DEVICE FOR ACQUISITIONING AND OUTPUTTING LATENTER HEAT

Description

[0001] The invention relates to a device for absorbing and releasing latent heat.

[0002] In heat exchangers, a fluid medium flows through the fluid lines of the heat exchanger, exchanging heat between the fluid medium and the heat exchanger medium. In conventional heat exchangers, the heat exchanger medium is water. Depending on the temperature difference between the water and the fluid medium, the water either releases heat to the fluid medium or absorbs heat from it, thereby changing the water's temperature. To increase heat transfer, the heat exchanger medium in such heat exchangers is often pumped through complex pump circuits to involve correspondingly larger masses and heat capacities in the heat exchange. Alternative, compact (decentralized) heat exchangers without such pump circuits rely on phase change materials to increase the exchangeable heat capacity, utilizing the latent heat that can be stored or released during a phase transition of the phase change material.These have the advantage that the relatively high specific heat capacity that can be stored or retrieved during the phase transition can be used for heat exchange.

[0003] Based on this, a fluid conditioning arrangement with a primary and a secondary heat exchanger is known from GB 2467812 A. The primary heat exchanger is filled with a phase change material. Furthermore, the fluid conditioning arrangement includes a control unit that controls the secondary heat exchanger as soon as the primary heat exchanger cannot cool and / or heat the fluid to a predetermined acceptable level. If this occurs, the control unit activates a booster with a heat pump, a cold heat exchanger, and a hot heat exchanger to raise the heat transfer back to the acceptable level. A disadvantage of this is that, due to the limited heat capacity of the phase transition, the fluid conditioning arrangement can only be partially operated using latent heat before conventional heat exchangers with their known disadvantages are activated.

[0004] WO 2017 / 151612 A1 discloses a device for the release and absorption of latent heat comprising a heat exchanger and a phase change material.

[0005] Based on this, the present invention aims to provide a device for absorbing and releasing latent heat, which enables improved use of latent heat for heat exchange.

[0006] This problem is solved by a device having the features of claim 1.

[0007] Advantageous embodiments of these aspects of the invention are specified in the corresponding dependent claims and are described below.

[0008] The invention relates to a device for releasing and receiving latent heat. According to the invention, the device comprises a heat exchanger with a reservoir that can be filled with or is filled with a phase change material. The reservoir is bounded by a wall that has a filling opening for filling or emptying the phase change material. The heat exchanger further comprises several fluid lines running through the reservoir, through which a fluid medium can flow. Each fluid line extends from a first opening in the wall to a second opening in the wall through the reservoir of the heat exchanger, so that the fluid lines are separated from each other by the reservoir.Thus, when the fluid medium flows through the heat exchanger, latent heat can be transferred from the phase change material to the fluid medium through heat exchange between the fluid lines and the reservoir, with the fluid medium absorbing heat, or absorbing heat from the fluid medium through the phase change material. Furthermore, the device includes a flow control system designed to generate and reverse the flow of the fluid medium along the fluid line.

[0009] The invention thus enables heat exchange between the fluid medium and the phase change material. During a phase transition from a first phase to a second phase, the phase change material can absorb heat released by the fluid medium in the form of latent heat, thereby cooling the fluid medium. Conversely, during a reverse phase transition from the second phase to the first phase, the phase change material can release latent heat to the fluid medium, causing the fluid medium to heat up. The first phase is preferably a solid phase and the second phase a liquid phase of the phase change material.

[0010] Phase change materials offer the advantage that heat exchange is possible not only with temperature changes, but also at the phase transition temperature of the respective phase change material at a constant temperature in the form of latent heat. Furthermore, the heat that can be accessed or stored as latent heat during the phase transition is relatively high: if, for example, the specific heat capacity of a ceramic material is approximately 1 kJ / kg K, while a phase change material, such as a salt hydrate, can store or release a heat capacity of 180 kJ / kg as latent heat during the phase transition at a phase transition temperature of 21 °C, then a temperature difference of 180 K would be required for the ceramic material to exchange the same amount of energy through heat transfer for the same mass.

[0011] The flow device enables, in particular, the generation of a flow of the fluid medium through the at least one fluid line, thereby advantageously increasing the heat exchange between the fluid medium and the phase change material. Furthermore, according to the invention, the flow device is designed to reverse the flow direction.

