Leakage sensor for a heat pump to detect a propane leak in a fluid circuit

Abstract

Leakage sensor (1) for a heat pump (2) for detecting a leak leading to the ingress of gas into a fluid circuit (3) defined at least partially by a fluid line, wherein the leakage sensor (1) has at least one structure-borne sound sensor (12) which is designed to detect structure-borne sound transmitted through the fluid and / or through the fluid line, and includes an evaluation unit (13) which is designed to evaluate the structure-borne sound detected by the structure-borne sound sensor (12) for the detection of a gas penetrating the fluid line through the leakage.

Description

[0001] The invention relates to a leakage sensor for a heat pump for detecting a propane leak in a fluid circuit, wherein the fluid circuit is in particular a hot water circuit connected to the heat pump, preferably a heating and / or a domestic hot water circuit.

[0002] The heat pump market is increasingly shifting towards the use of propane (R290) as a refrigerant. While propane has advantageous thermodynamic properties, it is flammable, necessitating special safety requirements for leak detection when used indoors. Future generations of heat pumps will operate with comparatively small refrigerant charges of 150 g or less, thus reducing the legal and regulatory safety requirements for indoor installation. However, this necessitates the implementation of suitable measures for detecting potential propane leaks to ensure the safety of users and the surrounding environment.

[0003] It is known in the prior art that leaks can occur in the refrigerant circuit. To detect these leaks, sensors for propane gas are sometimes installed in the floor area below the heat pump, since propane is heavier than air and accumulates near the floor in the event of a leak.

[0004] However, it is insufficiently taken into account that in the event of a leak, propane can enter a hot water circuit from the actual refrigerant circuit, for example the heating circuit or the hot water circuit for domestic hot water.

[0005] This is particularly true within the condenser if a hot water circuit running through it has leaks. Due to the pressure conditions prevailing in the condenser – propane pressure in the range of 10 to 20 bar compared to 1 to 4 bar in the hot water circuit – propane can enter the hot water circuit in the event of a leak.

[0006] This means that, on the one hand, the leak cannot be detected by known systems, and on the other hand, the propane escaping via the hot water circuit also poses a significant safety risk that is not adequately addressed by the solutions known in the prior art.

[0007] Against this background, the object of the invention is to overcome the aforementioned disadvantages and to provide a sensor for heat pumps for the reliable detection of propane leaks affecting a hot water circuit, which can detect such leaks and thereby increase operational reliability, especially when installing heat pumps indoors.

[0008] This problem is solved by the combination of features according to the main claim and the dependent claim.

[0009] According to the invention, a leakage sensor for a heat pump is proposed, which is suitable for detecting a leak that leads to the ingress of gas, in particular propane, into a fluid circuit defined at least partially by a fluid line. If gas or propane enters a fluid line through a leak, a characteristic hissing sound occurs, as well as the coupling of structure-borne sound characteristic of this phenomenon into the fluid line and the fluid. The fluid circuit is preferably a hot water circuit connected to the heat pump, i.e., a heating circuit or a domestic hot water circuit, and the fluid is preferably water. For this purpose, the leakage sensor has at least one structure-borne sound transducer, which can be, for example, a structure-borne sound microphone or a vibration sensor.The structure-borne sound sensor can also detect structure-borne sound in the range audible to the human ear (16 Hz to 20 kHz) and / or the ultrasonic range (above 20 kHz) and is designed, preferably in physical and especially direct contact with the fluid and / or fluid line, to detect structure-borne sound transmitted through the fluid and / or fluid line. For clarification, structure-borne sound refers to sound waves propagating in the fluid or fluid line and not to sound waves transmitted through air. Structure-borne sound can also manifest itself through vibrations of the fluid or fluid line, which can be detected by the structure-borne sound sensor. Furthermore, the structure-borne sound sensor can be designed to detect only structure-borne sound in order to exclude, for example, interference transmitted via airborne sound.Building on this, the leakage sensor further comprises an evaluation unit, which is preferably connected to the at least one structure-borne sound sensor via a signal connection and is designed to evaluate the structure-borne sound detected by the structure-borne sound sensor for the detection of a gas penetrating the fluid line through the leak.

