US3882934A

US3882934A - Heat exchanger

Info

Publication number: US3882934A
Application number: US259009A
Authority: US
Inventors: Stellan Knoos; Soren F S Ljungdahl; Bertil Ingemar Bostrom
Original assignee: AGA AB
Current assignee: AGA AB
Priority date: 1972-06-02
Filing date: 1972-06-02
Publication date: 1975-05-13
Anticipated expiration: 1992-05-13
Also published as: BE800401A

Abstract

A heat exchanger is formed from heat exchanger elements having coextensive parallel channels for carrying the fluids between which the heat transfer is to be accomplished. These channels are relatively narrow so as to permit efficient heat transfer from the fluid to the channel walls and may be formed from continuous strips of heat conducting material wound in a spiral. In order to minimize the pressure drop in the spiral shaped channels, they are fed into common channels after only a fraction of a full turn. Heat is transferred from the fluid in one of the heat exchange elements to the fluid in the other of such elements from the walls of the first element through a diaphragm which is interposed between the two elements to the walls of the second element. The components of the heat exchanger are mechanically clamped together so that they can readily be disassembled for replacement, repair or cleaning.

Description

[ May 13, 1975 Primary ExaminerCharles J. Myhre Assistant Examiner-Theophil W. Streule, Jr. Attorney, Agent, or FirmEdw'ard A. Sokolski [57] ABSTRACT A heat exchanger is formed from heat exchanger elements having coextensive parallel channels for carrying the fluids between which the heat transfer is to be accomplished. These channels are relatively narrow so as to permit efficient heat transfer from the fluid to United States Patent Knoos et al.

[ HEAT EXCHANGER [75] Inventors: Stellan Knoos, Malibu, Calif; Soren F. S. Ljungdahl, Taby; Bertil Ingemar Bostrom, Danderyd, both of Sweden [73] Assignees: AGA Aktiebolag, Taby, Sweden;

Stellan Knoos, Malibu, Calif. part interest to each [22] Filed: June 2, 1972 [21] Appl. No.: 259,009

21 Claims, 22 Drawing Figures the channel walls and may be formed from continuous strips of heat conducting material wound in a spiral. In order to minimize the pressure drop in the spiral shaped channels, they are fed into common channels after only a fraction of a full turn. Heat is transferred from the fluid in one of the heat exchange elements to the fluid in the other of such elements from the walls of the first element through a diaphragm which is interposed between the two elements to the walls of the second element. The components of the heat exchanger are mechanically clamped together so that they can readily be disassembled for replacement, repair or cleaning.

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HEAT EXCHANGER This invention relates to heat exchangers, and more particularly to a heat exchanger for transferring heat energy between two fluid media which utilizes a pair of heat exchanger elements each having coextensive narrow parallel channels for carrying the fluid.

A number of prior art heat exchanger devices have been devised which utilize relatively narrow channels for carrying the heat exchanging fluids. In some of these devices, the channels are wound in a spiral configuration as well as other circular and linear configurations. In many of these devices, the channels for the two fluids, between which heat exchange is desired, are run adjacent to each other with a common wall separating the fluids which also forms one of the walls for both of the adjacent channels. Various prior art patents describing heat exchangers of this general type include U.S. Pat. Nos. 1,325,637; 2,995,344; 1,669,062; and 2,578,059. Swedish patents of interest along these lines include Swedish Pat. Nos. 101,116; 106,617; 115,685; 115,176; 151,318; 166,790; 164,229; 198,092; 90,415; and 104,1 16. Many of these prior art devices have one or more of the following shortcomings. First, often severe problems are encountered in shielding the flow channels from each other and from the surrounding environment. This is a particularly significant problem where the two fluids are separated from each other by a common channel wall in view of the differential pressures on the opposite sides of this wall which impose substantial mechanical loads thereon. This often presents a reliability and maintenance problem and may require the use of expensive materials and sealing techniques to achieve the necessary mechanical strength.

For optimum heat transfer from the fluid medium from which the heat energy is to be derived to the flow channel walls and thence to the fluid medium to receive the heat energy, it is desirable that the flow channel be made as narrow as possible. This criterion for optimum heat transfer, however, must be considered in connection with the pressure drop that narrow channels produce. It is therefore necessary in any design that both these factors be considered. In certain prior art designs, one or the other of these considerations is severely compromised in favor of the other, which makes for a less than desirable end result.

Another significant factor to be considered in the design of this type of heat exchanger is that with relatively narrow channels there is a good possibility that at one time or another the channels may become clogged to seriously restrict the flow with a consequent intolerable pressure drop. In most prior art devices, the channels are permanently set in place by welding, soldering or the like, such that it is difficult or impossible to clean the channels should they become clogged, or to repair or replace them as separate units should this become necessary. It is further to be noted that where the heat exchanger is to be operated at very high temperatures, the material for joining the channels to their support member must be capable of withstanding such temperatures, which in certain instances increases the cost and problems involved in fabrication.