[0012] In a preferred embodiment, the fluid medium is a gas, in particular air. The device according to the invention is therefore particularly suitable for use as a decentralized ventilation component, without requiring any complex pump circuits.

[0013] The reservoir is preferably at least partially bounded by the wall. The wall can, in particular, have a cross-section that is at least partially polygonal, circular, and / or elliptical. The wall can, in particular, have the shape of a cylinder, a cuboid, or a cube.

[0014] At least one fluid line can have a cross-section, for example polygonal, circular and / or elliptical, at least in sections along the heat exchanger.

[0015] According to one embodiment of the invention, the flow device is further configured to reverse the flow of the fluid medium as soon as the temperature of the phase change material changes relative to the phase transition temperature of the phase change material.

[0016] Thus, the flow direction can be changed as soon as the heat capacity of the phase change material, which can be absorbed or released as latent heat, has been completely absorbed or released.

[0017] In an alternative embodiment, the flow device is designed to reverse the flow of the fluid medium as soon as the phase change material has absorbed or transferred a predefined proportion of the heat that can be absorbed or transferred in a phase transition of the phase change material, in particular a proportion of 50% to 80%.

[0018] In particular, it is provided that the flow direction is reversed by the flow device for a predefined first period only when the heat capacity of the phase change material, which can be absorbed or released as latent heat, has been completely absorbed or released, and that the flow device reverses the flow direction for a predefined second period as soon as the phase change material has absorbed or released a predefined proportion of the heat that can be absorbed or transferred during a phase transition of the phase change material. Thus, the cooling or heating capacity of the device can advantageously be adapted to time-varying temperature gradients in the environment.

[0019] The flow direction can be changed, particularly cyclically, by means of the flow device, so that the phase change material repeatedly absorbs or releases latent heat.

[0020] In a further embodiment of the invention, the flow device is also configured to cyclically reverse the flow of the fluid medium after a predefined period of time, in particular after a period of time between 300s and 700s. The flow device can, for example, be a fan.

[0021] According to one embodiment of the invention, the device has several fans. In particular, it is provided that at least two fans are configured and designed to generate opposing flows along the fluid line. This advantageously enables the reversal of the flow direction according to the invention by alternately switching fans with the opposite flow direction on and off.

[0022] According to one embodiment of the invention, the flow device and the at least one fluid line are movable relative to each other such that the flow direction can be reversed by a relative movement between the flow device and the at least one fluid line. In particular, it is provided that the heat exchanger is a rotary heat exchanger. Here, the flow device can, for example, guide two separate, counter-rotating flows through the heat exchanger, with the heat exchanger alternately absorbing or releasing latent heat while rotating.

[0023] The filling opening can, for example, be located directly on the reservoir of the heat exchanger. Preferably, the filling opening is reversibly closable by means of a closure corresponding to the opening. The reservoir can, in particular, be enclosed by its wall in such a way that the reservoir forms a cavity when the opening is closed.

[0024] The heat exchanger has several fluid lines. This allows for an advantageous increase in the heat transfer surface area, through which heat can be exchanged between the phase change material and the fluid medium as it flows through the fluid lines.

[0025] The fluid lines are separated from each other via the reservoir. This advantageously allows the reservoir to be filled, particularly through a single filling port. Furthermore, this embodiment increases the heat transfer surface area. The possibility of using few, and especially only one, filling port also advantageously reduces the risk of leakage, which could cause the phase change material to escape from the reservoir or allow foreign materials to enter.

[0026] In particular, the fluid lines are designed to run parallel to a longitudinal axis of the heat exchanger through the reservoir. This arrangement of the fluid lines advantageously reduces the pressure drop of the fluid medium as it flows through the heat exchanger, thus contributing to heat exchange. The heat exchanger can be a shell-and-tube heat exchanger.

[0027] Furthermore, in one embodiment of the invention, the fluid lines, viewed in cross-section through the heat exchanger, extend around circular arcs and are arranged concentrically around the longitudinal axis of the heat exchanger. This results in an advantageously large heat transfer surface area, and the heat exchanger can still be filled, in particular via a single filling opening.

