Method for operating the heat pump system; heat pump system for such a method

Abstract

The invention relates to a method for operating a heat pump system, wherein in at least one process step a useful fluid is tempered by a heat pump (14) of the heat pump system and wherein in at least one process step the useful fluid is heated by an auxiliary heater (16) of the heat pump system. It is proposed that the auxiliary heater (16) is activated in at least one process step by a heat exchanger (22) of the heat pump (14) depending on a flow parameter (S) of the useful fluid.

Description

State of the art

[0001] For example, a method for operating a heat pump system has already been proposed in document EP 2559953 A1, wherein in at least one process step a useful fluid is tempered by a heat pump of the heat pump system and wherein in at least one process step the useful fluid is heated by an auxiliary heater of the heat pump system. Disclosure of the invention

[0002] The invention relates to a method for operating a heat pump system according to claim 1 and a heat pump system according to claim 9. In at least one process step, a useful fluid is tempered by a heat pump of the heat pump system, and in at least one process step, the useful fluid is heated by an auxiliary heater of the heat pump system.

[0003] It is proposed that the auxiliary heater is activated in at least one process step of the process depending on a flow parameter of the useful fluid through a heat exchanger of the heat pump. According to the invention, the auxiliary heater is activated in at least one process step of the process when the flow parameter falls below a flow threshold value. The flow parameter is set, in particular, by a fluid handling unit, especially a pump, a compressor, or a fan of the heat pump system. The flow parameter is, for example, a volume flow rate, a mass flow rate, a flow velocity, or the like. The flow parameter can be directly detected, for example, by means of a flow sensor, determined by detecting a quantity correlated with the flow parameter, or expressed and processed by the quantity correlated with the flow parameter.A quantity that correlates with the flow parameter is, for example, the rotational speed and / or the power consumption of the fluid conveying unit.

[0004] The flow threshold is preferably defined as a function of an operating characteristic of the heat pump. In particular, the flow threshold divides a parameter range of the flow parameter into a target range, for which the heat pump is designed, and a deficit range, for which the heat pump is not designed. In particular, the heat pump exhibits an increased risk of wear when operating in the deficit range compared to the target range. The flow threshold can be a single value or can include an operating parameter of the heat pump system as a parameter, for example, the temperature of the working fluid, a requested heat demand, or the like. According to the invention, the heat pump system comprises at least one control unit. The control unit compares the flow parameter with the flow threshold.According to the invention, the control unit activates the auxiliary heater in at least one process step of the process, while the heat pump, in particular the compressor of the heat pump, is kept in an inactive state, in particular to prevent wear and tear of the heat pump, in particular the compressor.

[0005] Preferably, the heat pump heats the user fluid in at least one process step, particularly during heating operation of the heat pump system. Preferably, the heat pump cools the user fluid in at least one process step, particularly during cooling operation of the heat pump system. In particular, depending on its operating mode, the heat pump exchanges heat between a heat reservoir and the user fluid via a refrigerant circuit. The heat reservoir is preferably ambient air or, alternatively, a body of water or the ground. Preferably, the control unit regulates the heat pump, particularly a compressor, especially depending on the flow parameter and / or the temperature of the user fluid. The compressor is preferably arranged within the refrigerant circuit and is designed to circulate the refrigerant.The heat exchanger of the heat pump is integrated into the refrigerant circuit and is designed to transfer heat between the refrigerant and the working fluid. The heat exchanger of the heat pump is specifically designed as a condenser. Preferably, the control unit controls or regulates the auxiliary heater, particularly depending on the flow parameter and / or the temperature of the working fluid. The working fluid is preferably circulated by the fluid pump unit in a closed circuit, which can be formed wholly or partially by the heat pump system. The closed circuit preferably includes at least one, and preferably several, heat exchangers, in particular radiators, cooling elements, underfloor heating, or the like, to temper rooms, drinking water, or domestic hot water, in particular to heat or cool them.Alternatively, the service fluid is pumped to a dispensing point, in particular a tap, a ventilation outlet, or the like. The service fluid is, for example, heating water, domestic hot water, drinking water, and / or heating air. The control unit controls, in particular regulates, the fluid pumping unit to adjust the flow parameter, especially depending on the heat demand of a user of the heat pump system.

