US3161233A - Heat exchanger with variable configuration - Google Patents

Description

Dec. 15, 1964 J. E. AHERN HEAT EXCHANGER WITH VARIABLE CONFIGURATION 4 Sheets-Sheet 1 Filed March 20, 1961 INVENTOR. JOHN E. AHERN BMW ATTORNEY Dec. 15, 1964 J. E. AHERN HEAT EXCHANGER WITH VARIABLE CONFIGURATION 4 Sheets-Sheet 2 Filed March 20, 1961 n QE INVENTO N E. AH N ATTORNEY w OE Dec. 15, 1964 J. E. AHERN 3,161,233

HEAT EXCHANGER WITH VARIABLE CONFIGURATION Filed March 20, 1961 4 Sheets-Sheet 3 "Hummnmnm FIG. 3

INVENTOR. JOHN E. AHERN ATTORNEY Dec. 15, 1964 J. E. AHERN 3,161,233

HEAT EXCHANGER WITH VARIABLE CONFIGURATION Filed March 20, 1961 4 Sheets-Sheet 4 INV EN TOR.

6 L8 47 JOHN E. AHERN ATTORNEY United States Patent Ofitice 3,161,233 Patented Dec. 15, 1964 efficient.

3,161,233 IEAT EXCHANGER WETH VARIABLE tCGNFIGURATIGN John E. Ahern, Granada Hiils, Caiif., assigner to The Marquardt Corporation, Van Nuys, Calif., a corporation of California Filed Mar. 20, 1961, Ser. No. 97,4175 3 Claims. (Cl. 165 101) This invention relates to a heat exchanger with variable configuration, and more particularly to a heat exchanger operable over a wide range of conditions under which inlet temperature and inlet pressure of a fluid to be cooled increase by a considerable amount.

A heat exchanger for cooling at fluid having a relatively low inlet pressure and temperature should preferably have a large face area and a short flow depth for the fluid. However, when the inlet fluid temperature increases, a small face area and a long flow depth is more Of course, a long flow depth results in a considerably higher pressure loss through the heat exchanger and the higher pressure loss must be permissible because of an increase in inlet pressure. It has been proposed to supply an aircraft with liquid hydrogen as a source of fuel and to utilize the hydrogen to continually liquefy ambient air obtained from a scoop to provide an oxidant for the hydrogen. The ambient air entering such a cooling system would have a low inlet temperature and pressure at approximately sea level operation of the aircraft but at high altitudes and high flight speeds, high inlet temperature and pressure conditions would prevail. Thus, the heat exchanger arrangement which would be optimum for sea level flight conditions would not be the most suitable for the high altitude flight where a much larger air pressure loss is permissible and the air must be reduced in temperature by a substantially greater degree.

The heat exchanger of the present invention makes use of a baffling system for varying the configuration of the heat exchanger so that it presents a large face area to the air flow and a short air flow depth at sea level operation. At high altitude operation, the battles are moved into a position wherein a small face area and a long air flow depth is provided. Thus, for a fixed arrangement of heat exchanger tubing, the heat exchanger can operate over a wide range of conditions with increased performance eliiciency. When the baffles for the heat exchanger are positioned to present a small face area, the length of flow through the heat exchanger will be substantially greater and a lower refrigerant flow will provide the same airside performance as when the maximum face area configuration is used.

in the invention, the air is obtained from ascoop located exteriorly of a fuselage, and a pair of baffles can be moved to cause the air to flow serially over three separate sections of the heat exchanger under high. altitude flight conditions. For sea level operation, the three sections present one large face area of less depth since the baflies do not divide the air flow. When higher inlet temperatures and pressure are encountered, the large side face area is closed off and air is introduced to the end of I the heat exchanger to provide a substantially longer flow depth through the heat exchanger for the air. With the greater flow depth, the velocity of air through the exchanger will be sufiiciently higher because of the higher inlet pressure, and this will result in increasing the airside heat transfer coeflicient and the performance efliciency of the heat exchanger. Also, lower coolant flows can be utilized because of this high airside eificiency. For maximum performance, cross counter flow of the fluids is maintained by the use of suitable valving.

It is therefore an object of the present invention to provide a heat exchanger of variable configuration in which optimum performance is available under conditions of low available pressure loss and inlet temperature and at conditions of high available pressure loss accompanied With high inlet temperature.

