US3450199A - Heat exchanger - Google Patents

Description

June 17, 1969 v F. J. WARRELL.

" HEAT EXCHANGER Sheet of Filed July 10, 1967 INVENTOR FRED JLWARRELL ATTORNEYS United States Patent 3,450,199 HEAT EXCHANGER Fred J. Warrell, Mount Clemens, Mich., assignor to Continental Aviation & Engineering Corporation, Detroit, Mich., a corporation of Virginia Filed July 10, 1967, Ser. No. 652,175 Int. Cl. F28d 7/10; F28f 9/22, 13/00 US. Cl. 165-159 12 Claims ABSTRACT OF THE DISCLOSURE A heat exchange structure which prevents the formation of boundary layers of fluid along the exchange wall while attaining a transverse flow of fluid jets to impinge directly on the exchange walll.

BACKGROUND OF THE INVENTION Field of the invention The present inventon relates to heat exchangers and more particularly to jet impingement heat exchangers having a high rate of heat transfer through a surface or exchange wall in which the heat of a fluid is to be transmitted therethrough to a second fluid having a lower temperature.

Description of the prior art In the employment of heat exchangers there is a tendency for an insulating boundary layer of fluid to form adjacent the exchange wall which moves at a reduced speed and can produce a stagnant condition along the wall. Various methods have been tried to disperse the fluid in the boundary areas to obtain a more turbulent flow and thus improve the efliciency of the heat exchanger. One such means is disclosed in US. Patent No. 3,034,769 wherein separate ducts are utilized for directing fluid in jet streams against the exchange wall to obtain a more turbulent flow. Still another method, as disclosed in US. Patent No. 2,659,392, has a series of secondary walls dispersed throughout the fluid flow to increase the efficiency of the heat exchanger. These and other methods, while achieving a certain amount of success, have proved costly to construct. Another drawback in the previous attempts to solve the problem have been a loss in the overall pressure of the system such that additional energy has to be supplied to the system. Other disadvantages of the prior art structure such as excess number of parts and high manufacturing costs will become apparent in the description of the present invention.

SUMMARY According to the present invention, these difliculties are greatly reduced by means of applicants simplified structure which lowers fabrication costs while attaining an eflicient hydraulic flow for maximum dispersion of the fluid with a minimum of pressure loss. Applicant has conceived a heat exchanger structure for preventing the formation of an insulating layer on the heat exchange wall which utilizes orifice plates that initially direct the fluid in small jet streams to the heat exchange surface. The orifice plates are positioned such that the leading portion, with respect to the flow of the fluid, is secured to the heat exchange wall and the trailing portion is secured to the outer boundary of the passages provided on each side of the wall. By means of each small jet stream the fluid flow in each passage is controlled so that the fluid flowing adjacent to the heat exchange wall is prevented from continuing in a straight path along the heat exchange wall. This prevents the formation of a boundary layer along the heat exchange wall and also causes a pressure differential which assists in directing the fluid through the orifices to form jet streams that impinge on the heat exchange wall.

It is therefore an object of this invention to provide a heat exchanger matrix having a high heat transfer efficiency with low pressure loss characteristics.

It is a further object of the invention to provide a heat exchanger which is structurally strong and which has a high heat transfer efficiency and low pressure loss characteristics.

It is still another object of the present invention to provide a heat exchanger which will enable the device to be constructed from plates of like configuration so that the costs of producing the plates are reduced and for which a given heat transfer capacity will require less plate material then heretofore, thus further reducing the cost and also reducing the weight of the heat exchanger.

The exact nature of this invention as well as other objects and advantages thereof will 'be readily apparent from consideration of the following specification relating to the annexed drawings and in which:

FIG. 1 is a perspective view of a preferred construction of a heat exchanger;

FIG. 2 is a longitudinal vertical section of the heat exchanger of FIG. 1;

FIG. 3 is a sectional view taken on line 3-3 of FIG. 2;

FIGS. 4-9 are all longitudinal sectional views of modified constructions for carrying out the principles of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, wherein like reference characters designate like or corresponding parts throughout the several views, there is shoWn in FIG. 1, which illustrates a preferred embodiment, an opposed flow heat exchanger which comprises an outer tube 20 and concentric internal tube 22. Surrounding the internal tube 22 and within the outer tube 20 are positioned a plurality of funnel shaped members 24, for dividing the space between the tubes into a plurality of cells or chambers 26. The large diameter end of the funnel members 24 are Welded or otherwise fixedly secured in a fluid tight manner around its periphery indicated at 28. The smaller diameter ends of the funnel member are in turn secured to the internal tube 22 around its inner periphery indicated at point 30.

