Heat pump and method for operating the heat pump

Abstract

The present invention relates to a heat pump for heating and cooling a building and to a method for operating the heat pump.The heat pump comprises a refrigerant circuit with a first heat exchanger (1) configured to use ambient air as a heat source and heat sink, a second heat exchanger (3) configured to use a heating / cooling circuit of the building as a heat source and heat sink, a directional control valve (3) configured to set a flow direction of the refrigerant in the refrigerant circuit (100), a compressor (2) arranged between the first heat exchanger (1) and the second heat exchanger (3), an expansion valve (5) arranged between the second heat exchanger (3) and the first heat exchanger (1), and a third heat exchanger (7) arranged between the expansion valve (5) and the first heat exchanger (1) and configured to use the ground as a heat source and heat sink.

Description

[0001] The present invention relates to a heat pump for heating and cooling a building and to a method for operating the heat pump. Background of the invention

[0002] Heat pumps make it possible to use freely available energy from the environment to heat and / or cool a building, thus contributing to the reduction of CO₂ emissions in the building sector. In particular, a heat pump can be used for both heating and cooling because its heat exchangers can function as both evaporators and condensers. For example, by reversing the refrigerant cycle, a heat exchanger that acts as a condenser in heating mode can function as an evaporator in cooling mode, and vice versa. This allows, for instance, a secondary circuit of the corresponding heat exchanger to release heat to the building during heating mode and absorb heat from the building during cooling mode.

[0003] Heat pumps of this type typically contain an expansion valve through which the refrigerant exiting the condenser (the heat exchanger) is expanded before entering the evaporator (the heat exchanger). For precise metering of the refrigerant to be evaporated by the expansion valve, the refrigerant must be in liquid form upstream of the valve. To achieve this, a refrigerant receiver can be located upstream of the expansion valve, separating the liquid and gaseous phases of the refrigerant using gravity. However, if the refrigerant cycle is reversed, the receiver is located downstream of the expansion valve and is therefore ineffective, thus reducing the efficiency of the heat pump.

[0004] Reversing the refrigerant cycle can also be used to eliminate icing of a heat exchanger in an air-to-water heat pump's outdoor unit, which acts as an evaporator during heating operation. This can occur under certain weather conditions, particularly at ambient temperatures below 7°C to 10°C. In this case, reversing the refrigerant cycle means that heat, for example from the building's heating / cooling circuit, is supplied to defrost the heat exchanger, which then functions as a condenser. However, this means that the heat pump's heating operation must be interrupted during the defrosting process.

[0005] From DE 10 2006 024 871 A1, another method for defrosting an evaporator of an air-to-water heat pump is known, employing two different defrosting methods. In the first defrosting method, a fan in the evaporator, when the compressor is switched off, generates an airflow that passes through the evaporator. This results in natural defrosting, utilizing the heat of the ambient air. In the second defrosting method, a known reversal of the refrigerant cycle is carried out as described above. However, switching off the compressor, especially intermittent operation with frequent on / off cycles, has a negative impact on the compressor's service life.

[0006] If an air-to-water heat pump has access to an additional heat source for heating operation besides ambient air, this can also be used to defrost an iced-up heat exchanger. In this context, DE 10 2007 048 909 A1 discloses a heat pump arrangement with a first circuit branch with a first evaporator to which heat from ambient air can be supplied, and a second circuit branch with a second evaporator to which geothermal energy can be supplied. The two circuit branches are arranged in parallel and can be switched on or off individually. To defrost the first evaporator, refrigerant flows from the second evaporator via a compressor and a bypass line into the first evaporator, thereby defrosting it. However, providing a second circuit branch, which is arranged in parallel to the first circuit branch and can be operated alternatively to it, significantly increases the space requirements and complexity of the heat pump.

[0007] One object of the present invention is to overcome the disadvantages described above and to provide a compact heat pump, in particular a compact air-to-water heat pump, with increased service life and efficiency in heating and cooling operation.

[0008] To solve the problems, the characteristics of independent claims are proposed. Advantageous variations can be found in dependent claims. Disclosure of the invention

[0009] A heat pump according to the invention for heating and cooling a building has a refrigerant circuit in which a refrigerant circulates. The heat pump can, in particular, be designed as an air-to-water heat pump with an outdoor unit and an indoor unit.

[0010] The refrigerant circuit comprises a first heat exchanger, which uses ambient air as both a heat source and a heat sink, and a second heat exchanger, which uses the building's heating / cooling circuit as both a heat source and a heat sink. For heating the building (heating mode of the heat pump), the first heat exchanger can function as an evaporator and the second as a condenser; for cooling the building (cooling mode of the heat pump), the second heat exchanger can function as an evaporator and the first as a condenser. The first heat exchanger can be, in particular, a finned heat exchanger located in the outdoor unit of the heat pump. The second heat exchanger can be, for example, a plate heat exchanger whose secondary side is connected to the building's heating / cooling circuit.

[0011] Furthermore, the refrigerant circuit includes a directional control valve designed to adjust / reverse the flow direction of the refrigerant within the circuit, thus switching the heat pump from heating to cooling mode and vice versa. This directional control valve can be, in particular, a 4 / 2-way valve.