Another object of the present invention is to provide a heat exchanger in which the configuration can be changed by movable bafiiing to provide a large face area and short flow depth or a small face area and long flow depth.

Another object of the invention is to provide a heat exchanger in which the air flow path through the heat exchanger can be varied in accordance with inlet temperature and available pressure loss and in which the valving of the heat exchanger can provide for cross counter flow of the two fluids regardless of the air flow path.

A further object of the invention is to provide a heat exchanger with variable configuration which is suitable for liquefying air obtained from the atmosphere during flight with a low temperature liquid fuel, such as hydrogen, and which has optimum performance over a large range of flight conditions.

These and other objects of the invention not specifically set forth above will become readily apparent from accompanying description and drawings in which:

FIGURE 1 is a perspective view of the first form of the invention showing the batfies for changing the heat exchanger configuration.

FIGURES la and 11) show the position of the valves for the configuration of FEGURE 1.

FIGURE 2 is a vertical section along line 2-2 of FIGURE 1 showing the three sections of the heat exchanger and the bafiies in position to provide a large face area and short flow depth for the air.

FIGURE 3 is a partial view of the manifold of the heat exchanger of FIGURE 1 showing the direction of coolant flow when the baffles are moved to provide a small face area and a long flow depth.

PEGURES 3a and 3b show the position of the valves for the configuration of FEGURE 3.

FIGURE 4 is a vertical section similar to FIGURE 2 showing the position of the baffles for a small face area and a long flow depth.

FEGURE 5 is a section along line 55 of FIGURE 2 showing the construction of one of the baflies.

FIGURE 6 is an enlarged sectional View, partly in elevation, of one of the valves for controlling the coolant flow to the various sections of the heat exchanger.

FIGURE 7 is a sectional view along line 7--7 of FIG- URE 6 showing the passages of the inlet coolant valve during normal sea level operation.

. FIGURE 71: is a sectional view similar to FIGURE 7 showing the passages of the outlet coolant valve during normal sea level operation. p

FEGURE 8 is a sectional view along line 8-8 of FIG- URE 6 showing the paths through the inlet coolant valve during high speed, high altitude operation.

- tained within the fuselage.

, FIGURE 8a is a sectional view similar to FIGURE 8 showing the paths through the outlet coolant valve during high speed, high altitude operation.

Referringto the form of the invention illustrated in FIGURE 1, a passage has an inlet 21 for receiving the fluid to be cooled, such as ambient air. The inlet 21 can be in the form of an air scoop located exteriorly of an aircraft fuselage and the passageportion 22 is con- Passage 20' contains an enlarged bend portion 23 across which extends heat exchanger 24, and air discharged from the heat exchanger is directed by passage portion 22 to the outlet end25. In the event that the air or other fluid discharged from heat exchanger 24 is to be liquefied, the outlet end 25 will connect with additional heat exchangers (not shown) for this purpose.

The heat exchanger 24 is comprised of three separate sections 27, 28 and 29 and each of the sections has four separate passes 30, 31, 32 and 33 across the enlarged passage portion- 23. Upper manifolds 34, 35 and 36 connect with the end-of passes of each of the sections 27, 28

and 29, respectively, and lower manifolds 37, 38 and 39 connect with the end of the passes-33 for each of the sec- p tions 27, 28 and 29, respectively; The tubes of the multiple passes of each section are in series 'a'ndth'e passes are connected together at-the ends of the heat exchanger by bent sections 40, such as illustrated for connecting the passes 31 and 32 of all the sections. The inlet passage '45 which conducts the coolant, such as liquid hydrogen, to the heat exchanger divides into passages 46, .47 and 48 which connect, respectively, with the upper manifolds 34, and 36 of the heat exchanger section. A valve 49 connects the passage with the various branch passages '46, 47- and 48 and this valve determines the direction of flow into the various branch passes. In a similar manner, the outlet passage 50 is connected 'at valve 51 with branch passages 52, 53 and 54 which'com'municat'e with lower manifolds 37, 38 and 39, respectively. The setting of the valve 51 determines the directio'n of vflow in the various branch passages 52, 53 and 54.

