcuate scale for determining the relative ~osition o~ the inlet and outlet wi-th respect to each ot~her at a common end of the multiple coil heat .. exchangex;
FIG. 7 is a si.de elevational view o~ the coil-forming apparatus as viewed from the le~t o~ FIG. 6 illustrating the , . . .
~ coil-forming die rotatably mounted on a supporting shaft :~ extending through an upstanding frame and having a spiral like .; thread t~rminating at a coil-reversing plate adjacent the u~-standing frame;
. FIG~ ~ is a partial section taken along lines 8-~ in : FIG. 7 illustrating the coil-reversing plate of the coil~forming di.e having a first portion which radially extends outwarcl past the raclial ext-.ent of the spiral~like thread of the coil-forming die ~ and a second portion which axially extends toward the front surfac~ of the coil-iorming die; and, FIGS. 9-.l4 are progressive side elevational views of the rotal~ing coil-formlng die :included within the coil-forming apparatus . .
~ of this in~enti.on for fabricating the multiple coil heat exchanger 6~
accordiny -to the continuous coil-fvrming metllc)d of this irvention and fuxther illustratiny the structural fea-tures and arrangelnent of the coil-reversing plate provided for fahric,lt.inc3 the transi.ion seyment of the mult~ple coil heat e~chanyer.
DETAILED DESCRIPTION OF THE PREF~RRED EM~ODIMENTS
. There will be described accordiny to one embodiment of this invent.i.on a compact multiple coil heat exc1lanc~er having a high heat transfer density pex unit volume as shown in the illustrative emhodiment of FIGS. 1 - 4. The multiple coil heat exchanger includes a sinyle coil.ed -tube formed into an inner ~ 10 coil of spiral-like turns about a con~on axis and an outer coil :~ of like.spiral-like turns overlapping the inner coil and con--tinuousl.y jolned to the inner coil by a continuous transition segment at one end thexeof. The ~ult:i.ple coil heat exchanger can . be fa~ricated from a single conti.nuolls tube as shown in ~IGo 1 or from a multiple concentric tube as shown in FIG. 5. ~1'he ~ultiple .~ : concentric tube can be constructed accordinJ to U. S. Patent ~o.
3,730,229, filed March 11, 1971, issued May 1, 1~3 and assigrled .o the same assignee of the present inven,ion. One unique fea~ure ~ of the multiple coil heat exchanger according to this invention - ~ is that both the i.nlet and out3.et ~see FIGS. 1 and 3) may be provided at one end o the heat exchanger and further if ~esi.redt extend parallel to one another in a co~non plane to provide ~ e~.sy access to the rnu1tiple coi]. heat exchanger when installed `. in a modern rerigeration system.
,, .
~ The illustrative multi~le coil heat exchanger, accordiny ;, :t:o this ernbodiment of 'his ~nvention~i.s fabricated, by ~7ay o~ one example, USillg a mul.ti.ple coi7-1-orming apparatus having a coil-'. : .
~orrning die rotatably:~.ounted: thereon, as illustra ed in FIGS. 6 and :8. The coil-fcrmincJ die has a con~-inuous spiral thread sized ~: 30~ constructed to recei.ve the continuous tllbe and col~.mencin~
at one end of the coil-Eorming die and terminatin(3 at the other end at a coil-reversillcl plate. I'he coil-reversincJ plate - merges wi.th and is a continuation of the spiral-like t.hread of the coll-forming die. The coil-reversing plate.include, a first circum~erential segment ~hich includes a ramp to xadially extend the continuous tube outward past the radially extent o the inner tube and a second circ~.m~Eerential segment fox axially extending the con-tinuous tube over the last turn o- the inner coil.
The multiple coil heat exchanger is fabricated using ~' the coil-forming apparatws of this invention and a continuous coil-forming me~hod, as described with reference to FIGS.
9 - 14. It is to be unclerstood that the multiple coil heat ~, exchanger, according to this invention, may be fabricated on other coil~forming apparatus other than the illustratec1 coil-forming apparatus of thls invention and according to a method:which further departs from the continuous coil form:ing method which will be described.
' Referri.ng speci~ically to the drawings, there is shown in ~;'IGS. 1 - 4, a multiple coil heat exchanger constructed ` according to this i.nvention, generall.y desicJnated by reference ; numeral 100. The heat exchanger 100 is formed from a continuous tube 102 spirally coiled about; a co~non axis 104 as shoi~n in FIGS. 2 and 4 to form lnner and ou-ter concentric overlapping ' ' coils 106, 108.
The inner coil 306 includes a plurality of conti~uous turns of substant;.ally,e~ual radius coiled abowt and spacecl along the com~.on axis 104 in a spiral arrdrlgement. The `':'~ , ~ .
outer coil 108 is likewisc-~ formed in a spiral arrangement from the tube 102 of a pl~lrality o~ continuo-ls turns of substantially equ~l radius coiled concentrica~ily about and substantially coextensive with the inner coil 106. The outer coil 108 is spaced along the common axis 104 in the : opposite direction of the inner coil 106.
As shown in FIG. 3, the inner:and outer coils 106, 108 are joined unin~erruptecl by a continuous transition se~ment 110 at the far end of the heat exchancJer 100. The transition ~ 10 segment 110 forms a portion of the last turn of the inner : coil 106 and a portion of t.he ~irst turn of the outer coil 108.