The device of this invention overcomes the aforementioned shortcomings of prior art devices in the following rnanner: Firstly, the heat transfer fluxes are made very high by using extremely narrow channels for the fluid media. Despite the use of such narrow channels the pressure losses are kept under control by utilizing a plurality of coextensive channels which permit parallel flow. In the preferred embodiment, these channels are formed in a spiral winding with multiple inlets and exits along a turn of the winding so that a reasonably extensive channel length can be provided without the high pressure drop that would be presented if there were only a single inlet and outlet for each channel and the channels were fed singly rather than in parallel.

Further, the device of the invention tends to be leaktight by virtue of the fact that the two fluid mediado not run in adjacent channels having a common channel wall, but rather are in two separate heat exchanger ele ments which are separated from each other by a diaphragm. Thus, the channel walls themselves are subjected to extremely small mechanical loads and are less likely to leak than certain of the aforementioned prior art devices.

Further, the channel members and the associated components are not generally permanently attached to each other by soldering or welding or the like, the unit rather being held together by bolting or clamping techniques so as to enable ready disassembly for repair, cleaning or replacement of parts. Also, in view of the fact that no bonding medium is generally needed this obviates the aforementioned problems of achieving reliable bonding, particularly with operation under high temperatures.

Further, the device of the invention lends itself to relatively economical and simple fabrication with relatively inexpensive materials.

It is therefore an object of this invention to provide a highly efficient fluid heat exchanger which is of relatively economical construction.

It is a further object of this invention to provide a heat exchanger which can be readily disassembled for repair, cleaning or replacement of components.

It is still another object of this invention to provide a heat exchanger in which sealing problems between the two fluid exchange media are minimized.

Other objects of this invention will become apparent as the description proceeds in connection with the accompanying drawings, of which:

FIG. 1 is a perspective view illustrating a first embodiment of the invention;

FIG. 2 is a cross-sectional view taken along the plane indicated by 22 in FIG. 1;

FIG. 3 is a bottom plan view of the first embodiment with partial cutaway sections;

FIG. 4 is a perspective view illustrating the inlet and outlet flow channels of the embodiment of FIG. 1;

FIG. 5 is a flow diagram illustrating the fluid flow in the embodiment of FIG. 1;

FIG. 6 is a cross-sectional view illustrating the fluid channels of the heat exchange elements of the embodiment of FIG. 1;

FIG. 7 is a side elevational view, partially in crosssection, of a second embodiment of the invention;

FIG. 8 is a bottom plan view of the second embodiment;

FIG. 9 is a perspective view illustrating a heat exchange element of a further embodiment of the invention;

FIG. 10 is a top plan view of a heat exchanger element of another embodiment of the invention;

FIG. 11 is a crosssectional view taken along the plane indicated by 11l1 in FIG. l0;

FIG. 12 is a top plan view of a heat exchanger element of a further embodiment of the invention;

FIG. 13 is a cross-sectional view taken along the plane indicated by 13-13 in FIG. 12;

FIG. 14 is a cross-sectional view of a heat exchanger element of a further embodiment of the invention;

FIG. 15 is a cross-sectional view taken along the plane indicated by l515 in FIG. 14;

FIG. 16 is a cross-sectional view illustrating an embodiment of the invention utilizing stacked heat exchanging elements;

FIG. 17 is a cross-sectional view taken along the plane indicated by l7--l7 in FIG. 16;

FIG. 18 is a side elevational view partially in section illustrating a further embodiment of the invention;

FIG. 19 is a bottom plan view with partial cutaway sections of the embodiment;

FIG. 20 is a side elevation view partially in section illustrating an alternate form of the channels utilized in the heat exchangers of the invention which employs heat pipes;

FIG. 21 is a side elevation view partially in section illustrating an alternative configuration for a casing that may be utilized in the heat exchanger device of the invention; and

FIG. 22 is a cross sectional view illustrating an embodiment of the invention utilizing a single heat exchanger element.

Briefly described, the device of the invention comprises fluid heat exchanger elements having a plurality of coextensive narrow fluid channels which may be formed by a spiral winding or the like made from a flat strip of conductive material. The input is in parallel to the channels thus formed, with a plurality of common outlet and/or inlet channels being provided along the extent of the channels so as to minimize pressure drop therealong. In the case of channels formed from a spiral winding, a plurality of such common channels is provided along a single turn of the spiral. The channels for the fluid media providing the heat energy and those for the fluid media receiving such energy are separate units and are placed on opposite sides of a separating diaphragm through which the heat energy is transferred, such transfer occurring principally from the walls of the narrow channels to the diaphragm. The heat exchanger elements with the diaphragm therebetween are mechanically joined together by mechanical bolting or clamping means such that the device can be readily disassembled for cleaning, replacement or repair.

