AU2006346920A1

AU2006346920A1 - Heat exchanger

Info

Publication number: AU2006346920A1
Application number: AU2006346920A
Authority: AU
Inventors: Pierre Bignon
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-08-02
Filing date: 2006-08-02
Publication date: 2008-02-07
Also published as: WO2008015314A1; EP2052200B1; DE602006012560D1; CN101568789B; ATE458977T1; US20090139700A1; EP2052200A1; CN101568789A; CA2659181A1; JP2009545718A

Abstract

A heat exchanger that is applicable to a pump and a system where a plurality of tubular elements or cores, each comprising a support cylinder or half-cylinder and at least one curved heat exchange plate. Each plate separating a first cavity from a second cavity where the first cavity contains a liquid and the second cavity receiving a coolant causing the thermal expansion or contraction of the plate. The heat exchanger according to the invention makes it possible to withstand high mechanical stresses. This design makes it better to withstand high pressures despite a large diameter of the cylindrical heat exchange plates without an increase to the thickness of these plates. The pressure being exerted on the tubular elements is primarily radially, more particularly from the outside to the inside for the thinnest cylindrical heat exchange plate in contact with the cavity containing cold coolant or air.

Description

WO 2008/015314 PCT/FR2006/001870 HEAT EXCHANGER The present invention relates to a heat exchanger used to produce a liquid under pressure by expanding, particularly inside a pump. 5 A hydraulic pump and a hydraulic system incorporating such a pump is known in the prior art, particularly from the patent applications FR-A-2 851 796 and WO-A-2004/079194. The hydraulic system comprises a hydraulic pump, a hydraulic fluid reservoir and a hydraulic motor. The hydraulic pump comprises at least one pumping piston and a drive piston 10 constituted by two stages of the same differential piston. The pumping piston delimits a pumping chamber inside a pumping cylinder and the drive piston delimits a drive chamber inside a drive cylinder. The pumping piston and the drive piston are connected to each other by kinematic connecting means in such a way that an increase in the volume of the drive chamber corresponds to a decrease in the volume of the pumping chamber and vice versa. 15 The pumping chamber is hydraulically connected to the system's hydraulic fluid reservoir and to the system's hydraulic motor, which is powered by the hydraulic pump. The drive chamber of the pump is hydraulically connected to a tubular heat exchange bundle. A liquid with a high thermal expansion coefficient is present in the drive chamber and the tubular heat exchange bundle. This liquid with a high thermal expansion coefficient 20 is alternately placed in a heat exchange relationship with a hot source and with a cold source. Thus, the liquid with a high thermal expansion coefficient is alternately subjected to thermal expansions and thermal contractions, which respectively increase the volume of the drive chamber while decreasing that of the pumping chamber, thus forcing the hydraulic fluid into the hydraulic motor then into the system's reservoir, or decrease the volume of the drive 25 chamber, thus causing the intake of the hydraulic fluid from the system's reservoir. A pumping effect is thus obtained by the alternating hydraulic fluid discharge and intake movements. The tubular heat exchange bundle is constituted by a bundle of vertical tubes closed at their lower end and communicating with each other at their upper end via a collector into 30 which opens a conduit that connects to the drive chamber.

WO 2008/015314 PCT/FR2006/001870 2 The tubular heat exchange bundle is placed inside an enclosure divided by a horizontal partition. This thermally insulating partition is pierced with holes, thus allowing each tube to pass through the partition from one side to the other while maintaining as good an impermeability as possible between the partition and the tubes. 5 The enclosure is thus divided into a lower chamber comprising a circulating cold coolant and an upper chamber comprising a circulating hot coolant. The tubular heat exchange bundle is thus alternately placed in a heat exchange relationship with the cold coolant and with the hot coolant by means of an up-and-down movement inside the enclosure. This up-and-down movement is produced by a jackscrew. 10 The alternating thermal expansions and contractions to which the fluid with a high thermal expansion coefficient is subjected result in alternating expansions and contractions of the tubular heat exchange bundle, which has a tendency to stretch each tube, eventually causing fatigue in the tubes constituting the tubular bundle. The object of the invention is therefore to propose a heat exchanger that makes it 15 possible to withstand high mechanical stresses for a long time. This object is achieved by a heat exchanger comprising a plurality of tubular elements or cores, each comprising: - a supporting cylinder or half-cylinder, - at least one curved heat exchange plate, each plate separating a first cavity from a 20 second cavity, the first cavity containing a liquid and the second cavity receiving a coolant which causes the thermal expansion or contraction of the plate and thus, respectively, the compression or expansion of the liquid in the first cavity - an outer retaining tube or half-tube. According to another feature, the liquid has a high thermal expansion coefficient. 25 According to another feature, the outer retaining tube or half-tube, the heat exchange plate or plates, and the supporting cylinder or half-cylinder have decreasing diameters. According to another feature, the first and second cavities are delimited, on one side, by one of the heat exchange plates, and on the other side by the supporting cylinder or half cylinder or the outer retaining tube or half-tube, the heat exchange plate(s), the supporting 30 cylinder or half-cylinder and the outer retaining tube or half-tube being concentric.

