Patent Application
20250102203
The present invention relates to a heat pump for generating process heat and a system for generating process heat comprising the heat pump. The present invention also relates to a method for generating process heat and a control device which can control or regulate a heat pump to carry out the method.
The technology of heat pumps is generally well known. For example, heat pumps are used to absorb thermal energy from a first external medium (e.g., ambient air or liquids) by means of mechanical work and, in addition to the drive energy used for mechanical work, to transfer it to a second external medium as useful energy or useful heat. The second external medium is a medium to be heated. When implementing such a heat pump in a system for generating useful or process heat, for example, in a geothermal system, the first external medium can be used, for example, liquids contained in the earth's rock. In industrial processes, for example, warm exhaust gases or process fluids can also serve as the first external medium.
Currently, heat pumps are used, in particular, for heating buildings. However, applications have also become known in which heat pumps are used to generate heat required for industrial processes. Exemplary industrial methods include steam generation, drying processes, sterilization processes, distillation processes, cooking processes or industrial heat distribution processes. Such methods sometimes require high process temperatures of well over 100° C.
Simultaneously, in an industrial context, high demands are placed on the efficiency and the achievable overall thermal output of the heat pump. A low level of effort or low costs for the heat pump as such are also an important industrial requirement.
For example, a high-temperature heat pump is known from DE 10 2011 086 476 A1, which has a fluid circulation system for absorbing thermal energy through the fluid from a first reservoir using technical work and for releasing thermal energy through the fluid to a second reservoir for heating the second reservoir.
Another high-temperature heat pump is described in DE 10 2012 015 647 A1, which is composed of a compressor, a source and a useful heat exchanger, an internal heat exchanger, as well as a control valve and auxiliary units.
The object of the present invention is therefore to propose an improved heat pump that offers high efficiency as well as a high overall thermal performance and can simultaneously be implemented with little effort.
The task is solved by means of the objects of the independent Claims 1, 6, 8 and 15. Preferred embodiments of the present invention result from the features mentioned in the subclaims and furthermore from the present disclosure as a whole.
A first aspect of the invention relates to a heat pump for generating process heat comprising a closed working-medium circulation system which is designed to guide a fluid working medium in one direction of circulation and in which the units mentioned under a) to d) are fluidically connected in series in the direction of circulation on a technical level:
According to the invention, it is provided that a heat-exchanger unit is fluidically integrated on a technical level in the working-medium circulation system between the condenser unit and the expansion unit, which is designed to transfer thermal energy from the compressed fluid working medium in the liquid aggregate state to a third external medium.
In other words, a heat pump is provided in the case of which there are two heat sinks. A heat sink is a spatially limited area, for example, a body, that releases thermal energy stored in it or supplied to an adjacent medium in a non-retrieval manner. The two heat sinks are provided by the condenser unit and the heat-exchanger unit in the heat pump according to the invention: Thus, when the heat pump is used as intended, thermal energy is released in the condenser unit as a result of a phase change of the working medium from the gaseous to the liquid aggregate state during condensation. This energy, also known as heat in thermodynamics, is output to the second external medium that is adjacent to the condenser unit or when it flows through it. Since the second external medium is intended to have a lower temperature than the working medium, the transferred heat cannot be retrieved (first heat sink) and is available in the second external medium as useful or process heat. In addition, when the heat pump is used as intended, thermal energy is transferred from the liquefied working medium to the third external medium, which is adjacent to the heat-exchanger unit or when it flows through it. Since the third external medium is intended to have a lower temperature than the working medium, this heat cannot be retrieved (second heat sink) either and is available in the third external medium as additional useful or process heat.
The heat pump of the invention thus offers the advantage that the heat still contained in the hot liquid working medium after condensation is additionally available as useful heat at the heat-exchanger unit. For example, the useful heat recovered from the condenser unit can initially be used to generate steam directly with the second external medium, and the additional useful heat gained from the heat-exchanger unit can be used to generate steam or to heat a liquid. The heat pump of the invention is particularly well suited for generating process heat for processes that run at different temperature levels. In this case, the second external medium can preferably be used for a process at a higher temperature level and the third external medium for a process at a relatively lower temperature level.
