US3228460A

US3228460A - Heat exchange device

Info

Publication number: US3228460A
Application number: US324262A
Authority: US
Inventors: Richard L Garwin
Original assignee: International Business Machines Corp
Current assignee: International Business Machines Corp
Priority date: 1963-11-18
Filing date: 1963-11-18
Publication date: 1966-01-11
Anticipated expiration: 1983-01-11
Also published as: JPS414518B1; GB1016879A

Description

Jan. 11, 1966 R. L. GARWIN HEAT EXCHANGE DEVICE Filed Nov. 18, 1963 N QE I NVENTOR RICHARD L. GARWiN MEDQHUE ATTORNEY United States Patent 3,228,460 HEAT EXCHANGE DEVICE Richard L. Garwin, Scarsdale, N.Y., assignor to Internationai Business Machines Corporation, New York, N.Y., a corporation of New York Filed Nov. 18, 1963, Ser. No. 324,262 8 Claims. (Cl. 16581) This invention relates to heat transfer devices and more particularly to counter-flow heat exchangers for use in systems which provide extremely low temperatures for cryogenic devices and the like.

Heat exchangers are utilized in practically every type of refrigeration and gas liquefying system, and their use and operation is well known in these arts. Recently, however, due to the increased use of liquefied gases as fuel for liquid-fueled rockets and as a coolant for cryogenic devices, such as maser amplifiers which operate at temperature near absolute zero, refrigeration systems capable of producing low temperature liquids or of maintaining low temperatures have become more and more important. Indeed, the investigation of low temperatures and their effects has become the intensively studied area of cryogenics, the basic tools of which are systems capable of porducing low temperatures.

In the past, refrigeration equipment utilized to provide the liquefied gases at the required low temperatures was bulky and expensive and incapable of long periods of uninterrupted operation. Now, however, due to the relatively wide acceptance and utility of such systems, factors such as size, cost, reliability, and ease of assembly must be taken into consideration. Thus, an effort is being made to reduce structural complexity and assembly time in important refrigeration system components such as heat exchangers.

Prior art heat exchangers, while they have performed their function efliciently, have not been noted for their structural simplicity or case of assembly. Complex structure, of course, leads to difiiculty in assembly which in turn contributes to high production cost and relatively low reliability in operation. Difliculties have been encountered principally in mounting heat transfer elements within the heat exchanger and, in preventing leakage between the fluid channels of the heat exchanger. Problems have also arisen in matching temperature coefiicients of expansion of the various materials required and in maintaining solder joints and seals under extremely low temperature conditions. It appears, therefore, that a need exists for a heat exchanger which has simplicity of design, ease of assembly, relatively low cost and high reliability, in addition to good efficiency.

It is therefore an object of this invention to provide a counter-flow heat exchanger which is an improvement over prior art heat exchangers.

Another object is to provide a heat exchanger which is compact, relatively easy to assemble and low in cost.

A further object is to provide a heat exchanger which is operable and reliable at extremely low temperatures.

A feature of this invention is the utilization of means defining first and second fluid flow paths and heat transfer elements common to said paths to transfer heat therebetween.

Another feature of this invention is the utilization of a plurality of high heat conductivity heat-transfer elements which have a plurality of perforations therein, and, a plurality of relatively low heat conductivity spaceror blocking-elements which are interposed between the heat transfer elements. The spacer or blocking elements separate the heat transfer elements and simultaneously block certain ones of the perforations in the heat transfer elements so that at least two fluid flow channels are formed within Patented Jan. 11, 1966 a heat exchanger casing. In this fashion, uninterrupted paths of high-conductivity metal carry the heat from one stream to the other.

A further feature of this invention is the utilization of resilient retaining means which apply a compressive force to the heat transfer and blocking elements so that, regardless of the expansion and contraction encountered due to temperature changes, the axial position of the elements is controlled and the elements are held tightly together to prevent fluid leakage between channels.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention, as illustrated in the accompanying drawings.

In the drawings:

FIG. 1 is a longitudinal partially cut away cross-sectional view of the counter flow heat exchanger according to this invention and,

FIG. 2 is a cross-sectional view of the heat exchanger taken along lines 22 of FIG, 1 which shows the juxtaposition of heat transfer elements and spacer elements within the casing of the heat exchanger.