WO 2008/015314 PCT/FR2006/001870 3 According to another feature, each tubular element is closed at each of its ends by a flange, one of said flanges being adapted so as to allow the circulation of the liquid through the flange, the other flange preventing this circulation. According to another feature, each tubular element is closed at each of its ends by a 5 flange, at least one of said flanges being adapted so as to allow the circulation of the coolant or coolants through the flange. According to another feature, said flanges are adapted so as to allow the alternating circulation of a coolant heated by a hot source and a coolant cooled by a cold source. According to another feature, one of the heat exchange plates is equipped with a 10 plurality of first fins in contact with the liquid. According to another feature, one of the heat exchange plates is equipped with a plurality of first fins in contact with a coolant. According to another feature, one of the heat exchange plates is equipped with a plurality of second fins in contact with a coolant. 15 According to another feature, the various tubular elements are parallel to each other. According to another feature, the various tubular elements are held together by means of straps, each clamping a tubular element and attached to a threaded rod located between at least two tubular elements. According to another feature, the various tubular elements are held together by means 20 of straps, each clamping a tubular element and welded to each other. According to another feature, the various tubular elements are held together by means of straps, each clamping a tubular element and soldered to each other. According to another feature, each tubular element or core also comprises coolant conduits and spray nozzles adapted for spraying the coolant from the coolant conduits onto 25 the heat exchange plate. The invention also relates to a pump comprising: - a pumping piston adapted for actuating a control means via the movement of a fluid, - a drive piston connected by kinematic means to the pumping piston and adapted to being actuated by a movement of the liquid of the heat exchanger described above, 30 - a hot source, WO 2008/015314 PCT/FR2006/001870 4 - a cold source. According to another feature, the pump also comprises a bypass adapted for alternately feeding a coolant heated under pressure by the hot source and a coolant cooled at atmospheric pressure by the cold source into the tubular elements or cores of the heat 5 exchanger. The invention also relates to a system comprising: - the pump described above - a fluid reservoir - a control means. 10 Other features and advantages of the invention will emerge through the reading of the following detailed description of embodiments of the invention given merely as examples and in reference to the drawings, which show: - Fig. 1, a perspective view of a tubular element of the heat exchanger according to a first embodiment of the invention; 15 - Fig. 2, a cross-sectional view of the heat exchanger according to a second embodiment of the invention; - Fig. 3, a longitudinal sectional view of the heat exchanger according to a third embodiment of the invention; - Fig. 4, a cross-sectional view of the heat exchanger according to a fourth 20 embodiment of the invention. The identical references in the various figures designate similar or equivalent elements. The heat exchanger according to the invention comprises a plurality of tubular elements. Each tubular element comprises a supporting cylinder, at least one curved heat 25 exchange plate separating a first cavity from a second cavity, and an outer retaining tube. The first cavity contains a liquid and the second cavity receives a coolant which causes the thermal expansion or contraction of the plate, and thus the compression or expansion of the liquid of the first cavity. The heat exchange plate expands or contracts through contact with the coolant as a 30 function of the temperature of the coolant or coolants circulating through the heat exchanger, WO 2008/015314 PCT/FR2006/001870 5 thus causing a compression or expansion of the first cavity and hence of the liquid contained in that first cavity. The supporting cylinder and the outer retaining tube, which are composed of materials which are highly pressure resistant and can be poor thermal conductors, make it 5 possible to considerably limit the longitudinal expansion of the heat exchanger and thus to withstand high mechanical stresses longer than with the tubular heat exchange bundle known in the prior art. Fig. I represents a perspective view of a tubular element of the heat exchanger according to a first embodiment of the invention. 10 The heat exchanger comprises a plurality of tubular elements. In this first embodiment of the invention, each tubular element I comprises an outer retaining tube 6 containing two heat exchange plates 3c, 3f, respectively called the outer plate and the inner plate, which themselves contain a supporting cylinder 2. In this embodiment, the heat exchange plates 3c, 3 f are cylindrical. It is also possible to conceive of other 15 embodiments with one or more heat exchange plates which are curved but not cylindrical, or which form only a portion of a cylinder. The supporting cylinder 2 is for example a solid cylinder. The outer retaining tube 6, the two heat exchange plates 3c, 3f and the supporting cylinder 2 are substantially concentric. A first cavity, formed between the two heat exchange plates 3c, 3f, contains a liquid 20 4. Preferably, the liquid 4 has a high thermal expansion coefficient. The heat exchange plates allow a heat exchange between the coolant and the liquid 4. Thus, the liquid 4 expands or contracts as a function of the temperature of the coolant or coolants circulating through the heat exchanger, which causes the thermal expansion or contraction of the liquid 4. The compression or expansion created is even greater when the liquid does not have a high 25 thermal expansion coefficient and when the compression or expansion of the liquid 4 is merely due to the thermal expansion or contraction of the heat exchange plates. Two other cavities, respectively formed between one of the plates 3, and the outer retaining tube 6 and between the other plate 3 f and the supporting cylinder 2, respectively receive a hot coolant 5. and a cold coolant 5r in the liquid state.