All this makes better use of the energy supplied by the compression unit, such as electrical power, to generate useful heat for example. This significantly increases the efficiency of the heat pump according to the invention and enables a high useful heat output overall. Simultaneously, the technical complexity of the heat pump according to the invention is kept low, which reduces the effort. This also applies to the subsequent modification of a conventional heat pump without the heat-exchanger unit according to the invention. All this results in an extremely good cost-benefit ratio.
With regard to the terms used, it should be noted that “fluidically in series on a technical level” is to be interpreted as being functional. This means that the units in question can, but do not have to, be directly connected to each other. However, they are passed through by the working medium one after the other. With regard to the above-mentioned aggregate states of the working medium, a liquid aggregate state can also be referred to as liquid working medium and in the case of a gaseous aggregate state also as gaseous or vaporous working medium. In principle, in accordance with expert understanding, these aggregate states do not always exist in their pure form. For example, liquid working medium may contain parts or residues of gaseous working medium and vice versa. Permissible tolerances in this regard result from the generally known functional principle of a heat pump and the technical doctrine disclosed in the present case.
The evaporation unit, condenser unit and heat exchanger unit may preferably each comprise or be designed as a heat exchanger. Each of these units can preferably be flowed through by the external medium corresponding to it.
Preferably, the closed working-medium circulation system of the heat pump is filled with the fluid working medium.
The compression unit is used to compress the gaseous working medium by increasing the pressure and temperature. The compression unit can therefore also be referred to as a compressor. The gaseous working medium is brought from a lower to a higher pressure level in the compression unit by performing wherein mechanical work, the compression simultaneously leads to an increase in temperature in the working medium. For this purpose, the compression unit can preferably comprise a drive to provide for the mechanical work. This can preferably be an electric motor that converts electrical power into mechanical work.
The compression unit is preferably designed to drive the circulation of the working medium. The working medium evaporated in the evaporation unit can, for example, be sucked in, compressed and output under pressure by the compression unit. In this example, the driving force of the working medium circulation comprises a suction force on an input side of the compression unit and a compression force on an output side.
Different variants of compression units in heat pumps are known from prior art. These include, for example, reciprocating, rotary piston, screw, turbo, vane cell, rotary lobe or scroll compressors. For the heat pump according to the invention, reciprocating compressors are preferably taken under consideration, in particular, reciprocating compressors with a plurality of piston-cylinder units. When used in high-temperature heat pumps with large pressure differences, such compressors offer particularly high energy efficiency and mechanical stability.
The expansion unit can preferably comprise an expansion valve, which can also be referred to as a throttle or throttle valve. From a physical point of view, the expansion unit represents a flow resistance for the working medium, which decompresses as it flows through the expansion unit.
In the preferred embodiment of the heat pump of the invention, it is provided that the heat-exchanger unit comprises a supercooling unit. The supercooling unit is designed to cool the liquefied working medium in thermal interaction with the third external medium. Thereby, any components or residues of gaseous working medium can also condense.
The supercooling unit leads to a significantly improved utilization of the heat stored in the working medium or residual heat after the condenser unit.
In the preferred embodiment of the heat pump of the invention, a regulating device is provided which is designed to adjust the power at the heat-exchanger unit. The regulating device can be used, for example, to adjust the volumetric flow of the third external medium by the heat-exchanger unit. The regulating device or also another regulating device can also be used to adjust the volumetric flow of the working medium via the heat-exchanger unit.
Basically, the regulating device regulates the heat transfer from the working medium to the third external medium. Thus, the operation of the heat pump of the invention can be optimally adjusted to the internal processes of the heat pump on the one hand and the processes implemented with the third external medium on the other hand.
In the preferred embodiment of the heat pump of the invention, it is provided that a working-medium collection unit is provided in a fluid-technical manner between the condenser unit and the heat-exchanger unit, which is designed to separate the fluid working medium in the liquid aggregate state from the fluid working medium that still exists in the gaseous aggregate state and to convey the fluid working medium in the liquid aggregate state in the direction of the heat-exchanger unit.
In this way, for example, the above-mentioned residues of gaseous working medium can be separated. These can also be fed back into the condenser unit, for example. Furthermore, the working-medium collection unit can be designed to separate lubricant or oil residues (e.g., from the compression unit) from the working medium.