Referring now to FIGS. 1-6, one embodiment of the invention is illustrated. Housing 11 has first and second similar

heat exchange elements

12 and 13 mounted therein, these elements being separated from each other by diaphragm 15, preferably fabricated of a high thermal conductive material. The heat exchange elements l2 and 13 are held in tight engagement with diaphragm 15 within housing 11 by means of bolts 17 which threadably engage ring member 19. Ring member 19 is threadably attached to housing 11, the ends of the bolts applying force against the bottom wall of circular pan-shaped member 22 which drives against heat exchange element 13. Heat

exchange elements

12 and 13 are generally similar in configuration and have a plurality of coextensive generally

circular channels

23a and 23b formed therein. The effective length of each of these channels is one turn of the spiral windings from which they are joined. These channels are formed by

spiral windings

25a and 25b, which are wound around

central core portions

27a and 27b respectively.

Spiral windings

25a and 25b may be fabricated of a metallic strip or ribbon of a material having high thermal conductivity, such as copper, aluminum or steel. the

strip pins The

channels

23a and 23b are relatively narrow such as to provide highly efficient heat transfer from the fluid flowing in the channel to the walls of the strip material. In the fabrication of the spiral windings forming the heat transfer channels, the winding thereof may be facilitated by placing a wire 30 along the edge of the strip as it is wound, which effectively separates the windings from each other. Also, radial pins 32 may be utilized at several points along the windings to provide stiffening, these pins of course not being placed in the channels in such manner as to block the fluid flow therethrough. The spiral windings may be formed by the techniques described in our copending application Ser. No. 246,655 entitled METHOD FOR THE MAN- UFACTURE OF FINNED UNITS: FINNED UNITS MANUFACTURED ACCORDING TO THE METHOD AND APPLICATION OF SAID UNITS; this application having been filed on Apr. 24, 1972, now U.S. Pat. No. 3,789,494, granted Feb. 18, 1974 Inlet for the fluids fed to each of the heat transfer elements is provided by means of

tubular members

28a and 28b respectively. The fluid is exited by means of

tubular members

33a and 33b respectively. The fluid is fed from inlet member 28a to each of three radial distributor channels 4la-43a (see FIG. 4), which are formed in plate member 45a and are spaced at intervals therearound. Distributor channels 41a provide parallel fluid communication with flow channels 23a at 120 intervals around each turn of channels 23a. Collector channels 48a-50a are formed in plate member 450 and are spaced at 120 intervals located between distributor channels 41a-43a. Collector channels 48a-50a provide fluid communication with the parallel flow channels 23a at points halfway in between the distributor channels. Fluid communication is provided from collector channels 48a-50a to outlet tube 33a by means of the channel formed by grooved portion 52a of plate 45a. Thus, it can be seen that the fluid input is fed from distributor channels 4la-43a into the heat exchange flow channels 23a in parallel, flowing in the channels axially in opposite directions to the adjoining collector channels 48a-50a, from where they are appropriately fed to outlet member 33a. Thus, it can be seen that the fluid flows through an angular passage only 60 axially in the parallel spiral channels, thus minimizing the pressure drop.

Referring to FIG. 5, the fluid flow path is schematically shown of the fluid flow from inlet channel 28a through distribution channel 43a through the heat exchanger channels 23a to adjacent collector channels 48a and 50a, and thence through channel 42a to the outlet 33a. Flow of course occurs in the same manner for each of the other distributor channels and adjoining collector channels.

The construction and operation of the heat exchanger element 13 is the same as that just described for the heat exchanger element 12, the 12 designated components having the same function as the corresponding a designated components with the same numerals described for unit 12. It is to be noted that FIG.

3 best illustrates the components of heat exchange element 13.

Referring now to FIG. 6, the details of the channel forming windings of the heat exchanger elements are illustrated. As can be seen, the

channels

23a and 23b have a relatively narrow width, w, to the assure high heat-transfer rates between the channels walls and the fluid media. Further, the channels have a relatively large height, h, as compared with the width, this to assure large wetted areas and to lessen the pressure drop. It is also to be noted that the thickness dimension, t, of the channel walls is relatively large as compared with the width, w, this to give a low characteristic value for the temperature differential within the solid associated with the transfer of heat energy from the walls of the input heat exchange element to diaphragm 15 and from this diaphragm to the walls of the other heat exchange element. It is to be noted in this regard that the principal heat transfer between the fluids is accomplished through the channel walls and the diaphragm. The dimensions of typical operating embodiments of the device of the invention are as follows:

Channel width, w 0.2mm;

Channel height, h mm;

Thickness, t0.5 3 mm;

Diameter of the spiral 100 mm. It is to be noted that these dimensions are given for illustrative purposes only and that these various dimensions could vary widely in different designs.

