Device for transferring thermal energy into a fluid

Abstract

The invention relates to a device (1) for transferring thermal energy into a fluid, said device comprising a heat exchanger (2) which is located in a flow path (4) spatially delimited by a housing (3), the heat exchanger (2) having a plurality of flow channels (6) through which flow can pass along a main flow direction (5), the heat exchanger (2) having a heat storage capacity which can temporarily store thermal energy, a relatively high-energy fluid and a relatively low-energy fluid alternately flowing through the heat exchanger (2). The invention also relates to a method for using the device (1).

Description

[0001] Device for transferring heat energy into a fluid

[0002] The invention relates to a device for transferring or transmitting thermal energy into or to a fluid (heat regenerator), comprising a heat exchanger arranged in a flow path spatially defined by a housing. The heat exchanger has a plurality of flow channels through which flow can occur along a main flow direction. The heat exchanger has a heat storage capacity through which a defined amount of thermal energy can be temporarily stored.

[0003] The invention also relates to a method for using the device.

[0004] In addition to conventional heat exchangers (recuperators), regenerators can also be used to exchange heat between two fluids or to recover heat. They essentially consist of a porous or channeled heat storage unit. During a heating phase, a first, warm fluid flows through the heat storage unit and heats it up. The first fluid cools down. During a cooling phase, the stored heat is transferred to a second, cold fluid.

[0005] Applications of this technology can be found, for example, in the ventilation of buildings or enclosed spaces in general. So-called push-pull heat exchangers, such as those used for building ventilation, consist of a pipe into which a channeled ceramic element acts as a heat storage element and a fan with a reversible air flow direction are inserted. The unit is installed in the exterior wall of the building and alternately conveys warm indoor air (exhaust air) to the outside and, after reversing the air flow direction, cold outdoor air (fresh air) to the inside. This uses the heat from the exhaust air to preheat the fresh air.

[0006] To achieve high heat recovery efficiency, good heat transfer between the heat storage unit and the fluid must be ensured. The size of the surface area available for heat exchange and the heat transfer coefficient of the flow in the heat exchanger are crucial for this. The duration of the periods in which the heat exchanger is heated or cooled must be adapted to the heat capacity of the heat storage unit, for example, to prevent exhaust air, especially warm air, from being pumped further past the heat storage unit when the maximum heat capacity is reached.

[0007] The heat storage devices known in the prior art for such heat exchangers are usually made of a ceramic material. This is disadvantageous, for example, because the manufacturing costs are high. Furthermore, ceramics exhibit properties that are not necessary for use in ventilation systems for buildings or vehicles, such as resistance to high temperatures and aggressive media. Furthermore, the design options for the channel shape are severely limited, which has a negative impact on the level of heat transfer between fluid and matrix, the potential efficiency, and the operating range of the heat exchanger. Another disadvantage is that air humidity is adsorbed and desorbed in porous ceramics. This occurs particularly at and around the dew point.

[0008] To heat or air-condition the interior of a battery-electric vehicle, the required energy must be drawn from the vehicle's battery. This reduces the vehicle's range at high or low outside temperatures. Heat exchangers, such as regenerators, can also be used here to minimize energy consumption and thus increase the range.

[0009] Therefore, the object of the present invention is to create a device which at least partially solves the problems described with reference to the prior art and, in particular, makes it possible to transfer thermal energy between fluids, in particular thermal energy from a fluid with a higher energy level to a fluid with a lower energy level. These objects are achieved by the features of the independent claims. Advantageous further developments are specified in the dependent claims. The features individually recited in the claims can be combined with one another and / or with the facts of the description as desired. The description, particularly in conjunction with the figures, explains the invention and specifies additional embodiments.

[0010] A device is proposed for transferring thermal energy into a fluid or for transferring thermal energy to a fluid, comprising a heat exchanger which is arranged in a flow path spatially delimited by a housing, wherein the heat exchanger has a plurality of flow channels through which flow can pass along a main flow direction, wherein the heat exchanger has a heat storage capacity by means of which a, in particular defined, thermal energy can be temporarily stored, wherein the heat exchanger is alternately flowed through or can be flowed through by a fluid with a relatively higher energy and a fluid with a relatively lower energy.