[0010] The underlying technical concept is that if the fluid line leaks in the area of ​​the heat pump's condenser, gas, specifically propane, enters the fluid line due to the pressure difference, producing a hissing sound that propagates as structure-borne noise through the fluid line and the fluid itself. The leakage sensor according to the invention, as described, comprises a structure-borne noise transducer designed to detect the structure-borne noise generated by the hissing sound, or simply to detect the hissing sound. This transducer is in at least indirect, or preferably direct, contact with the fluid line or the fluid. Since not every detected structure-borne noise is caused by a leak and corresponds to a characteristic hissing sound, the evaluation unit analyzes the detected structure-borne noise to determine whether a leak is present through which gas (propane) is entering the fluid line.

[0011] Such an evaluation of the structure-borne sound and a leak detection based on it can be carried out in the evaluation unit, for example, by comparing it with and / or detecting structure-borne sound characteristics that are characteristic of a leak.

[0012] An advantageous further development provides that the evaluation unit contains at least one predetermined, characteristic reference structure-borne sound signal, indicative of gas ingress into the fluid line. "Contained" in this context means that the signal is either directly stored in the evaluation unit or retrievable by the evaluation unit. Furthermore, the evaluation unit is configured to compare the structure-borne sound signal detected by the structure-borne sound sensor with the at least one reference signal signal and to determine whether the structure-borne sound signal matches the reference signal signal within a predetermined tolerance as a leak, i.e., to assume a leak if the match is within the tolerance. The structure-borne sound signal and the reference signal signal specifically include their respective time profiles.

[0013] Accordingly, the evaluation unit can be designed to compare the structure-borne sound detected by the structure-borne sound sensor in the time domain with at least one reference structure-borne sound.

[0014] Additionally or alternatively, the evaluation unit can also be designed to compare the structure-borne sound detected by the structure-borne sound sensor in the frequency range with at least one reference structure-borne sound.

[0015] Depending on the desired level of fault tolerance, a leak can be assumed if a leak is detected in the time domain, or if a leak is detected in the frequency domain, or if a leak is detected in both the time and frequency domains.

[0016] Alternatively or additionally to signal comparison, leak detection can also be based on pattern recognition. For this purpose, it is preferably provided that at least one reference pattern, identifying or characterizing gas ingress into the fluid line, is stored or can be retrieved by the evaluation unit, and that the evaluation unit is also configured to analyze the structure-borne sound detected by the acoustic sensor in the time and / or frequency domain for the occurrence of a reference pattern. If a reference pattern is detected in the structure-borne sound, a leak is assumed, and the occurrence of the pattern is accordingly determined as the cause of the leak.

[0017] Furthermore, the evaluation unit can be designed to store the structure-borne sound detected by the structure-borne sound sensor as its progression over time and / or to transform the detected structure-borne sound or its progression into the frequency domain.

[0018] If a leak has been detected or identified, the evaluation unit can generate a message signal to report the leak, for example to a higher-level system or the heat pump.

[0019] Furthermore, the leakage sensor can have a direction sensor and / or the at least one structure-borne sound sensor can be arranged and designed in such a way that a direction can be detected from which the structure-borne sound propagates along the fluid and / or the fluid line.

[0020] Since the entire fluid line may not be relevant for the leakage, but only a section upstream or downstream of the fluid line starting from the leakage sensor, for example only the structure-borne sound which is coupled into the structure-borne sound sensor from a relevant direction can be evaluated.

[0021] Furthermore, the leakage sensor can also have two structure-borne sound transducers arranged along the fluid line in such a way that a section relevant for leak detection lies between the two transducers. Each of the two structure-borne sound transducers can also be equipped with a direction sensor, or the transducers themselves can be configured as direction sensors, so that the evaluation unit can determine the direction and, in particular, whether the detected leak is located in the relevant section of the fluid line.

[0022] In the context of a heat pump, for example, a first structure-borne sound sensor can be arranged at the flow inlet and a second structure-borne sound sensor at the flow outlet of a fluid channel of the heat exchanger of the heat pump, which determines the section of the fluid circuit relevant for the leakage, in which gas, in particular propane, can flow into the fluid, i.e. the water.

[0023] In order to make the leakage sensor multifunctional and therefore cost-effective, it can also be provided that it has a sound transmitter, wherein the sound transmitter and the structure-borne sound sensor span a measuring section through the fluid between them and are arranged offset from each other in the direction of flow of the fluid, so that a sound travel time of the sound signal from the sound transmitter along the measuring section to the structure-borne sound sensor through the fluid and / or the flow velocity of the fluid can be determined.