WO 2008/015314 PCT/FR2006/001870 6 One of the objects of the heat exchanger according to the invention is to compress or expand the liquid 4 by means of a heat exchange between the plates and the coolants 5,, 5f, with the liquid nevertheless remaining constantly in the liquid state. In order to optimize this heat exchange, particularly in terms of duration, these plates 3c, 3 r are made of a material 5 having very good thermal conductivity, i.e. a metal. This also allows a good heat exchange with the liquid 4, which is particularly important when the liquid 4 has a high thermal expansion coefficient. In order for the heat exchanger to better resist fatigue, the outer retaining tube 6 and the supporting cylinder 2 are composed of highly pressure-resistant materials. Thus, to give a 10 nonlimiting example, they are made of carbon composite or filament-wound material or glass. These materials also offer the advantage of having poor thermal conductivity (for example between 0.034 W/mK and 0.045 W/mK), thus also making it possible to considerably limit heat losses to the outside of the heat exchanger. When not using a liquid with a high thermal expansion coefficient, heat losses can be limited by the use of a liquid 15 having poor thermal conductivity. High pressures are exerted, particularly on the heat exchange plate in contact with the hot coolant 5. This plate has a small thickness, typically between several tenths of a millimeter and several millimeters, depending on the nature of the metal constituting the plate and the size of the exchanger as a function of the application. Thus, the speed of the heat exchange is increased, but without weakening the plate, since the 20 pressure is exerted on it primarily radially during expansion (and preferably toward the inside of the tubular element), as opposed to primarily longitudinally as in the prior art. Thus, unlike the tubular heat exchange bundle known in the prior art, the heat exchanger according to the invention makes it possible to use heat exchange plates of larger diameter for the same thickness, which are much more resistant to higher pressures, making 25 it possible to broaden the applications. The diameter of the plates can be increased with a constant thickness, either because the pressure is exerted from the outside inward and not from the inside outward, or because the plates' resistance to mechanical stresses is facilitated by the outer retaining tube 6 or the supporting cylinder 2, which are made of high pressure resistant material. If the outer retaining tube 6 or the supporting cylinder is metallic, it is 30 necessary to protect them from heat in order to prevent them from expanding, which would WO 2008/015314 PCT/FR2006/001870 7 reduce the efficiency of the system. It is therefore conceivable to cool the outside of the retaining tube with the fluid 5 f. In a variant of embodiment, the outer retaining tube 6 and the supporting cylinder 2 are both made of metal, but the tubular element comprises at each of its ends a flange which 5 is welded or soldered to the tube in order to allow these two elements 2, 6 to withstand high pressures. Preferably, the hot coolant 5c is contained between the outer retaining tube 6 and the outer heat exchange plate 3c, while the cold coolant 5f is contained between the inner heat exchange plate 3 f and the supporting cylinder 2. 10 Thus, when the heat exchange plate 3c is expanded, the heat exchange plate 3r will be subjected to radial compression stress. The presence of the supporting cylinder 2 makes it possible to help said inner heat exchange plate 3f withstand this compression stress, which is exerted on the tubular element radially in the direction of the supporting cylinder 2. The inner heat exchange plate 3r also comprises a plurality of first longitudinal fins 31 15 located inside the cavity containing the cold coolant 5 f. These first fins 31 make it possible to more easily withstand the radial compression stresses exerted on the tubular element as a result of the expansion of the outer heat exchange plate 3c. These first fins also serve to position the supporting cylinder 2 substantially at the center of the inner plate 3 f. The outer heat exchange plate 3, also comprises a plurality of second longitudinal fins 20 32 located inside the cavity containing the hot coolant 5c. These second fins 32 serve, in particular, to position the outer plate 3c substantially at the center of the retaining tube 6. Take the example in which the plates 3c and 3f are made of steel, the plate 3c has for example a thickness of 3 mm and the plate 3f has a thickness of 1 mm. The plate 3c can then sustain a pressure of 400 bar with the help of the outer retaining tube 6. The plate 3 f can 25 sustain the same pressure as the plate 3c despite its smaller thickness because the pressure is exerted from the outside inward. The cylindrical heat exchange plate 3r is alternately in contact with the cold coolant 5 f coming from the cold source, and with air when the flow of cold coolant 5 f is stopped. Fig. 2 represents a cross-sectional view of the heat exchanger according to a second 30 embodiment of the invention.