. 4 by a flexible link 66 in order to move the baflle along the tracks. The presence of the movable bafiles 57 and 63 make it possible to vary the configuration of the heat exchanger 24 to permit air entering the passage 20 to pass through all the heat exchanger sections simultaneously to provide a large face area and a short air flow"depth or to pass through the sections one after another to provide a small face area and a long air flow depth.

In FIGURE 2, the bafile 57 is located along the bottom of the duct and the battle is located altirig the top sur= face of the turn portior'i 23 so that neitherhafil'e inter feres with, the flow of the air through the assage 2th Thus, the air flows through the sections 27, as, and 29 of the heat exchanger 'simultarieousl'y, and the heat x= changer provides a large face area and a short flow depth: In FIGURE 4, the baffle 57 has been moved to extend between the bottom of thep'assage 20 and the junction between sections 27 and 28 so that the baflle 57 extends completely across the passage; Also, thebafile '63 has been moved toextend between upper surface of passage 20 and the .jllnCtlOll between heat exchanger sections 23 and 29.-1 Thus, all of the air enteringthe passagego is diverted by bafile" 57 through" the heat exchanger 27. and is then diverted by bafiieifi, through the section 28 and finally, all the aiiflows through theheat exchanger sec tion 29. Therefore, the heat exchanger. 24 presents to the air a small face area, namely that of an individual section, and a long now depth, namely the combined flow depth of all three heat exchanger sections;

It is understood thatthe position of the bane; 57 and 63 in FIGURE 2 Will be utilized both the fillet temperature; and pressure are relatively low so that suffi cient cooling can take place through the "depth of one section and the pressure drop through this on'e' deptli is compatible with the low inlet pressure. When them .let temperature and pressure greatly increases the hatlies 57 and 63 aremoved to the positions of '4 so that theair in serially transversing the three heat ex- When the air flow is unobstructed through the turn to provide a long flow depth and a small face area. Each side of the turn portion 23 of the passage 20 is equipped with a channel track 56 which extends along the inlet portion and curves upwardly to terminate at the location between the sections'27 and 28 of the heat exchanger. A flexible bafiie 57 is supported betweenthe channels 56 by a plurality of rods 59 having rollers 58at opposite ends which are guided by the channels. The bafiles can be made of'corrugated sheet material in order to conform to the changing shape of the channels 56 and the rods 59 extendbetween spaced corrugationstsee FIGURE. 5),

A-linear actuator, 60 of any .well known suitable construction canbe connected by a link 61 with the bafile57in order to move the same along the channel tracks 56.:

A second set of channel tracks 62 are located downstream of the heat exchanger 24 on opposite side's of, the

I flight conditions.

changer sections can still be reduced to the desired outlet temperature, The passage of the air through these three sections results in a substantially increased pressure loss but this pressure "can be accepted because of the increased inlet pressure available. As previously discussed,

the configurations of FIGURES *2 and 4 ar'e 'suitable for use in an enginewhi hiiquefies ambient air with a low temperature supply of fuel, such ashydrogen, 'Theconfiguration of FIGURE 2 is p artic'ulanly suitable to sea levelv static operation while, the/configuration of FIG- URE 4 is particularly suitable to high altitude high speed In order to obtain maximum performance from both configurations of theheat exchanger, across counter flow arrangement of the'fluids for both configurations is pro \fidedand this is accomplished bythe yalve structures of valves 49 and 51." Referring to FIGURE. '6, the struc ture of-valve 49"is illustrated and it is understood that the valve v51 hasv an identical. structure; The valve 49 comprises -a-:casing "containing a'vallve plugfll. The: i

passages45, 46, 47, and 48 terminate at openings spaced 90 degrees around the casing 70. At one cross section, illustnated; in FIGURE 7, the plug '71 ,contains'four cross passages 72', L73, 74, -;and which connect the passages 1. i45481with one another; at acentral terminal 76' when the duct 20. v The forward portions of these tracks commence at the: outer side of section 27 and curve'along the upper" surface of turnportion -23. T ea t portions of the tracks: 62 curve across the duct20 '-and terminate at a location between the heat exchanger sections. 28 and 29. A

flexible baflle 63, similar in construction to baflie"5,7, is v -'movablealong the tracks 62on'rollers 64 connected to? the end of shafts extending through the .corruga'tioni A1 linear actuator '65 can be-locatedat theendofi one of the channel tracks 62 and is connected withthe bathe 63 j external ports; 3

,valve .71 is positionedfto the left. Similarly, when the alve plug 71' of valve' -51} is positioned; to the left,-cross passages '72, 73 74', and 75' connect the I passages 50', 52, 53, jand54 with one anothenat the'centralterminal 76 Whn the valve plugs 71fand 71'-of.. valve-49and 51,.

respectively, aremoved totheright in :FIGURE. 6, the section illustrated in FIGURES 8.a:nd18a,align with tha In FIGURE 8, plug 71 of valve 49 con-- tains two paseages 80' and- :81 which are, separate fr'om v one another, and-"passage80 connects the passages 45 and'48 'while the passage 81connects passages 46' and 4,7.