Each funnel member 24 is provided with a plurality of orifices 36. Although the orifices 36 in the embodiment of FIG. 1 are shown as round holes and arrayed with their centers along trace lines 34 parallel with the principle axis of the tubes, it will be understood that the orifices could have various configurations such as slots, regular polygons, or irregular polygons and could be arrayed in another manner such as being in staggered relationship, for example.

Positioned within the tube 22 are a plurality of cone shaped members 40 with their apices 44 on the center line 48 and with their base portions fixedly attached to the inner wall of tube 22 by suitable means such as soldering or welding at point 52. In the same manner as funnel members 24 the cone members 40 are provided with a plurality of orifices 56 which are of the same size and shape as the orifices 26 and arrayed wherein corresponding orifices in the plate members 24 and 40 are located in opposed relation. It will be further noted that the circumferential points 28 and 52 are located substantially in a common vertical plane, as are the apices 44 and the plane of the circumferential points 30'.

In the construction shown in FIG. 2 the outer tube 20 is provided with an inlet 62 and an outlet 64 which in the present embodiment are used to supply cold fluid to the 3 heat exchanger. The hot fluid enters at the right hand end of tube 22 and leaves through the left hand end of the tube so as to flow in opposed relation to the flow of cold fluid. Thus, as seen in FIG. 2, the fluid to be heated enters the inlet 62 and after flowing through the space defined between the tube 20 and tube 22 leaves through outlet 64.

From the various disclosures of the different heat exchanger arrangements in the drawings illustrated in FIGS. 4-9, it is obvious that numerous modified constructions of the orifice plates may be presented for carrying out the objects of the present invention and a considerable number thereof have been illustrated. Any one of the diagramatic arrangements shown in FIGS. 4-9 may be used in the heat exchanger structure of the general type shown in FIG. 1. As only one type of heat exchanger has been illustrated in detail the invention will be first explained as it relates directly to the various basic orifice plate arrangements and modifications. In this way the operation of the heat exchanger structure of FIG. 1, when described subsequently, will be understood to function in accordance with the basic principles of the invention shown in FIGS. 4-9. In the various units illustrated in the figures the numeral 71 represents the heat transfer surface or exchange wall separating fluids 72 and 73 while the cooperating pair of deflecting plates are indicated at 74 and 75, and the outer boundary walls at 76. Orifice 77 are provided in plates 74 and 75 for directing the fluid flow in a manner to be explained.

The overall relative flow direction may be parallel flow, as illustrated in FIGS. 4 and 6 or opposed flow as shown in FIGS. and 7. The orifice plates 74 and 75 may be at any independent angle or arranged with the orifice plates parallel to the heat transfer surface 71 as shown in the modification of FIG. 6.

As shown at FIG. 7 any number of the units may be arranged in series so that each unit carries the total fluid flow. FIG. 8 shows that any number of the basic units may further be arranged in parallel so that each unit carries a portion of the total fluid flow. It will be noted in FIG. 8 that the units are arranged in opposed flow pattern as also shown in FIG. 2. FIG. 9 shows an alternative form in which turning vanes 78 are employed to accomplish the function of the orifices 77 in plates 74 and 75. While applicant discloses that exchange of fluid by jet streams of opposed temperatures at coaxial points on the heat exchange plate by orifices of substantially equal sizes it should be understood that a still satisfactory heat exchange of fluids can be arrived at by non-coaxial opposed fluid streams hitting at a substantially normal angle with the heat exchange plate and by a distribution of hole sizes in the overall spacing. Such a variation of hole sizes and spacing are, of course, arranged in a predetermined design providing an interdependent relationship.

In the parallel flow arrangement of FIG. 4 the cold fluid, represented at 72, is diverted by plate 74. In like manner the plate 74 diverts the flow of the hot fluid 73 to form a plurality of small fluid jets, indicated by the opposed arrows in the figure. In this manner, pairs of jets are directed toward the exchange wall 71 in opposed relation to impinge directly thereon and to produce maximum heat exchange between the fluids.