[0024] To optimize and minimize the cost of evaluation using the evaluation unit, a reference static structure-borne sound can be stored within it. This reference corresponds to structure-borne sound transmitted through a fluid and / or fluid line when no leakage is present. Therefore, even before a leakage is detected, the evaluation unit can be configured to only perform the evaluation if the structure-borne sound detected by the sensor deviates from the reference static structure-borne sound, or if the deviation is within a predetermined tolerance.

[0025] Alternatively, the leakage sensor can also be functionally integrated independently into a known sensor for determining the flow velocity.

[0026] Another aspect of the invention relates to a heat pump with a leakage sensor according to the invention. The heat pump has a heat exchanger, which is arranged, in particular, on or in a condenser of the heat pump. The heat exchanger is designed to transfer heat from a cooling circuit through which coolant flows to a fluid circuit through which fluid flows, wherein the heat exchanger has a fluid channel through which the fluid flows or the fluid channel is connected to the heat exchanger. The fluid channel has a flow inlet and a flow outlet downstream of it and defines the fluid circuit section by section. The leakage sensor or its structure-borne sound sensor is / are arranged along the fluid channel and / or directly at the flow outlet and / or directly at the flow inlet of the fluid channel, so that propane or other gas flowing into the heat exchanger due to a leak is detected.The resulting structure-borne sound ("hissing") is immediately detectable.

[0027] Assuming that the heat pump has a condenser, the leakage sensor is located on, but preferably outside, the condenser, but directly adjacent to it in terms of airflow.

[0028] Depending on the specific design of the heat pump, it may have a leakage sensor for each fluid circuit.

[0029] It should be noted that in the context of the invention or in the context of the present disclosure, “heat” is also to be understood as “cold” and “heating circuit” is also to be understood as “cooling circuit”, for example when the heat pump is used in reverse for cooling instead of heating.

[0030] All the characteristics described for the leakage sensor also apply analogously to the heat pump.

[0031] The features disclosed above can be combined in any way, provided that this is technically possible and they do not contradict each other.

[0032] Other advantageous embodiments of the invention are characterized in the dependent claims or are described in more detail below together with the description of the preferred embodiment of the invention with reference to the figure. It shows: Fig. 1 heat pump with leakage sensor.

[0033] The figure is a schematic example.

[0034] In Fig. Figure 1 schematically shows a heat pump 2 with a leakage sensor 1 according to the invention, whereby heat pumps and their operation are assumed to be known and are therefore not described in detail below.

[0035] In principle, heat pumps 2 define a coolant circuit 20, along which a coolant, at the time of registration in particular also propane gas, or propane for short, is pumped.

[0036] Along the refrigerant circuit 20, the propane flows from an evaporator 21 through a compressor 22, a condenser 23 and an expansion valve 28 back into the evaporator 21, whereby the propane compressed and thereby heated in the compressor 22 transfers heat in or at the condenser 23 via a heat exchanger 24 to a fluid circuit 3, which can be, for example, a heating circuit or a domestic hot water circuit of a building, so that the fluid is water.

[0037] Due to leaks along the coolant circuit 20, propane can escape from it and collect below the heat pump 2, which can be detected by gas sensors known in the prior art.

[0038] However, if the leak is located in the condenser 23 and / or the heat exchanger 24, propane from the coolant circuit 20 may not flow into the environment of the heat pump, but into a fluid channel 25 of the heat exchanger 24 and thus into the fluid circuit 3, causing propane bubbles to form within the fluid, resulting in a "hissing" sound and the coupling of structure-borne noise into the fluid line of the fluid circuit, i.e. the fluid channel 25, and / or into the fluid, i.e. the water flowing through the fluid channel 25.

[0039] To detect such an inflow of propane gas into the fluid circuit, a leakage sensor 1 is proposed according to the invention, which, according to the embodiment shown here, is arranged directly at a flow outlet 27 of a fluid channel 25 of the heat exchanger 24. When propane penetrates and the associated "hissing" sound occurs, the resulting structure-borne noise can therefore be detected directly.