WO 2008/015314 PCT/FR2006/001870 8 In this second embodiment, the heat exchanger comprises a plurality of tubular elements 1. Each tubular element I comprises an outer retaining tube 6 containing a single heat exchange plate 3, which itself contains a supporting cylinder 2. In this embodiment as well, the heat exchange plate 3 is, nonlimitingly, cylindrical. The supporting cylinder 2 is for 5 example a solid cylinder. The outer retaining tube 6, the heat exchange plate 3 and the supporting cylinder 2 are substantially concentric. A first cavity is formed between the heat exchange plate 3 and the outer retaining tube 6, and a second cavity is formed between the heat exchange plate 3 and the supporting cylinder 2. One of these cavities receives a liquid 4 while the other cavity receives a coolant 10 5. The liquid 4 has, for example, a high thermal expansion coefficient. It therefore enables a greater compression of the liquid compared to the expansion of the heat exchange plate alone, as explained above. As explained above, the heat exchange plate 3 is made of a material having very good thermal conductivity, i.e. of metal, in order to optimize the heat exchange. 15 Likewise, as explained above, the outer retaining tube 6 and the supporting cylinder 2 are composed of high pressure-resistant materials having poor thermal conductivity, such as, for example, a composite carbon or filament-wound material or glass. In this embodiment, hot and cold coolant 5 is alternately injected into the cavity provided for receiving said fluid. 20 Preferably, the liquid 4 is contained between the outer retaining tube 6 and the heat exchange plate 3, while the coolant 5 is contained between the heat exchange plate 3 and the supporting cylinder 2. Thus, when the heat exchange plate is expanded, it will be subjected to radial compression stress. The presence of the supporting cylinder 2 makes it possible to help the 25 heat exchange plate 3 withstand this compression stress, which is exerted in a plane transverse to the tubular element in the direction of said supporting cylinder 2. The heat exchange plate 3 also comprises a plurality of first longitudinal fins 31 located inside the cavity containing the liquid 4. These first fins 31 make it possible to increase the heat exchange surface.