The heat exchange is optimum due to the prevention of stagnant boundary layers along the portion of the exchange wall coextensive with the plates by the diversion effect of the plates. This, together with the transverse movement of the fluid from the central core of both the hot and cold fluid flow, having the maximum temperature of each of the fluids, produces a highly efficient heat exchange at the wall 71. It will be seen in FIG. 4, that the plates 74 and 75 are positioned at equal acute angles to the direction of fluid flow. While in the particular embodiment disclosed the walls 74 and 75 are located at substantially 10 degrees with the exchange wall 71 it is to be understood that the plates could be positioned at various acute angles. Applicant has found that orifice plates 4 74 and 75 positioned at acute angles within the range of 10 degrees to 20 degrees to the exchange wall 71 have proved most satisfactory in attaining the optimum exchange between the fluids while producing a minimum of pressure drop through the system.

- The arrangement shown in FIG. 5 is similar to FIG. 4 except in this embodiment the fluids are in opposed relation rather than parallel. It will be noted that in this figure the plates 74 and 75 are located so as to be in substantially parallel relation to each other while being coextensive in relation to the exchange wall. This form of the invention operates so that the cold fluid 72 is diverted by'the plate 74 at the point indicated at while the plate 75 diverts the flow of the hot fluid 73 at the point 86. It will be noted that the trailing edge portions of the plates 74 and 75 are joined to the boundary walls 76 at points 87 and 88 respectively. Thus, in this form of the invention the corresponding leading and trailing edges of the plates are located in common plane extending transverse to the plane of the exchange wall 71.

The operation of the form of the invention shown in FIG. 5 is identical to that as described for the FIG. 4. It-is evident therefore that by merely reversing one plate member, end for end, the heat exchanger of applicants present invention could be fabricated to accommodate either parallel flow or cross flow with a minimum of fabrication of parts.

In the form of the invention shown in FIG. 6, applicant shows a structure for obtaining heat exchange between parallel flows of fluids by means of orifice plates '92 and 94 which have a double L-shape in cross section. In this form of the invention the orifice plates are positioned parallel to the heat transfer surface or exchange wall 71 and are secured to the outer boundary walls 76 by means of substantially right angle flange members 95, 96, 97 and 98. In this modification the flanges at the leading edge of the orifice plates, 96 and 98, function to divert the fluid away from the exchange wall to break up the formation of boundary layers at a transverse common plane along the exchange wall. Here again orifices 77 are arranged in the- plates 92 and 94 so as to be in opposed relations so that the fluid jets formed by the fluid flow will impinge directly on the exchange wall 71 to obtain the maximum heat exchange. It will be seen in this form of the invention that an increased turbulent flow will be created which will produce a greater heat exchange effect while on the other hand the pressure loss will be greater than that disclosed in the form of the invention shown in FIGS. 4 and 5.

As explained above the arrangement of the heat exchange structure shown in FIG. 7 utilizes the basic concept of the opposed flow arrangement shown in FIG. 5 and demonstrates, by means of applicants unique arrangement of parts, a plurality of the units of FIG. 5 can be stacked to provide a series type heat exchanger.

In reference to the series arrangement shown in FIG. 7 it should be noted that the trailing edge portion of plate 74, indicated at 102, is arranged to lie in the transverse plane of trace line 103 so as to include the leading edge 104 of the plate which is the next most plate downstream in the fluid flow 72. In this manner applicant has devised a symmetrical heat exchanger which provides for a maximum interchange while forming a rigid structure when constructed as shown in FIG. 1.

FIG. 8 shows the basic unit described in FIG. 5 employed in an opposed flow form of the invention wherein the individual units are stacked in a parallel relationship. As this form of the invention is similar to the embodiment shown in FIG. 1 the description of its operation will follow below.

While for most applications the use of orifice plates has proved satisfactory other means for inhibiting the formation of boundary layers and for attaining a transverse flow of the fluid are considered within the scope of the invention. FlG. 9 thus discloses an embodiment wherein turning vanes are used to accomplish the functions of the orifices 77. While this embodiment is, of course, more costly to construct its use in a plate type exchange structure is considered advantageous to reduce the pressure drop through the system.

Turning now to the operation of the exchange structure of FIGS. 1-3 it can be seen that applicant has provided an opposed flow unit wherein the orifice plates 24 and 40 are in a series arrangement. It can be seen that by using a concentric tube structure applicant has formed the orifice plates 24 in identical funnel shaped or frustocone type members which allow the tubes 20 and 22 to be easily and quickly positioned in concentric relationship for ease of fabrication. Also, by positioning the large end 28 of one member 24 substantially in the transverse plane of the small end 30 of the subsequent member 24, the plane defined by section line 33, the resultant sandwich core type arrangement produces a structure that has a high strength to weight ratio both under axial and bending stresses.