H 3 In FIGURE 8a, the plug 71 of valve 51 contains passages 80 and 81' and passage 80' connects between passages 50 and 52 while passage 81' connects between the passages 53 and 54. The plugs 71 and 71' for the valves 49 and 51, respectively, are each connected by a shaft 83 to a linear actuator 84 which serves to move the valve plugs between the positions shown in FIGURES 7 and 8. A bellows S5 prevents leakage from the casing 70 and a pressure equalizing vent 86 prevents trapped fluid from interfering with the movement of the plugs. Any suitable signal can be introduced to the actuator 84 through lines 87 to move the valve plugs 71 and 71 into one of their two operating positions.

In the operation of the heat exchanger with the baflles in the position of FIGURE 2, the plugs 71 and 71' of the valves 49 and 56 are in the position shown in the FIG- URES 7 and 7a, respectively, to provide for cross counter flow through the sections of the heat exchanger 24. The low temperature coolant is introduced through passage 45 equally to all of the passages 46, 47, and 48 through the passages 72-75 in the valve plugs 71. Manifolds 34, 35, and 36 introduce the coolant to the first passes 30 of the heat exchanger sections 27, 28 and 29, respectively. The coolant flows serially through passes 30, 31, 32, and 33 of each of the heat exchanger sections and the manifolds 37, 38, and 39 receive the discharge coolant. Passages 52, 53, and 54 direct the discharged coolant through passages 73, 74', and 75 of valve 51 to the outlet passage 50.

When liquid hydrogen or other fuel is utilized as the coolant, the outlet passage 5!) can lead directly to a propulsion means for an aircraft in which the hydrogen can be combusted with an oxidant to produce thrust. Since the coolant flows in a cross counter flow relationship with the incoming air with the valve arrangement of FIGURES 7 and 7a, an efiicient heat transfer relationship exists wherein the warmest air encounters one side of the heat exchanger and the coldest coolant enters the other side. Thus, at sea level flight conditions, a large face area and a short air flow depth can be accompanied by cross counter flow of coolant.

In the operation of the heat exchanger with the bafilles in the position of FIGURE 4, plugs 71 and 71' of the valves 45 and 5t) are in the position shown in FIGURES 8 and 8a, respectively, to provide for cross counter flow through the sections of the heat exchanger. The low temperature coolant is introduced through passage 45 and all of the coolant is directed through valve passage 86 and passage 48 to the manifold 36 of section 29. As the coolant flows serially through the passes 30-33 of the section 29, it will be flowing in cross counter flow relationship with the air entering this section and flowing in the direction of arrow 9%) (see FIGURE 4). The coolant discharged from the section 29 is directed by passage 54 and valve passage 81 to the passage 53 entering the manifold 38 for the heat exchanger section 28. A coolant then flows through the four passes of heat exchanger 28 and is discharged at manifold 35, which is connected by passage 47 with passage 46 through valve passage 81 of valve 49. Since all the air is flowing in the direction of arrow 91 (see FIGURE 4) over the heat exchanger sec-- tion 28 and since the coldest coolant enters the rear manifold 38, the cross counter flow relationship is maintained in the section 28. All of the coolant is then directed by passage 46 through the manifold 34 to heat exchanger section 27. The coolant flowing through the four passes of section 27 is discharged at the manifold 37 and then is conducted through passage 52 and valve passage 80' of valve 51 to the outlet passage 50. The direction of the air flow over the section 27 is illustrated by arrow 92 (see FIGURE 4) so that it is apparent that the cross counter flow of the coolant is still maintained since the coldest fluid enters the manifold 34.

