Energy cell and device for converting heat into hydraulic energy - Patents.com

Abstract

An energy cell and device for converting heat into hydraulic energy efficiently provided with a pressure vessel. [Solution] A pressure vessel 2 has two chambers separated by an impermeable and elastic membrane 5, namely a first chamber 6 filled with a phase change material and a second chamber 7 filled with hydraulic oil, and the energy cell 1 is provided with a shell-and-tube heat exchanger that alternately heats and cools the phase change material to alternately switch the phase change material from a solidified phase to a molten phase or vice versa so that the volume of the first chamber alternately increases and decreases, and the wall of the pressure vessel is provided with a passage 26 configured to allow the flow of hydraulic oil from and / or into the second chamber upon increase and / or decrease in volume of the first chamber, respectively, and the shell-and-tube heat exchanger comprises several straight tubes.

Description

[Technical field]

[0001] The present invention relates to an energy cell and a device for converting heat into hydraulic energy.

[0002] More specifically, the present invention relates to energy cells and devices that utilize the properties of phase change materials, whose volume by definition changes with each phase change from a solidified phase to a molten phase or vice versa, and the volume change of the phase change material is used as a motor to generate hydraulic energy. [Background technology]

[0003] For example, such an energy cell is known from US 2011 / 0024075 A1 which describes an energy cell in the form of a cylinder and a piston movable within the cylinder sealing a chamber within the cylinder filled with a phase change material, which expands upon heating when the phase change material changes from a solidified to a molten form, thus moving the piston within the cylinder and which movement can be used to apply a mechanical force.

[0004] Alternately heating and cooling the phase change material within the cylinder causes it to alternately melt and solidify, and therefore alternately expand and contract in volume, resulting in inward and outward movement of the piston, which can be converted into movement to drive a motor or other device.

[0005] Another example of an energy cell is known from WO 2015 / 184516. In the energy cell of WO 2015 / 184516 a pressure vessel is provided in which two chambers are separated from each other by an elastic membrane. The first chamber is filled with a phase change material. The energy cell has a shell-and-tube heat exchanger for alternate heating and cooling of the phase change material, the first chamber alternately increasing and decreasing in volume as the membrane tightens and relaxes. The second chamber is filled with hydraulic oil. The wall of the pressure vessel is provided with passages configured to allow a flow of hydraulic oil from and / or into the second chamber upon a volume increase and / or volume decrease in the first chamber, respectively.

[0006] In the energy cell described in WO 2015 / 184516, a first chamber having a phase change material is positioned around a tube of a shell-and-tube heat exchanger configured to be connected to a supply of hot medium having a temperature above the melting temperature of the phase change material and to a supply of cold medium having a temperature below the melting temperature of the phase change material.

[0007] Such an energy cell is more efficient than a piston-cylinder embodiment since no friction losses occur as the membrane tightens and relaxes.

[0008] In order to achieve sufficiently large and uniform heat transfer between the heat exchange medium in the tubes of the shell-and-tube heat exchanger and the phase change material in the first chamber of the energy cell, the tubes are preferentially provided on their outer walls with fins extending radially outward from said outer walls.

[0009] The presence of these fins makes it possible to keep the construction of the shell-and-tube heat exchanger compact.

[0010] However, a disadvantage of fins is that they divide the first chamber into compartments, i.e. they may also cause axial pressure gradients between these compartments, in which case the temperature change, and therefore the volume change, of the phase change material in some of the compartments is still not perfectly uniform.

[0011] A second possibility for obtaining a sufficiently large heat transfer between the medium in the tubes of the shell-and-tube heat exchanger and the phase change material in the first chamber is the application of a so-called "multi-pass" shell-and-tube heat exchanger, in which the flow of the heat exchange medium in the tubes of the shell-and-tube heat exchanger passes through the first chamber with the phase change material several times in succession, the flow of the heat exchange medium in the tubes of the heat exchanger being reversed half a turn after each pass along the first chamber.

[0012] As a result, the heat exchange medium travels a longer distance within the tubes of the shell-and-tube heat exchanger than in a "single-pass" shell-and-tube heat exchanger in which the heat exchange medium is routed only once through the tubes of the shell-and-tube heat exchanger, and therefore the total heat exchange between the heat exchange medium and the phase change material in the first chamber in a multi-pass shell-and-tube heat exchanger is greater.

[0013] However, by covering this longer distance within the tubes of the multi-pass shell-and-tube heat exchanger, the pressure loss of this flow is higher after the flow of heat exchange medium has passed through the entire shell-and-tube heat exchanger: on the one hand, this is due to friction with the inner tube walls, and on the other hand, it is also due to friction when the flow of the heat exchange medium reverses after each pass of the heat exchange medium, mainly along the first chamber.

