US2084743A - Heat exchanger - Google Patents

Description

J. P. RATHBUN HEAT EXCHANGER Filed May 17 June 22, 1937.

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2 Sheets-Sheet June 22, 1937. l l J. P. RATHBUN 2,084,743

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ATTORNEY Patented June 22, 1937 PATENT OFFICE HEAT EXCHANGER John P. Rathbun, Prospect Park, Pa., assignor to Westinghouse Electric &, Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application May 17,

` 13 claims.

My invention relates to heat exchange apparatus, more particularly to heat exchange apparatus in which one iiuid is at least partially vaporized, and it has for an object to provide improved apparatus.

A further object is to improve the heat transfer rate of such apparatus.

l In accordance with my invention, I provide a shell or other vessel in which there are disposed heating elements, such as tubes containing heatlng iluid. Bafiles are arranged to provide a plurality of passages through which liquid ilows upwardly in contact with the heating elements to be heated thereby.l Other passages convey the iluid, out of Contact with the heating elements, from the upper ends of heating passages to the lower ends of the heating passages. The vapor formed in each heating passage is removed through the upper `portion of the shell. Thus,V

natural convection currents are utilized to provide maximum flow and heat transfer.

The above and other objects are effected by my invention as will be apparent from the following description and claims taken in connection with the accompanying drawings, forming a part of this application, in which:

Fig. l is a plan view, partly in section, of one embodiment of the apparatus;

Fig. 2 is a vertical longitudinal section thereof;

Figs. 3, 4, and 5 are transverse sectional views taken on the lines III-111, IV-IV, and VV, respectively of Fig. 2;

Fig. 6 is an enlarged broken perspective view showing the bailles; A Fig. 'l is a vertical longitudinal section of a Amodied form of heat exchanger;

Figs, 8 and 9 are transverse sectional views taken on the lines VIII-VIII and lX-IX of Fig. 7; and

Fig. 10 is a fragmentary section of a modified baule construction.

' Referring to the drawings in detail, the heat exchange apparatus comprises a cylindrical shell Il which may have an integral closure II at one end. The shell l0 contains' tubes I2 and I3 for circulating heating fluid, the tubes being arranged in a nest or bundle in the lower portion oi?A ,the shell, that is, somewhat below the top of the shell, as shown on the drawings. The tubes are secured at one end to a tube sheet I4, which is clamped between a flange l5 of the shell III and a flange I6 of a removable head I'l. The latter comprises an inlet chamber I 8 having an inlet connection I9 and an outlet chamber 2| havlng an outlet connection 22. at the opposite 1935, Serial No. 22,085

end, the tubes are secured to a floating tube sheet 23, to which a oating head 2l is secured. The floating head 24 provides a reversing chamber for directing the heating iluid from the tubes I2 to the tubes I3. It is to be understood that any suitable heating fluid may be used. For example, steam may be used as contemplated by the illustrated embodiment, in which case the tubes I2 may be greater in number than the tubes t3. The steam gives up its latent heat in the tubes I2 and the tubes I3 serve primarilyfor returning the condensate to the head I1. It is to be understood that any desired number of tube passes and any other desired arrangement of tube nest may be used.

As shown in Figs. 4 and 5, the -tube nest is spaced from the cylindrical wall of the shell Il, and curved bailles 25 partially enclose the tube nest, extending about the sides and partly about the bottom of the tube nest and providing downwardly extending passages 26 between the tubes and the cylindrical wall of the shell. The upper edges of the bafiies 25 extend approximateely to the top of the tube nest, and the lower edges extend-to the bottom of the tube nest but are in spaced relation to each other so as to provide communication between the lower ends of the passages 26 and the tube space which is partially enclosed by the baiiies 25. The tailles 25 may be continuous, as in the illustrated embodiment, extending from the tube sheet I4 to the ytube sheet 23.

'I'he tube space Vis divided transversely of the tubes, by two groups of bales, 28 and 29, arranged alternately, into a plurality of compartments I6 and a plurality of compartments 4l, arranged alternately. As shown in Fig. 4, the baille 28 comprises a member 30 which is disposed between the baiiles 25 and which is slightly more than semi-circular in Yform. It further comprises an approximately semi-annular member 3l extending between the bailies 25 and the shell up to the height of the bailles 25. Thus, the baille part 30 extends upwardly above the part 3l, to form slots 32 as shown in Figs. 4 and 6 for ilow of liquid, as hereinafter described. The baille parts 30 and 3| are secured, to each other and tothe baffles 25 in any suitable manner, as by welding. They together Vform tube supports adapted to slide on the bottomv of the shell.