[0012] Furthermore, the refrigerant circuit includes a compressor located between the first and second heat exchangers, and an expansion valve located between the second and first heat exchangers. In other words, during heating operation, the compressor is located downstream of the first heat exchanger and upstream of the second, and the expansion valve is located downstream of the second heat exchanger and upstream of the first. During cooling operation, the refrigerant flow direction is reversed, so that in this case, the compressor is located downstream of the second heat exchanger and upstream of the first, and the expansion valve is located downstream of the first heat exchanger and upstream of the second.The compressor can be, in particular, a variable speed compressor, and the expansion valve can be a thermostatic or electronic expansion valve.

[0013] The function of the refrigerant circuit described above, with the components mentioned, is known to experts and is therefore not explained in more detail here.

[0014] In addition to the usual components, the refrigerant circuit of the heat pump according to the invention includes a third heat exchanger, which is arranged between the expansion valve and the first heat exchanger and uses the ground as a heat source and heat sink. The position of the third heat exchanger "between the expansion valve and the first heat exchanger"This should be understood to mean that the third heat exchanger, or elements of the third heat exchanger, can also be arranged within the first heat exchanger. In particular, the third heat exchanger can be arranged between the expansion valve and an outlet of the first heat exchanger if the latter operates as an evaporator, and between an inlet of the first heat exchanger and the expansion valve if the latter operates as a condenser.

[0015] According to one embodiment, to utilize the ground as a heat source / sink, a secondary side of the third heat exchanger can be connected to a heat transfer circuit in which a heat transfer fluid circulates. The heat transfer fluid can be, in particular, a mixture of water and antifreeze (brine). Other suitable heat transfer fluids are also possible. In addition to the third heat exchanger, the heat transfer circuit can include a pump for circulating the heat transfer fluid within the circuit and a fourth heat exchanger. The fourth heat exchanger can be configured to transfer heat to or from the ground. The pump can, for example, be a variable-speed pump by means of which a flow rate of the heat transfer fluid in the heat transfer circuit can be adjusted. Alternatively or additionally, the pump can have a variable displacement volume.To adjust the flow rate, the pump can be connected to and controlled by a control unit of the heat pump. The pump can, for example, be located upstream of the fourth heat exchanger and downstream of the third heat exchanger. In particular, the pump can be integrated into a housing of the control unit.

[0016] According to one embodiment, the fourth heat exchanger can comprise at least one ground-source heat collector. This can be installed in the ground at a depth of 1 m to 10 m, particularly at a depth of 2 m to 4 m. At this depth, the ground-source heat collectors are subject to only minor seasonal temperature fluctuations, typically ranging from 7°C to 13°C. The at least one ground-source heat collector can be designed as a ground-source heat exchanger basket or as a flat ground-source heat collector, with the use of a ground-source heat exchanger enabling a particularly space-saving arrangement of the fourth heat exchanger. To also enable the space-saving use of a flat ground-source heat collector, it can, for example, have a corrugated surface area, thus providing more heat transfer surface for the same length and width. The corrugated surface can, for example,It can be formed by an essentially parallel arrangement of tubular heat transfer strands. Such a ground source heat collector is disclosed, for example, in DE 20 2019 003 763 U1.

[0017] Due to the shallow installation depth and small footprint of at least one ground source heat exchanger, it does not represent a significant additional effort in the planning and installation of the heat pump. For example, the installation of at least one ground source heat exchanger can be combined with the work to construct a foundation for the outdoor unit of the heat pump, thus optimizing the installation effort. In particular, no geological surveys of the ground or deep drilling are required in connection with the installation of the ground source heat exchanger(s).

[0018] According to one embodiment, the third heat exchanger can be attached to or within an inlet section of the refrigerant entering the first heat exchanger. For example, the third heat exchanger can be in thermally conductive contact with the inlet section and / or the first heat exchanger.

[0019] The inlet section can be arranged between the expansion valve and the first heat exchanger and configured to supply two-phase refrigerant at a low pressure level, evenly distributed, to the first heat exchanger during the heat pump's heating operation. Advantageously, the inlet section can extend into an interior space of the first heat exchanger, particularly to one or more of its heat transfer elements. For example, when using a finned heat exchanger, the inlet section can extend to its core tubes.

[0020] According to one embodiment, the inlet section to the first heat exchanger can comprise a plurality of distribution tubes that are fluidically and mechanically connected to the first heat exchanger. For example, the inlet section can include a Venturi distributor that is connected, for instance, to the expansion valve via a single tube and to the first heat exchanger via a plurality of distribution tubes. In this case, the third heat exchanger can, for example, be fluidically and / or mechanically connected to one or more of the plurality of distribution tubes, thereby establishing a thermally conductive contact.

[0021] According to one embodiment, the third heat exchanger can have a plurality of refrigerant connections that are fluidically connected to the inlet section of the first heat exchanger. The refrigerant connections can, for example, be located on a side of the third heat exchanger facing the first heat exchanger. Any other suitable position for attaching the refrigerant connections to / in the third heat exchanger is equally possible. In particular, if the first heat exchanger is designed as a finned heat exchanger, one or more of its core tubes can be directly connected to one or more refrigerant connections of the third heat exchanger via the inlet section, thereby enabling targeted distribution of the refrigerant to the individual fin stacks.