In the preferred embodiment of the heat pump of the invention, it is provided that a heat recovery unit is provided and designed in a fluid-technical manner within the working-medium circulation system in such a way that thermal energy is transferred from the compressed fluid working medium in the liquid aggregate state, if it flows from the condenser unit in the direction of the expansion unit, to the fluid working medium in the gaseous aggregate state when it flows from the evaporation unit in the direction of the compression unit.
In this way, additional heat from the heat-pump process can be returned to the evaporated working medium.
The heat recovery unit preferably includes a heat exchanger, which can also preferably include a recuperator or suction-gas heat exchanger. The term suction-gas heat exchanger implies that it is arranged between the evaporation unit and the compression unit and that gaseous or vaporous working medium flowing through the suction-gas heat exchanger is sucked in the direction of the compression unit.
There is a particularly favourable synergetic effect between the heat recovery unit and the regulating device of the heat-exchanger unit described above. The regulating device can be used to adjust the temperature level of the liquid working medium after passing through the heat-exchanger unit in such a way that it is sufficiently above the temperature level of the evaporated working medium that enters the heat recovery unit on its way to the compression unit. This ensures that the liquid working medium is always hot enough to transfer heat to the vaporous working medium.
This is also particularly favourable for starting up the heat pump as long as the working-medium circulation system has not yet been completely heated to operating temperature. For example, in order to ensure overheating of the evaporated working medium in the heat recovery unit, the supply of the third external medium with the regulating device can be reduced or blocked during the start-up phase of the heat pump so that the liquid working medium retains its heat for the process of subcooling at the heat recovery unit.
For the integration of the heat recovery unit, a steam pipe section of the working-medium circulation system arranged between the evaporation unit and the compression unit and a liquid line section of the working-medium circulation system arranged between the condenser unit and the expansion unit are preferably routed through the heat recovery unit. The fluid line section is particularly preferred between the working-medium collection unit and the expansion unit. The liquid line section is particularly preferably located between the heat-exchanger unit and the expansion unit.
Another aspect of the invention relates to a system for generating process heat comprising:
In principle, any unit that can contain or provide the corresponding medium can be considered a reservoir of external media. In particular, a heat source containing the medium can be considered as the reservoir of the first external medium. An example here would be the soil, which can contain warm liquids. However, reservoirs from industrial processes that contain, for example, warm exhaust gases or warm process fluids can also be considered. As a reservoir of the second and third external medium, interfaces of processes in which the useful heat of the heat pump is to be used are generally considered. Examples include steam-powered power or heat processes, such as the operation of a steam piston, drying operations, sterilization processes, distillation processes, cooking processes, or industrial heat distribution operations for example.
The external media can be the same or different. The second and third medium can also come from the same or different reservoirs.
Preferably, the first external medium and/or the second external medium and/or the third external medium may include water or be water. Water can also be present as water vapour.
Fluid substances or mixtures of substances which, due to their thermodynamic properties, evaporate at a relatively low temperature and can be raised to a higher temperature by compression are suitable as fluid working medium. Hydrocarbons (HC working medium), hydrofluoroolefins (HFO working medium) or hydrochlorofluoroolefins (HCFO working medium) are particularly suitable as work materials used in the heat pump according to the invention. In the case of HFO working medium, those substances with a GWP value (Global Warming Potential) of less than 25 are particularly suitable. Preferably, consideration should be given to R1336mzz-2, R1336mzz-E, R1233zd, R1224yd, butane, pentane or similar substances as working media.
The control device can be designed to perform both control as well as regulation operations. For the sake of simplification, it does not make a clear distinction between the terms “control” and “regulation”. It is generally self-evident to the person skilled in the art that he can provide measuring means as well as signal conduction or signal processing means as required in the heat pump or the system of the invention. This may be necessary, for example, for the implementation of control processes or also for pure control functions. Exemplary important measured variables for regulating and controlling the heat pump include temperatures and pressures.
The control device is preferably connected to or integrated with an power-supply unit. For example, the power-supply unit can supply electrical power, for example, to supply an electric motor of the compression unit. The control device, in turn, can control a speed of the compression unit for example. However, the control device can also control or control other elements of the system of the invention, such as the regulating device, the expansion unit or other elements such as valves or sensors.