The design is governed by the following considerations. In a heat exchanger involving two fluid media, three temperature differentials must be taken into consideration for a certain total heat transfer rate in the exchanger. These are: (l) the temperature differential between the first fluid and the wall material adjacent to that fluid; (2) the temperature differential between the second fluid and the wall material adjacent to that fluid; and (3) the temperature differential that occurs over the body of the wall material. The characteristic effective temperature differential between the two fluids for carrying out the overall heat transfer rate is the sum of these three differences. The object in most heat exchange designs is to minimize this total temperature difference. In view of the fact that for laminar flow the heat flux is inversely proportional to the heat exchanger channel width, this end result is furthered in this invention by making the channels very narrow, such that very high vlaues of heat flux between the fluid and the channel wall material can be achieved. Further, this object is attained by providing a large wetted area by making a large number of coextensive channels and the height of the spiral windings relatively large. Also, for optimum heat transfer from the windings to the diaphragm it is important that there be good thermal contact therebetween. This can be accomplished by grinding the edges of the windings perfectly flat such that when pressure is applied with the tightening of the bolts which are used to hold the device together, intimate contact at these interfaces is achieved. It also may be found helpful in achieving such intimate contact to utilize a diaphragm of relatively soft material and/or sharp edges on the windings which dig into the diaphragm. In certain instances it may be desirable to bond the heat exchange windings to the diaphragm to improve thermal contact therebetween.

In designing a high performance heat exchanger, the question of heat losses along the spiral strip also has to be taken into consideration. Obviously a thick and wide strip could presentserious heat losses in certain designs. This problem could be alleviated by fabricating the strip in sections which are separated from each other by thermally insulative portions.

It is to be noted that the heat exchanger of the invention can be utilized for both gaseous and liquid fluids, or for heat exchange between a gas and a liquid as well as between two liquids or two gases. As to be explained further on in the specification, it is also possible to utilize the device of the invention for transferring heat between fluids and solids.

It should be apparent that configurations for forming the channels other than the spiral configuration shown could be used in carrying out the basic concept of the invention as long as the channels are coextensive, i.e., run alongside each other, are narrow ehough to provide proper heat transfer to the channel walls, and means are provided for minimizing the pressure drop by the techniques described herein, such as the utilization of common channel means spaced along the narrow channels for distributing andcollecting the flows at several points along the channels. However, the use of a spiral configuration in forming the channels greatly facilitates and economizes the fabrication of the device of the invention and for these reasons appears to afford distinct advantages.

Let us now examine other embodiments of the invention. It is to be noted that for the other embodiments the same numerals are utilized to identify corresponding components of the first described embodiment.

Referring now to FIGS. 7 and 8, another embodiment of the invention is shown. This embodiment utilizes

heat exchanger elements

12 and 13 which are spirally wound around

central cores

27a and 27b respectively to form the fluid channels in the same fashion as the first embodiment. This embodiment principally differs from the first embodiment in the implementation of its distributor and collector channels and in the structure used for assembling the units together in sealed relationship with seal 15 which in interposed therebetween.

Distribution of the incoming fluid from

inlets

28a and 28b is provided directly to the

spiral channels

23a and 23b respectively by means of grooves or slots 60 which are milled in the top portions of the channel walls adjacent to the inlets. The collecting channels are implemented in the same fashion with slots 62 being milled in the channel walls in the vicinity of

outlets

33a and 33b. The

inlets

28a and 28b and

outlets

33a and 33b are located along the periphery of the windings and the

channels

60 and 62 are tapered towards the center to produce a more uniform flow velocity in the various channels, the objective in this regard being to provide resistance to decrease the velocity for the flow in the more centrally located channels. In this embodiment, the flow passage is l, in opposite directions from the

inlets

28a, 28b, to the

outlets

33a, 33b, as indicated by arrows 65. The device has

end plates

66 and 67 which are spaced apart by

cylindrical members

71 and 72, sealing for the fluid conveying portions being provided by means of

seals

68 and 69. The device is held together mechanically by means of bolts 78 which extend through

end plates

66 and 67. These bolts are tightened up to provide the necessary pressure between the ends of

spiral windings

25a and 25b and seal 15 to effect sealing therebetween.

Referring now to FIG. 9, an alternate configuration for the heat exchanger elements of the invention is illustrated. In this embodiment fluid is introduced through inlet 28 and flows from here to four distributor channels 75 which are spaced at 90 intervals around the unit. Distributor channels 75 are formed by holes in the heat exchanger windings 25. Channels 77 are similarly formed in the spiral windings to provide collector channels, these collector channels being spaced halfway in between the distributor channels. The collector channels 77 provide an exit for the fluid in a common channel (not shown) which may be formed around the periphery of unit 12. This embodiment thus provides 45 of angular flow.