[0014] In addition, in a multi-pass shell-and-tube heat exchanger, heat transfer between the heat exchange medium in the tubes and the phase change material in the first chamber is greater, but therefore not necessarily more uniform, than in a single-pass shell-and-tube heat exchanger. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] US Patent Application Publication No. 2011 / 0024075 [Patent Document 2] International Publication No. 2015 / 184516 Summary of the Invention [Problem to be solved by the invention]

[0016] The present invention aims to address at least one of the above and / or other disadvantages.

[0017] In particular, the invention aims to provide energy cells and devices for converting heat into hydraulic energy in the most energy efficient manner possible, i.e. with the greatest possible heat transfer and the conversion of heat into hydraulic energy with the least possible pressure and friction losses. [Means for solving the problem]

[0018] To this end, the present invention relates to an energy cell for converting heat into hydraulic energy, The energy cell includes a pressure vessel; The pressure vessel comprises two chambers separated from each other by an impermeable and elastic membrane; a first chamber filled with a phase change material whose density changes upon each phase change from a solid phase to a molten phase and vice versa, respectively; and a second chamber which is filled with hydraulic fluid when the energy cell is in use; The energy cell is provided with means for alternately heating and cooling the phase change material to alternately change the phase change material from a solid phase to a molten phase or vice versa such that the volume of the first chamber alternately increases and decreases; the pressure vessel wall is provided with at least one passageway configured to allow hydraulic fluid flow from and / or into the second chamber upon volume increase and / or volume decrease, respectively, in the first chamber; the means for alternately heating and cooling the phase change material includes a shell-and-tube heat exchanger; The shell and tube heat exchanger comprises a number of straight or nearly straight tubes passing through a first chamber filled with a phase change material; The shell-and-tube heat exchanger is characterized in that the tubes have an outside diameter not greater than 3.0 millimeters.

[0019] The advantages of such an energy cell according to the invention are numerous.

[0020] Firstly, due to the small outer diameter of the straight or nearly straight tubes of the shell-and-tube heat exchanger, these tubes can be arranged in large numbers in a limited space with small mutual distances, in other words, the tubes of the energy cell according to the invention can be arranged more densely than known energy cells.

[0021] In this way, the tubes in a confined space provide a large external heat exchange surface on the outer walls and a large internal heat exchange surface on the inner walls.

[0022] This allows the use of fin structures on the tubes of the shell-and-tube heat exchanger of the first chamber to be reduced or completely eliminated in the energy cell with dimensions that do not need to be increased excessively over those of known energy cells. In this way, in many cases, any axial pressure differentials that occur in energy cells with these fin structures on the tubes of the shell-and-tube heat exchanger can be reduced or completely avoided.

[0023] In addition, the lack of bends in the straight or nearly straight tubes results in limited pressure losses within the energy cell.

[0024] In addition to this, for generating hydraulic energy with the energy cell according to the invention, only an elastic deformation of the membrane occurs, and friction losses occur which are less than with energy cells including a piston-cylinder instead of a membrane for generating hydraulic energy.

[0025] To further enhance the above-mentioned advantages, it is of course possible to select a shell and tube heat exchanger having tubes with smaller outer diameters, preferably up to 2.5 millimeters, more preferably up to 2.0 millimeters, even more preferably up to 1.5 millimeters, and even more preferably up to 1.0 millimeters.

[0026] In a preferred embodiment of the energy cell according to the invention, the tubes of the shell-and-tube heat exchanger have no external fins.

[0027] As mentioned above, any axial pressure that arises within the energy cell can thus be reduced or avoided entirely and cannot act on these external fins.

[0028] In a next preferred embodiment of the energy cell according to the invention, the wall of the pressure vessel is implemented as a first tube around the longitudinal axis, and the openings on the longitudinal axis on both sides of the pressure vessel are hermetically sealed by two covers held within the pressure vessel at a distance from each other.

[0029] In this manner, the energy cell is constructed as a non-complex structure, thereby simplifying assembly of the energy cell and maintenance, repair, and / or replacement of components within the energy cell.

[0030] In this embodiment, preferably at least one of the two covers is removable, while preferentially both covers are removable and one or several seals are provided between each removable cover and the pressure vessel.

[0031] This makes assembly, and maintenance, repair, and / or replacement of the energy cell components easier.

[0032] Additionally, in this embodiment, preferably each of the tubes has a first end sealingly mounted within a first of the two covers and a second end opposite the first end sealingly mounted within a second of the two covers opposite the first cover.

