Heat pump system and method for a heat pump system

Abstract

The invention relates to a heat pump system 100 having a primary circuit 110 for conducting a refrigerant, a secondary circuit 120 for conducting water, a heat exchanger 113 for transferring heat between the refrigerant and the water, and an oscillator circuit. The oscillator circuit has a capacitor 126. The capacitor is arranged on the secondary circuit such that a capacitance of the capacitor depends on a fill level of the secondary circuit. The heat pump system comprises a controller configured to output a switching signal depending on a change in the capacitance of the capacitor. The invention also relates to a method for monitoring a water fill level in the secondary circuit.

Description

[0001] The invention relates to a heat pump system and a corresponding method for a heat pump system, in particular for monitoring a quantity of refrigerant in a secondary circuit of the heat pump system.

[0002] Heat pump systems usually have a primary circuit for carrying a refrigerant and a secondary circuit for carrying water, whereby heat can be transferred between the refrigerant and the water using a heat exchanger, for example a plate heat exchanger.

[0003] However, when using propane as a refrigerant, the problem has been recognized that a defect in the heat exchanger can cause refrigerant to enter the secondary circuit, in particular a heating area of ​​the secondary circuit of a house, which is not permitted in refrigerant circuits with a mass of refrigerant that is above a limit that is usually specified by law.

[0004] State-of-the-art technology involves protecting the secondary circuit of heat pump systems against refrigerant ingress into the house's distribution system using a safety valve and / or automatic vent valve. This allows flammable refrigerant entering the secondary circuit to be removed before it can escape into the house. Particularly in propane applications or other similarly flammable refrigerants, two valves / vent valves can also be provided, for example, in a supply and return line of the secondary circuit. In some cases, a microbubble separator, which may include an automatic vent valve, is also used.

[0005] The disadvantage is that, despite the installed vents and drain valves, a dangerous amount of flammable refrigerant, for example, more than 150 g, can enter the secondary circuit, i.e., the heating section, unnoticed. One particular difficulty is providing an accurate and reliable method for measuring flammable refrigerant in the secondary circuit, which can be used, for example, to open a drain valve.

[0006] One objective underlying the present invention is to provide an accurate and reliable method for measuring flammable refrigerant in the secondary circuit, based on which the amount of flammable refrigerant can be reduced to a non-critical level. This can increase the safety of the heat pump system.

[0007] According to a first aspect of the invention, a heat pump system is proposed with a primary circuit for conducting a coolant, a secondary circuit for conducting water, and a heat exchanger for transferring heat between the coolant and the water, wherein the heat pump system further comprises an oscillator circuit with a capacitor, wherein the capacitor is arranged on the secondary circuit in such a way that a capacitance, ie in particular a dielectric constant, of the capacitor depends on a fill level of the secondary circuit, wherein the heat pump system comprises a controller which is designed to output a switching signal as a function of a change in the capacitance of the capacitor, ie in particular a change in the dielectric constant of the capacitor.

[0008] It was found that, depending on the fill level in the secondary circuit, the dielectric constant or capacitance of a capacitor located on the secondary circuit changes. A change in the fill level in the secondary circuit indicates that refrigerant has entered the secondary circuit. Thus, a change in the dielectric constant / capacitance can be used to directly indicate that refrigerant has entered the secondary circuit, and a switching signal can be output. This can increase the accuracy and reliability of detecting the amount of flammable refrigerant in the secondary circuit, thus increasing the safety of the heat pump system.

[0009] In a preferred embodiment, the controller is configured to output a switching signal when a threshold value is exceeded depending on the change in capacitance or dielectric constant of the capacitor. The threshold value can, for example, be a frequency threshold of the oscillator circuit.

[0010] In a further preferred embodiment, the controller is configured to output a switching signal when a frequency value of the oscillator circuit exceeds a predefined frequency threshold. This means that a change in the capacitance or dielectric constant changes a frequency of an oscillator circuit that includes the capacitor. The frequency is highly sensitive to the change in the capacitance or dielectric constant and thus to a change in the fill level. This further increases the accuracy and reliability of detecting the amount of flammable refrigerant in the secondary circuit, and thus the safety of the heat pump system.