: ~ ~irst curved portion 112 of the transition segment 110 is oE
. increasing .raclius of curvature to radially extend the tube 102 . slightly past the radial extent of the-inner coil 106 r The second curved portion 114 is continuous with the firs-t curved .
portion 112 and extends the tube 102 from its incxeased radius o curvature axially over the last turn of the inner coil 106 to form the outer coil 108.
As shown in ~IGS. 1 and 3, the outer coil 108 includes a straight inlet segment 116 adaptea to ingress a heat transfer fluid and the .inner coil 106 includes a stralght outlet SeCJment 118 adapted to egress the heat trans:Eer .fluid. Both the inlet and outlet segments 116, 113 extend tangentially from the respective inner and outer coils 106, 108 and substanti.ally parallel to each other at the rear end of the heat exchanger 100 in a common plane that is transverse to the common axis lC4.
As illustrated~ the lnl.et and outlet segments 116, 11~ terminate within the common plane at substantially the same extended location. As will be further described wlth reference to the ~;' :
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continuous method of fabricatin~ the heat exchallger 100 according to this invention, the inlet and outlet segmeIlts 116, 118 may extend in other than parallel relationship to each other.
As shown in FIG. 2, the turns of the outer coil 108 are right handed turns having a pitch angle l for~ed between a plane transverse to the coI~on axis 104 and a plane including : a turn o~ the outer coil 108. As shown in FIG. 4, ~he turns of the inner coil 10~ are left handed turns having an dpposite pitch angle B2 ~ormed hetween a plane transverse the common axis 104 and 10 a plane including a turn of the inner coil 106. The pltch angles ~1 and ~2 are usually selected to be small ~o provide for the co~pact construct;.on of the turns of the inner and owter coils 106, 108, but sufficiently large to enable the turns of the ~
.inne~ and ouker coils 106, 108 to be formed contiguous and over-lapping without excessive deformation o~ the tuhe 102 during ~he continuous coil~forming method according to this inventi.on.
The relati~e size of the pitch angles 91 and ~2 are ~: ge;lerally a function of the diamete.r of the inner and outer coils 106, 108 alld of the ~iarr~eter of the tube 102. Gene.rally, small pitch an~les ~1~ 2 are permitted by includlng a relatively large diameter for the inner and outer coils 106, 10~, or a relatively small diarneter for.the tube 102. In one illus~rative embodiment of the multiple coil heat exchange~r 100, the pitch .` anyles ~1 9~ were selected t.o be in the range of approximately 4 ~20.and approximately equal to each other~
; As thus described, the mu].tiple coil heat exchanger 100 according to ~this invention, is constructed of a surficient number-of turns o the tube 102 -c.o provide a compact heat exchanger .1~ , - .
~` having a hlgh heat transfer densl;ty to meet the mlnimum si~e requirements and per.~ormance cîiteria o. modersl re~rigQrat sysk_ms.
... .
~ ~ , The multip].e coil heat e~changer 100 may be abricatrd from a sing].e continuous tube 102 as shown in FIGS. 1 to ~ or from a multiple concentric tube 120 as shown in FIG. 5. The , i.ncorporation of a multiple concen-~ric tube 120 in the multiple coil heat exchanger 100 of this invention results ; in a heat exchanger 100 haviny increased heat transfer area ~ ' to provide overal]. higher effi-ciency of the heat exchanger .
,. 100. The concentric l,ube 120 i.s illustrated to include a :~ : . conti~uous inner corregated tube 122 coneentric with a , ..10 , continuous non~corregated outer tube 1~4~ Heat is exchanged ~:, between a heat transfer fluid flowing within the inner tube 122 and a heat transfer flui.d flowin~ i.n the annular reg;.on 12~ provided between the outer surface of the inner tube 122 . . ana the inner.surface of the outer tube 124. The construction of one multiple concentric tube for fabricating a multlple coil ~eat exchanger acaordiny to this invention is desc.ribed i.n the '~ aforementioned patent assigned to the same assignee as the ' p.resent inventlon.
:. An end cap assembly 128 which is illustrated as heing ~ ~ecured over the opening 130 located at each terminal end of the ,, ou~er kube .l24 conv~lliently provides an inlet and outlet to r,he .
inner tube 122 and the annular resion 126. The i.nner tube 122 extends through the top portion 132 of the end cap ass~r~ly 128 to provide inlet/outlet port 134 for the inner tube 122.
~, short tube,se~ment 136 extending through a side portion of the end cap assembly 128 to provi.de an inlet/outlet p'ort 138 for the annular rcgion 126.
As shown in ~IGS. 6 and 7, a coil-forming appara-tus 140 accordi.n~ to this;irvention, is ill~s~rated for fabricatin~ a multi.p~e coil:heat exchanger 100 as prev.iously ~escribed.
: :
6~
In general, the coil-formillg apparatlls 140 includes a base plate 142 and an ups1-anding franie 14~ throuc3h which a hori~ontal supporting shaft 1~6 extencls which is rotatably mounted b~
appropriate bearings (not shown) on the frame 144; Attached to the supporting shaft 146 ls a coil-formlng die 148 rotatably mounted for ro~ation about the central axis 150 by suitable drive means (not shown), such as an electric motor. The coil~orminy die 148 is adapted for rotation in either a coil-forming direction as indicated by arrow 152 or a coil-releasing direction as indicated by the arrow 154 by the drive means. The coil-forming die has a continuous spiral , , like thread 178 cornmencing at one end o~ the die and terminating `~ - at a coil-reversing plate 180 located adjacent the upstanding ~rame l44 at the other end'of the coil-forming die.