[0033] Further, in this embodiment, the membrane is preferably also embodied as a second tube coaxially mounted within the pressure vessel wall such that the first chamber is surrounded by the membrane and the second chamber extends around the membrane between the pressure vessel wall and the membrane.

[0034] More preferably, the membrane is mounted with its free ends sealed within the two covers or between the covers and the pressure vessel wall.

[0035] This allows the seal to be located between the tubes and / or membranes in the cover, rather than in the pressure vessel wall. As a result, the pressure vessel wall does not need to be modified to accommodate this type of seal. As a result, standard tube construction can be used as the pressure vessel wall, while fully maintaining the mechanical strength of the pressure vessel wall.

[0036] This further simplifies assembly and maintenance of the energy cell.

[0037] Furthermore, given that the hydraulic fluid in the second chamber of the energy cell is outside the tubular membrane, the expansion of the membrane diameter required for the same volumetric displacement of hydraulic fluid is smaller than if the second chamber with hydraulic fluid were inside the membrane, which results in smaller stresses in the membrane and therefore a reduced risk of membrane failure.

[0038] In the following preferred embodiment of the energy cell according to the invention the phase change material has a melting temperature of 25°C to 90°C, preferably 25°C to 60°C.

[0039] The advantage of this is that heat can be recovered from a low temperature residual heat stream, for example a 60° C. compressed gas stream heated by the heat of compression in a compressor installation.

[0040] In this embodiment, the phase change material is preferably -wax, a fatty acid or a mixture of fatty acids, preferably palmitic acid or lauric acid, - a glyceride or a mixture of glycerides, or mixtures of these, is selected from the group comprising:

[0041] In this context, "wax" refers to a mixture of organic compounds composed primarily of alkyl chains having 12 or more carbon atoms, which are flexible near ambient temperatures but are typically harder and more brittle than fats and oils, and which typically melt at or in the interval of a melting temperature above 35°C to a low viscosity fluid having a dynamic viscosity below 1000 mPa.s.

[0042] Alternatively, the phase change material is preferentially a paraffin, preferentially an alkane having an even number of carbon atoms or a mixture of alkanes having an even number of carbon atoms, more preferentially octadecane.

[0043] In this context, "paraffin" refers to a mixture of alkane chains having 15 or more carbon atoms.

[0044] Waxes, fatty acids, glycerides, paraffins, or mixtures thereof are suitable phase change materials for the intended application, which have a low melting temperature, for example, about 45°C, depending on the type of wax, fatty acid, glyceride, or paraffin used, and which experience a significant increase in volume when changing from a solidified to a molten phase and return to their original volume when solidified.

[0045] Additionally, the appropriate selection of materials of this type can be tailored to the intended application based on the number of carbon atoms in the molecules of the material, the melting temperature, or the melting temperature interval.

[0046] In this regard, it is not excluded that different types of materials or mixtures of materials have such a low melting temperature that they are used as phase change materials whose volume increases significantly when changing from the solidified phase to the molten phase and returns to its original volume when solidified.

[0047] An alkane having an even number of carbon atoms or a mixture of alkanes having an even number of carbon atoms provides the maximum absolute ratio of the volume change of the phase change material upon phase change to the latent heat stored or released by the phase change material upon phase change, which absolute ratio is referred to hereinafter as the expansion capacity of the phase change material.

[0048] Octadecane has the advantages of having a relatively large expansion capacity, compatibility with all metals, and a relatively low melting temperature of 27° C. compared to most waxes. Octadecane is ideally suited for heat recovery from a relatively low temperature residual heat stream because, due to its relatively low melting temperature, there is a relatively large temperature difference between the residual heat stream and the phase change material upon phase change of the phase change material, and this temperature difference is the driving force for heat transfer between the residual heat stream and the phase change material.

[0049] Octadecane has a relatively large expansion capacity and is therefore highly suitable for converting the heat of the residual heat flow to hydraulic energy in a relatively large amount.

[0050] In the following preferred embodiments of the energy cell according to the invention, the tubes of the shell-and-tube heat exchanger are made of stainless steel, preferably AISI 304 stainless steel or copper.

[0051] The advantage of this type of material is its good thermal conductivity, which is favorable for the heat transfer between the heat exchange medium and the phase change material. Moreover, this type of material has good mechanical strength and rigidity, which means that the tubes of the shell-and-tube heat exchanger can withstand high pressures. Moreover, this type of material is characterized by good processability, which allows the smooth manufacture of large quantities of tubes using standard production techniques.