[0011] In a preferred embodiment, the secondary circuit comprises a gas separator, wherein at least the condenser is arranged on, in particular externally on, the gas separator in such a way that the capacity of the condenser depends on a fill level of the gas separator. This enables particularly precise detection of a quantity of refrigerant in the gas separator. Additionally or alternatively, the secondary circuit comprises a pipe downstream of the heat exchanger in the direction of water flow, wherein at least the condenser, or a further condenser, is arranged on, in particular externally on, the pipe in such a way that the capacity of the condenser depends on a fill level of the pipe.

[0012] In a preferred variant of one of the above embodiments, the gas separator and / or the tube comprises at least a large part of a non-conductive material. This allows a change in the dielectric constant to be detected very precisely.

[0013] In a further preferred embodiment, the oscillator circuit comprises at least one resonant circuit and / or an RC element. This means that the capacitor is connected as a frequency-influencing component of the resonant circuit and / or the RC element. In particular, a circuit corresponding to an astable multivibrator is preferred. This means that the capacitor is then connected as a frequency-influencing component of the astable multivibrator.

[0014] In a further preferred embodiment, the capacitor comprises a pole strip. In other words, the capacitor is implemented as a pole strip. The pole strip or conductor strip is preferably applied to the gas separator (or a tube) from the outside.

[0015] In an example in which the dielectric constant changes due to a change in fill level, a switching signal can be output, for example, by switching a multivibrator from a first position to a second position.

[0016] For example, the switching signal is a switch-on signal or a switch-off signal for a water pumping device and / or a shut-off device.

[0017] The controller is preferably configured to output a switching signal when a frequency threshold is exceeded depending on the change in capacitance or the change in the dielectric constant of the capacitor. For example, the frequency threshold is an upper frequency threshold. Then, the controller is preferably configured to output a switch-off signal when the frequency value exceeds the upper frequency threshold from bottom to top and to output a switch-on signal when the frequency value exceeds the upper frequency threshold from top to bottom.

[0018] Furthermore, the heat pump system is preferably designed to pump the water in the secondary circuit based on the switch-on signal and designed not to pump any water in the secondary circuit based on the switch-off signal.

[0019] In a preferred variant of the above embodiment, the secondary circuit comprises a circulation pump as a water pumping device. The controller is then configured to output the switch-off signal or the switch-on signal to the circulation pump, and the circulation pump is configured to pump the water in the secondary circuit based on the switch-on signal and to not pump the water in the secondary circuit based on the switch-off signal.

[0020] In a further preferred variant of the above embodiment, the secondary circuit comprises a shut-off device. The controller is then configured to output the switch-off signal or switch-on signal to the shut-off device, and the shut-off device is configured to open the shut-off device based on the switch-on signal and to close the shut-off device based on the switch-off signal.

[0021] Furthermore, the oscillator circuit preferably comprises at least one resistor.

[0022] According to a second aspect of the invention, a method for monitoring a water fill level in a secondary circuit of a heat pump system is proposed, wherein the heat pump system has a primary circuit for conducting a coolant, a secondary circuit for conducting water, a heat exchanger for transferring heat between the coolant and the water and an oscillator circuit, wherein the oscillator circuit has a capacitor, wherein the capacitor is arranged on the secondary circuit in such a way that a capacitance of the capacitor depends on a fill level of the secondary circuit, wherein the method comprises the steps of: conveying water within the secondary circuit, outputting a switching signal as a function of a change in capacitance of the capacitor and based on the switching signal, terminating the conveyance of water within the secondary circuit.

[0023] Preferably, the first step of conveying comprises controlling a circulation pump so that the circulation pump conveys the water in the secondary circuit.

[0024] Additionally or alternatively, a capacitance change is determined in the outputting step via a frequency change of the oscillator circuit.

[0025] Further additionally or alternatively, the third step of terminating the pumping of water preferably comprises at least one of the following steps: controlling the circulation pump so that the circulation pump does not pump the water in the secondary circuit, closing a first shut-off device and closing a second shut-off device.

[0026] Features of advantageous embodiments of the invention are defined in particular in the subclaims, wherein further advantageous features, embodiments and configurations can also be gathered from the above explanation and the following discussion by the person skilled in the art.

[0027] In the following, the present invention is further illustrated and explained with reference to exemplary embodiments shown in the figures. Fig. 1 is a schematic representation to illustrate a first embodiment of the heat pump system according to the invention, and Fig. 2 is a schematic flow diagram of an embodiment of the method according to the invention for monitoring a water level in a secondary circuit of a heat pump system.