As shown in FIG. 7, the coi,l-forming die 1~8 includes , a continuous spiraling left handed thread 178'commencing at the front surface 158 and terminating at a progressive c~irc~nferentially extendiny coil reversing plate 180 at the rear portion of the coil-forming die adjacent the upstanding 20 fxarne 144. The thread l78 is constructed to include a root 184 and adjacent thread side walls 186~ The thread side walls 186 and root 184 are cons,tructed and arranged to , partially circumscribe tube 102. The circumscribing of the tube 102 provides lateral circumferential support for the ~; tube 102 during the coi7-fo~ming operation, thereby preventing the tube 102 rom flattening. The pitch angle ~2 of the inner coil 106 is determined by the corresponding pitch angle of the thread 178. In one illus-trative embodiment of ~ the multiple coil heat exchanger according to this in~ention, ;~ 30 the root 184 and the thread side wâlls 18~ circumscr~be the ~ ube 102 slightly a~o~e the center a~is oE the tuhe 102.
The coil-reversillg plate lS0, as S}lOWn generall~ i n FIGS. 7 and 8, is constructed of a ci.rcular wedJe shaped disc 1~8 positioned a~out a celltral axis 150 at: he rear pOrtiOIl of : the coil-forming die 148. The disc 188 inc'ludes a circular planar wedginy surface 190 which supports a coaxial, radially extendi.ng ramp 192 of varying width. The construction of the , coil--reversing plate 180 is best shown with reference to FIG~ 9 and 11. r~he coil-reversing plate 180 is generally divided .into , , two continuous 180 circumferential seyments designated ~BC and ~ 10 CD~. The first circumferential segment ABC is shot~n in FIG. 9.
The root 1~4 and side wall 186 of the last thread at the rear porti.on of the co~ formincJ d.ie 148 merges radial.ly with the ramp 192. The ramp 192 of the first eircumferential segment ABC is constructed of uniform width to acco~modate the diameter of the tube ].02.
The ramp 192 is bound on the right side by the wedging surface 190 which provides a supporti.ng wall for the tube 102.
The ramp 192 and wedging surface 190 within ~he first circumfexentlal se~ment ABC provide a pseudo--thread for the tu~e 102 havinc; a ~0 pitch angle substantially equal to the pitch angle ~2 of the inner coi,l 106. The ramp 192 starts with a diameter equal to the i.nside diameter of the inrler coil 102 at A. As the ramp 192 circumfe.rentially proyresses t.:hrough the first circumferentlal segment ~BC, the ramp 192 continuously and,gradually extenàs radial.ty outward from the central axis 150 until t~e diameter ' of the ramp 192 is sliglltly greater than the inside diamPter o~ the outer aoiJ 1.08 at C.
The second circumferential se3ment CDA or the coil-reversing plate i80 is shown in FIG. 11. The ramo 192 through the second circ~mferential segment C~ is constr~cted to retain .its radial extcnded position from the common axis lS0 correspolldiny ; to slightly greater than the i.nside diameter of the outer coil : 108~ The rarnp 192 gra.dually decreases in ~rid~l frorn its ; initial width corresponding to the diameter of tube 102 at C
until the width of the ramp 192 vanishes upon mergin~ with the ~edging surface 190 at A. The ramL~ 192 wi.thin the second circumferential segment CDA is likewise bound on the ri.~ht side by the wedgin~ surface 190 which provides a supporting wall'for ~;~ the: tube 102. The ramp 192 and the wedc3ing surFace 190 throucJh 10: the second circumferentlal segrnent CDA provide a pseudo-thread .~ or the tube 102 having a pi.tch angle substantially equal to the pitch angle ~1 of the outer coil 108.
,.. . .
A~ adjusta~l~e clamp 156 is mounted to the front ~surface 158 of the coil~forming die 148. The adjustable clamp 156 includes a hook porti.on 160 to engage the free end 162 of ~ .
. the tube 10~ to secure the free:~end 160 to the coil-~orming die : 148 du~ing the oontinuous coil-forming operation. The upstanding ; : ~ frame~144 has trans~ersely mounted thereto an adjustable ro].ler : l ' .
support assembly I64 by a horizonta1 ~-shaped bracket lG6 :through which a rod 1.68 extends parallel there~7ith. A roller support 170 having a radi~lly extending lip portion 172 at each ~, .
~' end thexeof is slidably mourlted on the rod lG8 for movement parallel to the central axis 1.50 for continuous support of the ~, tube 102 as it is coiled upon the coil-forming die 148 in ~, accordance with the coil-forming method o~ this i~vention.
., Attached to the uppex portion of the upstanding ~rame 144 i.s an axcuate scale 174 partially circumserihincJ the coil forming die 14a~. ~rrhe~scal.e 17~ i.ncludes a plurality o~ scale marks 176 which are:used durlng ~the fabrication OL the multiple.
, . . ~ . ~
'.~ ;30 o~ heat eYchanger 100 to locate the pxecise ~ositi.on of the ~., : .
' inlet and outlet seyments 116, 118 relative to each.ot]ler as will be described hereina~t-er.