. The transverse bafiles 29 comprise a central baille part 33, similar in form to the baille part 30, also extending upwardly above the tube nest. It further comprises arcuate parts 34 between thefbaies 25 and the shell. The parts 34 extend upwardly to the upper edge of the part 33v and extend downwardly only to the lower edges of the bafes 25, thereby forming a port 35 in the bottom of the bale 29, through which liquid may iiow from one compartment 41 to the next' compartment 46.

The entire tube bundle, including the baiiles, may be removed as a unit through the left hand end of the shell upon disengaging the iianges I6 and I5.

'I'hevshell is provided with a liquid inlet 36 in the bottom thereof in the end adjacent the head structure I1 and with a liquid outlet 31 at the other end. It is formed with a vapor outlet 38 in the upper portion thereof adjacent the end wall I I. A lweirrlilmay be provided adjacent the floating head 24 to insure complete subm;rgence of the tubes in the liquid, and the shell may be Aextended beyond the weir 39 to provide a storage chamber 4I for liquid leaving the shell. A baille 42 may be provided at the top of the shell between the Weir 39 and the vapor outlet 318 and provided with a trough 43 adapted to collect and drain to the cylindrical wall of the shell any liquid particles collected by the baille 42. A liquid separator 44 may be provided at the vapor outlet 38 to separate out any liquid particles carried in suspension by the vaporleaving the shell. The liquid may be drained through a conduit 45 into the storage chamber 4I.

The.operation of the above-described `apparatus is'as follows: while the above-described apparatus is useful generally for vaporizing liquid; it is particularly adapted to be used as a reboiler in oil refinery apparatus, to separate a component or components of lower boiling point from a component or Icomponents of higher boiling point. Natural convection or thermosyphonic circulation of liquid in each compartment 46, 41 is eifected by the heating action of the tubes I2, I3, the liquid flowing upwardly through the space between the baiiies, over the upper edges of the baiiles 25, downwardly through the passages 26 around the lower edges of the bailies 25 back into the space between the bailles 25. In each of the compartments 46, 41, a portion of the circulating liquid is continually passed on to the next compartment and added to the liquid circulating therein, as will now be described. The liquid containing a mixture of components of both higher and lower boiling points is admitted to the shell I0 through the inlet 36 into the first compartment 46. It joins the liquid coming down through the passage 26, and the mixture iiows upwardly through the passage provided between the lower edges of the baffles 25 into the tube space enclosed by said baiiles. As it iiows upwardly itl comes in contact with the heating tubes I2 and I3 and is heated thereby. As it reaches the top of the tube nest, the components of lowest boiling points, or lighter fractions, vaporize and flow olf into the vapor space formed in the upper portion of the shell above the tube nest. One portion of the liquid rising to the top of the tube nest spills over the upper edges of the baiiles 25 and flows downwardly through the passages 26. From the latter, it is again admitted through the passage between the lower edges of the baffles 25 to the tube lspace enclosed by said baiiies and is recirculated as described. Another portion of the liquid rising to the top of the tube nest spills over the upper edges of the baffle parts 3|, through the notches 32, into the next compartment 41 between the baliles 28 and 29.

In the compartment 41, the liquid flows downwardly through the passages 26 to the bottom of the shell. One portion of the liquid then iiows upwardly through the tube space of the compartment 41, and another portion ows through the port 35finto the next compartment 46 between bailies 29 and 28. The portion of the liquid owing upwardly through'the tube space in the compartment 41 spills over the upper edges of the baiiles 25, giving off to the vapor space the vapor formed as it is passed over the tubes, and again passesl downwardly through the passages 26. The portion of the liquid passing through the port 35 joins the liquid in the next compartment 46 which is flowing upwardly through the tube space.

The liquid then flows successively through the remaining compartments 46 and 41 in the same manner as just described, the components of successively higher boiling points being gradually vaporized. From the last port 35, the liquid flows upwardly over the ends of the'tubes I2 and I3 and the oating head 24, and spills over the upper edge of the Weir 39 into the storage chamber 4I, from which it is withdrawn through the outlet 31. Y

In the above arrangement, the liquid iiows upwardly in contact with the heating tubes and downwardly out of contact with the tubes, thereby setting up natural convection currents within each compartment, resulting in increased rate of fiow and increased rate of heat transfer. The iiow from one compartment to the next is effected by gravity, the liquid'being admitted under pressure and rising to a sufliciently high level in the rst compartment to effectA such ilow, the' liquid levels in the successive compartments being successively lower.

