US 3123984 A
Description (OCR text may contain errors)
March 10, 1964 L. H. LEONARD, JR 4 REFRIGERATION APPARATUS 0 O '0 O 0 0 O (cw .1 I I 27 INVENTOR.
l LOUIS H. LEONARD JR.
March 10, 1964 LEONARD, JR 3,123,984
REFRIGERATION APPARATUS Filed Dec. 27, 1960 2 Sheets-Sheet 2 INVENTOR.
LOUIS H. LEONARD JR.
rates Patent 3,123,984 Patented Mar. 10, 1964 fine 3,123,984 REFREGERATKON APPARATUS Louis H. Leonard, in, De Witt, N.Y., assignor to Carrier Corporation, Syr cuse, N.Y., a corporation of Delaware Fitted Dec. 27, 1am, Sci. No. 83,129 9 Claims. (Cl. 62-125) This invention relates to refrigeration machines and more particularly to a specialized construction adapted for use with absorption refrigeration machines whereby leaks in liquid cooled heat exchangers may be detected. Constructions of the type herein described find a particular application aboard naval or other seagoing vessels and especially on submarines which are particularly susceptible to the occurrence of leaks due to the high submergence pressures encountered and wherein the detection of leaks is considered of substantial importance.
Absorption refrigeration machines conventionally comprise an absorber, an evaporator, a generator and a condenser operatively connected to form a refrigeration system. A more complete description of the type of system herein referred to is contained in Leonard application, Serial No. 2,206, filed January 13, 1960; now Patent No. 3,054,272. In such systems, both the condenser section and the absorber section generally comprise water-cooled heat exchangers. In the absorber section, it is necessary to remove the heat of condensation and dilution liberated by vaporized refrigerant as it is absorbed in the absorbent solution. In the condenser, it is necessary to remove the heat liberated by condensation of refrigerant vapor, or stated in another way, it is necessary to cool the refrigerant vapor sufficiently to cause it to condense. In each of these instances, it is common practice to provide a heat exchanger of the tube-and-shell type.
A tube-and-shell type heat exchanger basically comprises a pluraiity of heat exchange tubes passed through and secured in a leak-tight manner to a tube sheet which forms an end wall of a heat exchanger shell. A fluid header is secured to the end of the tube sheet and forms a fluid receiver or distributor for the passage of a cooling fluid such as water which passes through the heat ex change tubes. A similar construction is generally formed at the other end of the heat exchanger shell and means is provided to pass the cooling fluid to one header from which it passes through the heat exchange tubes to provide the desired cooling of a gas or liquid in the interior of the shell. The cooling fluid, which has picked up heat in its passage through the heat exchange tubes, is then emptied into the header at the opposite end of the heat exchanger from which it is suitably discharged.
In conventional absorption refrigeration machines, the pressure exerted by the cooling fluid at the joints between the heat exchange tubes and the tube sheet need not be extremely high nor are undue mechanical stresses likely to occur. Consequently, conventional rolling techniques for making a leak-tight joint between the heat exchange tubes and the tube sheets may be entirely adequate to prevent leakage. But, when an absorption refrigeration machine employing a tube-and-shell heat exchanger is installed in a submarine, it is highly desirable from the standpoint of economy and simplicity of operation to utilize sea water as the cooling medium flowing through the heat exchange tubes. Consequently, the pressure exerted on the joints between the heat exchange tubes and the tube sheet may be equal to or greater than the submcrgence pressure of the sea Water at the depth at which the submarine is operating. This pressure may, therefore, be of the order of several hunderd pounds per square inch when a submarine is operating at a substantial depth.
Under these conditions, the stresses imposed on the joints between the heat exchange tubes and the tube sheet may be extremely severe and suflicient to cause small leaks to develop in the joints. While small leaks may not seriously impair functioning of the refrigeration machine when used under normal surface operating conditions, they may be of sufficient magnitude to seriously reduce the refrigeration capacity of the absorption system when subjected to the great pressures encountered during submergence of the vessel. Furthermore, such leaks tend to become progressively worse and in time, the capacity of the machine may be greatly impaired under circumstances where it is difficult or impossible to correct the situation, as when fully submerged. In addition, leakage of sea water into the interior of an absorption refrigeration machine is extremely deleterious, not only because it seriously impairs the functioning of the absorbent solution, but also it may flood the machine or cause corrosion in its interior. Because of the very high heat loads, a submarine may be virtually disabled by failure of its air conditioning while operating below the surface of the ocean. Consequently, it is important to ascertain the existence of such leaks before they become serious so that proper corrective measures may be taken when the vessel is in port.