The heat-exchanger unit, especially as a supercooling unit, can also have a separate control system with similar functional capabilities. It is also possible to subordinate this separate controller to the control device described above. In principle, centralized or decentralized control architectures can be used. This also applies in the context of external processes in which the heat pump is to be used to obtain (geothermal) heat or to use the (industrial) useful heat generated, so that the heat pump or the system can be embedded in these processes in terms of control technology.
The control processes in the system according to the invention are preferably designed in such a way that the absorption of a sufficient amount of gaseous working medium is always ensured in the compression unit and that it does not unintentionally pass into the liquid phase during compression. In addition, the control processes are preferably designed in such a way that the heat-exchanger unit, especially as a supercooling unit, transfers only enough heat to the third external medium that there is still a sufficiently high temperature level at the heat recovery unit.
A further aspect of the invention relates to a method for generating process heat in which a fluid working medium is guided in a closed working-medium circulation system in one direction of circulation and in which the steps mentioned under a) to d) are sequentially passed through in the direction of circulation:
According to the invention, it is intended that between steps c) and d) a transfer of thermal energy from the compressed fluid working medium in the liquid aggregate state to a third external medium takes place (step c″).
In the method of invention, a heat pump according to the invention and/or a system according to the invention in accordance with the present disclosure can preferably be used.
With regard to possible embodiments or the operation of the heat pump according to the invention or the system according to the invention, it is noted that all features disclosed in the description of the method according to the invention with reference to the device (e.g., structure, properties, possible process parameters) can also be disclosed as independent possible features of the heat pump or the system. Analogously, any features disclosed with regard to the heat pump according to the invention or the system according to the invention with reference to the method (e.g., process parameters, step sequences, effects, means used) are also disclosed as independent features of possible embodiments of the method according to the invention.
With regard to the above-mentioned method steps, “sequential” refers to a consideration of a volume element of the fluid working medium that has been tracked throughout the method. Of course, the steps preferably run continuously and parallel to each other, while the fluid working medium circulates through the working-medium circulation system.
In the preferred embodiment of the method of the invention, it is provided that the compressed fluid working medium in the liquid aggregate state is supercooled during the transfer of the thermal energy to the third external medium.
In the preferred embodiment of the method of the invention, it is provided that the power for transferring the thermal energy from the compressed fluid working medium in the liquid aggregate state to the third external medium is adjusted. Preferably, the power is controlled, being particularly preferred, it is regulated.
In the preferred embodiment of the method of the invention, it is provided that after step c) and before the fluid working medium transfers the thermal energy to the third external medium, a separation of the fluid working medium in the liquid aggregate state from the still existing fluid working medium in the gaseous aggregate state takes place and a transfer of the fluid working medium to the transfer of the thermal energy to the third external medium takes place (step c′).
In the preferred embodiment of the method of the invention, it is provided that between steps c) and d), thermal energy is transferred from the compressed fluid working medium in the liquid aggregate state to the fluid working medium in the gaseous aggregate state, which is between steps a) and b) (step a′).
In the preferred embodiment of the method of invention, it is provided that at least one of the following temperature levels is achieved:
It is important that the temperature of the first external medium is below the temperature of the second and third external medium. Nevertheless, the temperature of the first external medium must be above the temperature of the working medium evaporated at step a), preferably so far above it that the working medium can be efficiently evaporated by means of the thermal energy supplied by the first external medium.
Within the above-mentioned temperature levels, useful heat outputs of more than 250 kW can be provided, in particular, even up to 5 MW.
A further aspect of the invention relates to a control device, designed and configured for controlling or regulating a heat pump according to the invention and/or a system according to the invention for carrying out a method according to the invention in accordance with the present disclosure.
As a general rule, all features disclosed herein with reference to a particular embodiment can also be combined with other embodiments of the invention. In parts, this also applies, in particular, to individual features, as long as it is not explicitly pointed out that there is an inseparable fluidic connection on a technical level between certain features which must be retained in order to implement the invention.
In the following, the invention is explained by means of exemplary embodiments and schematic drawings. Hereby, the figures show:
The heat pump 12 for generating process heat comprises a closed working-medium circulation system 14 which is designed to guide a fluid working medium 16 in a circulation direction 18. The system 10 comprises fluid working medium 16, which is located in the closed working-medium circulation system 14 of the heat pump 12.