[0052] In another preferred embodiment of the energy cell according to the invention, the membrane is made of an elastic material.

[0053] Preferably, the elastic material is an elastomer or a composite material or a rubber, preferably a nitrile rubber.

[0054] An advantage of a membrane made of an elastic material is that the membrane easily and uniformly follows the volumetric changes of the phase change material in the first chamber, making the membrane less susceptible to breakage.

[0055] In another preferred embodiment, the tubes of the shell-and-tube heat exchanger are grouped into one or several modular units, each modular unit having the tubes arranged around a reference axis of the modular unit.

[0056] This facilitates the manufacture and assembly of parts when constructing the energy cell, and facilitates disassembly for maintenance, repair, and / or replacement of parts of the energy cell.

[0057] Preferably, each modular unit has tubes arranged in parallel about a reference axis.

[0058] This facilitates the close stacking of the tubes necessary for uniform heat transfer between the heat exchange medium and the phase change material.

[0059] Instead, within each modular unit, the tubes are arranged diagonally toward one another about a reference axis.

[0060] This makes it possible to choose the distance between adjacent tubes in the modular unit smaller at the outlet of the energy cell than at the inlet of the energy cell. When supplying a hot heat exchange medium and since the temperature of this heat exchange medium and consequently the temperature difference between the heat exchange medium and the phase change material in the first chamber is higher at the inlet than at the outlet of the energy cell, the heating of the phase change material can therefore occur more uniformly over the entire length of the energy cell.

[0061] More preferably, within each modular unit, the centres of the tubes in planes perpendicular to the reference axis are arranged according to a regular pattern.

[0062] In this context, a "regular pattern" refers to a pattern in a two-dimensional plane that is composed of simple geometric shapes, such as triangles or squares, that self-replicate according to two intersecting dimensions of the plane.

[0063] This provides yet another improvement in uniform heat transfer between the heat exchange medium and the phase change material.

[0064] Preferentially, the regular pattern is a hexagonal pattern.

[0065] More preferably, within each modular unit, the centres of adjacent tubes in a plane perpendicular to the reference axis are disposed at a constant first distance from each other.

[0066] This provides yet another improvement in uniform heat transfer between the heat exchange medium and the phase change material.

[0067] Further preferably, the tubes of the pipe heat exchanger are grouped into several modular units with parallel oriented reference axes, and in a plane perpendicular to these reference axes, a second distance between a tube of one of the several modular units and an adjacent tube of one of the several modular units is greater than the above-mentioned first distance.

[0068] This offers the possibility of creating a reservoir between the modular units that continuously contains molten phase change material that is not susceptible to heat transfer between the heat exchange medium and the phase change material. The reservoir that always contains the molten phase change material can be easily retrieved, which consequently expands within the modular units. In this way, the action of the radial forces of the expanding phase change material on the tubes within the modular units is mitigated, so that dislocations of these tubes during the expansion of the phase change material are reduced or even avoided.

[0069] In a further preferred embodiment of the energy cell according to the invention, the tubes of the shell-and-tube heat exchanger have a wall thickness of at least 0.075 mm, preferably at least 0.080 mm, more preferably at least 0.090 mm, more preferably at least 0.100 mm.

[0070] The advantage of such a minimum wall thickness is that the tube can withstand high pressures, typically above 250 bar.

[0071] In the next preferred embodiment of the energy according to the invention, the tubes of the shell and tube heat exchanger are - supplying and discharging a hot medium capable of melting the phase change material, and / or - supplying and discharging a low-temperature medium capable of solidifying the phase change material; The device is configured to be connected to

[0072] This has the advantage of being able to utilise heat recovered from waste liquids that are often produced as a by-product of industrial processes, in the form of hot water, and which are typically dissipated as heat that cannot be used because the temperature is often insufficient to economically recover the energy using existing energy recovery systems.

[0073] In this preferred embodiment, the hot medium is preferably a gas stream compressed by a compressor installation.

[0074] Here, the heat of compression which heats the compressed gas stream in the compressor installation can be recovered by the energy cell according to the invention.

[0075] Furthermore, in this preferred embodiment, the energy cell is preferably provided with two collectors between which the tubes of the shell-and-tube heat exchanger extend, and each of these two collectors is provided with two connections, respectively a first connection to a high-temperature circuit with a high-temperature medium and a second connection to a low-temperature circuit with a low-temperature medium.

[0076] These collectors provide uniform supply and discharge of hot and / or cold media across the various tubes, which results in improved uniform heating and / or cooling of the phase change material within the energy cell.