Since the interior of tube-and-shell heat exchangers such as used in absorption refrigeration systems is closed and not exposed to view, and since the existence of small leaks is generally not apparent until they have become of sufficient size to impair the functioning of the refrigeration system, it would be highly desirable to provide some means of detecting these small leaks immediately upon their occurrence. A similar problem exists to a somewhat lesser degree in surface operating vessels at times when they are subjected to unusually severe mechanical stresses and strains. Therefore, it is also desirable to quickly locate the existence of leaks which may become progressively worse under severe operating conditions in such vessels.
Accordingly, it is the principal object of the invention to provide a refrigeration machine having improved means for detecting the existence of a leak in its heat exchangers.
It is a further object of this invention to provide an improved method and means for detecting leaks in a heat exchanger.
It is a still further object of this invention to provide an improved submarine refrigeration system.
In a preferred embodiment of this invention, these and other objects are achieved by providing a pair of tube sheets at the ends of the heat exchangers in the condenser and absorber sections of an absorption refrigeration machine. The pair of tube sheets are spaced from each other to form a chamber which is filled with a relatively incompressible fluid such as octyl alcohol (Z-ethyl-n-hexanol) which is noncorrosive and which is compatible with the fluids within the refrigeration machine. Means are provided to observe the effects of abnormal pressures on the fluid in the chamber which are indicative of leakage so that leakage from the chamber into the interior of the heat exchanger or leakage from the exterior of the heat exchanger into the chamber can be readily detected.
Such a construction possesses the advantage of forming a liquid seal in the chamber between the tube sheets and the heat exchange tubes as well as alfording a ready means of ascertaining the existence and type of leaks at the tube sheets. In the event that fluid within the chamber leaks into the interior of the heat exchanger, no immediate harm need result because the material chosen can be a liquid, such as octyl alcohol, Which is desirably present in the heat exchangers of the absorption machine under normal operating conditions.
These and other objects of this invention will become apparent by reference to the following detailed description and attached drawings wherein:
FIGURE 1 is a diagrammatic view of an absorption refrigeration machine; and
FIGURE 2 is a fragmentary cross-sectional view of the ends of a heat exchanger each embodying a form of the instant invention.
Referring to FIGURE 1 of the drawing, there is illustrated an absorption refrigeration system constructed in accordance with a preferred embodiment of this invention. The absorption refrigeration system comprises an absorber section and an evaporator section 11 located within shell 12. A plurality of heat exchange tubes 13 adapted to pass cooling water are located within the absorber section. A spray system 14 comprising a plurality of headers and suitable spray nozzles is located above tubes 13 for the purpose of discharging a finely divided spray of absorbent solution thereover.
As used herein the term strong solution refers to a solution strong in absorbing power and the term weak solution refers to a solution weak in absorbing power.
The term intermediate concentration is used to designate a solution having a concentration intermediate the concentration of weak and strong solution.
A suitable refrigerant for a system of the type herein described comprises vvater and a suitable absorbent solution comprises a solution of lithium bromide and water. The concentration of lithium bromide leaving the generator may desirably be about 65%.
Adjacent the lower portion of shell 12 and absorber section 10 is a sump 15 which is divided by vertically extending partition means 18 into an intermediate strength absorbent solution sump 16 and a weak absorbent solu tion sump 17. Both sumps collect absorbent solution sprayed over tubes 13 land sump 16 in addition receives strong solution from generator 34- which mixes therein to form absorbent solution of intermediate strength. A bypass line 1% may be provided to equalize fluid levels in the two sumps if desired. While for purposes of illustration, partition 18 has been shown as extending longitudinally of the machine, it will be appreciated that the illustration is schematic in nature and that partition 18 may extend transversely across sump 15 if desired.
Evaporator section 11, which is also located within shell 12, comprises a pan or vessel 20 within which are disposed a plurality of heat exchange tubes 21 which are adapted to carry a chilled fluid such as water to suitable heat exchangers located remotely from the refrigeration machine to provide cooling or dehumidification in the desired areas. Disposed above tubes 21 in the evaporator section is a suitable refrigerant distributor 22 which may include a plurality of headers each having a number of sprays in communication therewith to evenly distribute refrigerant over heat exchange tubes 21.