[0022] According to one embodiment, the third heat exchanger can be arranged in the inlet section of the first heat exchanger such that the plurality of distribution pipes of the inlet section are integrated into the third heat exchanger. For this purpose, the plurality of distribution pipes can, for example, be arranged within the third heat exchanger. The plurality of distribution pipes can also be configured to serve as collectors when the refrigerant circuit is reversed.

[0023] According to one embodiment, the third heat exchanger can be designed as a plate heat exchanger. This can either be arranged between the expansion valve and the inlet section or, as described above, attached to or within the inlet section. In particular, the plurality of distribution tubes can be integrated into the plate heat exchanger, e.g., arranged within the plate heat exchanger.

[0024] Alternatively, the third heat exchanger can be designed as a coiled tube heat exchanger. It is also possible to use a microchannel heat exchanger as the third heat exchanger.

[0025] According to one embodiment, the third heat exchanger can be arranged in the inlet section of the first heat exchanger such that at least one coil of the third heat exchanger abuts the plurality of distribution pipes of the inlet section (fluidically and / or mechanically). In particular, the third heat exchanger can be arranged in the inlet section of the first heat exchanger such that at least one coil of the third heat exchanger surrounds the plurality of distribution pipes of the inlet section. Advantageously, several, in particular all, coils of the third heat exchanger can abut or surround the plurality of distribution pipes.

[0026] The third heat exchanger can be used, in particular, to assist with defrosting the first heat exchanger during heating operation, where it acts as an evaporator, and to subcool the refrigerant before the expansion valve during cooling operation of the heat pump. Therefore, the third heat exchanger can have a lower capacity than the first two heat exchangers (e.g., 2% to 10% of the capacity of the first or second heat exchanger, respectively). During normal heating operation of the heat pump, the third heat exchanger can be deactivated, for example, by switching off the pump, and only used as an additional heat source at very low ambient temperatures, e.g., below -10°C. Furthermore, the third heat exchanger can be used if the first heat exchanger fails, for example, in the event of a technical malfunction (e.g., due to a fan defect, fan blockage due to icing, etc.).

[0027] In a method according to the invention for defrosting the first heat exchanger during the heating operation of the heat pump, upon detection of frost on the first heat exchanger, the compressor speed is first adjusted to a specific speed that is lower than the compressor speed during the preceding heating operation. Starting from the compressor speed during heating operation, this speed can be significantly, and expediently, abruptly reduced. If, for example, the compressor operates at 100 to 120 revolutions per second (rps) during heating operation, particularly at 110 rps, the speed can be reduced to, for example, 20 to 30 rps. In other words, the compressor speed is reduced by approximately 50% to 85%, and particularly by 70% to 85%, in the first step.The abrupt reduction in compressor speed causes a sudden pressure increase and a corresponding rise in the evaporation temperature in the first heat exchanger, resulting in its natural defrosting. The specific speed can be determined, for example, based on the degree of icing. In particular, a larger speed change can be set for a higher degree of icing / heavier icing of the first heat exchanger than for a lower degree of icing / lighter icing. It is also possible to increase the speed of a fan in the first heat exchanger during natural defrosting to accelerate the defrosting process by increasing the heat flow from the environment. This is particularly useful when the ambient temperature is 2°C or higher.

[0028] The presence or degree of frosting of the first heat exchanger can be detected, for example, using indirect parameters such as ambient temperature and / or the evaporation temperature of the first heat exchanger.

[0029] To support natural defrosting, a specific output of the third heat exchanger is set in a second step to defrost the first heat exchanger within a predetermined time. This specific output can, for example, be determined based on the degree of frost buildup on the first heat exchanger. In particular, the specific output can be the maximum output of the third heat exchanger. The second step of the process can be initiated simultaneously with the first step or at a later time, especially later than the first step.

[0030] According to one embodiment, the specific output of the third heat exchanger can be adjusted by means of the volume flow rate of the heat transfer fluid in the heat transfer circuit. In other words, the volume flow rate of the heat transfer fluid in the heat transfer circuit can be adjusted to achieve the desired output. The volume flow rate can be adjusted, in particular, by the heat pump's control device, which can, for example, control / regulate the pump speed to ensure the required volume flow rate is provided. To provide the maximum output of the third heat exchanger, the pump can be operated to achieve a maximum volume flow rate of the heat transfer fluid in the heat transfer circuit. In this way, as much heat as possible can be extracted from the third heat exchanger and transferred to the refrigerant circuit before it passes through the first heat exchanger.Additionally, heat output to the building's heating circuit via the secondary side of the second heat exchanger can be reduced, and this heat can instead be used to defrost the first heat exchanger.

[0031] By combining the steps of the procedure described above, initial frost buildup on the first heat exchanger can be removed efficiently and quickly without requiring active defrosting of the first heat exchanger or a compressor shutdown. This increases the service life and efficiency of the heat pump.

[0032] According to one embodiment, if the defrosting of the first heat exchanger is not completed within the predetermined time, active defrosting of the first heat exchanger can be initiated. Methods for actively defrosting the first heat exchanger can include, for example, reversing the refrigerant cycle and / or heating the first heat exchanger with, for example, heated air or another heated gas. Due to the preceding assisted natural defrosting, active defrosting can be carried out in a shorter time and with reduced frequency, which in turn can increase the efficiency of the heat pump.