[0077] Preferably, the two connections of each of the two collectors are provided with check valves arranged to alternately supply hot and cold media to the shell-and-tube heat exchanger.

[0078] The check valve ensures that either the hot or cold medium flows into the tubes of the shell-and-tube heat exchanger.

[0079] By avoiding the tubes of the shell-and-tube heat exchanger being supplied with hot and cold media simultaneously, a uniform temperature and therefore a uniform density of the phase change material in the first chamber is ensured, and as a result large pressure gradients in the first chamber are avoided.

[0080] The invention also relates to a device for converting heat into hydraulic energy, characterized in that it comprises one or several energy cells according to any of the preceding claims, Each shell-and-tube heat exchanger of one or several energy cells is connected through a valve system to a supply of cold medium, the supply temperature of which is lower than the melting temperature of the phase change material, and to a supply of hot medium, the supply temperature of which is higher than the melting temperature of the phase change material, the valve system being configured such that the cold medium and the hot medium are each alternately routed through the shell-and-tube heat exchanger for a specific, adjustable duration.

[0081] When the device comprises several energy cells, an advantage of such a device is that the cold and hot medium supplies do not need to be alternately powered on and off, but can instead be alternately routed to the various energy cells, so that the cold and hot medium supplies can be left flowing continuously whilst the alternating phase changes required for the operation of the different energy cells do not stop.

[0082] In a preferred embodiment of the device according to the invention, the second chamber of one or several energy cells is connected to a hydraulic circuit driving a hydraulic consumer.

[0083] Preferably, the hydraulic consumer is a hydraulic motor used to drive a generator.

[0084] In this manner, the device may generate useful electrical energy to power components of itself or other nearby devices, for example, in an industrial facility.

[0085] In a next preferred embodiment of the invention, the device comprises an even number of energy cells and the valve system is configured such that a first half of the number of energy cells have a supply of hot medium and another second half of the number of energy cells have a supply of cold medium during each operation of the device.

[0086] This allows the cold and hot media supplies to continue to flow at the same rate.

[0087] Furthermore, in this way there is always a cell feeding hydraulic fluid to the consumer, so that the consumer can be driven more regularly and always in the same direction.

[0088] In the following preferred embodiment of the device according to the invention, the valve system is controllably connected to a controller, which is provided with means for setting a specific adjustable duration and further with an algorithm for alternately routing the cold and hot media, respectively, to the shell-and-tube heat exchanger during said specific adjustable duration.

[0089] Such a controller would automatically provide for control and operation of the valve system with only minimal oversight required by a human operator.

[0090] In order to make the properties of the invention more clear, some preferred versions of an energy cell according to the invention will now be described, by way of example and without any limiting character, with reference to the accompanying drawings, in which: FIG. [Brief description of the drawings]

[0091] [Figure 1] 1 is a schematic perspective view of an energy cell according to the present invention; [Diagram 2] FIG. 2 is a cross-sectional view of the energy cell of FIG. 1 with parts removed. [Diagram 3] 1 shows very diagrammatically a device according to the invention provided with an energy cell according to the invention having a phase change material in a solidified state; [Figure 4] FIG. 4 shows the layout of FIG. 3 with the phase change material in a molten state. [Diagram 5] 1 is a cross-sectional view of an alternative embodiment of an energy cell according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0092] In this case, the energy cell 1 shown in FIG. 1 consists of a tubular pressure vessel 2 with removable covers 3 at either end 21, 22 which are retained within the pressure vessel 2 by retaining rings 4, in this case in the form of nuts.

[0093] The pressure vessel 2 is constructed to withstand very high pressures, for example up to 25,000 kPa (250 bar), as a function of the desired pressure in the particular application.

[0094] The space bounded by the pressure vessel 2 and the cover 3 is divided by a tubular membrane 5 into two chambers, a first chamber 6, each surrounded by the membrane 5 itself, and a second chamber 7, extending around the membrane 5, between the pressure vessel 2 and the membrane 5, as best seen in FIG. 2.

[0095] The membrane 5 is made of an impermeable elastic material such as rubber, for example nitrile rubber or an elastomer or composite material, and is sealingly fitted at each end, with its free end 8 within the associated cover 3 .

[0096] For that purpose, the above-mentioned free end 8 of the membrane 5 is provided with a boss 9 which can act as an integral seal, the cover 3 being implemented in the embodiment of FIG. 2 using two parts, a first part 3A being held in the pressure vessel 2 by the above-mentioned retaining ring 4 and a second part 3B being mounted in or against the first part 3A, and the above-mentioned free end 8 being fastened with the boss 9 of the membrane 5 in the chamber 10 enclosed between both parts 3A and 3B.