Pan 26, as illustrated in the drawing, has relatively high vertically extending walls to prevent transfer of re frigerant in the liquid state directly to the absorber section even when disposed at substantial angles to their normal position. The vertically extending walls of pan 2% terminate in eliminators 23 which provide a tortuous path for the passage of refrigerant vapor on its way to the absorber and thereby remove droplets of liquid refrigerant from spray system 22 which may have become entrained in the refrigerant vapor. Pump 25 passes accumulated absorbent solution of intermediate concentration from sump 16 through lines 26 and 27 to spray system 14 to maintain a continuous spray of absorbent solution over tubes 13.
Pump 28 passes absorbent solution relatively weak in absorptive capability through lines 29 and 3t to solution heat exchanger 31. Line 32 passes the weak solution from solution heat exchanger 31 to refrigerant distribution means 33 of generator 34. Distribution means 33 may suitably comprise a header having a plurality of spray nozzles in communication therewith disposed above the tube bundle 35.
Generator 34 comprises a shell 43 having vertically extending partition means 44-. Partition 44 may be secured to the upper portion of shell 43 and divides the generator into a first compartment and a second compartment 46. Heat exchange tube bundle 35 is disposed within first compartment 45'. Steam inlet 36 and a steam and condensate outlet 37 is provided to pass steam through the heat exchange tubes within tube bundle 35. A sump 38 having angular side walls is disposed adjacent the lower portion of shell 4-3 adjacent at least one end thereof and serves to receive strong solution concentrated by the generator and pass it through line 39 to heat exchanger 31. Preferably, sump 33 comprises a pair of sumps at each end of shell 43 each connecting with line 39 and extending below the bottom of shell .3 as Shown in the drawings.
Warm strong solution is passed from generator 43 through line 39 to solution heat exchanger 31 and is cooled by heat exchange with cold weak solution passing through the heat exchanger from line 3%? to line 32 on its Way to the generator. The cooled strong solution is then passed from heat exchanger 31 through line 40 into intermediate absorbent concentration solution sump 16 of absorber 19. Upon being discharged into sump 16 the strong solution is further cooled by flashing due to the lower pressure in absorber 10 than exists in generator 34. Sump 33 and lines 39 and 44 are sized so as to substantially prevent accumulation of solution in generator 34 while permitting gravity return of the strong solution into sump 16.
First compartment 4-5 and second compartment 46 of generator 34 are in communication lWith each other adjacent their respective lower portions because partition means 44 extends only part way down from the top of shell 43.
If desired, tan eliminator 49 may be disposed in second compartment 46 to further assure complete elimination of any remaining entrained solution. An outlet 50 and a refrigerant vapor line 51 is located above eliminator 49 and leaks from second compartment 46 to a condenser 52.
Condenser 52 comprises shell 53 and a sump 55 to collect condensed refrigerant vapor. A plurality of heat exchange tubes 54 are disposed within shell 53. Inlet line 58 and outlet line 59 are provided to pass cooling Water, which in the case of a seagoing vessel may comprise sea water, through tubes 54 to extract heat from the vaporized refrigerant and to condense it. Bypass valve 60 may be provided to bypass cooling fluid around tube 54, if desired.
From sump 55 condensed refrigerant flows through line 64 and line 65 and is discharged into evaporator pan 20. Lines 66 and 67 connect to evaporator pan 20 adjacent the bottom thereof for the purpose of assuring a drainage of the pan irrespective of the angular position of the absorption machine. It will be observed that a pair of each of lines 66 and 67 should be provided at both ends of pan 20 in order to take care of both pitch and roll conditions of the vessel. Lines 66 55a 67 drain substantially all of the refrigerant from pan 2t preventing refrigerant accumulation therein. Lines 66 and 67 discharge into refrigerant storage tank 68 thereby assuring that refrigerant will not be emptied from pan as into absorber it) under severe conditions of pitch and roll.
Pump 69 forwards refrigerant from storage tank 68 back through line '74 to refrigerant distributor 22 for respraying over heat exchange tubes 21 resulting in vaporization of refrigerant due to heat absorbed in the evaporator section from tlhe heat exchange fluid flowing through tubes 21 and cooling of the liquid refrigerant in the evaporator due to the low pressure in the absorber. It will be understood that absorber lit is in open communication with evaporator 11 through eliminators 23 and through spaces provided between the bottom of pan 2%) and the sides of shell 12 at various suitable locations.
vaporization or evaporation of refrigerant in evaporator 11 results in cooling of the heat exchange fluid in heat exchange tube 21 due to the heat which is removed from the heat exchange fluid to convert the refrigerant from a liquid state to a vapor state. Consequently, the fluid in heat exchange tubes 2-1 is continuously cooled by heat exchange with refrigerant in the evaporator. This cooled fluid is then transmitted to suitable remotely located heat exchangers through line 72 for cooling or dehumidification of the desired areas. The warmed fluid which has removed heat from the desired areas is then returned through line 71 to heat exchange tubes 21 for recooling.