[0033] In a method according to the invention for cooling a building using the heat pump described above, the flow direction of the refrigerant in the refrigerant circuit of the heat pump is first adjusted by means of the directional control valve such that the first heat exchanger of the refrigerant circuit acts as a condenser and the second heat exchanger of the refrigerant circuit acts as an evaporator. In this case, gaseous refrigerant compressed by the compressor is condensed in the first heat exchanger and from there flows into the third heat exchanger. A predetermined subcooling of the refrigerant upstream of the expansion valve is then set by means of the third heat exchanger.

[0034] According to one embodiment, the predetermined subcooling of the refrigerant can be set by means of the volume flow rate of the heat transfer medium in the heat transfer circuit. In particular, the volume flow rate of the heat transfer medium in the heat transfer circuit can be adjusted such that the predetermined subcooling is achieved. The volume flow rate can be set, in particular, by the control device of the heat pump, which can, for example, control / regulate the speed of the pump such that the required volume flow rate for setting the predetermined subcooling is provided.

[0035] In this way, excess heat from the building can be transferred to the third heat exchanger during the heat pump's cooling operation, where it can be used, for example, to regenerate the ground. Using the third heat exchanger to subcool the refrigerant before the expansion valve is particularly advantageous because a conventional refrigerant circuit does not have a manifold upstream of the expansion valve in the flow direction required for cooling operation. Specifically, the refrigerant can condense in the third heat exchanger at a lower temperature and therefore also at a lower pressure, thus requiring less energy to compress the refrigerant and thereby increasing the heat pump's efficiency.

[0036] The supercooled refrigerant is then expanded via the expansion valve and fed to the second heat exchanger, where it evaporates. This extracts heat from the building's heating / cooling circuit, thus cooling it.

[0037] In summary, it becomes clear that the invention makes it possible to increase the efficiency of the heat pump in both cooling and heating modes by using the third heat exchanger for assisted natural defrosting of the first heat exchanger in heating mode and for subcooling the refrigerant before the expansion valve in cooling mode.

[0038] The heat pump can include a processing unit that is configured, particularly in terms of programming, to carry out the procedure described above. This processing unit can, for example, be the heat pump's control unit. Control of the heat pump can also be supported, for example, by an app on a user's device, which can be connected to the heat pump's control unit via signal transmission. In this case, the user can, for example, read and display operating states via the app. Preferably, the user can make settings, such as setpoints, program operating sequences, and the like, via a human-machine interface.

[0039] Implementing the described methods as a computer program or computer program product with program code to execute all process steps is also advantageous, as this incurs particularly low costs, especially if an executing control device is already available for other tasks. Suitable data carriers for providing the computer program include magnetic, optical, and electrical storage media, such as hard drives, flash memory, EEPROMs, DVDs, etc. Downloading a program via computer networks (Internet, intranet, etc.) is also possible.

[0040] It is also possible for individual steps of the described procedures to be carried out on a geographically remote server or in the cloud. For this purpose, data from the heat pump's control unit can be transmitted to the server or cloud via a network, such as the internet. This data can include, for example, operating parameters of the heat pump, recorded temperatures, pressures, etc. Algorithms can then be run in the cloud or on the server, for example, to determine the specific speed of the compressor and / or the specific output of the third heat exchanger, or similar parameters. Furthermore, artificial intelligence or machine learning methods can be used to identify ranges of operating parameters and environmental conditions of the heat pump in which assisted natural defrosting, as described above, can be carried out particularly efficiently. Brief description of the characters

[0041] Figure 1 schematically shows a refrigerant circuit of a heat pump for heating and cooling a building according to an embodiment of the invention. Figure 2 schematically shows a section of the refrigerant cycle. Figure 1 , in which an embodiment of the third heat exchanger is shown. Figure 3a schematically shows a section of the refrigerant cycle. Figure 1 , in which a further embodiment of the third heat exchanger is shown. Figure 3b shows the third heat exchanger made of Figure 3a in a cross-sectional view. Figure 4 schematically shows a section of the refrigerant cycle. Figure 1 , in which a further embodiment of the third heat exchanger is shown. Figure 5 schematically shows a section of the refrigerant cycle. Figure 1 , in which a further embodiment of the third heat exchanger is shown. Figures 6a and 6bThe figures schematically show two different embodiments of geothermal baskets that can be used in a heat pump according to the invention. Detailed description of preferred embodiments

[0042] Exemplary embodiments of the present invention are described in detail below with reference to exemplary figures. The features of the exemplary embodiments can be combined in whole or in part, and the present invention is not limited to the described exemplary embodiments. In the figures, identical or comparable elements are provided with the same reference numerals, so that a repeated description of the elements is omitted unless necessary.

[0043] Figure 1 Figure 1 schematically shows a refrigerant circuit 100 of a heat pump for heating and cooling a building according to an embodiment of the invention.