The operation of the coil-forminy a~`~aratus 140 will be bect understood by nex-t descri~ing the continuous coil-formi.ncJ method of this invention for fabrlcatinc3 a compact multiple coil heat exchanger 100 having a high heat transfer density using such apparatus 140. Initially referring to FIG. 6, a length of continuous tube 102 is positioned between lip portions 172 of the roller support 170 while the free end 162 ls firmly secured within the fi.rst thread oE the coi.l-forming die 148 at a coil-starting position by the hook ~, portion 160 o~ the adjustable clamp 156. The free end 162 : j .
. extends sufficiently b'eyond the adjustable clamp 156 to provide the outlet segment 118 of the inner coil 106. The initial rotational position of the coil-forming die 148 is ;- observed with reference to the scale marks~ 176 of the arcuate . scale 174. The precise position of the inlet and outlet ~; segments 11~, llR relati~e to each other can be readi:ly : determined by terminating the continuous pil-fo.~ming operation when the final rotational position of the ccil-forming die 1~8 is at the appropriate selected scale maxk 176 of the . arcuate scale 174.
Next, referring to FIGS. 9 through l~s ~ the coilinc3 of the t~e 102 about the coil-forming die 148 in fabricating the inner coil 106, the transitiorl segment 110 and the outer coil 108 of the heat exchanger 100 is progressively shown.
Referring specifically to FI~. 9, the tuhe 102 having been : secured within the first thread of the coil-forming die 1~s8 by hook portion 16b is rotated about the central axis 150 in the direction of the arrow 194. As the coil-forming die 1s8 is continuowsly :rotated, ~he tube 102 is spirally coiled within the thread 178 formincJ two conti~uous turns of the inner coil 106 of equal radi.us and having a pi~ch angle 2 :The tube 102 is llOW positioned at the start of the coil-reversing plate 180 where the last thread of the coil-forming die 148 meryes with the ramp 192 at the flrst circumferential segment ABC.
The transit;.on segment 110 of the heat exchanger LOO
:,is f~bri.cated by the coil-reversing plate 180 by continuously 10. `rotating the coil-fo.rming die 1~8 through 360 as sbown in FIG. 10 throu~h FIG. 13~ ReferrincJ to FIG. 10, as the coil-forming die ~8 is rotated in the directi.on of arrow 19~, the ramp 192 in '.'the ~irst circumferenttial segment ABC gradually increases the ~~raclius of curvature of the tube 102 relative to the.last turn .,,~19~ ol the inner coil 106. As shown in FIG. 11, the rotation of lthe coil-reversing plate 180 through the fixst 180, con-. i . .
tinuously and gradually extends radially outward the tube 102 fro'm the center axis 150 until the radial exter.ded position or the be 102 is slightly greater than the inside diameter of the outer coil 108 at C to prevent possible binding bet~een the inner and outer coils 106, 108. The engagement of the tube 102 by the .1 , I ~irst circl~mferential 5ec,~ment ABC of the coil-reversing plate,180 :~ ~orins the first c~rv~d portion 112 of the transition seg~ent ., .
,1 110 to having a pitch angle sLIbstantially equal to the pitch '1 angle 2 of the inner coil 106.
~''l The second curved portion 114 of the tr~nsition .':1 .
'I seg~ent 110 is fabrlcated by -the second ci.rcumferentia~
segment C~A of the coil reversing pla~e 180 ~y the continuecl : : .
`, rotation ol. tne coil-rever~-;ing plate 18a through a second 180~
. :
-.~,'~ 30 as~shown in FIC7S. 11 throuc3h 13. Referring to FI~.'ll, the : tube I02 is now positioned at C corresponding ~o the start of the second circum~.erential segment CDA of the coil reversing ,:' : : .
~ 6~6~
plate 180. As heretofore described, the ramp 192 and wedyiny surface 190 provide a pseudo-thread for the tube 102 llaviny a pitch anyle substantially equal to the pitch angle ~1 of the outer coil 108.
As shown in FIGS. 1~ and 13, the second curved portion 114 of the transition segment 110 is fabricated b~
rotating the coil-forming die 1~8 in the direction of the arrow 194 through a seconcl 180. As the tube 102 is enyayed . by the second circumferential segment C~A through the second . 10 180~ of rotation of the coil forming die 1~8, the pitch:
.~ , `~ angle of the tube 102 is changed from the pitch angle 32 of the ~,. . .
inner coil lG6 to the pitch angle ~l of the outer coil 108.
The combined effect of the decreasincJ width of the xamp 192 i.n I the seconc~ circumferential segment CDA and the changing of .~ the pitch angle ~2 of the tube 102 to the pitch angle ~l of .` the outer co.il 108, causes the tube 102 to be progressi.veiy an.d .~ . axially extended over the las-t turn 196 of the inner coil 106 ~: ` as shown in FIGS. 12 and 13. The tube 102 having been axially extended over the last tuxn 196 over the inner coil 106 now corrcsponds to a portion of the first turn of the outer coil 108 having a pitch angle ~1 As shown in FIG. 14, the outer coi.l 10~ is formed fro~
the tub~ 102 by urther rotatin~ the coil--forming die 14~ in the . direction of th~ arrow 19~. As the coil-forming die 148 is ~: rotated, the tube 102 is coiled about the inner coil 106 to form . a plurality of conti.guous turns of equal radius coiled con-centrica].ly ahout~alld substantially coexteIIsive ~aith the inner :coil 106 in:a spiral.arranyement. The coil-forming operation is : .
termlnated when the rotational position of the coil-~forming die 30 148 corresponds to the selected scale~mark :176 or the arcuate `
scale 174 such that the inlet and outlet s~cJr.lents 116, 118 are located at -their desired respective locations. The comple~ed multiple c~il heat e~chancJer 100 is removed from the coil-fo-c~ ng die 148 by rotatin~ the coil~formin~ die in t~le coi.l-releasing directior~ 154 as sho~n in E'IG. 6 t~rhile -estraining the completed heat e~changer 100 from rotation.