The heat of dilution and condensation of the absorbent solution is removed from the absorber by passing sea Water or other cooling fluid through inlet 61 to tubes 13 and through outlet 6-2 Where the cooling fluid is passed to heat exchange tubes '54 of the condenser.
Capacity control of the absorption refrigeration machine described may be obtained through control of the concentration of strong solution returned from generator 34 to absorber 10. The concentration of the absorbent solution in turn is controlled by the steam input through line 36 by regulation of steam control valve 74. Bulb 73 or other suitable temperature sensing means is secured to outlet line 72 of evaporator 11 and senses the leaving water temperature from the evaporator. When the heat load to be rejected increases, the leaving Water temperature tends to rise. This rise is sensed by bulb 73 which opens steam valve 74 to a position such that it passes more steam to the generator. The additional steam supplied to the generator concentrates the absorbent to a higher degree which in turn increases the capacity of the refrigeration system by increasing the quantity of refrig erant absorbed by the more concentrated solution in the absorber.
To prevent solidification and consequent blocking of heat exchanger 31 by over-concentrated absorbent being cooled therein below the temperature at which it solidifies, a suitable bypass valve 42. may he provided as described in Leonard application Serial No. 2,203, filed January 13, 1960. A purge line 76 and suitable purge 78 are provided adjacent the lower portion of absorber It) to remove noncondensibles from the refrigeration system.
In operation the present invention provides an absorption refrigeration machine and system which is capable of operating in a plurality of angular positions such as may be encountered due to pitching and rolling of a seagoing vessel. Such a system is particularly advantageous for air conditioning of a submarine where in addition to the usual pitch and roll conditions substantial listing or trim conditions may be experienced. Further advantages of the refrigeration system described reside in its relatively noiseless operation and its rapid recovery rate in the event of extremely severe rolls. An additional important advantage of a refrigeration machine of the type described lies in the fact that neither the refrigerant nor the absorbent are noxious, toxic or otherwise dangerous to personnel so that leakage which might result from damage to the machine does not present a serious personnel hazard.
Referring particularly to the left hand portion of FIG- URE 2, there is shown a construction of a heat exchanger 69 embodying the instant invention. Heat exchanger 69 may comprise either a condenser section or an absorber section of the absorption refrigeration machine previously described. It will be understood that appropriate modifications in the physical construction of the heat exchanger will be made to especially adapt it to its intended purpose. For purposes of illustration heat exchanger 69 has been shown to comprise a condenser of the type illustrated at 52 of FIGURE 1.
Heat exchanger 69 comprises a shell 70, an inner tube sheet 71 and an outer tube sheet 72. Inner tube sheet "7'1 and outer tube sheet 72 are spaced from each other and secured to shell 70 and to each other by a weld 73. A chamber 74 is formed between the spaced tube sheets 71 and 72. It will be understood that other suitable constructions for providing a chamber between a pair of adjacent tube sheets may be employed for the purposes of this invention and the illustrated construction comprises merely one of a number of possible embodiments of this invention.
A passage 75, which is herein shown as being formed in outer tube sheet 72, communicates with the interior of chamber 74. A suitable drain valve 76 and drain line 77 is secured to tube sheet 72 and serves to withdraw fluids within chamber 74 when the valve 76 is opened. Another passage 78, which in the illustrated embodiment, is also formed in outer tube sheet 72, communicates with a valve 79 and a pressure gauge 80. A line $1, which may comprise a sight glass, is shown connected with the other end of valve 79 and may have appropriate indicia engraved thereon.
A plurality of heat exchange tubes 82 extend through inner tube sheet 71 and chamber 74 into outer tube sheet 72. These tubes are appropriately secured and sealed in leak-tight engagement with each of the tube sheets by a rolling operation performed at 83; and 34 respectively. The ends of tubes 32 are open and communicate with water box 85 formed by header 86. Cooling fluid such as sea water is withdrawn from or passed to water box 85 through line 87 depending upon the direction of flow of the cooling fluid through heat exchange tubes 82. It will be understood that a similar construction is desirably formed at the other end of shell 70 for a like purpose.