WO 2008/015314 PCT/FR2006/001870 9 The heat exchange plate 3 also comprises a plurality of second longitudinal fins 32 located inside the cavity containing the coolant 5. These second fins 32 serve both to position the supporting cylinder 2 substantially at the center of the plate 3 and to more easily withstand the substantial deformations that might result from the compression stresses 5 exerted transverse to the tubular element as a result of the expansion of the plate 3. As illustrated in Fig. 2, the tubular elements are substantially parallel to each other, and preferably vertical. They are preferably disposed in contact with each other so as to limit energy losses, and for example so that their axes form trihedra. This arrangement of the tubular elements, and the manner in which they are attached as described below, can also be 10 applied to the tubular elements I according to the first and third embodiments of the invention. Each tubular element 1 is clamped by a strap, not shown, which is attached to a threaded rod 7 located at the center of the trihedron. In order to make the heat exchanger more durable, the array of tubular elements 1 is 15 held together by a synthetic resin. In a variant of embodiment, the straps are welded or soldered to each other. In addition, each tubular element I is closed at each of its ends by a flange, not shown. Only one of said flanges needs to allow the liquid 4 to be circulated through said flange. In particular, the flanges adapted for circulating the liquid 4 must all be disposed on 20 the same side of the various tubular elements constituting the heat exchanger. On the other hand, it is possible for one or both of the two flanges to allow the coolant 5 to circulate through this or these flange(s). Fig. 3 represents a longitudinal sectional view of the heat exchanger according to a third embodiment of the invention. 25 In this third embodiment, the heat exchanger comprises a plurality of tubular elements 1. Each tubular element 1 comprises an outer retaining tube 6 containing a single heat exchange plate 3, which itself contains a supporting cylinder 2. In this embodiment as well, the heat exchange plate 3 is vertical and, nonlimitingly, cylindrical. The supporting cylinder 2 is for example a solid cylinder. The outer retaining tube 6, the heat exchange plate 30 3 and the supporting cylinder 2 are substantially concentric.

WO 2008/015314 PCTIFR2006/001870 10 A first cavity is formed between the heat exchange plate 3 and the outer retaining tube 6, and a second cavity is formed between the heat exchange plate 3 and the supporting cylinder 2. One of these cavities receives a liquid 4, while the other cavity receives a coolant 5. The liquid 4 has for example a high thermal expansion coefficient. It therefore enables 5 greater compression of the liquid compared to the expansion of the heat exchange plate alone, as explained above. As explained above, the heat exchange plate 3 is made of a material having very good thermal conductivity, i.e. of metal, in order to optimize the heat exchange. Preferably, the liquid 4 is contained between the outer retraining tube 6 and the heat 10 exchange plate 3, while the coolant 5 is received between the heat exchange plate 3 and the supporting cylinder 2. Thus, when the heat exchange plate 3 is expanded, it will be subjected to radial compression stress. The presence of the supporting cylinder 2 makes it possible to help the heat exchange plate 3 withstand this compression stress, which is exerted in a plane 15 transverse to the tubular element in the direction of said supporting cylinder 2. The heat exchanger also comprises, between the supporting cylinder 2 and the cavity containing the coolant 5, two conduits 8, 9 which feed the hot or cold coolant from the hot or cold source into the heat exchanger. These conduits are thermally insulated from each other by a first separator 10 and are thermally insulated from the cavity containing the coolant by a 20 second separator 11. The separators are made of a material with very low thermal conductivity, in order to avoid heat losses. Spray nozzles 12, 13 make it possible to spray the hot or cold coolant through capillary tubes running through the separators 10, 11 from the conduits 8, 9 to the cavity, which is initially filled with air and is intended to contain the hot or cold coolant 5. These 25 capillary tubes make it possible, at atmospheric pressure, to stop the coolants precisely at the outlet port when they are liquids, and to reduce the time it takes the coolants to go from the control valves to the heat exchange plate 3. This spraying is substantially radial and allows for a fast and complete spraying of the heat exchange plate 3. Fig. 4 represents a cross-sectional view of the heat exchanger according to a fourth 30 embodiment of the invention.