[0097] The second part 3B of each cover 3 abuts against the first part 3A and is fastened by a bolt 11 or the like.

[0098] Seals 12 and 13 are provided between the cover 3 , the pressure vessel 2 and the retaining ring 4 .

[0099] On its outer side facing the second chamber 7, the membrane 5 can be provided with one or several ribs 14, in this case circumferential ribs 14 having a certain thickness, which act locally as spacers between the membrane 5 and the pressure vessel 2 and can also act as reinforcing ribs 14 for the membrane 5. In the example shown, the ribs 14 and the membrane 5 are manufactured in one piece from the same material, although this is not strictly necessary.

[0100] Likewise, on the inside facing the membrane 5 the pressure vessel 2 can be provided with ribs 15 of a certain thickness, which are preferably also designed as circumferential ribs 15 and are arranged opposite the corresponding ribs 14 of the membrane 5.

[0101] Additionally, the energy cell 1 is provided with a shell-and-tube heat exchanger 16 in the form of a bundle of tubes 17 extending axially through the first chamber 6. For clarity, the radial dimensions, such as the outer and inner diameters of the tubes 17, are shown exaggerated.

[0102] The tubes 17 with their ends 18 can be mounted by means of sealing O-rings in passages 19 in the respective covers 3. However, it is also possible that the ends 1 of the tubes 17 can be welded into the passages 19 in the respective covers 3.

[0103] The space around the tube 17 in the first chamber 6 is filled with a phase change material 23 which is in a solidified state when the energy cell 1 is not in use and which in this state occupies a volume which is just sufficient to fill the first chamber 6 when the energy cell 1 is empty and not in use or which is slightly larger than the empty volume of this first chamber 6 so that the membrane 5 in this state is not radially tensioned or is only slightly tensioned.

[0104] The tube 17 forms a connection between the two ends 21 and 22 of the pressure vessel 2, which can act as an inlet and / or outlet for a low or high temperature medium that can be passed through the pressure vessel 2 to heat or cool the phase change material 23 to melt or solidify it.

[0105] When the energy cell 1 is in use, the second chamber 7 is filled with hydraulic oil 24 from a hydraulic circuit 31 which is hydraulically connected to the second chamber 7 through two connecting nipples 25 respectively screwed into passages 26 of the pressure vessel 2 and is provided with a hood 27 which prevents the membrane 5 from being pushed out of the pressure vessel 2 radially within the connecting nipples 25 or the passages 26.

[0106] The membrane 5 acts as an impermeable separation between the phase change material 23 in the first chamber 6 and the hydraulic fluid 24 in the second chamber 7 .

[0107] The use of the energy cell 1 according to the invention is very simple and will be explained below with reference to FIG. 3 in which the energy cell 1 is shown as part of a device 28 according to the invention for recovering heat from a supply A of high-temperature medium having a temperature higher than the melting temperature of the phase change material 23.

[0108] This hot medium supply A is connected to end 21 of the energy cell 1 through a valve system 29, while the other end 22 of the energy cell 1 is connected to a hot medium outlet B after it is routed through the shell-and-tube heat exchanger 16 of the energy cell 1.

[0109] Similarly, the energy cell 1 is connected through the valve system 29 described above to a cold medium supply C and a discharge D for the same medium after passing through the shell-and-tube heat exchanger 16 .

[0110] The supplied low temperature medium has a temperature lower than the melting temperature of the phase change material 23 .

[0111] The valve system 29 is such that alternating cold and hot media can be routed through the shell-and-tube heat exchanger 16 for specific, adjustable durations.

[0112] The valve system 29 is controllably connected to a controller 20. The controller 20 is provided with a setting tool for setting specific adjustable durations and further provided with an algorithm for alternately routing the cold and hot media through the shell-and-tube heat exchanger 16 for each specific adjustable duration.

[0113] The energy cell 1 is also connected through a connecting nipple 25 and another valve system 30 to a hydraulic circuit 31 for driving a hydraulic consumer 32, represented here as an example as a hydraulic motor 33 for driving a generator 34.

[0114] The valve system 30 is designed to ensure that fluid in the hydraulic circuit 31 always circulates in the same direction.

[0115] The device 28 functions as follows.

[0116] Starting from the state as shown in FIG. 3 where the phase change material 23 is in a solidified state for an initial period of, for example, about 15 seconds, the valve system 29 is controlled so that during this period hot medium from supply A is routed through the shell-and-tube heat exchanger 16 to exhaust B while the cold medium inlet C and outlet D are blocked.