In operation, the absorption refrigeration machine ernbodying a heat exchanger of the type described is assembled and valves 76, 79 are opened to drain any condensed moisture or other fluids which may have accumulated in chamber 74. Valve 76 is then closed and a suitable, compatible, substantially incompressible fluid such as octyl alcohol, in its liquid state, is poured into chamber 74 through line 81 at which time valve 7% is open. Chamber 74 is filled with the desired liquid to a level at least above that of the highest tube 82 and preferably to a level somewhere in line 31, which is located above pressure gauge 86 and valve 79. Valve 79 may then be closed after assuring that no trapped compressible fluids remain in the system such as in pressure gauge 80. Thereafter, variations of pressure within chamber 74 will be transmitted through the incompressible fluid and passage 78 to pressure gauge St where they will become observable.
If a leak is experienced between one of the tubes 82 and outer tube sheet 72, the pressure of cooling fluid, such as sea water, will be transmitted to the incompressible fluid in chamber 74 and manifest its existence by an abnormal rise in pressure on gauge 80. If on the other hand, a leak develops between inner tube sheet 71 and one of the heat exchange tubes 82, the incompressible fluid in chamber 74 will find its way through the leak into the interior of heat exchanger 69 due to the relatively low pressure maintained therein. Consequently, a leak of this type will manfiest itself by an abnormally low pressure reading on gauge 89. If the fluid in chamber 74 3,1 eases is selected to be compatible with the contents of the absorption refrigeration machine of which heat exchanger 69 is a part, no adverse effect need result from leakage of the fluid into the heat exchanger.
An additive which is commonly present in the absorption refrigeration machine such as octyl alcohol (2-ethyln-hexanol) makes a desirable liquid with which to fill chamber 74. Under these conditions leakage of octyl alcohol into the absorption refrigeration machine does not cause corrosion or have a deleterious effect on the performance of the refrigeration system, while at the same time the liquid octyl alcohol tends to form a liquid seal against the entrance of vapors or other foreign materials which might find their way into the absorption refrigeration machine.
While pressure gauge 80 has been shown by way of example as a convenient means for observing abnormal changes in pressure in chamber 74 which are indicative of leaks between a tube and its associated tube sheet, the
pressure gauge may be omitted if desired. Instead, valve A 79 may remain open and leaks detected by simply observing abnormal changes in the pressure or level of octyl alcohol in the chamber by means of sight glass 81. Under these circumstances, it is preferable to employ a vented plug 88 in the top of sight glass 81 to substantially prevent the ejection of large quantities of octyl alcohol from the top of sight glass 81 in the event of a large leak between outer tube sheet 72 and tubes 82.
Referring now to the right hand portion of FIGURE 2, there is shown a further modified form of indicator mechanism 90. Indicator mechanism 90 comprises a bellows 92 disposed within a can 91. Bellows 92 is sealingly attached at one end adjacent the bottom or side of can 91 which is desirably cylindrical in cross-section. An indicator bar 93 having appropriate indicia thereon is secured adjacent the upper portion of bellows 92 and projects through an aperture in can 91 to permit visual observation of the position of the bellows. The underside of bellows 92 is in communication with inner chamber 74 through passage 73 in outer tube sheet 72. Consequently, changes in pressure in inner chamber 74 are manifested by upward or downward movement of bellows 92 and indicator bar 3 from a predetermined normal range of positions.
It will be observed that by the practice of the invention, a simple and reliable indicator means is provided by which relatively small leaks between a tube sheet and its associated heat exchange tubes may be indirectly detected in spite of the relative difficulty of direct observation. Such an arrangement is particularly desirable for use in seagoing vessels such as submarines wherein the tubes and tube sheets may be subjected to severe mechanical stresses and strains or wherein they are exposed to high submergence pressures which may cause small leaks to develop into larger ones which seriously impair or render inoperative an absorption refrigeration system.
While preferred embodiments of this invention have been shown and described in detail for purposes of illustration, it will be understood that the invention may be otherwise embodied within the scope of the following claims.
1. In an absorption refrigeration machine comprising an absorber, a generator, a condenser and an evaporator operatively connected in a refrigeration circuit, said condenser and said absorber each comprising heat exchangers, the improvement comprising at least one of said heat exchangers having a pair of tube sheets at one end thereof, each of said tube sheets being spaced from each other and forming a chamber therebetween, each of a plurality of heat exchange tubes being sealingly engaged with both of said pair of tube sheets, a substantially incompressible fluid filling said chamber to a level above said tubes, and m a s re ponsive to both increased and decreased changes in pressure exerted on said fluid to indicate leakage at said chamber.