[0044] The refrigerant circuit 100 comprises a first heat exchanger 1, a compressor 2, a 4 / 2-way valve 6, a second heat exchanger 3, a refrigerant receiver 4, an expansion valve 5, and a third heat exchanger 7, which is arranged between the expansion valve 5 and the first heat exchanger 1. The individual components of the refrigerant circuit 100 are connected by refrigerant lines (not specified in detail), with solid arrows indicating the flow direction for heating the building (heating mode of the heat pump) and dashed arrows indicating the flow direction for cooling the building (cooling mode of the heat pump). In heating mode, the first heat exchanger 1 acts as an evaporator and the second heat exchanger 3 as a condenser, while in cooling mode, the functions of the first and second heat exchangers are reversed.

[0045] A temperature sensor 1.1 is installed in the first heat exchanger 1, and a further temperature sensor 1.3 and a pressure sensor 1.2 are arranged between the first heat exchanger and the compressor 2. Upstream of the compressor 2, a further temperature sensor 2.1, a further pressure sensor 2.2, and a high-pressure safety switch 2.3 are arranged. The illustrated temperature and pressure sensors can be used in a known manner for controlling and monitoring the expansion valve 5 and the compressor 2 in the heating and cooling operation of the heat pump.

[0046] In addition, two temperature sensors 7.1, 7.2 are installed upstream and downstream of the third heat exchanger, which can be used for its control / regulation and monitoring.

[0047] Each of the three heat exchangers shown, 1, 3, and 7, uses a different heat source and heat sink during heating and cooling operation of the heat pump. The first heat exchanger, 1, uses ambient air as both a heat source and a heat sink and can therefore be designed as a finned heat exchanger. The second heat exchanger, 3, uses the building's heating / cooling circuit as both a heat source and a heat sink and is therefore connected on its secondary side to a supply line (VL) and a return line (RL) of the heating / cooling circuit. The additional third heat exchanger, 7, uses the ground as both a heat source and a heat sink and is connected on its secondary side to a heat transfer circuit, 700, which includes a fourth heat exchanger, 71. This fourth heat exchanger is designed to transfer heat from the heat transfer circuit, 700, to the ground and vice versa.The fourth heat exchanger 71 can include at least one ground source heat collector, which can be, for example, a ground source heat basket, as in the . Figures 6a and 6b It can be shown, implemented in a specific way. However, it is also possible for the geothermal collector to be designed as a flat surface.

[0048] The heat transfer circuit 700 also includes a pump 72 and a temperature sensor 7.3. The pump 72 can, for example, be a variable-speed pump 72, which allows the flow rate of the heat transfer fluid in the heat transfer circuit 700 to be set for power control / regulation of the third heat exchanger. Alternatively or additionally, the pump 72 can have a variable displacement volume. Brine can be used as the heat transfer fluid, but other suitable heat transfer fluids are also possible. To set the flow rate, the pump 72 can be connected to a control device (not shown) of the heat pump and controlled by it. For this purpose, the control device can, for example, also receive signals from the temperature sensors 7.1 to 7.3.

[0049] In heating mode, the heat pump's gaseous refrigerant flows along the solid arrows from the first heat exchanger 1, where it has absorbed heat from the ambient air, through the 4 / 2-way valve 6, to the compressor 2. The 4 / 2-way valve 6 has two different positions, the corresponding flow paths of which are indicated by two solid and two dashed lines. In heating mode, the 4 / 2-way valve 6 is in a position where the refrigerant flows through it along both solid paths.

[0050] In the compressor, the refrigerant is compressed and flows as hot gas from compressor 2 via the 4 / 2-way valve 6 into the second heat exchanger 3. In heating mode of the heat pump, compressor 2 can, for example, operate at a speed of 100 to 120 rpm. ("revolutions persecond", revolutions per second), especially at 110 rps, to deliver a sufficient amount of refrigerant to heat the building into the second heat exchanger 3.

[0051] In the second heat exchanger 3, the refrigerant is liquefied, transferring the heat absorbed in the first heat exchanger 1 to the building's heating / cooling circuit (see arrows VL, RL, indicating the flow and return of the heating / cooling circuit). The condensed refrigerant then flows from the second heat exchanger 3 into the refrigerant receiver 4 and from there to the expansion valve 5. The refrigerant receiver 4 uses gravity to separate the liquid phase of the two-phase refrigerant exiting the second heat exchanger 3 from the gaseous phase, ensuring that only liquid refrigerant enters the expansion valve 5. The expansion valve 5 then reduces the pressure of the liquid refrigerant to an outlet pressure, allowing it to revert to a gaseous state in the first heat exchanger 1 and absorb heat in the process.

[0052] If frost is detected on the first heat exchanger 1 during the heating operation of the heat pump, the speed of the compressor 2 is reduced significantly, particularly abruptly, for example to 20 to 30 rpm. This abrupt reduction in compressor speed causes a sudden pressure increase and a corresponding increase in the evaporation temperature in the first heat exchanger 1, resulting in its natural defrosting. The required speed reduction can be determined, for example, as a function of the degree of frost buildup on the first heat exchanger 1. In particular, a larger speed reduction can be implemented for a higher degree of frost / heavier icing than for a lower degree of frost / lighter icing.

[0053] The presence or degree of frost buildup on the first heat exchanger 1 can be detected, for example, based on the evaporation temperature of the first heat exchanger 1 and / or the ambient temperature. The evaporation temperature can be determined using the temperature sensor 1.1 in the first heat exchanger 1, and the ambient temperature can be measured, for example, with an outdoor temperature sensor (not shown) of the heat pump. Alternatively or additionally, the resistance of an airflow through the first heat exchanger 1 can be determined for frost detection. For this purpose, measurement and control parameters of a fan motor (not shown) of the first heat exchanger 1 can be used, for example. Furthermore, frost detection can be carried out using optical, capacitive, and / or piezoresistive sensors. When using a finned heat exchanger, these sensors can be mounted in the fin area.