[0028] According to one embodiment of the invention, the at least one fluid line has structural elements for increasing heat transfer between the phase change material and the fluid medium. The structural elements are specifically designed to generate a flow in the region of the shaped elements. Preferably, this is a turbulent flow. The structural elements can, in particular, be bumps or dents.

[0029] According to one embodiment of the invention, the phase transition temperature of the phase change material is in the range of -50° to 100°C, particularly in the range of 10 K to 20 K relative to room temperature. Thus, by appropriately selecting the phase change material, an operating temperature adapted to room temperature can be advantageously chosen for the device. The device can also be advantageously operated at a constant temperature by utilizing latent heat.

[0030] In a further embodiment, the device is provided to have several heat exchangers. In particular, the heat exchangers are connected to each other in series via at least one fluid line, allowing the fluid medium to flow through the heat exchangers sequentially. Furthermore, in this embodiment, the respective reservoirs of the heat exchangers can be filled with different phase change materials. These different phase change materials can exhibit monotonically increasing or decreasing phase transition temperatures, particularly along the fluid connection. This advantageously enables a successive damping of the fluid medium's temperature as it flows through the device.This is particularly advantageous in the case of relatively high and / or fluctuating temperature differences between an input and an output of the device, whereby the heat capacities of the respective phase change materials are optimized and used accordingly by selecting the phase transition temperatures as described above.

[0031] According to one embodiment of the invention, the phase change material comprises at least one of the following: a salt hydrate, alcohol, ester, in particular fatty acid ester, or an organic material, in particular paraffin.

[0032] The material of the heat exchanger, in particular the wall and / or the at least one fluid line, can, for example, comprise polymers, composite materials, graphite, SiC, or metals, especially copper or stainless steel. In particular, the wall, together with the reservoir and the at least one fluid line, can form a microencapsulated, dimensionally stable heat exchanger made of a phase-change composite material.

[0033] In one embodiment of the invention, the heat exchanger, the PCM reservoir, or the at least one fluid line is manufactured by at least one of the following methods: injection molding, extrusion, additive and / or subtractive manufacturing.

[0034] In the following, exemplary embodiments as well as further features and advantages of the invention will be explained with reference to the figures. The figures show: Fig. 1 shows a first embodiment of a heat exchanger of the device; Fig. 2A shows a second embodiment of a heat exchanger of the device, wherein Fig. 2B a sectional drawing of the heat exchanger made of Fig. 2aFigure 1 shows a diagram in which several fluid lines running through the heat exchanger are visible; Figure 3 shows a third embodiment of a heat exchanger of the device; Figure 4 shows a fourth embodiment of a heat exchanger of the device; Figure 5 shows a fifth embodiment of a heat exchanger of the device; Figure 6 shows a sixth embodiment of a heat exchanger of the device; Figure 7 shows a seventh embodiment of a heat exchanger of the device; Figure 8 shows an embodiment of the device according to the invention; and Figure 9 shows temperature profiles measured with air flow at an inlet and an outlet of a heat exchanger according to the invention compared to the outlet of a conventional ceramic heat exchanger;

[0035] Fig. 1Figure 1 shows a first embodiment of a heat exchanger 11 of the device 10 according to the invention, the flow device 12 not shown here. The heat exchanger 11 has a wall 6 that defines a reservoir 2 which can be filled with or is filled with a phase change material. The wall 6 is cylindrical, so that the heat exchanger 11 extends about a longitudinal axis A. The heat exchanger 11 also has a filling opening 5 through which the reservoir 2 can be filled with the phase change material. Several fluid lines 1 extend from a first opening 3 to a second opening 4 through the heat exchanger 11, so that a fluid medium can flow through the fluid lines 1 for heat exchange with the phase change material. The fluid lines 1 are arranged parallel to each other and separated from each other by the reservoir 2.This ensures, on the one hand, a correspondingly large heat transfer surface between the fluid lines 1 and the reservoir 2, resulting in advantageously efficient heat exchange. Furthermore, this arrangement of the fluid lines 1 allows the reservoir 2 to be filled via a single filling opening 5, which simplifies the operation of the heat exchanger 11 and reduces the risk of leakage.