The ramp 192 of the coil-reversing plate l80 ~ithin the first circumferential segment ABC has been described as gradually extending radially outward until the diameter of the ramp lg2 is slightly greater than the inside diameter of the ;
1~ outer coil 108. The radially extending portion of the ramp 192 can be constructed to circumscribe a greater or lesser ~, portion of the coil-reversing plate 180 than 180 to provicle the first circum~erential segment ABC. Whe~ the radially ~ .
ext:endin.g outwaxd portion of the ramp 192 circumscribes greater than 180 o~ the. coi]-reversing plate 180, the circumferential segment ABC provides a more:gradual radial bending of the ~irst curved portion 112 of the transition segment 110 to provide easy removal of the heat exchanger 100 from the coil-orming die 148.
20 The. second circumferential secJmerlt CDA o~ the coil-reversiny plate 180 has been described to progressively axial.ly extend the tube 102 over the last turn 196 of the inner coil 106 as shown in FIGS. l? and 13. The second circlunferential segment CD~ of the coil-reversing plate 180 may also be constructed to circumscribe greater or less than 180 o~ the coil-reversing plate 180. Changing the extent of the second circum~erential segment CDA only requires that there be no undue inter~erence wi.th the last turn 196 of the inner coil 106 as i ~ . . .
the second circumferential slegment CDA axially extends the tube 30 102 over the last turn 196. By axial.ly extendlng the tube 102 ~4~
over the inner coil 106 when the transition segment 110 has been e~tended radially ouh~arcl to sli.glltlv qreat~r than thc~ outside diameter of the inner coi.l 106, tll~ outer coi~ 10~ rnay be iabricatecl Wit}lOut exertillg unclue compressive forces on the inner coil 106 which would otherwise tend to fu1-ther flatten the inner coil 106 as well as inhibit the removing of the heat exchanger 100 from the coil-forming die 14~ upon completion.
With the coil-formina ~pp~ratus as thus descri~e~' ~ccordIng -ko this invention, a multiple coil`heat ex~hanc~er can ~e iormed into a compact configuration oi minimum si~e whi.l.e having a hi~h heat transfer density as measured in BTI~'s/
hour/surface area. The heat transier capacity of the multiple coil heat exchanc3er m~y be iurther lncreased with a n~inimum increase in size by coiling on an additional layer ,of coi.ls concentrical.ly about the outer coil 108. This can be achieved by attaching to the front surface 158 of the coil-form~ng die 148, after the inner coil 106 has beeII,start2d, an additional coi'1-xe~ersing plate of the t~pe previously ~escri.bed. The coi1-reversing plate radially extends the outer coil 108 to a , raflially extendec~ positlon sllghtly c~reater than the outside ' di.ameter of the outer coil 108 and axially extencls tube 102 ~' over the outer coil 108 to fo.rm a concentric and coextensiye , :~ thi`rd coil while cont.inu.ing the rotation of the coi.l-forming ~, die 14~.
' The pitch diameter of the coil~formin~3 die 148 required for coiling 'a tu~e into a multi.ple coil heat ~' exchanger 100 requires taking several factors into consideration.
For example, one ~actor is the minim~n bending ra~ius for the ~ube 102 ~rhich general~ hould ~e;~larger thall so.ne multiPle ~30 of the diameter of the tube 102~ tQ avoid damage to the t-~e, SUCIl as e~cessive tube disiortion arlcl cracks. ~ second consi.dera-ti.on is that as the diameter of the coi.l is decrecls~!d, there is a corresponding reduction in the len~th of the multip:le coil heat exchanger 100 that can he formed from a pre-determined length of tube 102 ~or a specified number of ~urns.
In one embodiment, a coil~forming die 148 for forming a concentric heat exchan~er 100 from a tube 102 ha~ing a 1 1/2 inch outer diameter has a pitch diameter of about 9 3/4 inches.
~he extent that thread sidewalls 186 circumscri~e ~ 10 the tube 102 is a function of the amount of positive lateral -~ support needed to prevent flattening of the t~e 102. For ., ~
example, for a 1 1/2 inch outer diameter tube 102, a circumscribing of the tube 102 by capproximately 1/16 of an inch above the center line of the tube 102 is usually found sufficien~O ~en i the pi~ch diameter and the extent of positive lateral support are selected as in the aforementioned examples, the inner coil 106 can be coiled with a sufficiently large bending radius to avoid excessi~t2 distortion or flattening. The coil forming ~ ~le 148 can be made from steel with a numerically con~ro31ed machining tool or from an aluminum sand casti.ng through use of a wooden pattern and a suitable sand mold.