[0006] The inventive design allows the working fluid to be advantageously heated even when the heat pump is not being operated or is only being operated to a limited extent. In particular, a buffer tank as a substitute heat sink can be dispensed with in order to achieve low-wear operation of the heat pump. A heat pump system implementing the inventive method can be advantageously compact and cost-effective. Furthermore, any reduction in comfort for a user of the heat pump system operated according to the inventive method can be advantageously minimized, even when the heat pump is not in operation.

[0007] It is further proposed that in at least one process step, particularly during the heating operation of the heat pump system, the auxiliary heater is activated depending on the flow parameter, while the heat pump remains in an inactive state. A minimum flow threshold is stored in the control unit. This minimum flow threshold is determined, in particular, by a minimum operating time of the heat pump's compressor. The minimum flow threshold can be set at the factory or during calibration or maintenance of the heat pump system at its operating location. The minimum operating time of the compressor specifies, in particular, the minimum duration for which the heat pump's compressor must operate continuously, especially during the heat pump's cycling operation.The minimum operating time is preferably determined based on the compressor's wear rate, particularly by the compressor manufacturer. Specifically, the control unit deactivates the heat pump or prevents its activation if the flow parameter falls below the minimum flow threshold. The design according to the invention advantageously keeps the wear rate of the heat pump, and especially the compressor, low.

[0008] Furthermore, it is proposed that in at least one process step, particularly during the heating operation of the heat pump system, the expected operating time of the heat pump is determined as a function of the flow parameter. Preferably, the control unit determines, based on the flow parameter, the required utilization rate of the heat pump to meet a requested heat demand. Specifically, the control unit deactivates the heat pump or prevents its activation if the compressor's operating time at the determined utilization rate is less than the minimum compressor operating time. For example, a relationship between the flow parameter and the heat pump's utilization rate is stored in the control unit's memory as a characteristic curve, a table, or a functional relationship.The design according to the invention allows the wear rate of the heat pump, in particular the compressor, to be kept advantageously low.

[0009] It is further proposed that in at least one process step, particularly during the heating operation of the heat pump system, the heat pump and the auxiliary heater are operated alternately. The control unit contains, in particular, an additional flow threshold. This additional flow threshold is preferably greater than the minimum flow threshold. The additional flow threshold is preferably determined based on a dead time of the heat pump's compressor. This additional flow threshold can be set at the factory or during calibration or maintenance of the heat pump system at its operating location. The compressor's dead time specifies, in particular, a minimum duration for which the heat pump's compressor must be continuously off, especially during the heat pump's cycling operation.The dead time is determined, in particular, based on the compressor's wear rate, specifically by the compressor manufacturer. During the dead time, the control unit keeps the heat pump, and especially the compressor, out of operation. Specifically, if the heat pump is in the dead time and the required utilization rate of the heat pump to meet a demand for heat is not achieved, the heat pump activates the auxiliary heater instead. The design according to the invention advantageously minimizes any reduction in comfort for the user of the heat pump system.

[0010] It is further proposed that in at least one process step, particularly during the heating operation of the heat pump system, the auxiliary heater is activated to heat the working fluid during a dead time of the heat pump, especially the one already mentioned. The design according to the invention allows for an advantageously wide range of usable utilization rates of the heat pump.

[0011] Furthermore, it is proposed that the activation of the auxiliary heater be enabled or disabled depending on the flow parameter within a predefined time window. This time window is specifically requested by a user of the heat pump system. Preferably, activation of the auxiliary heater based on the flow parameter is only possible within this time window in at least one operating mode of the heat pump system. In particular, the control unit disables activation of the auxiliary heater based on the flow parameter in this operating mode of the heat pump system. It is conceivable that the control unit could activate or deactivate the auxiliary heater outside the time window based on an operating parameter of the heat pump system other than the flow parameter. The time window is specifically intended to define the user's presence time at a location where the heat pump system is in operation.In the simplest case, particularly as the default setting, the time window defines daytime operation as within the time window and nighttime operation as outside the time window. Preferably, a user of the heat pump system can define the time window, or in particular several time windows, down to the minute. The design according to the invention allows energy costs for operating the auxiliary heater to be advantageously kept low.

