USE FOR DETECTING REFRIGERANT LEAKS IN A REFRIGERATION CIRCUIT ARRANGED IN A CLOSED ENCLOSURE

Description

[0001] The invention relates to the use for detecting refrigerant leaks in a refrigeration circuit.

[0002] Modern heating systems are often equipped with heat pumps that extract heat from the environment to heat buildings and / or water. This requires a refrigeration circuit in which a refrigerant circulates. This refrigerant is usually gaseous at ambient temperature and pressure and therefore escapes as a gas if there is a leak in the refrigeration circuit. Common refrigerants, e.g. the so-called R290, for which the present invention is particularly suitable, should not enter buildings in an uncontrolled manner for various reasons. Some refrigerants are also flammable, so that uncontrolled distribution must be avoided for this reason alone. If a refrigeration circuit cannot be located outside of buildings, it is therefore located inside a sealed housing, which is located, for example, in a basement or an adjoining room of a building.This means that escaping refrigerant can initially only escape into the interior, from where it can be discharged from the building into the atmosphere. Since the discharge of refrigerant into the environment is often desired, or discharge into the atmosphere is sometimes difficult, it is also known to install a connecting chamber in the connection between the interior and the environment. This chamber is filled with an adsorbent that binds escaping refrigerant. Depending on the dimensions of such an adsorbent filling, this can be sufficient to bind the entire refrigerant content of a refrigeration circuit, preventing it from escaping into the atmosphere or into a building.

[0003] As prior art, DE 10 2011 116 863 A1 describes a method for securing a device for a thermodynamic cycle, which is operated with a process fluid that contains or consists of at least one environmentally hazardous, toxic, and / or flammable substance. In the event of a leak in the device for a thermodynamic cycle, an adsorbent is brought into contact with the process fluid, in particular ammonia, propane, or propene, and the substance is selectively bound by the adsorbent. The adsorbent is regenerated after use. Activated carbon is proposed as an adsorbent, among others; the adsorbent can be in the form of a bed, a molded body, a paint, a spray film, or a coating.The support structure of the molded body can consist of a microstructure, a lamellar structure, a tube bundle, a pipe register, or sheet metal and must be mechanically stable and significantly increase the surface area. Circulation of the potentially contaminated air is usually continuous, but can also be initiated by a sensor that activates the ventilation when a threshold is reached or when an emergency is detected. Adsorption can be carried out inside or outside an enclosed space.

[0004] DE 195 25 064 C1 describes a refrigeration machine with a gas-tight housing that accommodates all of the machine's refrigerant-carrying components. A chamber is provided that connects the interior of the gas-tight housing to an outlet, and the chamber is filled with a refrigerant-sorbent. The amount of sorbent is dimensioned such that any escaping refrigerant can be absorbed and kept away from the environment. The chamber filled with the sorbent is open to the environment. For refrigerants that are heavier than air, the chamber is open at the bottom; for refrigerants that are lighter, it is open at the top, so that a conveying fan is not required. The sorbent is introduced into the housing and completely encloses the refrigeration machine or the refrigerant-carrying devices.On its way out, baffles are provided to prevent short-circuit flows and force escaping gas through the sorbent. A double-walled design, in which the sorbent is enclosed in the double jacket, is also possible. A refrigerant measuring device can be provided at the outlet of the chamber filled with the sorbent to the environment.

[0005] Measuring devices for refrigerants are also known. Load measuring points and measurement methods for load measurement are described, for example, in US 2002 / 0021117 A1. This utilizes the ohmic resistances in the activated carbon bed, which change during loading and produce a signal.

[0006] EP 3 693 078 A1 and DE 10 2019 118984 A1 also describe loading measurements within activated carbon beds or their measurements at the outlet or inlet. In all these cases, however, the aim is to determine the extent to which the bed has already been loaded and whether further loading is possible or whether an adsorbent replacement is necessary. Since these described devices are used for quantitative separation, they are correspondingly slow and can hardly be used as measuring instruments themselves.

[0007] On the other hand, it is not enough to simply prevent uncontrolled refrigerant leaks for the operation of a heat pump. It is also important to detect leaks of any size as early as possible in order to initiate countermeasures (warning, maintenance, shutdown, fault reporting). Various types of refrigerant detectors are known for this purpose; these can be installed inside the housing, particularly electrochemical sensors. However, such sensors suffer from various disadvantages, including being expensive, prone to failure (e.g., due to possible contamination, e.g., by siloxanes, or cross-sensitivities, e.g., to water vapor), having a limited service life, and / or requiring intensive maintenance.

[0008] The object of the present invention is to at least partially solve the problems described with reference to the prior art. In particular, one object is to provide a method for detecting and / or quantitatively determining the presence of a refrigerant leak in a refrigeration circuit, wherein the method is simple and suitable for everyday operation of a refrigeration circuit and requires little maintenance, ideally for its entire service life.