[0040] Although the leakage sensor 1 and its functionality in the context of the in Fig. As described in section 1, the following applies regardless of the heat pump 2 shown, so that the Fig. The leakage sensor shown can also be considered independently of the heat pump.

[0041] Basically, the leakage sensor 1 has at least one structure-borne sound sensor 12 and an evaluation unit 13, wherein the illustrated leakage sensor 1 also has a sound transmitter 11 in order to simultaneously function as a flow sensor or to determine the flow velocity of the fluid flowing through the fluid line 3.

[0042] The structure-borne sound sensor is in contact with the body with a fluid channel 10 through which the fluid flows directly, or in contact with the body with the fluid itself.

[0043] To detect a leak, the evaluation unit 13 is designed to compare the structure-borne sound detected by the structure-borne sound sensor 12 with a reference structure-borne sound and / or a reference pattern that are characteristic of a leak or the "hissing" sound produced by the leak. If a leak is detected based on this comparison, the evaluation unit 13 generates a signal to report the leak to the heat pump 2 or another higher-level system.

Claims

[1] Leakage sensor (1) for a heat pump (2) for detecting a leak leading to the ingress of gas into a fluid circuit (3) defined at least partially by a fluid line, wherein the leakage sensor (1) has at least one structure-borne sound sensor (12) which is designed to detect structure-borne sound transmitted through the fluid and / or through the fluid line, and includes an evaluation unit (13) which is designed to evaluate the structure-borne sound detected by the structure-borne sound sensor (12) for the detection of a gas penetrating the fluid line through the leakage. [2] Leakage sensor according to claim 1, wherein at least one predetermined reference structure-borne sound (pattern) indicative of gas penetration into the fluid line is stored in the evaluation unit (13) and the evaluation unit (13) is formed, to compare the structure-borne sound detected by the structure-borne sound sensor (12) with at least one reference structure-borne sound, as well as to determine leakage based on the agreement of the structure-borne sound with the reference structure-borne sound within a predetermined tolerance. [3] Leakage sensor according to claim 2, wherein the evaluation unit (13) is formed, to compare the structure-borne sound detected by the structure-borne sound sensor (12) in the time domain with at least one reference structure-borne sound and / or to compare the structure-borne sound detected by the structure-borne sound sensor (12) in the frequency range with at least one reference structure-borne sound. [4] Leakage sensor according to any one of the preceding claims, wherein at least one reference pattern indicating the ingress of gas into the fluid line is stored in the evaluation unit (13) and the evaluation unit (13) is formed, to evaluate the structure-borne sound detected by the structure-borne sound sensor (12) in the time domain and / or frequency domain for the occurrence of a reference pattern and to determine the occurrence of a reference pattern as a leakage. [5] Leakage sensor according to one of the preceding claims, wherein the evaluation unit is configured to store the structure-borne sound detected by the structure-borne sound sensor (12) as its progression over time and / or to transform the detected structure-borne sound or its progression into the frequency domain. [6] Leakage sensor according to any one of the preceding claims, wherein the evaluation unit (13) is designed, To generate a notification signal to report a leak upon detection of a leak. [7] Leakage sensor according to one of the preceding claims, wherein a direction sensor and / or the structure-borne sound sensor (12) is arranged and configured to detect a direction from which the structure-borne sound propagates along the fluid and / or the fluid line. [8] Leakage sensor according to any one of the preceding claims, further comprising a sound generator (11), wherein the sound transmitter (11) and the structure-borne sound sensor (13) span a measuring section through the fluid between them and are arranged offset from each other in the direction of flow of the fluid, so that a sound travel time of the sound signal from the sound transmitter (11) along the measuring section to the structure-borne sound sensor (12) through the fluid and / or the flow velocity of the fluid can be determined. [9] Heat pump (2) with a leakage sensor (1) according to one of the preceding claims, wherein the heat pump has a heat exchanger (24) which is designed to transfer heat from a cooling circuit (20) through which coolant flows to a fluid circuit (3) through which fluid flows, wherein the heat exchanger (24) has a fluid channel (25) through which the fluid flows, or the fluid channel (25) is connected to the heat exchanger (24), wherein the fluid channel (25) has a flow inlet (26) and a downstream flow outlet (27) and determines the fluid circuit (3) section by section, wherein the leakage sensor (1) is arranged along the fluid channel (25) and / or directly at the flow outlet (27) of the fluid channel (25).

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