[0012] It is further proposed that in at least one process step, the auxiliary heater is activated when the heat pump is activated. The electric auxiliary heater can be activated simultaneously with the heat pump, after activation of the heat pump (particularly triggered by activation), or before activation of the heat pump. The auxiliary heater is preferably activated during the cooling operation of the heat pump system when the heat pump is activated. In particular, the auxiliary heater is designed to at least partially compensate for the cooling capacity of the heat pump, at least during the settling-in phase of the refrigerant circuit. Preferably, the control unit deactivates the auxiliary heater when the compressor reaches a steady-state operating point. The design according to the invention advantageously keeps cooling capacity peaks low when the auxiliary heater is activated.In particular, even with a relatively low value of the flow parameter, the risk of falling below a dew point or freezing point at a heat exchanger through which the useful fluid flows, for example a floor heating system or a fan convector, can be advantageously kept low.

[0013] It is further proposed that in at least one process step, the flow parameter is detected by a flow sensor. The flow sensor can be arranged, in particular, downstream or upstream of a heat exchanger, especially a condenser, of the heat pump through which the useful fluid flows. Alternatively, the flow sensor is integrated into this heat exchanger, especially the condenser. The design according to the invention allows the flow parameter to be detected advantageously reliably and precisely. In particular, the risk of misinterpreting a quantity correlated with the flow parameter can be advantageously minimized.

[0014] Furthermore, it is proposed that in at least one process step, the flow parameter is determined as a function of an operating parameter of the heat pump system. In particular, a power input of the heat pump system is measured by means of a power sensor and / or a rotational speed of the fluid pumping unit is measured by means of a tachometer in order to determine the flow parameter. The inventive design allows the process to be implemented with an advantageously simple and cost-effective heat pump system.

[0015] Furthermore, a heat pump system according to claim 9 is proposed. The heat pump system is designed, in particular, for temperature control of a building. Alternatively, the heat pump system is designed for temperature control of a vehicle, a temporary structure, or another at least partially enclosed space. The heat pump can be configured as a compression heat pump or as an absorption heat pump. In particular, the heat pump comprises at least one heat exchanger, in particular a condenser, for transferring heat to the working fluid. In particular, the heat pump comprises a compressor for circulating a refrigerant. The heat pump system comprises, in particular, a working fluid guide for conveying the working fluid. The heat exchanger of the heat pump is, in particular, connected to the working fluid guide. The auxiliary heater is, in particular, connected to and / or arranged within the working fluid guide.The auxiliary heater is preferably designed as an electric auxiliary heater. Alternatively, the auxiliary heater is a gas-fired heating device, an oil-fired heating device, a solar thermal device, or another heat-generating device connected to the service fluid circuit. The heat pump system preferably comprises the fluid pumping unit for pumping, and in particular circulating, the service fluid through the service fluid circuit. The heat pump system preferably includes at least one sensor for directly detecting the flow parameter and / or for detecting a quantity correlated with the flow parameter. Alternatively, the control unit processes the flow parameter as a setting value and reads it from a control signal of the fluid pumping unit, in particular without measurement. The control unit comprises at least one control electronics module.In particular, the control electronics comprise a processor unit and memory, as well as an operating program stored in the memory. Alternatively, the control electronics are implemented by an analog logic circuit. The control unit is specifically programmed, designed, and / or equipped to execute the method according to the invention. In particular, the minimum flow threshold, the further flow threshold, the minimum compressor runtime, the compressor dead time, and / or the time window are stored in the memory of the control unit. The design according to the invention allows for an advantageously compact and cost-effective heat pump system. In particular, the installation of a buffer tank can be omitted. In particular, a significantly high level of user comfort can still be achieved.