In a multiple coil~-forming apparatus according to .
this invent;.on, a multiple coi.l concentric heat exchanger can be fabricated from both a thin wall, about 0.0~8 inches~
:, .
and a heavy wall, about 0.065 ~ 0.109 inches, tube 102.
In modern refrigeration s~stems~ a typical diameter for a tube 102 used to fabricate a rnultiple coil heat exchanser 100 may be in the order of 1 1/2 inches, though different sizes can be accommodated acco~-ding to the ooil-~orming apparatus and 0 ~ continuous coil-form.ng method of this irlventi.on.
, , The contiIluous outer tube 124 of a multiple concentric tube 120 is pre-ferably Eormed of carbon steel which, after all mechanical workiny, is ~ully annealed and lea}~ tested for `~ cracks and faulty welds. The coil-forming die 148 descIibed herein is shown as cylindrical havin~ a uniform diameter although other shapes may be employed dependiny upon the desired configuration of the mulkiple coil heat exchanger 100. For example, the inner and outer coils can be fabricated in the shape of a cone having decreasin~ diameters along their length. With a different shaped coil~forming die, howeverj a collapsing die may be necessary to xelease the completed multlple co~l heat exchanger ~; lO0 therefrom.
~; In a heat eXchanyer in accordance with this inveIltion, a high density heat exchange capacity is obtained. The heat exchanger is made of a heat exchange tube which has been ,i bent into a co1l~d structure formed of an inner coil composed of a plurality of li~e-sized turns and an outer coil also composed of a plurality of like-sized turns, but closely wrapped about the inner coil. The inner and outer coils are joined by a contiguous transition seyment, whih, starting at one end of the inner coil, is radially extended relative to the inner coil and axially wedged over th~ inner coll to commence the second outer coil.
The term "coil" as used hereln means a plurality of ` turns or loops of a heat exchanye tube around an axis where the turns are spaced along the axis and axe yenerally of the same size. A mult;ple coil structure thus means at least a pair or ,-' : : , :
such coils, one wrapped over the other, w~th each coil formed of generally l1~e-sized turns.
' : ~
` :
A heat exchanger in accordance with this .iIIvelltion is :Eormed by ~AJrappl.ng a loncJituclinal h~at e~chanye tube over a di~
provi.deci wi.th a screw -thread si.~ed to at least parti.all.y circumferentially suppol-t the tube. The die is mounted for rotat~on about an axis so that upon die rotation ~he hea~
exchanye tube is wound up on the thread of the die to form flrst an inner coil.
' At an axial end of the die is a circumferentia~ coil reversing surface in alignment with the' die thread. This sur.ac~
has a first portlon which spirals outwardly so that the h~at exchange tube is radially bent above the turns of the inner col~.
The coil-reverslng surface has a seco'nd portion which axially ramps towards the other axial end of the die to direct the previously raclially outwardl~ bent heat e.{change tube over the inner aoil and thus commence a second or outer coil.
With an apparatus in accorda'nce with this invention~
a heat exchanger in accordance with this invention can be formed and completed iIl a sinqle step of continuous rotabion of the die .in one direction. The multi.ple coil struc:ture is compact and yields a high density of heat exchancJe capacity. The process for making a heat exchanger in accordance with the invention aclvantageously reduces mechanical working of the heat exchange tube so that a more consistent qu~lit~, such as more uniform diameter of the bent tube, in a shorter time is obtained.
The invention herein has been clescribed with reference to particular ernbodiments, it is to be understood that these en~odimen~s are merely illustrative ~f the principles and application of this invention. Thus, it is to be unders~oocl .
, that numerous modifications rnay be maae in the illustrative embod~ments and other arranqements may be devised withc~ut departin~ from the spirit and scope Q~ this inventiorl.
Claims (26)
1. A multiple coil heat exchanger comprising a coiled tube formed with an inner coil having a plurality of contiguous turns coiled about a common axis in a spiral arrangement having a pitch in one direction and an outer coil having a plurality of contiguous turns coiled concentrically about said inner coil along said common axis in a spiral arrangement having a pitch in the opposite direction, and a continuous transition segment formed from said tube joining said inner and outer coils at one end thereof, said transition segment including a first curved portion of increasing radius of curvature to radially extend said tube relative to said inner coil and a second curved portion for axially extending said tube over said inner coil in forming said outer coil.
2. The multiple coil heat exchanger according to Claim 1 including ingress and egress means for said coiled tube each having a straight segment of said tube and respectively extending tangentially from the inner and outer coils at one end of said coiled tube and terminate in a common plane sub-stantially transverse to said common axis.
3. The multiple coil heat exchanger according LO Claim 2 wherein said ingress and egress means extend substantially parallel to each other in said common plane.
4. The multiple heat. exchanger according to Claim 2 wherein said ingress and egress means extend in an other than parallel relationship to each in said common plane.
5. The multiple heat exchanger according to Claim 1 wherein said continuous transition segment forms a portion of the last turn of said inner coil and a portion of the first turn of said outer coil.
6. A heat exchanger comprising a multiple coil structure having a common axis and formed from a continuous tube having inlet and outlet ends, said structure including an inner coil formed of said tube beginning from said inlet end and having a plurality of abutting and substantially identical turns coiled about and spaced along said common axis to the other end of said structure, an outer coil formed of said tube and having a plurality of abutting and substantially identical turns coiled concentrically of and substantially coextensive with said inner coil and spaced along said common axis toward said inlet end, and a continuous transition segment joining said inner and said outer coils at said other end of said structure and having a first curved portion radially extending said tube relative to said inner coil and a second curved portion which extends over said inner coil.