[0011] The quantity and / or time of the thermal energy that can be temporarily stored can be specified or defined with reference to the operation of the device. In particular, means can be provided with which the temporal and / or volumetric flows through the device can be predetermined, so that the required heat storage capacity of the heat exchanger can also be predetermined or defined.

[0012] A device can be used, for example, for ventilating and / or temperature-regulating a building or for ventilating and / or temperature-regulating the interior of a motor vehicle. The flow path can be formed by a pipeline or, for example, by the air ducts of a motor vehicle. The heat exchanger is arranged in the flow path in such a way that a fluid, in particular air, can flow through it. When a first and / or warm air flows through the heat exchanger, heat or thermal energy can be absorbed by the heat exchanger and stored at least temporarily. When a second and / or cold air is then passed through the heat exchanger, it can absorb the heat or thermal energy stored in the heat exchanger.In the same way, other energies contained in the fluid, such as the evaporation enthalpy of air humidity, can be temporarily stored as heat or thermal energy in the heat exchanger.

[0013] This allows heat or thermal energy to be absorbed from indoor air, especially stale air, and transferred to the fresh air supplied from outside. Energy loss during air exchange can thus be reduced.

[0014] The heat exchanger is preferably flowed through in opposite directions when releasing heat or thermal energy and absorbing heat or thermal energy, thereby improving heat transfer to the air. The heat exchanger is preferably flowed through in opposite directions when releasing heat or thermal energy and absorbing heat or thermal energy, thereby improving heat transfer to the air.

[0015] Depending on the sequence of heat transfer steps, the freshly supplied air from outside can be heated or cooled. In addition to heat transfer between outside and inside air, an air flow can also be directed through or past heated components, such as the power electronics and / or battery of a vehicle, and the waste heat generated there can be used to heat fresh air for the interior.

[0016] The fluid flowing through the heat exchanger always has a temperature level. The fluid can have a higher energy level and thus be warmer, or a lower energy level and thus be colder. The heat or thermal energy is transferred from the fluid to the heat exchanger as it flows through the heat exchanger, and is then released from the heat exchanger to the fluid as it subsequently flows through the heat exchanger with a fluid of lower energy level.

[0017] It is possible for the flow path to have a conveying device or to be fluidically connected to a conveying device by which the fluid can be conveyed through the flow path. A suitable conveying device could, for example, be a fan arranged in the flow path. Alternatively, the fan of a vehicle air conditioning or ventilation system can also be used to direct a fluid flow, particularly in a targeted manner, through the heat exchanger.

[0018] It is possible for the heat exchanger to be formed (at least partially) from a plurality of foils, wherein the foils are at least partially structured and the foils are stacked on top of one another to form a layer stack. A preferred embodiment is characterized in that the foils stacked on top of one another to form a layer stack are wound and / or wound, in particular around at least one rotational axis.

[0019] In this way, a matrix can be created that has a large surface area wettable by the fluid and has a plurality of flow channels between the individual films through which the fluid can flow. The films then simultaneously serve as a heat storage device, absorbing the heat or thermal energy of a first and / or warm fluid and ultimately releasing the heat or thermal energy to a second and / or cold fluid when flowing through it.

[0020] The foils can be made of metal or plastic. Metal foils or plastic foils are simple and particularly cost-effective to manufacture. The material properties can be easily adapted to the respective area of ​​application, which enables the precise production of a heat exchanger for a specific purpose. It is possible for at least one of the foils to be electrically conductive and to be electrically connected to a voltage source. An electrically conductive foil can provide additional heating for a fluid flowing past. The foil can be connected to a voltage source and heated or capable of being heated using its ohmic resistance. The electrical insulation of the current-carrying foils from neighboring foils can be achieved by adjacent, electrically non-conductive foils.These can, for example, be made of a non-electrically conductive material or have a non-conductive coating.

[0021] The heat exchanger can be made of a composite material, using a material with relatively higher thermal conductivity and a material with relatively lower thermal conductivity.