[0028] In the accompanying drawings and the explanations to these drawings, corresponding or related elements are - where appropriate - identified by corresponding or similar reference numerals, even if they are found in different embodiments.

[0029] Fig. 1 shows a schematic diagram illustrating a first embodiment of a heat pump system. The heat pump system 100 comprises a primary circuit 110 for carrying a refrigerant and a secondary circuit 120 for carrying a heat transfer medium such as water.

[0030] In the present exemplary embodiment, the primary circuit 110 comprises a refrigerant / air heat exchanger 111, for example in the form of an evaporator, a compressor 112, a refrigerant / water heat exchanger 113, for example in the form of a condenser, an expansion device 114, for example in the form of a throttle device, and a refrigeration circuit reversing device 115. The primary circuit 110 is thermally connected to the secondary circuit 120 via the heat exchanger 113, wherein the heat exchanger 113 can be a plate heat exchanger, for example.

[0031] In the present exemplary embodiment, the secondary circuit 120 comprises a gas separator 121, a first shut-off device 122, which can be configured, for example, as an electrically controlled valve, a second shut-off device 123, and a circulation pump 124. The gas separator 121 comprises a safety valve 125. The safety valve 125 can be opened when a predefined threshold pressure is exceeded. The gas separator 121 also comprises a capacitor 126. The capacitor 126 is part of an oscillator circuit. The capacitor 126 is arranged on the secondary circuit 120 such that a capacitance of the capacitor 126 depends on a fill level of the secondary circuit 120. For example, the capacitor 126 is provided as a pole strip on the gas separator 121.

[0032] The heat pump system 100 comprises a controller configured to output a switching signal depending on a change in capacitance of the capacitor.

[0033] In the embodiment shown, the switching signal is output to the first shut-off device 122. Additionally or alternatively, the switching signal can also be output to the second shut-off device 123 and / or the circulation pump 124. Depending on the switching signal, the first shut-off device 122, the second shut-off device 123, and / or the circulation pump 124 are controlled such that water is pumped or not pumped in the secondary circuit.

[0034] For example, the switching signal can be understood as a switch-on signal if water is pumped according to the switching signal and the switching signal can be understood as a switch-off signal if no water is pumped according to the switching signal.

[0035] This means that the controller is configured to output a switch-off signal depending on the change in capacitance of the capacitor, for example, when the frequency value of the oscillator circuit exceeds a frequency threshold, wherein the first shut-off device 122 and / or the second shut-off device 123 are configured to close and / or the circulation pump 124 is configured to stop pumping water in the secondary circuit. Furthermore, the controller is configured to output a switch-on signal depending on the change in capacitance of the capacitor, for example, when the frequency value of the oscillator circuit exceeds the frequency threshold, wherein the first shut-off device 122 and / or the second shut-off device 123 are configured to open and / or the circulation pump 124 is configured to stop pumping water in the secondary circuit.

[0036] The secondary circuit 120 comprises a flow area, a heating area 128, and a return area, with the gas separator 121 and the first shut-off device 122 being arranged in the flow area, and the first shut-off device 122 being arranged downstream of the gas separator 121 in the direction of water flow. Particularly advantageously, the first shut-off device 122 is a valve, for example a solenoid valve, which is switched, in particular closed, based on the determined frequency value at the gas separator 121. The second shut-off device 123 is arranged in the return area of ​​the secondary circuit 120. Particularly advantageously, the second shut-off device 123 is a check valve.

[0037] In the embodiment shown, the gas separator 121 comprises a vent 127 designed to discharge a refrigerant that enters the gas separator 121. Preferably, the first shut-off device 122 and the second shut-off device 123 are controlled such that after the refrigerant has been completely discharged, the first shut-off device 122 and the second shut-off device 123 are opened. This means that depending on the change in capacitance of the capacitor, for example, if the frequency value of the oscillator circuit exceeds the frequency threshold again, a switching signal can be output again, on the basis of which the first shut-off device 122, the second shut-off device and / or the circulation pump 124 are switched.

[0038] In addition or alternatively to the condenser 126 on the gas separator 121, the condenser 126 can also be provided on the pipe 129 between the gas separator 121 and the heat exchanger 113.