[0054] To support natural defrosting, a specific output of the third heat exchanger 7 is set in a second step to defrost the first heat exchanger 1 within a predetermined time. For this purpose, a suitable flow rate in the heat transfer fluid circuit 700 can be set using the pump 72. The specific output can also be determined, for example, as a function of the degree of frost buildup on the first heat exchanger 1. In particular, the specific output can be a maximum output of the third heat exchanger 7. The second step can be initiated simultaneously with the first step or at a later time than the first step.

[0055] In this way, heat can be extracted from the third heat exchanger 7 and supplied to the refrigerant circuit 100 before it flows through the first heat exchanger 1. Additionally, heat loss to the building's heating circuit via the secondary side of the second heat exchanger 3 can be reduced, and this heat can instead be used to defrost the first heat exchanger 1. Using the measures described, any initial frost buildup on the first heat exchanger 1 can be removed efficiently and quickly without requiring active defrosting or stopping the compressor 2. This increases the service life and efficiency of the heat pump.

[0056] If it is not possible to defrost the first heat exchanger 1 within the predetermined time, active defrosting, in particular a refrigerant cycle reversal, can be carried out.

[0057] To reverse the refrigerant circuit 100, the 4 / 2-way valve 6 can be switched to a second position, in which the refrigerant flows through it along the paths indicated by the dashed lines. The 4 / 2-way valve also assumes this position in the cooling mode of the heat pump, in which the second heat exchanger 3 operates as an evaporator and the first heat exchanger 1 as a condenser.

[0058] In cooling mode, the heat pump's gaseous refrigerant flows along the dashed arrows from the second heat exchanger 3, where it has absorbed heat from the building's heating / cooling system, via the 4 / 2-way valve 6, to the compressor 2. In the compressor 2, the refrigerant is compressed and then flows as a hot gas via the 4 / 2-way valve 6 into the first heat exchanger 1. In the first heat exchanger 1, the refrigerant liquefies, releasing the heat absorbed in the second heat exchanger 3 to the ambient air. The condensed, two-phase refrigerant then flows from the first heat exchanger 1 to the third heat exchanger 7, where it is further subcooled by releasing heat to the heat transfer circuit 700 and thus to the ground, and is therefore completely liquefied.The liquid refrigerant then flows to the expansion valve 5 and is expanded there to an outlet pressure, so that it can transition back into a gaseous state in the second heat exchanger 3 and absorb heat in the process. In this case, the refrigerant receiver 4 is located downstream of the expansion valve 5 and is therefore non-functional. Its function is replaced in the cooling mode of the heat pump according to the invention by the subcooling of the refrigerant in the third heat exchanger 7, which increases the efficiency of the heat pump even in this operating state. In this context, it is also possible to design the installation position of the third heat exchanger 7 such that its connections (not shown in detail) to the refrigerant circuit 100 can assume a receiver function. For this purpose, the third heat exchanger 7 can, for example, be rotated by 90° relative to the connection shown in the figure. Figure 1The position shown is rotated so that the connections are located at a lower and an upper end of the third heat exchanger 7.

[0059] Figure 2 schematically shows a section of the refrigerant circuit 100. Figure 1Figure 1 shows an embodiment of the third heat exchanger 7. The inset depicts the third heat exchanger 7 with the associated temperature sensors 7.1, 7.2 and the heat transfer circuit 700, as well as the first heat exchanger 1 with the associated temperature and pressure sensors 1.1 to 1.3. In the present embodiment, the third heat exchanger 7 is designed as a plate heat exchanger, the secondary side of which (not shown in detail) is connected to the heat transfer circuit 700. The plate heat exchanger is arranged between the expansion valve 5 and the first heat exchanger 1. In this region of the refrigerant circuit 100, the refrigerant has its lowest temperature during the heating operation of the heat pump, so that particularly efficient heat transfer from the ground-connected heat transfer circuit 100 to the refrigerant can take place there via the third heat exchanger 7.

[0060] In particular, a primary side of the plate heat exchanger (not shown in detail) is located upstream and directly adjacent to an inlet section of the first heat exchanger 1 (not shown in detail) in the refrigerant circuit 100. In this way, the third heat exchanger 3 is arranged in close proximity to the first heat exchanger 1, so that the heated refrigerant experiences only minimal heat losses on its way from the third to the first heat exchanger 7, 1.

[0061] Figure 3a schematically shows a section of the refrigerant circuit 100. Figure 1 , in which a further embodiment of the third heat exchanger 7 is shown, and Figure 3b shows the third heat exchanger 7 from Figure 3ain a cross-sectional view. In this case, the third heat exchanger 7 is mounted in a common housing (not specified) with the first heat exchanger 1. The third heat exchanger 7 is designed as a shell-and-tube heat exchanger, the tubes 7a of which are at least partially mechanically connected to core tubes 1a of the first heat exchanger 1, which is designed as a finned heat exchanger. In this way, a thermally conductive contact between the third and the first heat exchanger 7, 1 can be established, and the heat transfer to the refrigerant can be further improved.

