Heat pump circuit and method for operating such a circuit

Abstract

The invention relates to a heat pump circuit (1) for providing useful heat at a temperature of more than 130°C. The invention further relates to a method for operating such a heat pump circuit (1).

Description

[0001] 2024PF00650

[0002] 1

[0003] Description

[0004] Heat pump cycle and method for operating such a

[0005] The invention relates to a heat pump circuit for providing useful heat, in particular useful heat with a temperature of more than 100°C. The invention further relates to a method for operating such a heat pump circuit.

[0006] Conventional heat pump circuits for providing high-temperature heat, i.e., usable heat with a temperature above 130°C, are generally known in the art. They typically comprise a first heat exchanger designed to heat, evaporate, and superheat a working fluid, a compressor, a second heat exchanger designed to dissipate usable heat for external use by cooling the working fluid, and an expansion valve. Due to physical limitations, heat pump circuits exhibit coefficients of performance (COP) of less than 2.5. The COP is the ratio of the heat output (kW) delivered under specific operating conditions to the electrical power input. Therefore, economical operation is highly dependent on current electricity prices.While the first heat exchanger can be operated, for example, using low-calorific waste heat to save electrical power and thus improve the coefficient of performance, the compressor must always be supplied with electrical power.

[0007] Further state of the art is represented by publications US 4,896,515 A and US 2007 / 0017242 Al.

[0008] Based on this prior art, it is an object of the present invention to provide an alternative heat pump circuit and an alternative method for operating such a heat pump circuit. 2024PF00650

[0009] 2

[0010] To solve this problem, the present invention provides a heat pump circuit for supplying useful heat at a temperature above 130°C, through which a working medium flows, comprising a first heat exchanger designed to heat, evaporate, and superheat the working medium at a medium process pressure level using waste heat supplied from the outside, in particular low-calorific waste heat; a compressor arranged downstream of the first heat exchanger designed to compress the working medium to an upper process pressure level; a second heat exchanger arranged downstream of the compressor designed to dissipate useful heat for external use by cooling the working medium; and a turbine arranged downstream of the second heat exchanger designed to compress the working medium to a condensation pressure at ambient temperature level, corresponding to a lower process pressure level.To expand and provide at least some, preferably all, of the energy required to operate the compressor, a condenser is arranged downstream of the turbine, designed to condense the working fluid and dissipate heat to the environment, and a pump is arranged downstream of the condenser, designed to compress the working fluid to the average process pressure level before it is fed back to the first heat exchanger. Thanks to the fact that the heat supplying the first heat exchanger is in the form of waste heat, particularly low-calorific waste heat, and that the energy required to operate the compressor is provided via the turbine, coefficients of performance (COPs) with values ​​significantly above 2.5 can be achieved, which can theoretically approach infinity.

[0011] According to the invention, the heat pump circuit is designed to be operated with CO2 as the working medium, although other working media can also be used in principle.

[0012] According to one embodiment of the present invention, the compressor and the turbine are mounted on a common shaft 2024PF00650

[0013] 3 or on two interconnected shafts. Accordingly, the compressor is mechanically driven via the turbine.

[0014] Alternatively or additionally, a generator can be provided, which is driven by the turbine.

[0015] Preferably, the turbine is designed to provide the energy required to operate the pump, thereby further improving the coefficient of performance of the heat pump circuit.

[0016] Advantageously, a regulation is provided which is designed to regulate the turbine work in such a way that it corresponds at least essentially to the sum of the compression work of the compressor and the pumping work of the pump.

[0017] Furthermore, the present invention provides a method for operating a heat pump circuit according to one of the preceding claims, comprising the following successive steps, to solve the aforementioned problem:

[0018] Heating, evaporating, and superheating a working fluid to a medium process pressure level using the first heat exchanger, wherein the working fluid is CO2; compression of the working fluid to an upper process pressure level using the compressor, whereby a further temperature increase of the working fluid occurs; removal of useful heat for external use while simultaneously cooling the working fluid using the second heat exchanger; expansion of the working fluid to a condensation pressure at ambient temperature level, corresponding to a lower process pressure level, using the turbine; condensation of the working fluid using the condenser, releasing heat to the environment, and increasing the pressure of the working fluid to the medium process pressure level using the pump, wherein the turbine provides at least the energy required to operate the compressor, 2024PF00650

[0019] 4 in particular the energy required to operate the compressor and the pump.

[0020] Preferably, the energy provided by the turbine corresponds to the energy required to operate the compressor and the pump.

[0021] Further features and advantages of the present invention will become clear from the following description with reference to the accompanying drawing. Therein is

[0022] Figure 1 shows a schematic view of a heat pump circuit according to an embodiment of the present invention and

[0023] Figure 2 is a TS diagram to illustrate a method according to the invention for operating the heat pump circuit shown in Figure 1.

[0024] Figure 1 shows a heat pump circuit 1 according to an embodiment of the present invention, through which a working fluid, in this case CO2, flows, and which is designed to provide usable heat at a temperature of more than 130°C. The heat pump circuit 1 comprises as its main components a first heat exchanger 2, a compressor 3, a second heat exchanger 4, a turbine 5, a condenser 6, and a pump 7. The first heat exchanger 2 is designed to heat, evaporate, and superheat the working fluid at a medium process pressure level using waste heat, in particular low-calorific waste heat, supplied from the outside in the direction of arrow 8. The compressor 3, arranged downstream of the first heat exchanger 2, then compresses the working fluid to an upper process pressure level.The second heat exchanger 4, located downstream of the compressor 3, is designed to dissipate usable heat for external use by cooling the working fluid, as indicated by arrow 9. The turbine 5, located downstream of the second heat exchanger 4, is designed to cool the working fluid to a condensation pressure of 2024PF00650.