[0016] The method and / or the heat pump system according to the invention are not / should not be limited to the application and embodiment described above. In particular, the method and / or the heat pump system according to the invention may, to achieve a functionality described herein, have a different number of individual elements, components, units, and process steps than those specified herein. Furthermore, values ​​within the specified limits of the value ranges stated in this disclosure shall also be considered disclosed and freely usable. Drawings

[0017] Further advantages will become apparent from the following description of the drawings. The drawings illustrate an embodiment of the invention, the invention being defined by the claims.

[0018] They show: Fig. 1 is a schematic representation of a heat pump system according to the invention and Fig. 2 is a schematic flow diagram of a method according to the invention. Description of the exemplary embodiment

[0019] Figure 1Figure 1 shows a heat pump system 12. The heat pump system 12 comprises at least one heat pump 14 for temperature-controlling a useful fluid. The heat pump 14 is, for example, designed as a compression heat pump. The heat pump 14 particularly comprises at least one heat exchanger 22 for transferring heat from a refrigerant of the heat pump 14 to the useful fluid. The heat exchanger 22 is preferably designed as a condenser for liquefying the refrigerant. The heat pump 14 preferably comprises a further heat exchanger 24, in particular an evaporator, which is designed to transfer heat from ambient air to the refrigerant. The heat pump 14 particularly comprises at least one compressor for circulating the refrigerant. The heat pump 14 is shown here as a compact unit, which is particularly intended for installation outside a building.Alternatively, the heat pump 14 is designed as a split heat pump or as a brine heat pump.

[0020] The heat pump system 12 preferably comprises a fluid guide 26 for guiding the fluid. The heat exchanger 22 is preferably arranged in the fluid guide 26. The fluid guide 26 preferably forms a closed fluid circuit, in particular a heating circuit, for the fluid together with external fluid guide components, for example, radiators 28, underfloor heating, a hot water storage tank 30, or the like. The fluid guide 26 is designed to distribute the fluid spatially and / or temporally to several consumers, especially the external fluid guide components. In particular, the fluid guide 26 includes at least one switching element 40, for example, a multi-way valve, to switch between different consumers and / or to distribute the fluid to different consumers.Preferably, the heat pump system 12 comprises at least one fluid pumping unit 32, in particular a pump, for pumping, in particular circulating, the useful fluid through the useful fluid guide 26. The fluid pumping unit 32 is preferably arranged upstream of the heat exchanger 22 within the useful fluid guide 26.

[0021] The heat pump system 12 comprises at least one auxiliary heater 16, in particular an electric auxiliary heater, for heating the utility fluid. The auxiliary heater 16 preferably comprises at least one heating wire, in particular in the form of a heating element. The heating wire is preferably arranged within the utility fluid channel 26, in particular in direct contact with the utility fluid. Alternatively, the heating wire is embedded in a channel wall of the utility fluid channel 26 or arranged on an outer wall of the utility fluid channel 26. The auxiliary heater 16 is preferably arranged downstream of the heat exchanger 22 of the heat pump 14 within the utility fluid channel 26. The auxiliary heater 16 preferably has a maximum heating output of more than 1 kW, more preferably more than 3 kW, and particularly preferably less than 5 kW. The auxiliary heater 16 preferably has a maximum heating output of less than 25 kW, more preferably less than 15 kW, and particularly preferably less than 10 kW.The auxiliary heater 16 can be switched between power levels or continuously regulated.