A counterflow heat exchanger is a device which takes advantage of the recirculation of a low temperature fluid which has been utilized previously to maintain some component such as a maser at a given low temperature. The recirculated low temperature fluid is utilized to pre-cool incoming fluid at a relatively high temperature to a lower temperature by transfer of heat in the heat exchanger by some heat transfer means. The transverse flow of heat from stream to stream is facilitated, and the flow of heat along the heat exchanger is impeded as much as possible, for best efliciency. In this manner, extremely low temperatures are achieved relatively quickly and the efiiciency of the refrigeration system is enhanced. In the usual refrigeration system, several heat exchangers may be utilized to obtain heat transfer at several different points in the system.

T o simplify the following description, Where portions of the heat exchanger of this invention correspond to other portions, the same reference number will be utilized, it being understood that the input and output sections of the heat exchanger are structurally identical.

Referring now to FIG. 1, there is shown a counter-flow heat exchanger 1 having an outer casing 2 of relatively low heat conductivity material such as stainless steel. Heat exchanger casing 2 forms the boundary of a first fluid flow path or channel through which, in the usual case, a relatively low temperature, low pressure fluid is recirculated after having cooled some component, such as a maser, at a point, not shown, beyond heat exchanger 1, The first fluid flow path or channel is shown generally at 3 in FIG. 1. A second fluid flow path or channel, shown generally at 4, is disposed internally of and coaxially of the first fluid flow path or channel 3. The second fluid flow path or channel 4 is partially defined by inflow and outflow tubulation 5 and by an enlarged resilient portion 6 thereof, both preferably having a circular cross-section. Tubulation 5, made preferably of stainless steel extends into casing 2 through a circular aperture 7 in cup-shaped end piece 8, the outer surface of which fits tightly against a portion of the inner surface of casing 2. A flange 9 on the extremity of end piece 8 engages the extremity of easing 2 to limit the distance of insertion of end piece 8 into casing 2. A counter sunk portion 10 about circular aperture 7 is adapted to receive the end of a cylindrical sleeve 11 which is receivable on tubulation 5. Sleeve 11, preferably of stainless steel, is soldered at an end 12 to tubulation 5, and, flange 9 is soldered to the extremity of easing 2. In this manner, axial movement of tubulation 5 and resilient portion 6 is prevented and a compressive force is exerted by resilient portion 6 in a manner to be more fully described hereinafter.

In FIG. 1, a plurality of annular spacer or blocking elements 13, preferably made of nylon or other low heat conductivity material, is shown disposed internally of a portion of easing 2, the annular spacer or blocking elements 13 defining another portion of the second fluid flow path or channel 4. Also disposed internally of casing 2 is a plurality heat transfer elements 14 of high heat conductivity material such as copper or other suitable material. Elements 14 are of circular cross section (see FIG. 2) and are interposed periodically between spacer or blocking elements 13 along the length of casing 2.

FIG. 2 shows clearly the juxtaposition of spacer or blocking elements 13 and heat transfer elements 14 within casing 2. Spacer or blocking elements 13 are contiguous with the surface of heat transfer elements 14 over a minor portion which divides elements 14 into

major portions

16 and 17. Thus,

major portions

16 and 17 are interposed in first and second flow paths 3 and 4, respectively. It should be noted that heat transfer elements 14 are common to both first and second flow paths 3, 4 and that fluid flow through paths 3, 4 is made possible by virtue of a plurality of perforations 18 which extend through each of the heat transfer elements 14 and permit the passage of fluid through

major portions

16 and 17. Spacer or blocking elements 13, act to space apart heat transfer elements 14 so that lateral rather than longitudinal transfer of heat between fluids is accomplished and block certain ones of perforations 18 to prevent passage of fluid therethrough. By virtue of the arrangement of heat transfer elements 14 and blocking elements 13, a portion of second fluid flow path 4 is formed which consists of the annular blocking elements 13 and minor portions 15 of heat transfer elements 14. Reference numeral 15, while directed to annular blocking element 13, is intended to define a minor portion of heat transfer element 14. The minor portion 15, therefore, is that portion of element 14 which is in registry with blocking element 13. It should be clear that perforations 18 which are in registry with annular blocking element 13 transmit no fluid and accordingly act as a portion or boundary of second flow path or channel 4.