[0022] This serves primarily to reduce heat conduction within the carrier material, which can reduce the efficiency of the regenerator. Preferably, the material with the higher thermal conductivity is interrupted at short intervals in the direction of flow, allowing good efficiency to be achieved even when using materials with high thermal conductivity.

[0023] It may also be expedient if the material with the relatively higher thermal conductivity is interrupted into several sections along the main flow direction. This can be achieved, for example, by films with slits. The main flow direction can, in particular, extend at least partially parallel to a longitudinal axis of the device, the heat exchanger, and / or the housing.

[0024] The structured part of the foils can have cross-sectional narrowing or turbulence-generating structures, which can be used to throttle the fluid flow in the direction of flow. This allows for targeted flow throttling. The throttling can be used to improve heat exchange between the flowing fluid and the channel wall, or to induce a phase change in the fluid. The turbulence-generating structures can be designed asymmetrically so that they have different levels of effectiveness in the two flow directions. A heat exchanger with integrated throttling can be particularly advantageous in the design of refrigeration machines, as the heat exchanger can also simultaneously assume the function of the throttle.

[0025] It is possible for the heat exchanger and throttle to be integrated into a single component. This reduces the number of required components and can significantly simplify a system or device. This is particularly advantageous for use in refrigeration systems.

[0026] According to a further aspect, a method for heating or cooling a room using a device (described here) is proposed, wherein a, in particular first, higher-temperature fluid flows through the heat exchanger, the thermal energy of the (higher-temperature) fluid being transferred to the heat exchanger. Subsequently, a, in particular second, lower-temperature fluid flows through the heat exchanger, the thermal energy stored in the heat exchanger being transferred to the (low-temperature) fluid. This can reduce the energy required for heating or air conditioning, thus increasing the range of battery-electric vehicles.

[0027] The device proposed here is intended to be used in particular to improve the range of battery-electric vehicles, as less energy from the batteries needs to be used for ventilation, cooling, or heating of the interior. By utilizing the waste heat from the vehicle's drive components, such as the battery, power electronics, and electric drive motor, energy consumption can be further reduced, which also has a positive effect on the range.

[0028] The technical details and / or modes of operation specified with reference to the device can also be used to characterize the method, and vice versa. In particular, the device can be configured to carry out the method, or the method can be carried out using a device proposed here.

[0029] The invention and the technical environment are explained in more detail below with reference to the figures. It should be noted that the figures show a particularly preferred variant of the invention, but are not limited thereto. Identical components in the figures are provided with the same reference numerals. They show, by way of example and schematically:

[0030] Fig. 1 : a building with a device for transferring heat energy; and

[0031] Fig. 2: a heat exchanger of the device in a cross section.

[0032] Fig. 1 shows a building 15 in which a device 1 for transferring thermal energy is arranged. The device 1 comprises a flow path 4 with a first opening 16 and a second opening 17. The first opening 16 is located inside the building 15 and the second opening 17 outside the building 15. The flow path 4 extends from a room 13 of the building 15 to an outdoor area 18 of the building 2. A conveying device 7 and a heat exchanger 2 are arranged in the flow path 4. The heat exchanger 2 extends along a longitudinal axis 14 and has a plurality of flow channels 6. The flow channels 6 extend parallel to the longitudinal axis 14 or to a main flow direction 5. The heat exchanger 2 extends along the longitudinal axis 14 with a length 19.

[0033] By means of the conveying device 7, an air flow 20 can be generated in the flow path 4. The conveying device 7 can be operated such that used air from the room 13 of the building 15 enters the flow path 4 via the first opening 16, flows through the heat exchanger 2, and flows out of the flow path 4 into the outdoor area 18 via the second opening 17. In this case, the first opening 16 serves as an air inlet and the second opening 17 as an air outlet. If the used air flows through the flow path 4 from the first opening 16 to the second opening 17, the heat exchanger 2 can temporarily store thermal energy of the air flow or the used air.