[0039] Fig. 2 shows a schematic flow diagram of an embodiment of the method according to the invention for monitoring a water level in a secondary circuit of a heat pump system. The heat pump system can correspond to heat pump system 100.

[0040] In a first step 210 of the method 200, water is pumped within the secondary circuit. In particular, pumping water may include controlling a circulation pump, i.e., supplying the circulation pump with electrical energy so that the circulation pump pumps the water in the secondary circuit.

[0041] In a second step 220, a switching signal is output depending on a change in the capacitance of the capacitor. The change in capacitance can be determined, in particular, via a change in the frequency of the oscillator circuit.

[0042] In a third step 230, the pumping of water within the secondary circuit is stopped based on the switching signal. Stopping the pumping of water preferably comprises at least one of the following steps: controlling the circulation pump so that the circulation pump does not pump water in the secondary circuit, closing a first shut-off device, and closing a second shut-off device.

[0043] The switching signal can in particular be a switch-off signal, on the basis of which a first shut-off device 122, a second shut-off device 123 and / or a circulation pump 124 is then controlled in a further step in such a way that no water is pumped in the secondary circuit.

[0044] Although various aspects or features of the invention are shown in combination in the figures, it will be apparent to those skilled in the art—unless otherwise stated—that the illustrated and discussed combinations are not the only possible ones. In particular, corresponding units or feature complexes from different embodiments can be interchanged.

[0045] Further considerations regarding the invention follow: In order to prevent refrigerant from entering the residential building via the water circuit in the event of an internal leak in the refrigerant / water heat exchanger, the water level in the gas separator is monitored.

[0046] Monitoring is preferably carried out by evaluating the dielectric constant of an electrically conductive pole strip acting as a capacitor, for example, on the outside of a particularly cylindrical contour through which water flows, for example, on a cylindrical non-conductive gas separator. The capacitor is connected as a frequency-influencing component of an astable multivibrator or oscillator. A reduction in the water level influenced by gas filling reduces the capacitance of the capacitor, thereby increasing the frequency of the oscillator. An evaluation circuit then switches, for example, media flow-limiting actuators (e.g., a shut-off valve, a media conveying device, etc.) when the frequency threshold is exceeded.

[0047] To increase safety, the evaluation circuit can be designed as a low-pass element, so that only at sufficiently low frequencies is a relay activated, which supplies the media flow-limiting actuators (shut-off valve, media conveying device) with voltage so that the secondary medium is conveyed.

[0048] A key element of the invention lies in the electronic detection of the fill level through corresponding capacitance changes, preferably in a multivibrator circuit. This design operates contactlessly and is insensitive, compared to a float, for example, which is susceptible to interference due to jamming, contamination, and other flow influences.

[0049] Furthermore, the frequency changes allow a system to be implemented with a higher level of safety, as drift in measured values ​​and transmission elements is less likely. This is achieved in particular by outputting a switching signal based on a change, i.e., a change in capacitance or a change in the dielectric constant, e.g., via a frequency change of the oscillator circuit. This is thus a relative circuit that reacts to a change in fill level independently of temperature, pressure, etc.

[0050] By measuring "analog" values, advance warning management and a control cascade can be carried out when gas filling is imminent.

[0051] A non-contact electronic detection, preferably via the frequency of a multivibrator circuit, which is influenced by the dielectric constant of a capacitor surrounding the separator, has an increased level of safety compared to known solutions and generates a measured value proportional to the gas content.

[0052] The new technology can be used in all new heat pump developments that use flammable refrigerants to operate the refrigeration circuit.

[0053] Preferably, a pole strip is used, i.e., the condenser preferably comprises a pole strip, wherein the pole strip is more preferably applied vertically externally to a "standing" separator cylinder, which is preferably made of non-conductive material. Additionally or alternatively, the pole strip can be applied externally to a pipe contour, which is preferably made of non-conductive material, downstream of the heat exchanger in the flow direction.

[0054] In a preferred embodiment, the multivibrator or oscillator comprises the (water level detection) capacitor and one or more resistors as the frequency-determining component. Additionally or alternatively, the multivibrator or oscillator comprises the capacitor and an inductor as frequency-determining components.