[0009] This object is achieved by the use according to the independent claim. Advantageous embodiments and further developments of the invention are specified in the dependent claims. The description, particularly in conjunction with the drawings, illustrates the invention and provides further exemplary embodiments.

[0010] The use contributes to the detection of a leak in a refrigeration circuit filled with a refrigerant, which is arranged in the interior of a sealed housing and is connected to the outside environment only via a connecting chamber provided with an adsorbent filling for the refrigerant. Refrigerant escaping from the refrigeration circuit into the interior is adsorbed in the adsorbent filling, generating heat, and the temperature is measured at at least one point in the adsorbent filling. If an absolute temperature threshold and / or a threshold for the temperature rise per unit time is exceeded, a leak is then concluded.

[0011] When a substance is adsorbed onto a suitable adsorbent material, adsorption enthalpy is released, which heats the adsorbent material together with the adsorbed substance. For a refrigerant such as R290 and, for example, activated carbon as an adsorbent, this is an amount of energy per adsorbed mass unit that is easily measured as a temperature increase. By measuring the temperature in the innermost area of ​​the adsorbent filling, where escaping refrigerant is first adsorbed, even small leaks can be detected simply by a temperature increase. If a measurement and / or recorded or stored measured values ​​of the temperature measurement(s) indicate that a predefined absolute threshold value is exceeded and / or that a predefined threshold value for a temperature increase per unit time is exceeded, this can be (automatically) interpreted as an indication of a leak, whereby countermeasures (e.g.warning message, maintenance, shutdown, fault message) can be initiated.

[0012] The adsorbent filling in the connecting chamber preferably has at least one inner sub-region and one outer sub-region, with the temperature being measured in each of these sub-regions. More than two sub-regions can be provided. The sub-regions do not need to be structurally separated from one another, e.g., by a collar, a grid, or the like. The sub-regions can comprise different volumes of the adsorbent filling, although it is preferable to define them with approximately the same volume fraction depending on the number. The "inner" or first sub-region is usually closest to the interior, while the "outer" sub-region (or further sub-regions) are located further away from the interior or are spaced apart from sub-regions located further inside. If more than two sub-regions are provided, temperature measurements do not need to be provided or performed in all sub-regions.It is possible to take a (direct) temperature measurement at one point in each sub-area.

[0013] At the beginning of a leak, refrigerant enters the inner compartment, causing a temperature increase there, while no refrigerant can yet be detected in the outer compartment. Over time, and / or in the case of very large leaks, a temperature increase also occurs in the outer compartment, while in the inner compartment, the temperature drops again as it becomes more saturated with adsorbed refrigerant. Dividing the compartment into more compartments can increase measurement accuracy. In any case, this method not only detects the presence of a leak, but also determines the magnitude of a leak more accurately than with a single temperature measurement.Since the temperature in the connection chamber can vary depending on the season and ambient or operating conditions, it is advisable to determine a reference temperature that is not affected by a leak and to determine only the difference between the temperatures measured in the adsorbent filling and this reference temperature for further analysis. The reference temperature can be measured in the interior or in the environment.

[0014] In particular, the value (or height) of the measured temperature and / or the speed of a temperature increase in the sub-areas or in each sub-area are used to determine the size and / or the duration of the leak.

[0015] The currently measured temperature values ​​and / or the rate of temperature change can be compared with previous and / or stored values ​​from the same and / or another sub-area. From this, key values ​​and / or correlations can be determined (automatically) that characterize the area of ​​spread of the leak, the amount of refrigerant involved, and / or the temporal behavior of the leak. This information can be used to initiate further actions, such as targeted notifications for maintenance, shutdown, or malfunctions.

[0016] The object is also achieved by using the device for detecting a refrigerant leak in a refrigeration circuit which is arranged in an interior space of a sealed housing which is connected to an external environment only via a connecting chamber provided with an adsorbent filling for the refrigerant, wherein at least one temperature sensor is arranged in the adsorbent filling in the connecting chamber and is connected to an evaluation unit via a measuring line.

[0017] Temperature sensors are robust and low-maintenance, and have a very long service life, just like a typical adsorbent. The temperature sensor is in direct contact with the adsorbent in the connecting chamber. The temperature sensor itself and / or the (electronic or electrical) measuring line can, for example, be routed out of the connecting chamber at the side. The evaluation unit can include a computer and a (data) storage device.

[0018] The connecting chamber preferably has at least one inner sub-region and one outer sub-region, with a temperature sensor arranged in each of the sub-regions. If more than two sub-regions are provided, at least one temperature sensor can be provided in each sub-region; however, it is also possible for at least one sub-region to be designed without a temperature sensor.

[0019] In the event of a leak, escaping refrigerant first reaches the inner sub-area and only later - when the absorption capacity of the adsorbent filling in this area is reached - the (further) outer sub-area, so that additional information about the magnitude of the leak and / or the amount of refrigerant that has already leaked can be obtained by temperature sensors in both sub-areas (or even further sub-areas).