In the working-medium circulation system 14, the units mentioned under a) to d) are fluidically connected in series in the direction of circulation 18 on a technical level.
The working-medium circulation system 14 comprises a) an evaporation unit 20 which is designed to transfer thermal energy from a first external medium 22 to the fluid working medium 16 and to convert the fluid working medium 16 from a liquid aggregate state 24 to a gaseous aggregate state 26.
For this purpose, the system 10 comprises a reservoir 28 of the first external medium 22, which is fluidically connected to the evaporation unit 20 of the heat pump 12 on a technical level.
The working-medium circulation system 14 also includes b) a compression unit 30, which is designed to compress the fluid working medium 16 in the gaseous aggregate state 26 under pressure and subject to an increase in temperature.
The working-medium circulation system 14 further comprises c) a condenser unit 32 which is designed to transfer thermal energy from the compressed fluid working medium 16 to a second external medium 34 and to convert the compressed fluid working medium 16 from the gaseous aggregate state 26 to the liquid aggregate state 24.
For this purpose, the system 10 comprises a reservoir 36 of the second external medium 34, which is fluidically connected on a technical level to the condenser unit 32 of the heat pump 12.
The working-medium circulation system 14 also includes d) an expansion unit 38 which is designed to decompress the compressed fluid working medium 16 in the liquid aggregate state 24 under pressure and subject to a reduction in temperature.
In the heat pump 12, it is provided that a heat-exchanger unit 40 is fluidically integrated on a technical level between the condenser unit 32 and the expansion unit 38 in the working-medium circulation system 14, which is designed to transfer thermal energy from the compressed fluid working medium 16 in the liquid aggregate state 24 to a third external medium 42. In the present exemplary embodiment, the heat-exchanger unit 40 preferably comprises a supercooling unit 44.
The system 10 comprises a reservoir 46 of the third external medium 42, which is fluidically connected on a technical level to the heat-exchanger unit 40 of the heat pump 12.
In the present exemplary embodiment, the heat pump 12 preferably comprises a regulating device 48. The regulating device 48 is designed to adjust the power at the heat-exchanger unit 40. For example, the regulating device 48 can be designed as a valve that sets a volumetric flow of the third external medium 42 through the heat-exchanger unit 40.
In the present exemplary embodiment, it is preferably provided that a working-medium collection unit 50 is provided in a fluid-technical manner between the condenser unit 32 and the heat-exchanger unit 40, which is designed to separate the fluid working medium 16 in the liquid aggregate state 24 from any remaining remnants of fluid working medium 16 in the gaseous aggregate state 26, where applicable, and to convey the fluid working medium 16 in the liquid aggregate state 24 in the direction of the heat-exchanger unit 40.
Furthermore, in the exemplary embodiment shown, a heat recovery unit 52 is provided and designed in a fluid-technical manner within the working-medium circulation system 14 in such a way that thermal energy from the compressed fluid working medium 16 in the liquid aggregate state 24, if it flows from the condenser unit 32 in the direction of the expansion unit 38, can be transferred to the fluid working medium 16 in the gaseous aggregate state 26 when it flows from the evaporation unit 20 to the compression unit 30.
For the operation of the heat pump 12, the system 10 comprises a control device 54, which is at least actively connected to the compression unit 30 of the heat pump 12. The control device 54 is designed and configured for controlling or regulating the heat pump 12 in order to carry out a method for generating process heat according to the invention. In the exemplary embodiment shown, the control device 54 also controls the regulating device 48 via corresponding signals 56.
The method of generating process heat according to the invention is now explained by means of a corresponding T-h diagram, which is shown in
In a purely exemplary manner, in this exemplary embodiment, the first 22, second 34 and third 42 external medium are each water.