[0062] Figure 4 schematically shows a section of the refrigerant circuit 100. Figure 1Figure 1 shows a further embodiment of the third heat exchanger 7. Here, the third heat exchanger 7 is designed as a coiled-tube heat exchanger, the secondary side of which (not specified) is connected to the heat transfer fluid circuit 700. A primary side (not specified) of the coiled-tube heat exchanger is directly adjacent to an inlet section 10 of the first heat exchanger 1, the inlet section 10 having several distribution pipes 10a, two of which are shown. The coils 7b on the secondary side of the third heat exchanger 7 can also be adjacent to the inlet section 10 in such a way that at least one coil 7b, or preferably all coils 7b, surrounds the distribution pipes 10b of the inlet section 10 (not shown). The coils 7b can be in direct mechanical contact with the distribution pipes 10b, so that heat conduction can also take place here.

[0063] Figure 5schematically shows a section of the refrigerant circuit 100. Figure 1 , in which a further embodiment of the third heat exchanger 7 is shown. In this case, the third heat exchanger 7 is, as in the one shown in Figure 2 The embodiment shown is designed as a plate heat exchanger, the secondary side of which, not further specified, is connected to the heat transfer circuit 700. In contrast to the one shown in Figure 2The plate heat exchanger shown is integrated into the inlet section 10 of the first heat exchanger 7. Specifically, the distribution pipes 10a of the inlet section 10 constitute the primary side of the third heat exchanger 7, so that heat transfer occurs in close proximity to the first heat exchanger 1, enabling particularly efficient defrosting of any ice buildup on the latter. For the fluidic connection of the third heat exchanger 7 to the individual distribution pipes 10a, the third heat exchanger 7 includes several refrigerant connections 7c, which are located on the side of the third heat exchanger 7 facing the first heat exchanger 1. Any other suitable position for attaching the refrigerant connections 7c to / in the third heat exchanger 7 is also possible.The refrigerant connections 7c allow the third heat exchanger 7 with the integrated distribution pipes 10a to be connected directly to individual core tubes 1a of the first heat exchanger 1, which is designed as a finned heat exchanger. Either all core tubes 1a or only individual core tubes 1a of the finned heat exchanger can be connected to the refrigerant connections 7c of the third heat exchanger 7.

[0064] Figures 6a and 6b Figure 71a and 71b schematically show two different embodiments of geothermal baskets that can be used in a heat pump according to the invention.

[0065] In particular, it shows Figure 6aThree frustoconical geothermal baskets 71a of different heights, each with several webs 710b to which a spirally wound pipe 710a is attached. The pipe 710a can be made of plastic. Other materials that allow for a spiral winding of the pipe are also possible. The webs 710b can be designed as support strips or support tubes and may, for example, include retaining loops (not shown) for fixing the wound pipe 710a. It is also possible that openings (not shown) are provided in the webs 710b by means of which the pipe 710a can be attached to the webs 710b, e.g., with equal spacing between the turns. For example, DE 20 2008 008 391 U1 shows a geothermal basket with a spirally wound plastic pipe and four ribs on which semicircular recesses are attached at equal intervals, into which the plastic pipe is clipped.

[0066] The in Figure 6a The cone-shaped geothermal baskets 71a shown can, for example, have an upper diameter of 2 m to 2.5 m and a lower diameter of 1 m to 1.5 m. The height of the geothermal baskets 71a can, for example, be 2.5 m to 3 m (left geothermal basket 71a), 1.5 m to 2.5 m (middle geothermal basket 71a), and 1 m to 1.5 m (right geothermal basket 71a). Other dimensions for the geothermal baskets 71a are also possible. The geothermal baskets 71a can, for example, be installed in the ground at a depth of 1 m to 10 m, particularly at a depth of 2 m to 4 m. It becomes clear that a single geothermal basket 71a can be sufficient to provide the required heat for the third heat exchanger 7 or to transfer the heat dissipated via this to the ground.

[0067] Figure 6bThe document shows a cylindrically shaped geothermal heat exchanger 71b, which also comprises a spirally wound pipe 710a, in particular a flexible plastic pipe, to which an inlet pipe 710d is connected. However, in this case, no webs 710b are used to fix the windings of the pipe 710a, but rather these are connected to each other by means of several bands / ropes 710c. This allows the windings to be compressed before installation in the ground, so that the geothermal heat exchanger 71b has a lower height, for example, for transport. For example, DE 20 2008 013 524 U1 shows a helical geothermal heat exchanger with a cylindrical shape, which is formed from an elastic pipe with connecting ends, wound turn by turn into a spiral. The turns are connected at the beginning and end by a band or rope, which determines the desired height of the geothermal heat exchanger.The coils are pulled apart until the tape / rope is taut and then clipped into holders which fix a distance between the coils.

[0068] The in Figure 6b The geothermal heat exchanger basket 71b shown, for example, can have a diameter of 0.5 m and a height of 2 m. The pipe 710a can, for example, have an inner diameter of 20 mm and a total length of 55 m. However, other dimensions for the geothermal heat exchanger basket 71b are also possible. The geothermal heat exchanger baskets 71b can, for example, be installed in the ground at a depth of 1 m to 10 m, particularly in a range of 2 m to 4 m. It becomes clear that even here, a single geothermal heat exchanger basket 7 can be sufficient to provide the required heat for the third heat exchanger 7 or to transfer the heat dissipated via it to the ground.