It will be seen that the orifices 36 and 56 of the orifice plates are aligned on trace lines 45 to attain applicants opposed direct jet impingement on the exchange wall 22. The orifices of applicants structure could, of course, be substantially the same size or progressively increasing in size without departing from the principle of the invention. Further, in this structure the acute angle formed by the orifice plate members with respect to principal counter-line 48 is approximately 15 degrees, which provides a heat exchanger having properties of eificient heat exchange with a minimum of pressure loss while achieving a rigid unitary structure.

It is also evident that a further modification of th invention could be attained by rotating one plate member substantially 90 degrees with respect to the opposite plate member in a skewed relationship so that the heat exchanger could be fabricated to accommodate overall cross-flow.

It should be understood, of course, that the foregoing disclosure relates to only preferred embodiments of the invention and that numerous modifications or alterations may be made therein without departing from the spirit and scope of the invention as set forth in the appended claims.

What is claimed is:

1. A heat exchange structure comprising:

(a) a heat exchange wall member spaced between boundary members providing fluid passages on either side thereof,

(b) diverting means disposed on either side of said wall means in opposed paired relation so as to be coextensive in the direction of fluid flow,

(c) each said diverting means positioned with respect to the direction of fluid flow in its associated passage wherein the fluid is directed away from said exchange wall, and

(d) each diverting means of said pair having a plurality of orifice means therein arranged so that fluid jets created thereby impinge directly on said exchange wall.

2. The structure as defined in claim 1, wherein:

(a) said diverting means are orifice plates inclined toward the direction of fluid flow to form acute angles with said wall means, and

(b) said orifice means comprise a plurality of holes in said plates wherein each hole in one plate is in axial alignment with a corresponding hole in said opposed plate.

3. The structure as defined in claim 2, wherein said acute angles are equal and have a value in the range of degrees to 20 degrees.

4. The structure as defined in claim 1, wherein:

(a) each of said diverting means are plates having a double L cross section whose central portions are positioned parallel to the exchange wall member, and

(b) the orifice means are holes in said central portions.

5. The structure as defined in claim 2, wherein the fluid flow in said passages is in parallel relation so that said pair of orifice plates form equal acute angles with said exchange wall member.

6. The structure as defined in claim 2-, wherein the fluid flow in said passages is in opposed relation and said orifice plates are arranged in parallel relation so that the leading and trailing edges thereof form equal acute angles with said exchange wall member.

7. The structure as defined in claim 1, wherein said diverting means are plate members having turning vanes that direct the fluid in said passages to impinge substantantially normal to said exchange wall.

8. A heat exchange structure comprising, in combination:

(a) coaxially-disposed outer and inner tubes,

(b) said inner tube providing a heat-transfer partition adapted to contain a first flowing stream of fluid and to have a second floiwing stream of fluid at a different temperature contained between said outer and inner tubes,

(0) said heat exchanger further comprising a first fluid diverting means disposed between said outer tube and said inner tube, and a second fluid diverting means disposed within said inner tube,

(d) said first and second fluid diverting means arranged in opposed paired relation so as to be coextensive in the direction of fluid flow, and

(e) each diverting means of said pair having a plurality of orifices arranged therein such that each orifice in said first diverting means is in alignment with a corresponding orifice in said second diverting means wherein fluid jets created thereby impinge directly on either side of said inner tube.

9. The structure as defined in claim 8, wherein:

(a) said first diverting means is a funnel-shaped orifice plate having its small diameter end positioned around said inner tube and its large diameter end encircled by said outer tube, and

(b) said second diverting means is a cone-shaped orifice plate having its apex positioned in the plane of said funnel-shaped orifice plate small diameter end and its base positioned in the plane of said funnelshaped orifice plate large diameter end.

10. The structure as defined in claim 9 wherein said funnel-shaped orifice plate and said cone-shaped orifice plate are concentrically positioned wherein they form equal angles with said inner tube.

11. The structure as defined in claim 10 wherein the angle formed is of the order of ten degrees to twenty degrees.

12. The structure as defined in claim 10 wherein a plurality of paired orifice plates are arranged in series such that the base of each cone-shaped orifice plate is positioned substantially in the plane of the small diameter end of the next succeeding funnel-shaped orifice plate.

References Cited UNITED STATES PATENTS 1,880,533 10/1932 Thomas -179 2,451,629 10/1948 McCullum- 165179 ROBERT A. OLEARY, Primary Examiner. T. W. STREULE, Assistant Examiner.

US. Cl. X.R. 165135, 154

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