. It is understood that suitable control means can be utilized to correlate the positions of the valve plugs 71 i and 71' of the valves 49 and 51 with the positions of the baflles 57 and 63. When the baffles are moved into the airstream, as illustrated in FIGURE 4, to provide a small face area and a long air flow depth, the plugs 71 and 71' are moved to the right in FIGURE 6 to provide the flow paths shown in FIGURES 8 and 8a. On the other hand, when the baffles are in their stored position, as illustrated in FIGURE 2, the actuator 84 will maintain the plug 71 and 71 in the position corresponding to FIGURES 7 and 7a so that cross counter flow will be maintained with a large face area and a short flow depth. The number of passes of each of the heat exchanger sections can be varied in accordance with any desired operational char acteristics and also the numbers of sections which make up the heat exchanger can be varied in conformance with any desired characteristics. It is understood that because of the higher pressure drop across the configuration of FIGURE 4, the small face area of this configuration can provide the same mass flow as the large face area of FIG- URE 2 which operates under a smaller pressure differential. Also, since the temperature entering the configuration of FIGURE 2 is lower than that entering the configuration of FIGURE 4, the greater amount of cooling in FIGURE 4 can provide a discharge temperature substantially the same as that leaving the configuration of FIGURE 2.

It is apparent that various other types of heat exchanger arrangements can be utilized where the heat exchanger is divided into sections and baffling is used to conduct the air in sequence to heat exchanger sections when a long air depth flow path is required. Any suitable valving for the cooling and various actuations for the shutters and battles can be used. Various other modifications are contemplated by those skilled in the art without departing from the spirit and scope of the invention as hereinafter defined by the appended claims.

What is claimed is:

l. A heat transfer device having a configuration variable with operating conditions comprising heat exchanger means located transversely within a duct through which flows a fluid to be cooled, said heat exchanger means comprising a plurality of heat exchanger sections located side by said in a plane transversely across said duct, a first movable baflle located within said duct upstream of said heat exchanger means and located along the surface of the duct to provide a configuration of large face area and short flow depth, a second movable baflle located within said duct downstream of said heat exchanger means and located along the surface of the duct to provide a configuration of large face area and short flow depth, said first and second baffles permitting all of the fluid in said duct to pass through the full face area of said heat exchanger means when in position along the surface of said duct, means for moving said first and second baffles inwardly from the duct surface to reverse the flow of air through adjacent sections and pass all the fluid flow serially through each section to provide a configuration of small face area and long flow depth, inlet and discharge passages for a coolant utilized in said heat exchanger means, and valve means in said inlet and discharge passages for regulating the flow of coolant to said sections to maintain cross counter flow of the coolant for both configurations, said heat exchanger means comprising three sections, said valve means in said inlet passage distributing the coolant equally to said three sections on the downstream side and said valve means in said discharge passage discharging the coolant equally from the upstream side of. the heat exchanger sections when both said first and second battles are in position along the surface of said duct to provide a large face area and a small flow depth, said valve means in said inlet and discharge passage introducing fluid to the first section on the downstream, then to the second section on the upstream and finally to the third section on the downstream side to maintain cross counter flow when the first and second baffles are in their inward positions to provide a small face area and a long flow 7 depth, each of said valve means comprising avalve plug slidable in a valve housing connected with passages leading to the heat exchanger sections, each of said valve plugs containing two separate sets of valve passages, the first set of valve passages in each plug being operative simul-. taneously for one configuration of ,said heat exchanger means and the second set being operative simultaneously for the other configuration of said heat exchanger means.

2. A heat transfer device as defined in claim '1 having actuator means for moving the first andsecond bafiles and having valve actuator means for moving said valve plugs upon change in configuration of said bafles.

3. A heat transfer device as defined in claim 2 wherein said second baffle in its inwardly extending position extends between the :upper surface and .said second and third sections.

the junction between References Cited in the file ofthis patent UNITED STATES PATENTS 1,634,903 l Hodgkinson "July 5,1927

I 1,922,220 Sprag ue Aug. 15, 1933 2,213,324 Niemitz Sept. 3, 1940 2,487,484 Sirripelaar ..Nov. 8, 1949 2,930,593 Blum Mar. 29, 1960 FOREIGN PATENT S 7 1,067,337 France Jan. 27, '1954

Claims (1)