[0069] Due to the shallow installation depth and small footprint of the geothermal baskets 71a and 71b shown, they do not represent a significant additional effort in the planning and installation of the heat pump. For example, the installation of a geothermal basket 71a or 71b can be combined with the work to create a foundation for the outdoor unit of the heat pump, thus optimizing the installation effort.

Claims

1. Heat pump for heating and cooling a building with a refrigerant circuit (100) in which a refrigerant circulates, comprising: - a first heat exchanger (1) configured to use ambient air as a heat source and heat sink; - a second heat exchanger (3) configured to use a heating / cooling circuit of the building as a heat source and heat sink; - a directional control valve (3) configured to set a flow direction of the refrigerant in the refrigerant circuit (100); - a compressor (2) arranged between the first heat exchanger (1) and the second heat exchanger (3); - an expansion valve (5) arranged between the second heat exchanger (3) and the first heat exchanger (1);and - a third heat exchanger (7) arranged between the expansion valve (5) and the first heat exchanger (1) and configured to use the ground as a heat source and heat sink, wherein the third heat exchanger (7) is attached to or within an inlet section (10) of the refrigerant entering the first heat exchanger (1).

2. Heat pump according to claim 1, wherein the inlet flow path (10) into the first heat exchanger (1) comprises a plurality of distribution pipes (10a) which are fluidically and mechanically connected to the first heat exchanger (1).

3. Heat pump according to claim 1 or 2, wherein the third heat exchanger (7) has a plurality of refrigerant connections (7c) which are fluidically connected to the inlet section (10) in the first heat exchanger (1).

4. Heat pump according to at least one of the preceding claims, wherein the third heat exchanger (7) is designed as a plate heat exchanger.

5. Heat pump according to one of claims 2 to 4, wherein the third heat exchanger (7) is arranged in the inlet section (10) into the first heat exchanger (1) such that the distribution pipes (10a) of the inlet section (10) are integrated into the third heat exchanger (7).

6. Heat pump according to claim 2, wherein the third heat exchanger (7) is designed as a coiled tube heat exchanger.

7. Heat pump according to claim 6, wherein the third heat exchanger (7) is arranged in the inlet section (10) into the first heat exchanger (1) such that at least one helix (7b) of the third heat exchanger (7) is adjacent to the plurality of distribution pipes (10b) of the inlet section.

8. Heat pump according to claim 6 or 7, wherein the third heat exchanger (7) is arranged in the inlet section (10) into the first heat exchanger (1) such that at least one helix (7b) of the third heat exchanger (7) surrounds the plurality of distribution pipes (10b) of the inlet section (10).

9. Heat pump according to at least one of the preceding claims, wherein a secondary side of the third heat exchanger (7) is connected to a heat transfer circuit (700) in which a heat transfer medium circulates and which, in addition to the third heat exchanger (7), comprises a pump (72) and a fourth heat exchanger (71).

10. Heat pump according to claim 9, wherein the fourth heat exchanger (71) comprises at least one ground source heat collector.

11. A method for defrosting a first heat exchanger (1) acting as an evaporator in a refrigerant circuit (100) of a heat pump according to at least one of the preceding claims, comprising the steps of: - setting a speed of a compressor (2) of the refrigerant circuit (100) to a specific speed which is lower than a speed of the compressor (2) in a heating mode of the heat pump when frosting of the first heat exchanger (1) is detected in the heating mode of the heat pump; and - setting a specific power of a third heat exchanger (7) in the refrigerant circuit (100) in order to defrost the first heat exchanger (1) in a predetermined time.

12. Method according to claim 11, wherein the third heat exchanger (7) is connected to a heat transfer circuit (700) and the specified power is set by means of a volume flow of a heat transfer medium in the heat transfer circuit (700).

13. Method according to claim 11 or 12, wherein if the defrosting of the first heat exchanger (1) is not completed in the predetermined time, an active defrosting of the first heat exchanger (1) is initiated.

14. A method for cooling a building using a heat pump with a refrigerant circuit (100) according to at least one of claims 1 to 11, comprising the steps of: - setting a flow direction of a refrigerant in the refrigerant circuit (100), in which a first heat exchanger (1) of the refrigerant circuit acts as a condenser and a second heat exchanger (3) of the refrigerant circuit (100) acts as an evaporator, by means of a directional control valve (6); - compressing gaseous refrigerant by means of a compressor (2); - condensing the compressed refrigerant in the first heat exchanger (1); - setting a predetermined subcooling of the refrigerant upstream of an expansion valve (5) of the refrigerant circuit (100) by means of a third heat exchanger (7) in the refrigerant circuit (100); - expanding the subcooled refrigerant by means of the expansion valve (5); and - evaporating the expanded refrigerant in the second heat exchanger (3).

15. Method according to claim 14, wherein the third heat exchanger (7) is connected to a heat transfer circuit (700) and the predetermined subcooling of the refrigerant is set by means of a volume flow of a heat transfer medium in the heat transfer circuit (700).

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