WO 2008/015314 PCT/FR2006/001870 11 In this fourth embodiment, the heat exchanger comprises a plurality of cores 101. Each core 101 comprises two elements 107, which are symmetrical to each other. The two elements 107 are impermeably joined to each other at a joint 100. Each core 101 comprises two retaining half-tubes 106 oriented with their concave side toward the outside of 5 the core. The two half-tubes 106 therefore have their backs to each other. Each retaining half tube 106 contains a heat exchange plate 103, which itself contains a supporting half-cylinder 102. In this embodiment, the heat exchange plate 103 is semicylindrical. The heat exchange plate 103 is inserted so as to rest against a shoulder 114 inside a retaining half-tube 106 and is held against this shoulder by a retaining means, for example a weld. 10 A first cavity is formed between the heat exchange plate 103 and the retaining half tube, and a second cavity is formed between the heat exchange plate 103 and the supporting half-cylinder 102. One of these cavities receives a liquid 104 while the other cavity receives a coolant 105. The liquid 104 has, for example, a high thermal expansion coefficient. It therefore enables a greater compression of the liquid compared to the expansion of the heat 15 exchange plate alone, as explained above. As explained above, the heat exchange plate is made of a material having very high thermal conductivity, i.e. of metal, in order to optimize the heat exchange. Preferably, the liquid 104 is contained between the retaining half-tube and the heat exchange plate 103, while the coolant 105 is sprayed onto the heat exchange plate 103 by a 20 spray device contained in the supporting half-cylinder 102. Thus, when the heat exchange plate 103 is expanded, it will be subjected to radial compression stress. The presence of the supporting half-cylinder 102, as well as the shape of the exchange plate 103, makes it possible to help this exchange plate 103 withstand the compression stress, which is exerted in a plane transverse to the tubular element in the 25 direction of said supporting half-cylinder 102. The spray device of each supporting half-cylinder 102 comprises two conduits 108, 109, which feed the hot or cold coolant from the hot or cold source into the heat exchanger. These conduits are thermally insulated from each other and are thermally insulated from the cavity receiving the coolant. Spray nozzles 112, 113 make it possible to spray the hot or cold 30 coolant from the conduits 108, 109 onto the heat exchange plate 103. This spraying is WO 2008/015314 PCT/FR2006/001870 12 substantially radial and allows for a fast and complete spraying of the heat exchange plate 103. It is possible for the perimeter of the heat exchange plate not to be circular or cylindrical. Lobed shapes suggesting a fluted cake mold or arched shapes make it possible to 5 benefit from an increased length of the perimeter, thus contributing to a greater linear expansion of the heat exchange plate, and hence to its compressive displacement of the liquid located inside the cavity 104. In the four embodiments of the invention described above, the coolants 5, 5c, 5 r are for example water, and the liquid 4 is for example ethanol. The thermal expansion coefficient 10 of ethanol is 1.1 - 10 -

K

-

'. The hot coolant 5, is heated by a cold source [sic] and the cold coolant 5f is cooled by a cold source. The hot source is for example a solar panel. In that case, the flow of energy produced by the hot source being low, it is particularly important to reduce heat losses to a minimum in 15 order to conserve the available energy. The heat exchanger according to the invention is intended to be installed in a pump which also comprises a pumping piston adapted for actuating a control means via the movement of a fluid (hydraulic liquid or gas), a drive piston connected by kinematic means to the pumping piston and adapted to being actuated by a movement of the liquid 4 coming 20 from the heat exchanger described above, by a hot source and by a cold source [sic]. The pump contains, for example, several heat exchangers. The pump, in order to operate, also comprises a bypass which makes it possible to alternately feed a hot coolant heated by the hot source and a cold coolant cooled by the cold source into the tubular elements I of the heat exchanger in order to create alternating thermal 25 expansions and contractions, thus making it possible to actuate the drive piston. The pump according to the invention is intended to be installed in a system which also comprises a control means, for example a motor, and a fluid reservoir. The system is, for example, an air conditioner. In that case, the pumping chamber takes in and compresses gas and serves as a compressor. The hot source is for example one or WO 2008/015314 PCT/FR2006/001870 13 more solar panel(s) or an isothermal tank for storing hot coolant, which can be used at night. The cold source is for example an ornamental pond or a swimming pool. In a variant, the system is a hydraulic system producing household electricity. In that case, the control means is a hydraulic motor. The hot source is for example one or more solar 5 panel(s) and/or an isothermal tank for storing a coolant, which can be used at night. The cold source is for example a tank, an ornamental pond or a swimming pool. In a variant, the system is a hydraulic system producing household electricity from geothermal energy. In that case, the hydraulic pump operates a hydraulic motor, which drives an electrical generator. The hot source in that case is constituted by hot water produced by 10 geothermal energy, and the cold source is for example constituted by the natural environment, i.e. hillside runoff, a river, the sea, etc. When the system comprises a hot source constituted by solar panels, the prevailing pressure in the hot coolant circuit should be relatively high in order to maintain the coolant (for example water) in the liquid state; part of the pressure generated by the system is used to 15 re-inject the coolant into the solar panel. Otherwise, the water evaporates. On the other hand, the prevailing pressure in the cold coolant circuit can be the ambient pressure. Thus, in that case, the use of a heat exchanger with tubular elements according to the first embodiment described above is particularly suitable.