7. A heat exchanger according to Claim 6 wherein said first curved portion is of-a progressively increasing radius of curvature.
8. The heat exchanger according to Claim 6 wherein said inlet and outlet ends are at the same end of said structure and are in a substantially common plane.
9. The heat exchanger according to Claim 8 wherein said inlet and said outlet ends terminate substantially parallel to each other in said common plane.
10. The heat exchanger according to Claim 8 wherein said inlet and said outlet ends terminate in an other that parallel relationship in said common plane.
11. The heat exchange, according to Claim 6 wherein said inner coil has a pitch in one direction and said outer coil has a pitch in the opposite direction.
12. The heat exchanger according to Claim 11 therein said transition segment changes in pitch from the pitch of said inner coil to the pitch of said outer coil.
13. The heat exchanger according to Claim 12 wherein said first and second pitches are substantially equal.
14. A heat exchanger comprising a multiple coil structure formed from a continuous coiled tube having a common axis and inlet and outlet ends substantially disposed in a common plane at one end thereof, said structure including an inner coil formed of said tube beginning in said common plane and having a plurality of inner turns coiled about and spaced along said common axis to the other end of said structure at a first pitch angle, an outer coil formed of said tube and having a plurality of outer turns coiled over and substantially coextensive with said inner coil and spaced along said common axis extending to said common plane at a second pitch angle which is opposite to said first pitch angle, and a continuous transition segment joining said inner and said outer coils at said other end of said structure and having a pitch which transitions from said first pitch angle to said second pitch angle.
15. The heat exchanger according to Claim 14 wherein said transition segment includes a first curved portion to radially extend said tube relative to said inner coil and a second curved portion which axially extends over said inner coil.
16. The heat exchanger as set forth in Claim 13 wherein said first and second pitches are substantially equal in magnitude.
17. A multiple coil heat exchanger having a common axis and formed from a continuous concentric tube, said structure including an inner coil formed from said tube into a plurality of contiguous turns coiled about said common axis in a spiral arrangement having a pitch in one direction, an outer coil formed from said tube into a plurality of contiguous turns concentrically about and coextensive with said inner coil and spaced along said common axis in a spiral arrangement having an equal pitch in the opposite direction, a continuous transition segment joining said inner and outer coils at one end of said heat exchanger, said transition segment including a firs-t curved portion of increasing radius of curvature to radially extend said tube to a radial position slightly greater than the radial extent of said inner coil and a second curved portion for axially extending said tube over said inner coil in forming said outer coil, said transition segment constructed of a portion of the last turn of said inner coil and a portion of the first turn of said outer coil, and an inlet and outlet for said tube each including a straight segment of said tube extend tangentially from the inner and outer coils at one end of said heat exchanger in a common plane substantially transverse to said common axis, said inlet and outlet extending sub-stantially parallel to each other in said common plane.
18. A method of forming a tube into a multiple coil heat exchanger comprising the steps of securing one end of said tube at a coil-starting position, coiling said tube in a spiral about an axis to form an inner coil having contiguous turns extending in one direction away from said coil-starting position, bending a transition segment of said tube radially outward past the radial extent of said inner coil and axially toward said coil-starting position, and coiling said tube in a spiral direction about said inner coil to form a concentric outer coil having continuous turns over said inner coil and extending in the opposite direction toward said coil-starting position.
19. The method according to Claim 18 further including terminating the coiling of said tube when the other end of said tube is substantially in the same plane as said one end of said tube to provide an inlet and outlet for said heat exchanger in said plane at the same end of said heat exchanger.
20. The method according to Claim 18 further including coiling said tube into inner and outer coils of substantially equal and opposite pitches.
21. The method according to Claim 18 wherein coiling said transition segment further includes changing the pitch of said tube from the pitch of said inner coil to the pitch of said outer coil.
22. A method of forming a continuous tube into a multiple coil heat exchanger having inlet and outlet ends at one end thereof comprising the steps of securing one end of said tube at a coil-starting position, continuously coiling said tube in a spiral direction about an axis to form an inner coil of a plurality of contiguous turns extending in one direction away from said coil-starting position at a first pitch angle, extending said tube radially outward past said inner coil and axially toward said coil-starting position, continuously coiling said tube in a spiral direction about said inner coil to form a concentric outer coil of a plurality of contiguous turns substantially coextensive with said inner coil and extending in the opposite direction towards said coil-starting position at a second pitch angle substantially equal and opposite to said first pitch angle, and terminating the coiling of said tube with the other end at said coil-starting position.
23. The method according to Claim 22 further including terminating the coiling of said tube at said coil starting position to provide an inlet and outlet for said heat exchanger formed of straight segments of said tube extending tangentially from said inner and outer coils parallel to one another in a common plane transverse to said axis at said coil-starting position.