[0117] The heat of the high temperature medium heats the phase change material 23 so that it begins to melt, resulting in an increase in volume of the phase change material 23 and forcing the membrane 5 radially outwards, reducing the volume of the second chamber 7 and forcing hydraulic oil 24 from this second chamber 7 into the hydraulic circuit 31 at a pressure that depends on the hydraulic resistance of this hydraulic circuit 31 and in particular the load required by the consumer 32.

[0118] During a subsequent period, as shown in FIG. 4, the cold medium, instead of the hot medium, is now routed through the shell-and-tube heat exchanger 16 by appropriate control of the valve system 29.

[0119] This causes the molten phase change material 23 to solidify and reduce in volume, causing hydraulic fluid to flow back from the hydraulic circuit 31 to the energy cell 1 .

[0120] In this way, the energy cell 1 acts as if it were a beating heart that alternately pumps hydraulic fluid to the consumer 32 .

[0121] In practice, a device 28 having an even number of energy cells 1 in the hydraulic circuit 31 will be activated each time, while the valve system 29 will ensure that each time during operation of the device 28, a first half of the number of energy cells 1 has a supply of warm medium and another half of the number of energy cells 1 has a supply of cold medium.

[0122] FIG. 5 shows a variant of the energy cell 1 integrated into a collector 35 in which part of the valve system 29 has double connectors at each end 21 and 22 of the energy cell 1 in the form of check valves 36 at each of two connections 37 and 38 provided in each collector 35 for connection with the high temperature and low temperature circuits.

[0123] In the example shown, the pressure vessel 2 and the membrane 5 are implemented as coaxial cylinders, but other configurations making it possible to elastically stretch the membrane 5 when the phase change material 23 expands are not excluded.

[0124] Instead of using a phase change material 23 that expands when melted, it is not excluded to use a phase change material that contracts when melted.

[0125] The invention is in no way limited to the embodiments described by way of example and shown in the figures, rather the energy cell according to the invention can be implemented in any shape and size without going beyond the scope of the invention as defined in the claims. [Explanation of symbols]

[0126] 1 Energy Cell 2. Pressure vessels 5. Impermeable and elastic membrane 6 First Chamber 7 Second Chamber

Claims

1. The energy cell (1) is provided with a pressure vessel (2), The pressure vessel (2) comprises two chambers separated by an impermeable and elastic membrane (5): a first chamber (6) filled with a phase change material (23) whose density changes upon each phase change from a solidified phase to a molten phase or vice versa, a second chamber (7) which is filled with hydraulic fluid (24) when the energy cell (1) is in use; Equipped with The energy cell (1) is provided with means for alternately heating and cooling said phase change material (23) to change said phase change material (23) alternately from a solidified phase to a molten phase and vice versa, such that the volume of said first chamber (6) alternately increases and decreases; a wall of the pressure vessel (2) is provided with at least one passage (26) configured to allow a flow of hydraulic fluid (24) from and / or into the second chamber (7) upon a volume increase and / or a volume decrease of the first chamber (6), said means for alternately heating and cooling said phase change material (23) comprising a shell-and-tube heat exchanger (16); the shell-and-tube heat exchanger (16) comprises several straight or nearly straight tubes (17) passing through the first chamber (6) filled with the phase change material (23); 1. An energy cell for converting heat into hydraulic energy, comprising: The tubes (17) of the shell and tube heat exchanger (16) have an outer diameter of up to 3.0 millimeters.

1. An energy cell comprising:

2. 2. Energy cell according to claim 1, characterized in that the tubes (17) of the shell-and-tube heat exchanger (16) have an outer diameter of maximum 2.5 millimeters, preferably maximum 2.0 millimeters, more preferably maximum 1.5 millimeters, even more preferably maximum 1.0 millimeters.

3. 3. Energy cell according to claim 1 or 2, characterized in that the tubes (17) of the shell-and-tube heat exchanger (16) are devoid of external fins.

4. The wall of the pressure vessel (2) is implemented as a first tube around a longitudinal axis, The openings on both sides of the pressure vessel (2) on the longitudinal axis are hermetically sealed by two covers (3) held within the pressure vessel (2) at a distance from each other.

3. An energy cell according to claim 1 or 2.

5. 5. An energy cell according to claim 4, characterized in that at least one of the two covers (3), preferably both covers (3), are removable and one or more seals (12) are provided between each removable cover (3) and the pressure vessel (2).

6. 5. An energy cell according to claim 4, characterized in that for each of the tubes (17), a first end (18) is sealingly mounted in a first cover (3) of the two covers (3) and a second end (18) opposite the first end (18) is sealingly mounted in a second cover (3) of the two covers (3) opposite the first cover (3).