[0036] Fig. 2A and Fig. 2B Figure 1 shows a second embodiment of a heat exchanger 11 of the device 10 according to the invention. Here, the fluid lines 1 extend parallel to each other through the heat exchanger 11, wherein these, as in the figure shown in Fig. 2A The front face shown is visible and arranged in a circle around the longitudinal axis A. The diagram is from Fig. 2B allows a view behind the wall 6 of the heat exchanger 11 into the reservoir 2 of the heat exchanger 11, so that the fluid lines 1 running through it are visible.

[0037] Fig. 3 Figure 1 shows a third embodiment of a heat exchanger 11 of the device 10 according to the invention. The fluid lines 1 run analogously to the second embodiment. Fig. 2through the heat exchanger 11, which additionally has a filling opening 5 for filling the reservoir 2 with a phase change material. In this third embodiment, the fluid lines 1 of the heat exchanger 11 each have a circular cross-section with a diameter of 10 mm. The length of the fluid lines 1 along the longitudinal axis A of the heat exchanger 11 is approximately 200 mm in this third embodiment. The reservoir 2 of the heat exchanger shown in this third embodiment has a volume of approximately 2 liters. If the reservoir 2 is filled, for example, with a salt hydrate with a melting point of 21 °C, the heat absorbed or released as latent heat during the phase transition for the heat exchanger 11 of this third embodiment corresponds to approximately 460 kJ.

[0038] Fig. 4Figure 1 shows a fourth embodiment of a heat exchanger 11 of the device 10 according to the invention. The fluid lines 1 have a hexagonal cross-section perpendicular to their direction of extension through the heat exchanger 11.

[0039] Fig. 5Figure 1 shows a fifth embodiment of a heat exchanger 11 of the device 10 according to the invention. Here, the fluid lines 1 also run parallel to each other through the heat exchanger 1, and, viewed in cross-section through the heat exchanger 11 perpendicular to the longitudinal axis A of the heat exchanger 1, are formed around circular arcs 13. The circular arcs 13 are arranged concentrically around the longitudinal axis A. This shape and arrangement of the fluid lines 1 offers, on the one hand, an advantageously large heat transfer surface. Since the circular arcs 13 in this fifth embodiment do not form complete circles, but are interrupted by a section 14, the reservoir 2 can also be advantageously filled via a single opening 5.

[0040] Fig. 6 Figure 1 shows a sixth embodiment of a heat exchanger 11 of the device 10 according to the invention. Similar to the one in Figure 11, the heat exchanger 11 of the device 10 according to the invention is shown. Fig. 5In the fifth embodiment shown, the fluid lines 1, viewed here in cross-section through the heat exchanger 11, are formed around circular arcs 13, which are arranged concentrically around the longitudinal axis A. In contrast to the fifth embodiment, the circular arcs 13 are arranged here along two halves of the heat exchanger 11 and separated from each other by two sections 14.

[0041] Fig. 7 Figure 7 shows a seventh embodiment of a heat exchanger 11 of the device 10 according to the invention. The fluid lines 1 run analogously to the sixth embodiment shown in Figure 8. Fig. 6 through the heat exchanger 11, which additionally has a filling opening 5 for filling the reservoir 2 with a phase change material.

[0042] Fig. 8Figure 1 shows an embodiment of the device 10 according to the invention, comprising a heat exchanger 11 and a flow device 12. The device 10 shown here further includes an optional filter 7. The filter 7 is designed to filter foreign particles from the fluid medium flowing through the device 10. The flow device 12 and the filter 7 each have a cross-section that corresponds to the cross-section of the heat exchanger 11, so that the heat exchanger 11, the filter 7, and the flow device 12 can be arranged in series, and the flow device 12 can generate and reverse a flow of a fluid medium through the fluid lines 1.Thus, according to the invention, when the fluid medium flows through the heat exchanger 11, latent heat can be transferred from the phase change material to the fluid medium by absorption by the fluid medium, or absorbed by the phase change material by release of heat from the fluid medium. The flow device 12 can, for example, be a fan.

[0043] Fig. 9 shows measured temperature profiles for a device 10 according to the invention with the chamber filled with a phase-change material. Fig. 3The heat exchanger 11 shown in the diagram is depicted. The curves, shown in various shades of gray, depict temperature profiles at the outlet of a fluid line 1 of the heat exchanger 11 according to the invention, compared to the air temperature at the outlet of a fluid line 1 of a conventional ceramic heat exchanger during operation. The identical temperature at the respective inlets of both heat exchangers is also shown. A fan was used as the flow device 12 in each case. For the measurements shown, the device 10 was operated in a test rig, with the flow device 12 alternately directing cold air from a cooler at a temperature of 17°C and warm air from a heater at a temperature of 25°C through the device 10. A salt hydrate with a phase transition temperature of 21°C was used as the phase change material.