Referring now to FIGS. and 11, another embodimnent is illustrated. In this embodiment, embodiment distributor channels 79 are in the form of slots formed in the cover plate 80 of the device, with the collector channels 33 being in the form of milled out portions of the spiral windings. The

windings

25a and 25b and diaphragm are similar to those for the previous embodiments.

Referring now to FIGS. 12 and 13, still another configuration for the heat exchanger elements is shown. In this embodiment the fluid intake is distributed by means of distributor channels in the form of flow distributing meshes 87 which are placed over the top edges of the spiral windings 25a. The collector channels are in the form of grooves 90 milled in the windings, these channels being covered by plates 91 to avoid the short circuiting of the flow paths. The meshes 87 operate to produce a pressure drop for the flow passing therethrough of such a magnitude that the inlet flow is distributed relatively uniformly over the channels. Other techniques may be used for implementing the function of meshes 87 in uniformly distributing the flow, such as for example the use of a porous plate.

Referring now to FIGS. 14 and 15, another embodiment of the invention is illustrated. Central plug unit 27a has four inlet channels 95 formed therein and four outlet channels 97 which communicate with a common channel 99 which is connected to outlet 33a. Flow distributor channels for carrying the fluid flow to the channels 25a of windings 23a is provided by milled out portions 101 of the windings, each of which communicates with a separate one of channels 95. The collector channels are similarly formed by milled out portions of the spiral windings (not shown) which connect with outlet channels 97.

Referring now to FIGS. 16 and 17, a further embodiment of the invention is illustrated. Shown here is a section of a large heat exchanger utilizing a plurality of heat exchanger units stacked one on the other. These units are all contained within a cylindrical housing 11 having inlet channels 28 and outlet channels 33 formed in the walls thereof. As for the previous embodiments the spiral windings 25 are wound around a central core 27. A cylinder 110 surrounds each of the heat exchanger elements and is joined to the housing 11 in sealed relationship. The inner wall of the housing and the walls of cylinders 110 have a plurality of apertures 114 formed therethrough to permit the entrance and exit of the fluid to and from each of the heat exchanger units. In the embodiment shown there are three equally spaced inlet channels 116 and three equally spaced outlet channels 117 for each of the heat exchange elements. Distributor channels 116 and collector channels 117 are provided by milling out the windings in an inwardly tapered shape as described for previous embodiments. As can be seen, each heat exchanger system has its own separate inlet and

outlet channels

28 and 33 respectively so that the fluid flows in each of these systems are separated from each other. Thus, it can be seen that a convenient technique is provided for integrating a number of heat exchange devices of the invention, having separate fluid inputs and outputs, in a single stack.

The cylinder members are utilized around each of the spiral elements to assure proper sealing and clamping pressure around the units. O-ring seals 120 are provided between housing 11 and cylinders 110 to assure that there are no leaks between the different fluid systems.

In utilizing systems of the type shown in FIGS. 16 and 17, very large systems can be constructed using relatively small components. Such a composite heat exchanger system could be completely disassembled for repair, replacement and cleaning of components. The various units can be mechanically clamped together utilizing one of the clamping techniques described in connection with the previous embodiments.

Referring now to FIGS. 18 and 19, a heat exchanger in accordance with the invention that could be used for fluid flows with change of phase accompanying the heat exchange is illustrated. This embodiment has a structure somewhat similar to the embodiment of FIGS. 7 and 8, and includes top and

bottom plates

67 and 66 which are drawn together by means of bolts 78 and nuts 79 to clamp the

heat exchange elements

12 and 13 in sealed relationship against diaphragm 15. As for previous embodiments, the

distributor channels

120 and 121, and the collector channels 124 are milled out of the spiral windings.

The input fluid which may be a liquid is fed to each of the four inlets of heat exchanger element 13 which are located near the periphery of the spiral windings. The liquid enters each of the four distributor channels 120. These channels extend inwardly only a fraction of the radius and hence cause distribution of liquid into only the outermost channels. The fluid flows radially 45 in opposite directions as indicated by the arrows, to second distributor channels 121. Channels 121 extend all the way to core 27b, these channels being dead-ended at the core. The fluid then flows radially 45 in opposite directions from channels 121 to collection channels 124, which are connected to fluid outlet 135.

During its passage through the spiral windings, the liquid will vaporize, with the density of the fluid thus decreasing and its flow velocity increasing substantially. The vapor will have a tendency to locate itself above the liquid and in the hotter parts of the spiral. Hence, this embodiment should preferably be located with diaphragm 15 horizontally oriented, with the liquid heat exchanger 13 below the diaphragm. The bottom portions of the outer channel of exchanger 13 will be filled with liquid. After the fluid has gone through a turn and flows from channel 121 to channels 124, less liquid will be present in the channels. In the top portion of the inner channels 125, pure vapor will be present possibly in a superheated stage if temperature conditions so permit. In this way, pure vapor is drawn from the exit channel 135. Upper heat exchanger element 12 may be of the type shown in FIG. 6.