In Figs. 7, 8, and 9, I show a modied baiiie arrangement, the remainder of the structure being the same as in Figs. 1 to 5. A curved baiile member 5I extends about the sides and bottom of the tube nest in spaced relation to the wall of the shell, providing passages 52 and 53, shown in Figs. 8 and 9, respectively. The baffle member 5I may be continuous between the tube sheets. The tube space is divided by transverse baflies 54 into compartments 55. The balile 54, as shown in Fig. 9, comprises an intermediate member 56 having openings through which the tubes extend and arcuate members 51 between the circular member 5I and the shell I0. Ihe lower edges of the latter are in spaced relation to form a port 58, while the upper edges of the parts 56 and 51 are spaced a short distance above the top of the baille member 5I and the tube nest. As shown in Fig. 8, an arcuate baille member 59 between the curved baille member 5I and the shell provides a division Wall between the passages 52 and' 53, and extends continuously from one side to the other to a height even with the top edge of the baille member 5I. The curved baille member 5I is formed with a slot 6I in the bottom thereof In the part of each compartment 55 adjacent the passage 52, that is, from the tube sheet I4 or the baille 54 to the baille 59, while it is continuous adjacent the passage 53, that is, from the the weir 39. f f

10 through the slot 6iu into the tube space.

wardly. joins tlie liquid entering through the inlet 35, and rechters the tube space through the slot 8l. The flow of this portion is effected by the natural convection or thermo-syphonic circu- -5 lation induced by the heatingaction of the tubes. The portion of the liquid entering the passage 53 flows downwardly to the bottom thereof and/then through the port 58 in the baille 54 into the next compartment. In the latter, it flows upwardly The cycle of operation just described is then repeated in each compartment. From the last port 58, the liquid ows upwardly over the ends of the tubes andthe floating head 2l and spills over In this embodiment, the liquid flows upwardly in contact with heating tubes and downwardly out ofcontact therewith as in the rst embodiment. The passages 52 provide recirculation of liquid within the several compartments, while the passages 53 provide for flow from one compartment to the next. In this case, the convection currents through thepassages 53 assist the gravity flow of the liquid from the inlet to the outlet end of the tube space, since the head of the heavier unheated liquid in the passages 53 exceeds the head of the lighter boiling liquid ilowing upwardly into the tubes in the next compartment. C A

As shown in Fig. l0, the curved bailies 25a may be made in sections so as to be removable. Each of the transverse bailles 28a and 29a is integral, instead of comprising separate parts as in Figs. 4 and 5. Each baffle section 25a extends between adjacent transverse bailles and is detachably secured thereto by angle members and bolts shown at 62. Upon removing the curved baille sections 25a, access to the tubes is provided for periodically cleaning the same. In all other respects, the baille structure of Fig. 10 may be the same as that shownin Figs. 1 to 6.

A :further advantage of the present invention is that all oi the liquid is caused to rise repeatedly to the surface, at least once in each compartment, where the vapor separates from the yliquid to a much greater extent because of the low hydrostatic head.

While I have shown my invention in several forms, it will be obvious to those-skilled in the` 50` art that it is not so limited, but is susceptible of various other changes and modications without departing from the spirit thereof and I desire, therefore, that only such limitations shall be placed thereon as are imposed in the prior art or as are set forth in the appended claims.

What I claim is:

1. In heat exchange apparatus, the combination of baille means providing a plurality of circuits each comprising a downwardly extending passage and an upwardly-extending passage, means for heating the liquid in the upwardly extending passage to vapcrize a portion of the liquid and thereby to effect thermo-Siphonic circulation of the liquid in the circuit, a dome or vapor space communicating with the upper portions of the several upwardly-extending passages for receiving thel vaporized uid, and means for conveying at least a portion of the liquid from one circuit to the next.

2. In heat exchange apparatus, the combination of a shell, heating elements within the shell. baule means within the shell providing a plurality of upward passes for liquid to be heated in contact with said heating elements and a plurality of 75 downward passes out of contact with the heating elements and arranged to provide iiow of liquid through a plurality of upward passes successively, the liquid flowing through upward and downward passes alternately, the upper portion of the interior of the shell constituting a vapor space in communication with the upper ends of the several upward` passes and receiving the vapor formed therein.