[0044] At time t=0, the flow device 12 was switched on and warm air flowed through the ceramic heat exchanger according to the invention as well as the conventional ceramic heat exchanger. At the discontinuities further along the flow path, the flow direction was reversed and cold or warm air was alternately flowed through the heat exchangers 11.

[0045] In the first few minutes after t=0, the ceramic heat exchanger shows only a very small difference between the air temperatures at the inlet and outlet, without this having a significant overall effect. In contrast, the PCM heat exchanger showed a considerable effect in reducing the air temperature for much longer periods than the ceramic heat exchanger, without even exhausting its storage capacity. Furthermore, the device 10 according to the invention advantageously allows for longer cycles compared to the conventional ceramic heat exchanger, which is beneficial in terms of the energy efficiency of the device 10. Reference symbol list

[0046] Fluid line 1 reservoir 2 First opening 3 Second opening 4 Filling opening 5 wall 6 filter 7 device 10 Heat exchanger 11 Flow device 12 circular arc 13 Section 14 longitudinal axis A

Claims

1. A device (10) for releasing and absorbing latent heat, comprising: - a heat exchanger (11) comprising a reservoir (2) which can be filled with or is filled with a phase-change material and which is delimited by a wall (6) having a filling opening (5) for filling or emptying the phase-change material, as well as a plurality of fluid lines (1) extending through the reservoir (2), through which a fluid medium can flow, wherein each fluid line (3) extends through the reservoir (2) of the heat exchanger (11) from a respective first opening (3) in the wall (6) to a respective second opening (4) in the wall (6), such that the fluid lines (3) are each separated from one another by the reservoir (2) and such that, when the fluid medium flows through the heat exchanger (11), latent heat can be transferred via heat exchange between the fluid lines (1) and the reservoir (2), so that latent heat can be transferred to the fluid medium from the phase-change material via heat absorption by the fluid medium, or absorbed by the phase-change material from the fluid medium via heat release, and - a flow device (12) which is configured to generate and reverse a flow of the fluid medium along the fluid line (1).

2. The device (10) according to claim 1, wherein the flow device (12) and the at least one fluid line (1) are movable relative to one another in such a way that the direction of flow can be reversed during relative movement between the flow device (12) and the at least one fluid line (1).

3. The device (10) according to claim 1 or 2, further comprising at least one filling opening (5) in fluid connection with the reservoir (2) of the heat exchanger (10) for filling or emptying the phase-change material.

4. The device (10) according to one of the preceding claims, wherein the fluid lines (1) each run through the reservoir (2) parallel to a longitudinal axis (A) of the heat exchanger (11).

5. The device (10) according to claim 4, wherein the fluid lines (1) extend in cross-section through the heat exchanger (11), viewed perpendicular to the longitudinal axis (A), around arcs of a circle (13), in particular wherein the arcs of a circle (13) are arranged concentrically around the longitudinal axis (A) of the heat exchanger (11).

6. The device (10) according to one of the preceding claims, wherein the at least one fluid line (1) comprises structural elements for enhancing heat transfer between the phase-change material and the fluid medium.

7. The device (10) according to one of the preceding claims, wherein the phase transition temperature of the phase-change material lies in the range from -50° to +100 °C, in particular in a range between 10 K and 20 K relative to the ambient temperature surrounding the device (10).

8. The device (10) according to one of the preceding claims, wherein the phase-change material comprises at least one of the following: a salt hydrate, an alcohol, an ester, in particular a fatty acid ester, or an organic material, in particular paraffin.

9. The device (10) according to one of the preceding claims, comprising a plurality of heat exchangers (11) which are in fluid communication with one another in series via their respective at least one fluid line (1), and wherein their respective reservoirs (2) each contain phase-change materials with phase transition temperatures that differ from one another.

10. The device (10) according to claim 9, wherein the phase transition temperatures of the respective phase-change materials in the respective reservoirs (2) decrease or increase monotonically along the fluid connection.