Referring now to FIG. 20, the use of a heat pipe for at least one of the spiral windings is illustrated. The upper spiral winding, rather than being formed of a single strip as for the previous embodiments, is formed from two strips 140 separated by a spacer 142, the spiral heat pipe channel 146 being formed between the strips. The inner walls 140a of this channel are covered with a capillary pumping wick of sintered metal or the like, as is conventionally utilized in heat pipes. Flow channels 148 are formed between the walls of adjacent windings of channel 146, spacer wire 150 being utilized to space these walls from each other. Proper sealing between

channels

146 and 148 can be achieved by soldering the strips to diaphragm in conjunction with spacer wire 19. The advantage of using the heat pipe spiral in implementing the invention provides better heat conduction in the spiral system in a direction perpendicular to diaphragm 15. The use of heat pipe spiral permits a spiral height that is typically one order of magnitude greater than possible with a solid core ribbon. However, this approach presents drawbacks, such as added heat conduction along the channels, added overall complexity, sealing problems, and less rigidity. Also, of course, if the heat pipe is soldered to the diaphragm, disassembly for cleaning and repair becomes more difficult. Spiral strip 25 may be of solid material as for the previous embodiments.

Referring now to FIG. 21, a packaging structure which can be utilized in the invention, and which could enable operation at very high working pressures in a unit having relatively low weight and size, is illustrated. The cover plates 162 of the assembly have thin highstrength diaphragms 160 which cover them. These cover plates can be molded from a material which preferably has low thermal conductivity, such as a suitable plastic or ceramic material, and need not have especially high strength. With a system of this kind, very high working pressures can be used and still the weight and size can be kept small. The package is held together by means of clamping rings 170 and bolts 171, with ring member 173 being used to provide a guide for positioning rings 174 which encircle the

heat exchange elements

12 and 13. Diaphragms 160 could initially be made flat so that they will buckle to the appropriate shape on the tightening of bolts 17].

It should be apparent that the invention could be practiced in an implementation where heat transfer is accomplished between a fluid and an external heat source or sink. This end result could be achieved by utilizing a single fluid heat exchange element in conjunction with a diaphragm as described herein with heat transfer to the diaphragm from a source or from the diaphragm to a sink, as the case may be. The diaphragm could in such an implementation be formed by a wall of a portion of such source or sink. An embodiment of the invention along these lines is illustrated in FIG. 22. Heat exchanger element 12 is the same as that of the embodiment of FIG. 7. However, rather than utilizing a second similar heat exchanger element, the spiral windings are clamped against top wall portion 15 of heat source or sink 180. Top wall portion thus replaces the diaphragm of the previous embodiments and transfers thermal energy between element 12 and member 180, which may comprise a solid body or other device which functions as a heat source or sink for heat exchanger element 12. The heat exchanger element is clamped to member 180 by means of bolts 78 which threadably engage the walls of this member.

The device of this invention thus provides a highly efficient heat exchanger which is of simple and economical fabrication and which can be readily disassembled for replacement, repair or cleaning of components.

While the invention has been described and illustrated in detail, it is to be clearly understood that this is by way of example only and is not to be taken by way of limitation, the spirit and scope of this invention being limited only by the terms of the following claims.

We claim:

1. A heat exchanger comprising:

inlet means and outlet means for said fluid,

a heat exchange element for receiving the flow of said fluid, said heat exchange element comprising a member having a plurality of coextensive narrow fluid channels formed on a single surface thereof, said channels being defined by walls extending from said surface, multiple distributor means spaced at intervals along said channels for distributing the fluid from said inlet means to all of said fluid channels in parallel, multiple collector means spaced from said distributor means at intervals along said channels for collecting the fluid in all of said channels in common channels at intermediate positions along said fluid channels located at distances from the distributor means which are substantially less in extent than the full length of said coextensive channels and means for feeding the fluid from said last mentioned common channel to said outlet means, and

means for transferring thermal energy between said heat exchange element and a heat conductive medium, the ends of said channel walls away from said surface abutting against said last mentioned means in fluid tight relationship, whereby thermal energy is transferred between said channel wall ends and said last mentioned means.