[0034] The conveying device 7 can then be operated such that fresh air from the outside area 18 enters the flow path 4 via the second opening 17, flows through the heat exchanger 2, and flows from the flow path 4 into the room 13 of the building 15 via the first opening 16. In this case, the second opening 17 serves as an air inlet and the first opening 16 as an air outlet. As the fresh air flows through the flow path 4 from the second opening 17 to the first opening 16, the heat exchanger 2 can release the temporarily stored thermal energy to the air flow or the fresh air. This preheats the fresh air flowing into the building 15.

[0035] Fig. 2 shows the heat exchanger 2 in a cross-section along the section line II-II shown in Fig. 1. The heat exchanger 2 is arranged in a housing 3. The heat exchanger 2 comprises a plurality of structured foils 9 and smooth foils 8. The structured foils 9 and the smooth foils 8 are stacked alternately on top of one another to form two layer stacks 10, and the layer stacks 10 are wound around a rotation axis 11 to form the heat exchanger 2, such that the foils 8, 9 form the plurality of flow channels 6. At least one of the foils 8, 9 is electrically conductive and is connected to a voltage source 12 (electrically conductive).

[0036] List of reference symbols

[0037] 1 device

[0038] 2 heat exchangers

[0039] 3 housings

[0040] 4 Flow path

[0041] 5 Main flow direction

[0042] 6 flow channel

[0043] 7 Conveyor device

[0044] 8 smooth foil

[0045] 9 structured foil

[0046] 10 layer stacks

[0047] 11 axis of rotation

[0048] 12 Voltage source

[0049] 13 Room

[0050] 14 Longitudinal axis

[0051] 15 buildings

[0052] 16 first opening

[0053] 17 second opening

[0054] 18 Outdoor area

[0055] 19 length

[0056] 20 Airflow

Claims

Patent claims 1. Device (1) for transferring thermal energy into a fluid, with a heat exchanger (2) which is arranged in a flow path (4) spatially delimited by a housing (3), wherein the heat exchanger (2) has a plurality of flow channels (6) through which flow can pass along a main flow direction (5), wherein the heat exchanger (2) has a heat storage capacity by means of which thermal energy can be temporarily stored, and wherein the heat exchanger (2) is alternately flowed through by a fluid with a relatively higher energy and a fluid with a relatively lower energy.

2. Device (1) according to claim 1, characterized in that the flow path (4) has a conveying device (7) or is fluidically connected to a conveying device (7) by means of which the fluid can be conveyed through the flow path (4).

3. Device (1) according to one of the preceding claims, characterized in that the heat exchanger (2) is formed from a plurality of films (8, 9), wherein the films (8, 9) are at least partially structured and the films (8, 9) are stacked on top of one another to form a layer stack (10).

4. Device (1) according to claim 3, characterized in that the films (8, 9) stacked on top of one another to form a layer stack (10) are wound or wound around at least one axis of rotation (11).

5. Device (1) according to one of the preceding claims 3 or 4, characterized in that the foils (8, 9) are made of metal or plastic.

6. Device (1) according to one of the preceding claims 3 to 5, characterized in that at least one of the films (8, 9) is electrically conductive and is electrically conductively connected to a voltage source (12).

7. Device (1) according to one of the preceding claims, characterized in that the heat exchanger (2) is made of a composite material, wherein a material with a relatively higher thermal conductivity and a material with a relatively lower thermal conductivity are provided.

8. Device (1) according to claim 7, characterized in that the material with the relatively higher thermal conductivity is interrupted into several sections along the main flow direction (5).

9. Device (1) according to one of the preceding claims, characterized in that the structured part of the foils (8, 9) has cross-sectional narrowing or turbulence-generating structures, by means of which a throttling of the fluid flow in the flow direction can be generated.

10. A method for heating, cooling or ventilating a room (13) using a device (1) according to one of the preceding claims, characterized in that the heat exchanger (2) is flowed through with a fluid of higher temperature, the thermal energy of the fluid being transferred to the heat exchanger (2), the heat exchanger (2) then being flowed through with a fluid of lower temperature, the thermal energy stored in the heat exchanger (2) being transferred to the fluid.

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