3. In heat exchange apparatus, the combination of a shell, a tube nest therein, baiiles disposed transversely of the tubes and providing a. plurality of compartments, other bafiles in the compartments providing rst vertical passages through which the tubes extend and second vertical passages substantially without tubes, the vertical passages in each compartment being in communication at the upper ends whereby liquid flows upwardly in the first passages and then downwardly in the second passages, a plurality of said transverse bailies having a port providing communication between the lower ends of the second passage of one compartment and the first passage of the next compartment to provide flow of liquid successively through the compartments. l

4. In heat exchange apparatus, the combination of a shell, a tube nest therein, baiiies disposed transversely of the tubes and providing a plurality of compartments, the tubes being arranged to provide rst vertical passages through which the tubes extend and second vertical passages substantially without tubes, the vertical passages in each compartment being in communication at the upper ends whereby liquid flows upwardly in the rst passages and then downwardly in the second passages, a plurality of said transverse bailies having a port providing communication between the lower ends of the second passage of one compartment and the rst passage of the next compartment to provide ow of liquid successively through the compartments.

5. In heat exchangeapparatus, the combination of a shell, a tube nest therein, baffles disposed transversely of the tubes and providing a plurality of compartments, vother bailles in the compartments providing rst vertical passages through which the tubes extend and second vertical passages substantially without tubes, the vertical passages in each compartment being in communication at the upper ends whereby liquid ows upwardly in the first passages and then downwardly in the second passages, and means providing flow of liquid successively through the several compartments.

6. In heat exchange apparatus, the combina.-

contact with said tubes while flowing longitudinally of the shell from the inlet to the liquid outlet.

7. In heat exchange apparatus, the combination of a shell, a tube nest within the lower portion of the shell, the upper portion of the shell constituting a vapor space, an inlet for admitting liquid adjacent one end of the shell, an

outlet for withdrawing liquid adjacent the other end of the shell, a vapor outlet communicating with said-vapor space, and a baille or baiiies disposed transversely of said tubes between said liquid inlet and said liquid outlet and providing a plurality of compartments for the liquid owing between said inlet and outlet, said tubes being arranged to provide lanes for .ilow of liquid. from 5 the top of the tube nest to the bottom thereof,

and said bailles being formed to provide communication between adjacent compartments in such manner that the liquid flowing from the liquid inlet to the liquid" outlet flows upwardly in contact with the tubes at least oncein a plurality of said compartments.

8. In heat exchange apparatus, the combination of a shell, heating elements within the shell, baille means within the shell providing a plurality l5 of passages for ilow of liquid upwardly in contact with said heating elements and a plurality of downward passages for ilow of liquid downwardly out of contact with heating elements, said baille means being arranged to provide ilow of liquid through said heating and downward passages alternately and to provide ilow of liquid upwardly at least once through each of a plurality of said heating passages, and means for removing vapor from the liquid at the upper end of each heating passage.

9.`In heat exchange apparatus, the combination of a shell having a liquid inlet and a liquid outlet, a bundle of tubes arranged horizontally in the shell, baiiles arranged transversely of the tubes and dividing the tube containing portion of the shell into compartments through which liquid ilows successively from said liquid inlet to said liquid outlet, the liquid flowing upwardly through each compartment in contact with said tubes, and means providing a passage for ow of liquid within the shell and out of contact with tubes from the top of one compartment to the bottom of the next compartment, and means for removing vapor from the liquid at the top of each compartment.

10. In heat exchange apparatus, the combination of a shell, a tube bundle arranged horizontally within the shell, bailies arranged transversely of the tubes and providing a plurality of passes ilow of liquid within the shell out of contact with to provide space for flow of liquid downwardly within the shell from the top to the bottom of the tube bundle substantially out of contact with tubes, means including transverse baflles in said space providing passages arranged to convey liquid from the top of one heating pass to the bottom of another heating pass to cause liquid to ilow through a plurality of said heating passes successively in iiowing from saidv liquid inlet to s aid liquid outlet, and means for removing vapor from the liquid at the top of each heating pass.

12. A heat exchanger comprising a shell having a liquid inlet and a vapor outlet, a bundle of heating tubes disposed horizontally therein,

vbailles disposed transversely of the tubes and dividingl the tube containing portion of the shell into compartments through which liquid ows successively, said tubes being arranged to provide lanes for flow of liquid from the top to the .bottom of the tube bundle out of contact with tubes, said baffles providing a liquid inlet for each g of a plurality oi said compartments only at the bottom thereof and a liquidv outlet for each of said plurality of compartments only at the top thereof, whereby liquid is caused to ilow 'upwardly at least once through each ofsaid plurality of compartments in contact with the heating tubes therein.

13. In heat exchange apparatus, the combination of a shell having a liquid inlet, a liquid outlet, and va vapor outlet, a group of heating elements within the shell, and baille means causing the liquid to ow from the bottom to the top of the group of heating elements a plurality of times in owing from said liquid 'inlet to said liquid outlet.

JOHN P. RATHBUN.

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