[0025] 5

[0026] The heat pump circuit 1 expands to an ambient temperature level corresponding to a lower process pressure level and provides the energy required to operate the compressor 3, preferably also the energy required to operate the pump 7. For this purpose, the shafts on which the turbine 5 and the compressor 3 are mounted can be coupled to each other or coupled to each other via a coupling (not shown in detail), as indicated by the dashed line 10 in Figure 1. Alternatively, it is also possible to arrange the turbine 5 and the compressor 3 on a common shaft. In this case, the heat pump circuit 1 further comprises a generator 11, which is driven by the turbine 5 and provides the electrical energy to operate the pump 7. It is also possible, in principle, to drive only the generator 11 via the turbine 5, which provides the electrical energy required to operate the compressor 3 and the pump 7.A control unit 12 regulates the turbine work such that it corresponds, at least substantially, to the sum of the compression work of the compressor 3 and the pumping work of the pump 7. The condenser 6, located downstream of the turbine 5, is designed to condense the working fluid and dissipate heat to the environment, as indicated by arrow 13. The pump 7, located downstream of the condenser 6, recompresses the working fluid to the average process pressure level before it is fed back to the first heat exchanger 2, whereupon the cycle begins again.

[0027] Figure 2 shows an exemplary TS diagram associated with the previously described heat pump cycle 1, where the plotted points a to f correspond to points a to f in Figure 1. From point a to point b, the working fluid is evaporated and superheated to approximately 90°C by the externally supplied low-calorific waste heat at a mean process pressure level of about 70 bar. Subsequently, the working fluid is compressed from point b to point c in compressor 3 to a pressure of approximately 100 bar, corresponding to an upper process pressure level, while simultaneously being heated to approximately 140°C. By releasing usable heat in the heat exchanger, the process fluid is converted into usable heat.

[0028] In the 6-meter 4, the temperature drops from point c to point d to approximately 100°C. The expansion in the turbine 5 leads to a pressure drop from point d to point e to approximately 40 bar, which corresponds to a lower process pressure, and to a temperature drop to approximately 30°C. In the condenser 6, heat is extracted from the working fluid from point e to point f. Subsequently, the pressure of the working fluid is raised back to the average pressure level using the pump 7. If points a to f are connected sequentially in the TS diagram, the connecting lines form the shape of a distorted number 8.

[0029] The advantage of the heat pump circuit 1 described above according to the invention is that, ideally, no electrical energy needs to be supplied from the outside to operate the compressor 3 and the pump 7.

[0030] Although the invention has been illustrated and described in detail by the preferred embodiment, the invention is not limited by the disclosed examples and other variations can be derived by a person skilled in the art without departing from the scope of protection of the invention. In particular, the temperature and / or pressure levels can differ significantly from those mentioned with reference to Figure 2.

[0031] Regardless of the grammatical gender of a particular term, persons with male, female or other gender identities are included.

Claims

2024PF00650 7 Patentansprüche 1. Heat pump circuit (1) for providing useful heat, in particular useful heat with a temperature of more than 100°C, through which a working medium flows, comprising a first heat exchanger (2) designed to heat, evaporate and superheat the working medium at a medium process pressure level using waste heat supplied from the outside, in particular low-calorific waste heat, a compressor (3) arranged downstream of the first heat exchanger (2) designed to compress the working medium to an upper process pressure level, a second heat exchanger (4) arranged downstream of the compressor (3) designed to discharge useful heat for external use by cooling the working medium, a turbine (5) arranged downstream of the second heat exchanger (4) designed to compress the working medium to a condensation pressure at ambient temperature level, which corresponds to a lower process pressure level,to expand and to provide at least some, preferably all, of the energy required to operate the compressor (3), a condenser (6) arranged downstream of the turbine (5), which is designed to condense the working medium and dissipate heat to the environment, and a pump (7) arranged downstream of the condenser (6), which is designed to compress the working medium to the mean process pressure level before it is fed back to the first heat exchanger (2), characterized in that the heat pump circuit (1) is designed to be operated with CO2 as the working medium.

2. Heat pump circuit (1) according to claim 1, characterized in that the compressor (3) and the turbine (5) are located on a common shaft or on two shafts that can be coupled together.

3. Heat pump circuit (1) according to one of the preceding claims, characterized in that a generator (11) is provided which is driven by the turbine (5). 2024PF00650 4. Heat pump circuit (1) according to one of the preceding claims, characterized in that the turbine (5) is designed to provide the energy required to operate the pump (7).

5. Heat pump circuit (1) according to one of the preceding claims, characterized in that a control (12) is provided which is designed to control the turbine work in such a way that it corresponds at least substantially to the sum of the compression work of the compressor (3) and the pumping work of the pump (7).

6. Method for operating a heat pump circuit (1) according to one of the preceding claims, comprising the successive steps: - Heating, evaporating and superheating a working medium at a medium process pressure level using the first heat exchanger (2) , wherein the working medium is CO2, - Compression of the working medium to an upper process pressure level using the compressor (3) , whereby a further temperature increase of the working medium takes place, - Discharge of useful heat for external use while simultaneously cooling the working medium using the second heat exchanger (4) , - Expansion of the working medium to a condensation pressure at ambient temperature level, corresponding to a lower process pressure level, using the turbine (5) , - Condensation of the working medium using the condenser (6) with the release of heat to the environment and - Increasing the pressure of the working medium to the mean process pressure level using the pump (7) , wherein the turbine (5) provides at least the energy required to operate the compressor (3), in particular the energy required to operate the compressor (3) and the pump (7). 2024PF00650 7. Method according to claim 6, characterized in that the energy provided by the turbine (5) corresponds to the energy required to operate the compressor (3) and the pump (7).

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