24. A method of forming a continuous length of tube into a multiple. coil heat exchanger having inlet and outlet ends at one end thereof comprising the steps of securing a straight segment of said tube to form said inlet end at a coil-starting position, continuously coiling said tube in a spiral direction about an axis to form an inner coil of a plurality of contiguous turns extending in one direction away from said coil-starting position at one pitch angle, continuously extending said tube at said one pitch angle in a substantially radial direction outward past the radial extent of said inner coil and axially at another pitch angle over said inner coil towards said coil-starting position, continuously coiling said tube in a spiral direction about said inner coil to form a concentric outer coil of a plurality of contiguous turns substantially coextensive with said inner coil and extending in the opposite direction to said coil-starting position at said other pitch angle, said other pitch angle substantially equal and opposite to said one pitch angle, and terminating the coiling of said tube with the other end of said tube at said coil-starting position to form said outlet end from a straight segment of said tube extending parallel to said inlet end in a common plane transverse to said axis at said coil-starting position.
25. A heat exchanger in which a heat exchange tube having an inner tube is formed into a coiled structure about an axis comprising, an inner coil formed of said heat exchange tube said inner coil being formed with a plurality of like-sized turns wrapped about and spaced along said axis; an outer coil formed of said heat exchange tube and being formed with a plurality of like-sized turns wrapped concentrically about said inner coil and spaced along said axis; said inner and outer coils being joined at one common axial end with a contiguous transition segment of said heat exchange tube, said contiguous transition segment being formed of a first curved portion having an increasing radius of curvature to radially extend the heat exchange tube rela-tive to the inner coil and further being formed with a second curved portion, which is contiguous with the first curved portion, and which second portion is axially wedged over said inner coil to commence said outer coil.
26. A method of forming a heat exchanger from a generally straight longitudinal heat exchange tube enclosing an inner tube comprising the steps of mounting one end of the heat exchanger tube to one axial end of a threaded rotatable die having a screw thread with a root sized to receive said heat exchange tube at said one axial end wit at least partial circumferential support therefor; rotating said die in one direction to wind the heat exchange tube onto the thread of the die to form a plurality of turns of an inner coil of said heat exchange tube; upon completion of said inner coil continuing to rotate said die in said one direction while wedging said heat exchange tube radially outwardly and subsequently axially towards said one axial end of the die to commence a first turn of a second coil concentric with and over the inner coil; and, continuing to rotate the die in said one direction to bend said heat exchange tube and form said second coils with a plurality of turns.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US8356879A | 1979-10-11 | 1979-10-11 | |
| US083,568 | 1979-10-11 | ||
| US14189480A | 1980-04-21 | 1980-04-21 | |
| US141,894 | 1980-04-21 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1146160A true CA1146160A (en) | 1983-05-10 |
Family
ID=26769442
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000362221A Expired CA1146160A (en) | 1979-10-11 | 1980-10-10 | Multiple coil heat exchanger |
Country Status (6)
| Country | Link |
|---|---|
| CA (1) | CA1146160A (en) |
| DE (1) | DE3030509A1 (en) |
| DK (1) | DK327880A (en) |
| FR (1) | FR2467372A1 (en) |
| NO (1) | NO802788L (en) |
| SE (1) | SE8005501L (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4599773A (en) * | 1979-10-11 | 1986-07-15 | Thermodynetics Inc. | Method of forming a multiple coil heat exchanger |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102008035164A1 (en) * | 2008-07-28 | 2010-02-04 | Lloyd Werft Bremerhaven Gmbh | Pipe bending tool for use during piping of e.g. plants, has lever arranged in base, bending tap and retaining element arranged at lever, and guiding element comprising spiral recess for partially retaining pipe |
| CN111829377B (en) * | 2019-04-23 | 2021-08-13 | 山东大学 | Rotationally symmetric loop heat pipe |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3349842A (en) * | 1964-09-28 | 1967-10-31 | Vapor Corp | Heat exchanger coil assembly |
| US3742567A (en) * | 1967-03-28 | 1973-07-03 | Sulzer Ag | Method of making a heat transfer device |
| US3522840A (en) * | 1968-12-04 | 1970-08-04 | Borg Warner | A heat exchange and pressure relief device therefor |
| US3639963A (en) * | 1969-10-08 | 1972-02-08 | Vapor Corp | Method of making a heat exchanger coil assembly |
| BE774214A (en) * | 1970-10-22 | 1972-02-14 | Zifferer Lothar R | HELICOIDAL CONDENSER |
| US3739615A (en) * | 1971-06-01 | 1973-06-19 | R Tressel | Method of making wrinkle-free thin-walled coiled tubing |
-
1980
- 1980-07-30 DK DK327880A patent/DK327880A/en not_active Application Discontinuation
- 1980-08-01 SE SE8005501A patent/SE8005501L/en not_active Application Discontinuation
- 1980-08-12 DE DE19803030509 patent/DE3030509A1/en not_active Ceased
- 1980-09-19 NO NO802788A patent/NO802788L/en unknown
- 1980-09-19 FR FR8020183A patent/FR2467372A1/en active Granted
- 1980-10-10 CA CA000362221A patent/CA1146160A/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4599773A (en) * | 1979-10-11 | 1986-07-15 | Thermodynetics Inc. | Method of forming a multiple coil heat exchanger |
Also Published As
| Publication number | Publication date |
|---|---|
| SE8005501L (en) | 1981-04-12 |
| FR2467372B1 (en) | 1985-03-15 |
| FR2467372A1 (en) | 1981-04-17 |
| DK327880A (en) | 1981-04-12 |
| DE3030509A1 (en) | 1981-04-23 |
| NO802788L (en) | 1981-04-13 |
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| Date | Code | Title | Description |
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| MKEX | Expiry |