[0022] The heat pump system 12 comprises at least one control unit 20. The control unit 20 is preferably designed to control the heat pump 14. The control unit 20 is preferably designed to control or regulate the auxiliary heater 16. The control unit 20 is designed to carry out a method 10, which is particularly described in Figure 2The heat pump system 12 preferably comprises at least one temperature sensor for controlling the heat pump 14 and / or the auxiliary heater 16. In particular, the heat pump system 12 comprises at least one flow temperature sensor 34. The flow temperature sensor 34 is preferably arranged downstream of the heat exchanger 22 and the auxiliary heater 16 within the working fluid circuit 26. Optionally, the heat pump system 12 comprises at least one inlet temperature sensor 36. The inlet temperature sensor 36 is preferably arranged upstream of the heat exchanger 22 and downstream of the fluid pumping unit 32 within the working fluid circuit 26. Preferably, the heat pump system 12 comprises at least one outdoor temperature sensor 38 for detecting an ambient temperature.The heat pump system 12 optionally includes a flow sensor 18, in particular a flow rate sensor, for detecting a flow parameter S of the service fluid through the service fluid guide 26 and, in particular, through the heat exchanger 22 of the heat pump 14. The heat pump system 12 preferably includes at least one user interface 41. The user interface 41 can include a display and an input device, in particular a keypad, a touchscreen, slider, rotary control, or the like, and / or a wireless, in particular radio wave-based, communication unit for operating the heat pump system 12 by means of an external input device, for example, a smartphone, a tablet, or the like. The communication unit can, for example, include a WLAN interface, a Bluetooth interface, a ZigBee interface, or the like.

[0023] Figure 2Figure 10 shows a flowchart for the operation of the heat pump system 12. In at least one process step of the process 10, a useful fluid is tempered by the heat pump 14 of the heat pump system 12. The process 10 includes, in particular, a heating operation in which the useful fluid is heated by the heat pump 14. The process 10 preferably includes a cooling operation 46 in which the useful fluid is cooled by the heat pump 14. The process 10 includes at least one process step, in particular as part of the heating operation and / or the cooling operation 46, in which the useful fluid is heated by the auxiliary heater 16 of the heat pump system 12. The auxiliary heater 16 is activated in at least one process step of the process 10 depending on a flow parameter S of the useful fluid through the heat exchanger 22 of the heat pump 14.

[0024] Method 10 includes, in particular, a flow parameter determination 42. In the flow parameter determination 42, the control unit 20 determines the flow parameter S. The flow parameter S can, for example, be detected by means of the flow sensor 18, determined by means of an operating parameter of the fluid conveying unit 32, or considered to be given based on a setting of the control unit 20 for the fluid conveying unit 32, in particular without measurement. Method 10 includes, in particular, an operating mode check 44. In the operating mode check 44, the control unit 20 checks a specification as to whether the heat pump system 12 should perform heating or cooling operation 46. The specification can, for example, be a user input, an operating profile of the heat pump system 12 stored in the memory of the control unit 20, or an input from an external central control, in particular a building central control, for example, a smart home system.

[0025] In cooling mode 46, the auxiliary heater 16 is activated when the heat pump 14 is activated, particularly if the flow parameter S is less than a cooling operation flow threshold. If, in cooling mode 46, the flow parameter S is greater than the cooling operation flow threshold, the auxiliary heater 16 is preferably not activated. The cooling operation flow threshold is specifically designed to prevent a dew point from being reached on a heat exchanger through which the useful fluid flows. In particular, the auxiliary heater 16 heats the useful fluid at least until the compressor of the heat pump 14 has reached a minimum speed and / or a steady-state operating point. The cooling operation flow threshold is preferably stored in the memory of the control unit 20.

[0026] In heating mode, the activation of the auxiliary heater 16 is enabled or disabled depending on the flow parameter S and within a predefined time window. In particular, the method 10 includes a time window check 48. During the time window check 48, the control unit 20 verifies whether the execution time of the method 10 falls within or outside the time window. If the execution time of the method 10 falls within the time window, the control unit 20 activates or deactivates the auxiliary heater 16 depending on the flow parameter S. If the execution time of the method 10 falls outside the time window, the control unit 20 executes a heat pump operation 58 of the method 10. The time window is preferably defined by a user via the user interface 41. Preferably, at least one default setting for the time window is stored in the control unit 20.

[0027] In heat pump operation 58 of method 10, the control unit 20 keeps the auxiliary heater 16 in an inactive state or deactivates the auxiliary heater 16. In particular, the heat pump 14 heats, and in particular exclusively heats, the useful fluid in heat pump operation 58 of method 10. In heat pump operation 58, the heat pump 14 can be operated continuously or intermittently. During intermittent operation of the heat pump 14, a minimum compressor runtime and a compressor dead time are maintained, in particular regardless of any requested heat demand and in particular regardless of the flow parameter S.