1. A HEAT TRANSFER DEVICE HAVING A CONFIGURATION VARIABLE WITH OPERATING CONDITIONS COMPRISING HEAT EXCHANGER MEANS LOCATED TRANSVERSELY WITHIN A DUCT THROUGH WHICH FLOWS A FLUID TO BE COOLED, SAID HEAT EXCHANGER MEANS COMPRISING A PLURALITY OF HEAT EXCHANGER SECTIONS LOCATED SIDE BY SAID IN A PLANE TRANSVERSELY ACROSS SAID DUCT, A FIRST MOVABLE BAFFLE LOCATED WITHIN SAID DUCT UPSTREAM OF SAID HEAT EXCHANGER MEANS AND LOCATED ALONG THE SURFACE OF THE DUCT TO PROVIDE A CONFIGURATION OF LARGE FACE AREA AND SHORT FLOW DEPTH, A SECOND MOVABLE BAFFLE LOCATED WITHIN SAID DUCT DOWNSTREAM OF SAID HEAT EXCHANGER MEANS AND LOCATED ALONG THE SURFACE OF THE DUCT TO PROVIDE A CONFIGURATION OF LARGE FACE AREA AND SHORT FLOW DEPTH, SAID FIRST AND SECOND BAFFLES PERMITTING ALL OF THE FLUID IN SAID DUCT TO PASS THROUGH THE FULL FACE AREA OF SAID HEAT EXCHANGER MEANS WHEN IN POSITION ALONG THE SURFACE OF SAID DUCT, MEANS FOR MOVING SAID FIRST AND SECOND BAFFLES INWARDLY FROM THE DUCT SURFACE TO REVERSE THE FLOW OF AIR THROUGH ADJACENT SECTIONS AND PASS ALL THE FLUID FLOW SERIALLY THROUGH EACH SECTION TO PROVIDE A CONFIGURATION OF SMALL FACE AREA AND LONG FLOW DEPTH, INLET AND DISCHARGE PASSAGES FOR A COOLANT UTILIZED IN SAID HEAT EXCHANGER MEANS, AND VALVE MEANS IN SAID INLET AND DISCHARGE PASSAGES FOR REGULATING THE FLOW OF COOLANT TO SAID SECTIONS TO MAINTAIN CROSS COUNTER FLOW OF THE COOLANT FOR BOTH CONFIGURATIONS, SAID HEAT EXCHANGER MEANS COMPRISING THREE SECTIONS, SAID VALVE MEANS IN SAID INLET PASSAGE DISTRIBUTING THE COOLANT EQUALLY TO SAID THREE SECTIONS ON THE DOWNSTREAM SIDE AND SAID VALVE MEANS IN SAID DISCHARGE PASSAGE DISCHARGING THE COOLANT EQUALLY FROM THE UPSTREAM SIDE OF THE HEAT EXCHANGER SECTIONS WHEN BOTH SAID FIRST AND SECOND BAFFLES ARE IN POSITION ALONG THE SURFACE OF SAID DUCT TO PROVIDE A LARGE FACE AREA AND A SMALL FLOW DEPTH, SAID VALVE MEANS IN SAID INLET AND DISCHARGE PASSAGE INTRODUCING FLUID TO THE FIRST SECTION ON THE DOWNSTREAM, THEN TO THE SECOND SECTION ON THE UPSTREAM AND FINALLY TO THE THIRD SECTION ON THE DOWNSTREAM SIDE TO MAINTAIN CROSS COUNTER FLOW WHEN THE FIRST AND SECOND BAFFLES ARE IN THEIR INWARD POSITIONS TO PROVIDE A SMALL FACE AREA AND A LONG FLOW DEPTH, EACH OF SAID VALVE MEANS COMPRISING A VALVE PLUG SLIDABLE IN A VALVE HOUSING CONNECTED WITH PASSAGE LEADING TO THE HEAT EXCHANGER SECTIONS, EACH OF SAID VALVE PLUGS CONTAINING TWO SEPARATE SETS OF VALVE PASSAGES, THE FIRST SET OF VALVE PASSAGES IN EACH PLUG BEING OPERATIVE SIMULTANEOUSLY FOR ONE CONFIGURATION OF SAID HEAT EXCHANGER MEANS AND THE SECOND SET BEING OPERATIVE SIMULTANEOUSLY FOR THE OTHER CONFIGURATION OF SAID HEAT EXCHANGER MEANS.

Images