Claims

1. Heat exchanger comprising a plurality of tubular elements or cores (1, 101), each comprising: 5 - a supporting cylinder or half-cylinder (2, 102), - at least one curved heat exchange plate (3, 3c, 3f, 103), each plate separating a first cavity from a second cavity, the first cavity containing a liquid (4, 104) and the second cavity receiving a coolant (5, 5c, 5f, 105) which causes the thermal expansion or contraction of the plate and thus, respectively, the compression or expansion of the liquid in the first cavity, 10 - an outer retaining tube or half-tube (6, 106).

2. Heat exchanger according to claim 1, characterized in that the liquid (4) has a high thermal expansion coefficient. 15

3. Heat exchanger according to claim 1 or 2, characterized in that the outer retaining tube or half-tube (6, 106), the heat exchange plate or plates (3, 3c, 3 r, 103), and the supporting cylinder or half-cylinder (2, 102) have decreasing diameters.

4. Heat exchanger according to any of claims I through 3, characterized in that the first 20 and second cavities are delimited, on one side, by one of the heat exchange plates (3, 3,, 3r, 103), and on the other side by the supporting cylinder or half-cylinder (2, 102) or the outer retaining tube or half-tube (6, 106), the heat exchange plate(s) (3, 3c, 3 r, 103), the supporting cylinder or half-cylinder (2, 102) and the outer retaining tube or half-tube (6, 106) being concentric. 25

5. Heat exchanger according to any of claims 1 through 4, characterized in that each tubular element (1) is closed at each of its ends by a flange, one of said flanges being adapted so as to allow the circulation of the liquid (4) through the flange, the other flange preventing this circulation. 30 WO 2008/015314 PCT/FR2006/001870 15

6. Heat exchanger according to any of claims 1 through 5, characterized in that each tubular element (1) is closed at each of its ends by a flange, at least one of said flanges being adapted so as to allow the circulation of the coolant or coolants (5, 5,, 5c) through the flange. 5

7. Heat exchanger according to claim 6, characterized in that said flanges are adapted so as to allow the alternating circulation of a coolant heated by a hot source and a coolant cooled by a cold source.

8. Heat exchanger according to any of claims I through 7, characterized in that one of 10 the heat exchange plates (3) is equipped with a plurality of first fins (31) in contact with the liquid (4).

9. Heat exchanger according to any of claims 1 through 8, characterized in that one of the heat exchange plates ( 3 f) is equipped with a plurality of first fins (31) in contact with a 15 coolant (5f).

10. Heat exchanger according to claim 8 or 9, characterized in that one of the heat exchange plates (3, 3c) is equipped with a plurality of second fins (32) in contact with a coolant (5, 5 c). 20

11. Heat exchanger according to any of claims I through 10, characterized in that the various tubular elements (1) are parallel to each other.

12. Heat exchanger according to claim 11, characterized in that the various tubular 25 elements (1) are held together by means of straps, each clamping a tubular element and attached to a threaded rod (7) located between at least two tubular elements. WO 2008/015314 PCT/FR2006/001870 16

13. Heat exchanger according claim 11, characterized in that the various tubular elements are held together by means of straps, each clamping a tubular element and welded to each other. 5

14. Heat exchanger according claim I11, characterized in that the various tubular elements (1) are held together by means of straps, each clamping a tubular element and soldered to each other.

15. Heat exchanger according claim 11, characterized in that each tubular element or core 10 (1, 101) also comprises coolant conduits (8, 9; 108, 109) and spray nozzles (12, 13; 112, 113) adapted for spraying the coolant from the coolant conduits (8, 9; 108, 109) onto the heat exchange plate (3, 103).

16. Pump comprising: 15 - a pumping piston adapted for actuating a control means via the movement of a fluid, - a drive piston connected by kinematic means to the pumping piston and adapted to being actuated by a movement of the liquid (4) of the heat exchanger according to any of claims 1 through 15, 20 - a hot source, - a cold source.

17. Pump according to claim 16, characterized in that the pump also comprises a bypass adapted for alternately feeding a coolant heated under pressure by the hot source and a 25 coolant cooled at atmospheric pressure by the cold source into the tubular elements or cores (1) of the heat exchanger.

18. System comprising: - the pump according to either of claims 16 and 17, 30 - a fluid reservoir, WO 2008/015314 PCT/FR2006/001870 17 - a control means.