2. An absorption refrigeration machine as defined in claim 1 wherein the absorption refrigeration machine is of the type utilizing a hydroscopic absorbent solution comprising lithium bromide and wherein said substantially incompressible fluid comprises octyl alcohol.
3. An absorption refrigeration machine as defined in claim 1 wherein said means responsive to pressure comprises an indicator responsive to the level of fluid in said chamber to detect leakage to and from said chamber due to pressure being exerted on said liquid.
4. An absorption refrigeration machine as defined in claim 1 wherein said means responsive to pressure comprises a pressure gauge.
5. An absorption refrigeration system comprising an absorber, an evaporator, a generator, and a condenser, said absorber and said condenser comprising heat exchangers, the improvement comprising one of said heat exchangers having an inner tube sheet and an outer tube sheet, said tube sheets both being disposed in spaced relationship at one end of said heat exchanger, a plurality of heat exchange tubes in said heat exchanger having open portions adapted to pass a heat exchange fluid, said plurality of heat exchange tubes passing through said inner tube sheet and being in sealed engagement therewith, said plurality of tubes also passing into said outer tube sheet and being in sealed engagement therewith, a fluid header disposed about the open portions of said heat exchange tubes, means including said spaced inner and outer tube sheets defining a substantially closed chamber between said tube sheets, inlet means communicating with said chamber to admit a substantially incompressible fluid into said chamber, and means to indicate the pressure exerted on the fluid in said chamber to indicate leakage of said chamber at the joints between said heat exchange tubes and said tube sheets.
6. An absorption refrigeration system as defined in claim 5 wherein said heat exchanger comprises an absorber vessel in an absorption refrigeration system adapted for use aboard a submarine vessel and wherein said fluid header is adapted to be exposed to submergence pressures.
7. An absorption refrigeration system as defined in claim 5 wherein said heat exchanger comprises a condenser vessel in an absorption refrigeration system adapted for use aboard a submarine vessel and wherein said fluid header is adapted to be exposed to submergence pressures.
8. An air conditioning system for use in a submarine vessel comprising a refrigeration machine, said refrigeration machine comprising a heat exchanger of the tubeand-sheet type, said heat exchanger comprising an inner tube sheet and an outer tube sheet, said tube sheets both being disposed in spaced relationship at one end of said heat exchanger, a plurality of heat exchange tubes in said heat exchanger having open portions adapted to pass a heat exchange fluid, said plurality of heat exchange tubes passing through said inner tube sheet and being in sealed engagement therewith, said plurality of tubes also passing into said outer tube sheet and being in sealed engagement therewith, a fluid header disposed about the open portions of said heat exchange tubes, said fluid header being adapted to pass sea water at high pressures when said vessel is submerged, means including said spaced inner and outer tube sheets defining a substantially closed chamber between said tube sheets, inlet means communicating with said chamber to admit a substantially incompressible fluid into said chamber, and means responsive to deviation from normal pressure exerted on the fluid in said chamber to indicate leakage of said chamber at the joints between said heat exchange tubes and said tube shee.
9. A heat exchanger comprising an inner tube sheet and an outer tube sheet, said tube sheets both being disposed in spaced relationship at one end of said heat exchanger, a plurality of heat exchange tubes in said heat exchanger having open portions adapted to pass a heat exchange fluid, said plurality of heat exchange tubes passing through said inner tube sheet and being in sealed engagement therewith, said plurality of tubes also passing into said outer tube sheet and being in sealed engagement therewith, a fluid header disposed about the open portions of said heat exchange tubes, means including said spaced inner and outer tube sheets defining a substantially closed chamber between said tube sheets, inlet means communicating with said chamber to admit a substantially incompressible fluid into said chamber and means to indicate deviation from normal pressure exerted on the incompressible fluid in said chamber to indicate leakage of said chamber at the joints between said heat exchange tubes and said tube sheets.
References Cited in the file of this patent UNITED STATES PATENTS 1,948,550 Voorheis Feb. 27, 1934 2,658,728 Evans Nov. 10, 1953 2,743,089 Gardner et a1 Apr. 24, 1956 2,893,701 Bell July 7, 1959 FOREIGN PATENTS 1,128,665 France Jan. 9, 1957