2. A heat exchanger for transferring thermal energy between a pair of heat conductive media comprising:

inlet means and outlet means for said fluid,

one of said media comprising a heat exchanger element for receiving the flow of said fluid, said heat exchanger element comprising a member having a plurality of coextensive narrow fluid channels formed on a single surface thereof, said channels being defined by walls extending from said surface, multiple distributor means spaced at intervals along said channels for distributing the fluid from said inlet means to all of said fluid channels in parallel, multiple collector means spaced from said distributor means at intervals along said channels for collecting the fluid in all of said channels in common channels at position along said fluid channels located at distance from the distributor means which are substantially less in extent than the full length of said coextensive channels and means for feeding the fluid from said last mentioned common channel to said outlet means, and

means interposed between all of the channels of said heat exchanger element and the other of said heat conductive media for transferring thermal energy between said two media, the ends of said channel walls away from said surface abutting against said I last mentioned means whereby thermal energy is transferred between said channel wall ends and said last mentioned means.

3. The device of claim 2 wherein the other of said heat conductive media comprises a member of solid material, said means interposed between said heat exchanger element and said member comprising a wall of said member of solid material.

4. The device of claim 2 wherein the other of said heat conductive media comprises a second heat exchanger element similar to said first heat exchanger element and a fluid flowing in said second element, said means interposed between said units comprising a diaphragm forming an edge seal for each of said channels.

5. The device of claim 4 and further including means for applying mechanical pressure against both of said heat exchanger elements urging them towards each other to provide good thermal contact between said elements and said diaphragm, the thermal energy being transferred from one fluid to the other fluid through the intermediary of the walls of the heat exchanger elements and said diaphragm.

6. The device of claim 4 wherein the channels of each of said heat exchanger elements are formed from a single conductive strip wound in a spiral configuration, one of the edges of the strip of one of said elements abutting against one side of said diaphragm, one of the edges of the strip of the other of said elements abutting against the opposite side of said diaphragm.

7. The device of claim 5 wherein said means for applying mechanical pressure against said elements comprises a housing for said heat exchanger elements and screw means threadably attached to said housing for tightening said elements against each other within said housing.

8. The device of claim 2 and further including a housing for containing said heat exchanger element, said distributor means comprising an inlet for receiving the fluid extending from said housing, a plurality of distributor channels formed in said housing for receiving fluid from said inlet and communicating said fluid to separate portions of said fluid channels, and said collector means comprising collector channels formed in said housing between said distributor channels for commonly receiving the fluid flowing in said fluid channels from said distributor channels, and outlet means for receiving the fluid from said collector channels.

9. The device of claim 6 wherein said distributor means for distributing fluid to said channels and said collector means for collecting fluid from said channels comprises apertures extending through said channels and spaced from each other at intervals around the spiral, said apertures extending through separate sections of said spiral.

10. The device of claim 9 wherein said apertures are tapered.

11. A heat exchanger for transferring heat energy from one fluid to another comprising:

a housing,

first and second heat exchanger elements mounted in said housing, each of said elements including a plurality of coextensive fluid channels formed from a strip of material wound in a spiral, a fluid inlet and outlet in said housing, multiple fluid distributor channel means extending essentially radially across said spiral and spaced at intervals about a full turn of said spiral, said fluid distributor channel means receiving fluid from said inlet and feeding said fluid in parallel to said channels, and multiple fluid collector channel means extending essentially radially across said spiral, said collector channel means being spaced from said distributor channel means so as to receive in parallel the fluid flow from said distributor channel means after it has passed through a portion of a single turn of said spiral channels, said collector channel means feeding fluid to said outlet, and a diaphragm interposed between the spiral windings of said first and second heat exchanger elements, one of the edges of each of said spiral windings of said first and second heat exchanger abutting against an opposite surface of said diaphragm, thermal energy being transferred between said heat exchanger elements through said diaphragm,

whereby the fluid is fed to each distributor channel means and flows in parallel around adjacent channels of each of said heat exchanger elements to a collector channel means after traversing only a portion of a full turn of said spiral.

12. The device of claim 11 and further including means for mechanically clamping said heat exchanger elements together in said housing with mechanical pressure being applied by said spiral windings against the opposite surfaces of said diaphragm to provide good thermal contact between said windings and said diaphragm.

13. The device of claim 11 wherein said distributor and collector channels are formed in said housing.

14. The device of claim 11 wherein said distributor and collector channels comprise apertures formed in said spiral windings.

15. The device of claim 13 wherein said distributor and collector channels are tapered.

16. The device of claim 12 wherein said housing means comprises a hollow cylinder having an open end and a closed end, said heat exchanger elements, said diaphragm and said distributor and collector channel means being contained within said cylinder, said means for mechanically clamping said heat exchanger elements together comprising a pan member fitted into the open end of said cylinder to cover said open end and bolt means threadably attached to the edge portion of the open end of said cylinder, said bolt means driving against said pan member thereby applying force thereagainst to drive said heat exchanger elements together.