[0055] The oscillator's frequency signal can be evaluated (digitally), for example, using a pulse counting method within a gate time. Additionally or alternatively, the oscillator's frequency signal can be evaluated (digitally) using a cycle time determination method. Additionally or alternatively, the frequency signal can be verified cyclically using stimuli, for example, by adding an additional capacitor and evaluating the resulting frequency change, to increase intrinsic safety. The oscillator's frequency signal can also be evaluated (analogously) using other suitable circuitry, such as a low-pass and / or band-pass filter.

[0056] The invention relates to a heat pump system having a primary circuit for conducting a refrigerant, a secondary circuit for conducting water, a heat exchanger for transferring heat between the refrigerant and the water, and an oscillator circuit. The oscillator circuit has a capacitor. The capacitor is arranged on the secondary circuit in such a way that a capacitance of the capacitor depends on a fill level. The heat pump system comprises a controller configured to output a switching signal depending on a change in the capacitance of the capacitor. The invention also relates to a method for monitoring a water fill level in the secondary circuit.

Claims

1. Heat pump system (100) comprising: a primary circuit (110) for conducting a refrigerant, a secondary circuit (120) for conducting water, a heat exchanger (113) for transferring heat between the refrigerant and the water, and an oscillator circuit, wherein the oscillator circuit has a capacitor (126), wherein the capacitor (126) is arranged on the secondary circuit (120) in such a way that a capacitance of the capacitor (126) depends on a fill level of the secondary circuit (120), wherein the heat pump system (100) comprises a controller which is designed to output a switching signal depending on a change in capacitance of the capacitor (126).

2. Heat pump system (100) according to claim 1, wherein the controller is configured to output a switching signal when a threshold value is exceeded depending on the change in capacitance of the capacitor (126).

3. Heat pump system (100) according to claim 2, wherein the controller is configured to output a switching signal when a frequency value of the oscillator circuit exceeds a predefined frequency threshold.

4. Heat pump system (100) according to one of the preceding claims, wherein the secondary circuit (120) comprises a gas separator (121) and wherein at least the condenser is arranged on, in particular externally on, the gas separator (121) in such a way that the capacity of the condenser (126) depends on a fill level of the gas separator (121), and / or the secondary circuit (120) comprises a pipe (129) in the flow direction of the water after the heat exchanger (113) and wherein at least the condenser is arranged on, in particular externally on, the pipe (129) in such a way that the capacity of the condenser (126) depends on a fill level of the pipe (129).

5. Heat pump system according to claim 4, wherein the gas separator (121) and / or the pipe (129) comprises at least a large part of a non-conductive material.

6. Heat pump system (100) according to one of the preceding claims, wherein the oscillator circuit comprises at least one resonant circuit and / or an RC element.

7. Heat pump system (100) according to one of the preceding claims, wherein the capacitor (126) comprises a pole strip.

8. The heat pump system (100) according to claim 2, wherein the threshold value is an upper frequency threshold value of the oscillator circuit, wherein the controller is configured to output a switch-off signal when the frequency value exceeds the upper frequency threshold value from bottom to top and is configured to output a switch-on signal when the frequency value exceeds the upper frequency threshold value from top to bottom, wherein the heat pump system (100) is configured to pump the water in the secondary circuit (120) based on the switch-on signal and is configured not to pump the water in the secondary circuit (120) based on the switch-off signal.

9. Heat pump system (100) according to one of the preceding claims, wherein the heat pump system (100) comprises at least one shut-off device (122), wherein the controller is designed to control the at least one shut-off device (122) based on the switching signal and / or wherein the heat pump system (100) comprises a water delivery device (124), wherein the controller is designed to control the water delivery device (124) based on the switching signal.

10. A method for monitoring a water level in a secondary circuit (120) of a heat pump system (100), wherein the heat pump system (100) has a primary circuit (110) for conducting a refrigerant, a secondary circuit (120) for conducting water, a heat exchanger (113) for transferring heat between the refrigerant and the water, and an oscillator circuit, wherein the oscillator circuit has a capacitor (126), wherein the capacitor (126) is arranged on the secondary circuit (120) such that a capacitance of the capacitor (126) depends on a fill level of the secondary circuit (120), wherein the method comprises the steps of: conveying (210) water within the secondary circuit (120), outputting (220) a switching signal depending on a change in capacitance of the capacitor (126) and based on the switching signal, terminating (230) the conveying of water within the secondary circuit (120).

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