Referring again to FIG. 1, it may be seen that enlarged resilient portion 6 of tubulation 5 has a radially extending portion 19 which is bent at a small acute angle from the vertical. Also, resilient portion 6 has an extremity extending radially inwardly which is also bent at a small acute angle with respect to the vertical. The angular displacement of portion 19 and extremity 20 is due to the positioning of extremity 20 against the first and last of the plurality of blocking elements 13 such that a compressive force is applied to elements 13 and maintained thereon by soldering cylindrical sleeve 11 at its end 12 to tubulation 5. The compressive force acts on blocking elements 13 and heat transfer elements 14 so that the intervening wall formed by the elements 13 and minor portion 15 of heat transfer elements 14 is substantially fluid tight even though contraction of

elements

13 and 14 takes place when contacted by the low temperature fluids. Using the foregoing technique, the axial movement of

elements

13 and 14 is controlled and a substantially fluid-tight wall is maintained intermediate the

major portions

15, 16 of heat transfer elements 14. Referring again to FIG. 2, it may be seen that perforated heat transfer elements 14 completely fill casing 2. Elements 14 are not, however, attached to the inner surface of casing 2, but rather are in slidably engaging relationship therewith so that elements 14 can freely move when expansion and contraction due to temperature changes takes place. Spacer or blocking elements 13 must be maintained within casing 2 in a given radial position and this is accomplished by providing radially extending fingers or protuberances 21 which, like heat transfer elements 14, are in slidably engaging relationship with the inner surface of casing 2. In connection with the use of spacer or blocking elements 13, only the formation of two flow paths or channels has been indicated within casing 2. There is, however, no reason why a number of concentric spacer or blocking elements could not be provided to form three or more flows paths or channels within a heat exchanger casing. Under such circumstances, appropriate inflow and outflow tubulation would have to be provided for each of the resulting channels. It is also possible to solder, connect, or otherwise aflix the spacer elements 13 to the heat-transfer elements 14, providing a gas-tight connection by means of a bellows or spring enclosure like the end-

piece

19 and 20. Copperclad phenolic spacers have been successfully utilized.

In FIG. 1, inflow and outflow tabulation 22 is soldered into excentrically displaced circular aperture 23 to carry recirculated low pressure fluid to and from first fluid flow path 3.

A successful operating model of heat exchanger 1 was constructed having the following dimensions:

Overall length 4.25 inches. Casing diameter 1.05 inches.

Casing thickness 16 mils.

Heat Transfer element diameter 1.469 inches.

Heat Transfer element thickness 15 mils.

Spacer diameter 1.03 1 inches. Spacer thickness 30 mils. Perforations 15 mil diameter on 30 mil centers.

Heat exchanger 1 may be assembled by soldering a pre-assembled portion consisting of

tubulation

5 and 22 and end pieces 8 to casing 2 at flange 9. Blocking or spacer elements 13 and heat transfer elements may then be stacked alternately until a total of fifty-five spacer elements 13 and fifty-four heat exchange elements 14 are disposed within casing 2. At this point, a second preassembled portion identical to that referred to above is inserted and soldered to complete the assembly of heat exchanger 1.

From the foregoing, it is clear that heat exchanger 1 may be assembled relatively easily and that it consists of easily obtainable, relatively inexpensive parts. The arrangement of the various parts requiring a minimum of soldering operations results in increased reliability as well as minimizing the overall cost of such heat exchangers.

In operation, a high pressure stream of gas at 300 p.s.i. passes along second fluid flow path 4 and heat is absorbed by a stream of low pressure gas at 15 p.s.i. in first fluid flow path 3. The low pressure fluid is a gas which is being recirculated to heat exchanger 1 to cool an incoming gas to a temperature where expansion through a Joule-Thompson valve will cause the gas to liquefy.

While a counter-flow heat exchanger has been described herein as a preferred embodiment, it should be appreciated that the same structure may be utilized as a heat transfer device in which the fluids flow in the same direction. In such an arrangement, there would be a lateral transfer of heat between the streams but no temperature differential would be apparent from one end of the heat exchanger to the other. In the counter flow type heat exchanger, while there is a similar lateral transfer of heat, there is a temperature differential from one end of the heat exchanger to the other. Apart from the temperature differential due to flow direction, there is no diflerence in the operation or structure of the heat exchanger for either type of flow.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is: 1. A heat exchanger for transferring heat between fluids at diflerent temperatures comprising:

means defining a first fluid flow path, means defining a second fluid flow path disposed coaxially of said first path and heat transfer elements common to said first and second flow paths interposed in said paths to transfer heat therebetween, said means defining a second fiow path including a plurality of discrete low heat, conductivity spacer elements disposed internally of and lengthwise of at least a portion of said first fluid flow path and periodically interposed between said heat-transfer elements and input and output tubulation having enlarged resilient transition portions, an extremity of each of said portions being connected to a spacer element to apply a compressive force to said spacer elements and said heat transfer elements to compensate for dimensional changes due to temperature variation to prevent fluid leakage between said first and second flow paths and to control the axial movement of said spacer and heat transfer elements. 2. A heat exchanger for transferring heat between fluids at different temperatures comprising:

means defining a first fluid fiow path, means defining a second fluid flow path disposed c0- axially of said first path, heat transfer elements common to said first and second flow paths interposed in said paths to transfer heat between said first and second flow paths, said means defining a second flow path including a plurality of discrete low heat-conductivity spacer elements disposed internally of and lengthwise of at least a portion of said first fluid flow path and periodically interposed between said heat-transfer elements, and means for maintaining the radial positioning of said spacer elements including a plurality of protuberances integral with said elements and adapted to slidably engage said means defining a first flow path. 3. In a heat exchanger for transferring heat between fluids at different temperatures having a low heat conductivity casing:

heat transfer means comprising a plurality of heat conductive elements having a plurality of perforations therein to permit the passage of fluid therethrough disposed internally of said casing, means interposed between said elements to block the passage of fluid through certain ones of said perfora tions thereby forming at least two discrete channels for fluid flow within said casing,

and resilient retaining means adapted to position said conductive elements and said blocking means within said casing to control the axial movement of said elements and said blocking means and means integral with said blocking means to position said blocking means within said casing to prevent radial movement thereof.

4. In a heat exchanger heat transfer means according to claim 3 wherein said blocking means includes an endless strip of low heat conductivity material.

5. In a heat exchanger heat transfer means according to claim 3 wherein said blocking means includes an annulus of low heat conductivity material.

6. In a heat exchanger heat transfer means according to claim 3 wherein said resilient retaining means comprises:

inflow and outflow tubulation for one of said channels each having a portion thereof rigidly fixed to said casing and an enlarged portion having an inwardly extending extremity connected to one of said blocking means adapted to maintain said conductive elements and said block-ing means in compression to provide at least two discrete channels the intervening wall of which is substantially fluid tight and compensates for dimensional variation due to changes in temperature.

7. In a heat exchanger heat transfer means according to claim 3 wherein said means integral with said blocking means to radially position said blocking means comprises:

a plurality of protuberances extending radially from said blocking means, said protuberances being in slidably engaging relationship with said casing.

8. In a heat exchanger heat transfer means according to claim 3 further comprising:

inflow and outflow tubulation for at least another of said channels fixedly connected to said casing.

References Cited by the Applicant UNITED STATES PATENTS 604,823 5/1898 Forbes l179 1,724,351 8/1929 Henderson et al. 81 X 1,863,586 6/1932 Wilke 165-135 2,451,629 10/1948 McCollum 165154 X 2,580,715 1/1952 Baber 165-81 2,879,976 3/1959 Rose a- 165154 X FREDERICK L. MATTESON, 111., Primary Examiner.

Claims

1. A HEAT EXCHANGER FOR TRANSFERRING HEAT BETWEEN FLUIDS AT DIFFERENT TEMPERATURE COMPRISING: MEANS DEFINING A FIRST FLUID FLOW PATH, MEANS DEFINING A SECOND FLUID FLOW PATH DISPOSED COAXIALLY OF SAID FIRST PATH AND HEAT TRANSFER ELEMENTS COMMON TO SAID FIRST AND SECOND FLOW PATHS INTERPOSED IN SAID PATHS TO TRANSFER HEAT THEREBETWEEN, SAID MEANS DEFINING A SECOND FLOW PATH INCLUDING A PLURALITY OF DISCRETE LOW HEAT, CONDUCTIVITY SPACER ELEMENTS DISPOSED INTERNALLY OF AND LENGTHWISE OF AT LEAST A PORTION OF SAID FIRST FLUID FLOW PATH AND PERIODICALLY INTERPOSED BETWEEN SAID HEAT-TRANSFER ELEMENTS AND INPUT AND OUTPUT TUBULATION HAVING ENLARGED RESILIENT TRANSITION PORTIONS, AN EXTREMITY OF EACH OF SAID PORTIONS BEING CONNECTED TO A SPACER ELEMENT TO APPLY A COMPRESSIVE FORCE TO SAID SPACER ELEMENTS AND SAID HEAT TRANSFER ELEMENTS TO COMPENSATE FOR DIMENSIONAL CHANGES DUE TO TEMPERATURE VARIATION TO PREVENT FLUID LEAKAGE BETWEEN SAID FIRST AND SECOND FLOW PATHS AND TO CONTROL THE AXIAL MOVEMENT OF SAID SPACER AND HEAT TRANSFER ELEMENTS.