7. 5. An energy cell according to claim 4, characterized in that the membrane (5) is embodied as a second tube placed coaxially within the wall of the pressure vessel (2) such that the first chamber (6) is surrounded by the membrane (5) and the second chamber (7) extends around the membrane (5) between the wall of the pressure vessel (2) and the membrane (5).

8. 8. An energy cell according to claim 7, characterized in that the membrane (5) is sealingly mounted with its free ends (8) within the two covers (3) or between the covers (3) and the wall of the pressure vessel (2).

9. Energy cell according to claim 1 or 2, characterized in that the phase change material (23) has a melting temperature between 25°C and 90°C, preferably between 25°C and 60°C.

10. The phase change material (23) wax, a fatty acid or mixture of fatty acids, preferably palmitic acid or lauric acid, a glyceride or a mixture of glycerides, or Mixtures of these selected from the group comprising:

10. The energy cell of claim 9.

11. 10. Energy cell according to claim 9, characterized in that the phase change material (23) is a paraffin, preferably an alkane with an even number of carbon atoms or a mixture of alkanes with an even number of carbon atoms.

12. 12. Energy cell according to claim 11, characterized in that the phase change material (23) is octadecane.

13. Energy cell according to claim 1 or 2, characterized in that the tubes (17) of the shell-and-tube heat exchanger (16) are made of stainless steel, preferably AISI 304 stainless steel, or of copper.

14. 3. Energy cell according to claim 1 or 2, characterized in that the membrane (5) is made of an elastic material.

15. 15. Energy cell according to claim 14, characterized in that the elastic material is an elastomer or a composite material or a rubber, preferably a nitrile rubber.

16. 3. Energy cell according to claim 1 or 2, characterized in that the tubes (17) of the shell-and-tube heat exchanger (16) have a wall thickness of at least 0.075 millimeters, preferably at least 0.080 millimeters, more preferably at least 0.090 millimeters, even more preferably at least 0.100 millimeters.

17. The tubes (17) of the shell and tube heat exchanger (16) are Supplying and discharging a high temperature medium capable of melting the phase change material (23), and / or Supplying and discharging a low temperature medium capable of solidifying said phase change material (23); configured to be connected to 3. An energy cell according to claim 1 or 2.

18. 20. The energy cell of claim 17, wherein the hot medium is a gas stream compressed by a compressor arrangement.

19. 18. An energy cell according to claim 17, characterized in that the energy cell (1) is provided with two collectors (35) between which the tubes (17) of the shell-and-tube heat exchanger (16) extend, and each of these two collectors (35) is provided with two connections (37, 38), namely a first connection (37) for connection with a high-temperature circuit comprising the high-temperature medium and a second connection (38) for connection with a low-temperature circuit comprising the low-temperature medium.

20. 20. An energy cell according to claim 19, characterized in that the two connections (37, 38) of each of the two collectors (35) are provided with a check valve (36) configured to provide alternately hot and cold media to the shell-and-tube heat exchanger (16).

21. 1. A device for the conversion of heat into hydraulic energy, comprising: A device (28) comprising one or more energy cells (1) according to claim 1 or 2, each shell-and-tube heat exchanger (16) of the one or more energy cells is connected through a valve system (29) to a supply of cold medium whose supply temperature is lower than a melting temperature of the phase change material (23) and to a supply of hot medium whose supply temperature is higher than the melting temperature of the phase change material (23), the valve system (29) being configured such that, in an alternating manner, each of the cold medium and the hot medium is routed through the shell-and-tube heat exchanger (16) for a specific, adjustable duration; A device characterized in that

22. 22. The device according to claim 21, characterized in that the second chamber (7) of the one or more energy cells (1) is connected to a hydraulic circuit (31) for driving a hydraulic consumer (32).

23. 23. A device according to claim 22, characterized in that the hydraulic consumer (32) is a hydraulic motor (33) for driving a generator (34).

24. A device (28) comprising an even number of energy cells (1), said valve system (29) being configured such that during each operation of the device (28) a first half of the number of energy cells (1) has a supply of hot medium and another half of said number of energy cells (1) has a supply of cold medium, 22. The device of claim 21 .

25. 22. The device of claim 21, wherein said valve system (29) is controllably connected to a controller (20) provided with adjustment means for setting said specific adjustable durations and further provided with an algorithm for alternately routing said cold medium and said hot medium through said shell-and-tube heat exchanger (16) during each of said specific adjustable durations.

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