In the method for generating process heat, the fluid working medium 16 is guided in the circulation direction 18 in the working-medium circulation system 14. Thereby, the steps mentioned under a) to d) are sequentially run through in the direction of circulation 18:
First, in one step a) a transfer of thermal energy from the first external medium 22 to the fluid working medium 16 and a transfer of the fluid working medium 16 from the liquid aggregate state 24 to the gaseous aggregate state 26 takes place. This is achieved by way of example using the evaporation unit 20 shown in
Optionally, in this example, at a step a′) with working medium 16 in the gaseous aggregate state 26, which is connected in parallel between the steps c) and d) explained later, thermal energy is transferred from compressed fluid working medium 16 in the liquid aggregate state 24 to the fluid material 16 in the gaseous aggregate state 26, which is just between step a) and the following step b). The transfer of thermal energy is achieved by using the heat recovery unit 52 shown in
At the following step b), the fluid working medium 16 is compressed in the gaseous aggregate state 26 under an increase in pressure and temperature. The compression is achieved by way of example using the compression unit 30 shown in
At a step c), thermal energy is then transferred from the compressed fluid working medium 16 to a second external medium 34 and the compressed fluid working medium 16 is transferred from the gaseous aggregate state 26 to the liquid aggregate state 24. This is achieved by using the condenser unit 32 shown in
An optional step c′) now follows, which takes place after step c) but before step c), which will be explained later. At step c′), the fluid working medium 16 in the liquid aggregate state 24 is separated from the fluid working medium still present 16 in the gaseous aggregate state 26 if the latter is still present. This is followed by conveying the fluid working medium 16. All this is achieved by way of example using the working-medium collection unit 50 shown in
There is also a step c″) that takes place between steps c) and d). In this case, a transfer of thermal energy takes place from the compressed fluid working medium 16 in the liquid aggregate state 24 to a third external medium 42. This is achieved by using the heat-exchanger unit 40 shown in
This is followed by step a′) on the side of the working medium 16 in the liquid aggregate state 24, which, as described at the beginning, follows between steps c) and d). The compressed fluid working medium 16 leaving the heat-exchanger unit 40 in the liquid aggregate state 24 transfers thermal energy in the heat recovery unit 52 to the fluid working medium 16 in the gaseous aggregate state 26, which is just between steps a) and b).
At the following step d), the compressed fluid working medium 16 is expanded in the liquid aggregate state 24 under pressure and subject to a reduction in temperature. This is achieved by using the expansion unit 38 shown in
Based on the described exemplary embodiment of the method, concrete tests were carried out by the applicant, the results of which are summarised in the table below. Tests I and III were carried out with conventional systems for generating process heat, whose heat pumps do not have a second heat sink. Experiments II (corresponding to I) and VI (corresponding to III) were carried out with the system 10 for generating process heat according to the invention, as described in
During the tests, the temperature 58 of the first external medium 22 was between 20° C. and 150° C., the temperature 64 of the second external medium 34 between 50° C. and 250° C. and the temperature 74 of the third external medium 42 between 40° C. and 200° C. R1233zd was used as working medium 16 in the heat pump 12.
In operation of the heat pump, the temperature 58 of the first external medium 22 was measured in ° C. at the inlet 60 into the evaporation unit 20 and at the outlet 62 from it. Furthermore, the temperature 64 of the second external medium 34 was measured in ° C. at the inlet 66 into the evaporation unit 32 and at the outlet 68 from it. At the inlet 70 and the outlet 72 of the heat-exchanger unit 40, the temperature 74 of the third external medium 42 was also measured in ° C. In the conventionally carried out tests I and III, the fields for 70 and 72 are therefore empty, since no heat-exchanger unit 40 was available. The table also shows: the heat output 76 transferred at the condenser unit 32, the heat power transferred at the heat-exchanger unit 4078 (therefore empty for tests I and III), the heat power transferred at the evaporation unit 2080 and the output 82 transmitted via the compression unit 30, here as an example as electric drive power. All power values are shown in kW. Finally, the table shows: the COP value 84 determined in the experiment, the theoretically achievable COP value 86 and the ratio of COP value 84/theoretically achievable COP value 86, which is also referred to as grade 88. The COP value 84 is also known as the coefficient of performance and indicates the total heat output 76+78 in relation to the drive power 82 required for it.
A comparison of tests I and II as well as III and IV clearly shows that, in tests II and IV, both the COP value 84 and the grade 88 could be significantly increased compared to conventional tests I and III when the method for generating process heat was carried out according to the invention using the system according to the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2022 101 440.1 | Jan 2022 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2023/051259 | 1/19/2023 | WO |