17. The device of claim 11 and further including a pair of circular plate members, said heat exchanger elements being sandwiched between said plate members, said fluid distributor and collector channel means comprising grooves formed at spaced intervals in said plate members adjacent to said spiral windings.

18. The device of claim 12 wherein said means for clamping said heat exchanger elements together comprises a pair of end plate members, said heat exchanger elements being sandwiched between said end plate members, and bolt means for drawing said end plate members towards each other.

19. The device of claim 11 and further comprising a wire placed between the windings of said spiral to provide spacing therebetween.

20. A plurality of heat exchangers as set forth in claim 11, said heat exchangers being stacked vertically one on the other, said housing means comprising a cythe first set of radial channels, and said collector channel means comprises a set of radial channels spaced between said second set of channels for receiving the fluid flow in the spiral therefrom whereby fluid flows in a first direction in said spiral from said first set of distributor channels to said second set of channels and in a direction opposite to said first direction from said second set of channels to said collector channels.

Claims

1. A heat exchanger comprising: a fluid, inlet means and outlet means for said fluid, a heat exchange element for receiving the flow of said fluid, said heat exchange element comprising a member having a plurality of coextensive narrow fluid channels formed on a single surface thereof, said channels being defined by walls extending from said surface, multiple distributor means spaced at intervals along said channels for distributing the fluid from said inlet means to all of said fluid channels in parallel, multiple collector means spaced from said distributor means at intervals along said channels for collecting the fluid in all of said channels in common channels at intermediate positions along said fluid channels located at distances from the distributor means which are substantially less in extent than the full length of said coextensive channels and means for feeding the fluid from said last mentioned common channel to said outlet means, and means for transferring thermal energy between said heat exchange element and a heat conductive medium, the ends of said channel walls away from said surface abutting against said last mentioned means in fluid tight relationship, whereby thermal energy is transferred between said channel wall ends and said last mentioned means.

2. A heat exchanger for transferring thermal energy between a pair of heat conductive media comprising: a fluid, inlet means and outlet means for said fluid, one of said media comprising a heat exchanger element for receiving the flow of said fluid, said heat exchanger element comprising a member having a plurality of coextensive narrow fluid channels formed on a single surface thereof, said channels being defined by walls extending from said surface, multiple distributor means spaced at intervals along said channels for distributing the fluid from said inlet means to all of said fluid channels in parallel, multiple collector means spaced From said distributor means at intervals along said channels for collecting the fluid in all of said channels in common channels at position along said fluid channels located at distance from the distributor means which are substantially less in extent than the full length of said coextensive channels and means for feeding the fluid from said last mentioned common channel to said outlet means, and means interposed between all of the channels of said heat exchanger element and the other of said heat conductive media for transferring thermal energy between said two media, the ends of said channel walls away from said surface abutting against said last mentioned means whereby thermal energy is transferred between said channel wall ends and said last mentioned means.

10. The device of claim 9 wherein said apertures are tapered.

11. A heat exchanger for transferring heat energy from one fluid to another comprising: a housing, first and second heat exchanger elements mounted in said housing, each of said elements including a plurality of coextensive fluid channels formed from a strip of material wound in a spiral, a fluid inlet and outlet in said housing, multiple fluid distributor channel means extending essentially radially across said spiral and spaced at intervals about a full turn of said spiral, said fluid distributor channel means receiving fluid from said inlet and feeding said fluid in parallel to saId channels, and multiple fluid collector channel means extending essentially radially across said spiral, said collector channel means being spaced from said distributor channel means so as to receive in parallel the fluid flow from said distributor channel means after it has passed through a portion of a single turn of said spiral channels, said collector channel means feeding fluid to said outlet, and a diaphragm interposed between the spiral windings of said first and second heat exchanger elements, one of the edges of each of said spiral windings of said first and second heat exchanger abutting against an opposite surface of said diaphragm, thermal energy being transferred between said heat exchanger elements through said diaphragm, whereby the fluid is fed to each distributor channel means and flows in parallel around adjacent channels of each of said heat exchanger elements to a collector channel means after traversing only a portion of a full turn of said spiral.

20. A plurality of heat exchangers as set forth in claim 11, said heat exchangers being stacked vertically one on the other, said housing means comprising a cylindrical housing for housing said units, the distributor and collector channel means for each of the heat exchanger elements comprising radial apertures formed in the windings of the heat exchanger elements.

21. The device of claim 11 wherein said distributor channel means comprises a first set of radial channels for providing fluid to the flow channels near the periphery of said winding, a second set of radial channels extending radially across the entire spiral spaced between the first set of radial channels, and said collector channel means comprises a set of radial channels spaced between said second set of channels for receiving the fluid flow in the spiral therefrom whereby fluid flows in a first direction in said spiral from said first set of distributor channels to said second set of channels and in a direction opposite to said first diRection from said second set of channels to said collector channels.