[0028] Method 10 includes, in particular, a threshold test 50. The threshold test 50 is executed, in particular, when an execution time of method 10 falls within the time window. In the threshold test 50, the control unit 20 compares the flow parameter S with a minimum flow threshold SO. The minimum flow threshold SO is preferably stored in the memory of the control unit 20. The minimum flow threshold SO is, in particular, determined as a function of the minimum runtime of the compressor of the heat pump 14. In a calibration phase of method 10, a predicted runtime of the heat pump 14 is determined as a function of the flow parameter S. In particular, the minimum runtime of the compressor cannot be achieved when the heat pump 14 is operated without the auxiliary heater 16 below the minimum flow threshold SO.If the flow parameter S is smaller than the minimum flow threshold SO, the control unit 20 preferably executes an auxiliary heater operation 52. In the auxiliary heater operation 52, the auxiliary heater 16 is activated, while the heat pump 14 is kept in an inactive state.

[0029] In particular, if the flow parameter S is greater than the minimum flow threshold SO, the control unit 20 preferably performs a further threshold test 54 of method 10. In the further threshold test 54, the control unit 20 preferably compares the flow parameter S with a further flow threshold S1. The further flow threshold S1 is preferably stored in the memory of the control unit 20. The further flow threshold S1 is determined, in particular, as a function of the dead time of the compressor of the heat pump 14. In particular, the dead time of the compressor cannot be maintained below the further flow threshold S1 when the heat pump 14 is operated without the auxiliary heater 16. If the flow parameter S is smaller than the further flow threshold S1, and in particular larger than the minimum flow threshold SO, the control unit 20 preferably performs an alternating operation 56 of method 10.In alternating operation 56, the heat pump 14 and the auxiliary heater 16 are operated alternately. In alternating operation 56 of procedure 10, the auxiliary heater 16 is activated to heat the utility fluid during a dead time of the heat pump 14. In particular, in alternating operation 56, the auxiliary heater 16 is activated as a substitute when the heat pump 14 is in a dead time and would otherwise need to be activated to meet a requested heat demand.

Claims

1. Method for operating a heat pump system, wherein, in at least one method step, the temperature of a useful fluid is controlled by a heat pump (14) of the heat pump system, and wherein, in at least one method step, the useful fluid is heated by an auxiliary heater (16) of the heat pump system, characterized in that, in at least one method step, the auxiliary heater (16) is activated by a heat exchanger (22) of the heat pump (14) depending on a flow parameter (S) of the useful fluid, while the heat pump (14) is kept in an inactive state, wherein the auxiliary heater (16) is activated when the flow parameter (S) falls below a flow threshold value.

2. Method according to Claim 1, characterized in that, in at least one method step, an expected run time of the heat pump (14) is determined depending on the flow parameter (S).

3. Method according to either of the preceding claims, characterized in that, in at least one method step, the heat pump (14) and the auxiliary heater (16) are operated alternately.

4. Method according to any of the preceding claims, characterized in that, in at least one method step, the auxiliary heater (16) is activated in order to heat the useful fluid during a dead time of the heat pump (14).

5. Method according to any of the preceding claims, characterized in that activation of the auxiliary heater (16) is enabled or blocked depending on the flow parameter (S) as a function of a prescribed time window.

6. Method according to any of the preceding claims, characterized in that, in at least one method step, the auxiliary heater (16) is activated when the heat pump (14) is activated.

7. Method according to one of the preceding claims, characterized in that, in at least one method step, the flow parameter (S) is detected by a flow sensor (18).

8. Method according to any of the preceding claims, characterized in that, in at least one method step, the flow parameter (S) is determined depending on an operating parameter of the heat pump system.

9. Heat pump system having at least one heat pump (14) for controlling the temperature of at least one useful fluid, having at least one auxiliary heater (16) for heating the useful fluid and having at least one control unit (20) configured for carrying out a method according to any of the preceding claims.

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