[0020] In a special embodiment, a temperature sensor is arranged in the interior as a reference sensor, which is also connected to the evaluation unit (via an electronic or electrical measuring line). This reference sensor provides a temperature that is unaffected by leakage and essentially corresponds to the temperature in the connection chamber, so that only the difference between the temperatures measured in the connection chamber and the reference temperature needs to be considered when interpreting the data.

[0021] The evaluation unit can be configured to trigger a warning and / or protective measures (automatically) when an absolute temperature threshold and / or a threshold for the temperature rise per unit of time (or the respective difference from a reference temperature) is exceeded. This can include a display notification, a message to a remote maintenance center, or even a shutdown of the refrigeration circuit.

[0022] A schematic embodiment of the invention, to which it is not limited, and its functionality will now be explained in more detail with reference to the drawing. It shows: Fig. 1: a refrigeration circuit in a sealed housing with associated sensors for leaks.

[0023] Fig. 1shows a schematic of a refrigeration circuit 1, filled with refrigerant 2, which is arranged in an interior space 4 of a housing 3. The refrigeration circuit 1 typically contains components not explained in detail here, such as a compressor, an expansion element, an evaporator and a condenser, which in turn may also have supply lines that are sealed through the housing. For internal leaks to such supply lines, there are other measuring systems that are not the subject of discussion here. The following only concerns leaks of refrigerant 2 that lead to the escape of refrigerant 2 into the interior space 4, where the refrigerant is quickly distributed by diffusion and, due to the resulting overpressure in the interior, tries to escape through a connecting chamber 6 into an environment 5 (open environment or building). This is prevented by an adsorbent, e.g. activated carbon, which adsorbs the refrigerant 2.Suitable adsorbent fillings 7 are available for R290 and other natural refrigerants, some of which can also be flammable. These are porous and have a large surface area, allowing effective adsorption to take place, releasing heat. In the event of a leak, refrigerant 2 initially enters an inner section 8 of the adsorbent filling 7, where the temperature initially increases in an adsorption zone 10, which can be measured by a first temperature sensor 11 and passed on to an evaluation unit 14 via a measuring line 15. In the simplest case, this already makes it possible to monitor for leaks. Over time (when the adsorbent in the first section becomes increasingly saturated), the adsorption zone 10, in which mainly heat is released, migrates further outwards and then also enters an outer section 9, in which the temperature can also be measured by a second temperature sensor 12.By evaluating the temperature measurements from the first 11 and second 12 temperature sensors, not only can a leak be detected, but its size and duration can also be estimated. Using a third temperature sensor 13 as a reference, temperature fluctuations not attributable to a leak can be compensated for, which also works with only one temperature sensor 11 in the adsorbent filling. Only the difference between the reference temperature at the third temperature sensor 13 and the temperature in the adsorbent filling is ever considered. The evaluation unit 14 detects whether a predeterminable absolute threshold has been exceeded and / or whether a predeterminable threshold has been exceeded for the temperature increase per unit of time and interprets this as an indication of a leak.In general, the evaluation unit is part of a control and regulation unit of an entire heating system and can trigger warning signals, warning displays, messages to a remote maintenance center and / or direct measures up to and including a shutdown of the refrigeration circuit 1.

[0024] The present invention allows for the reliable detection of refrigerant leaks and the initiation of appropriate measures using a simple, robust and largely maintenance-free instrumentation consisting of one or more temperature sensors in an adsorbent filling. List of reference symbols

[0025] 1Refrigeration circuit 2Refrigerant 3Housing 4Interior 5External environment 6Connection chamber 7Adsorbent filling 8Inner section 9Outer section 10Adsorption zone 11First temperature sensor 12Second temperature sensor 13Third temperature sensor (reference sensor) 14Evaluation unit 15Measuring line

Claims

1. Use of at least one temperature sensor for detecting a leak in a refrigeration circuit (1) filled with a refrigerant (2), which refrigeration circuit is arranged in an interior space (4) of a sealed housing (3), which is connected to an external environment (5) only via a connecting chamber (6) provided with an adsorbent filling (7) for the refrigerant (2), wherein refrigerant (2) leaking from the refrigeration circuit (1) into the interior space (4) is adsorbed in the adsorbent filling (7) with heat being generated, wherein the temperature is measured at at least one point in the adsorbent filling (7) and it is inferred that there is a leak if an absolute threshold value and / or a threshold value for the increase in temperature per unit of time is exceeded, wherein the at least one temperature sensor (11) is arranged in an inner subregion (8) of the connecting chamber (6), which is in direct contact with the adsorbent (10) of the connecting chamber and is connected via a measuring line (15) to an evaluation unit (14), and wherein the value of the measured temperature and / or the rate of temperature increase in the inner subregion (8) is used to infer at least the magnitude or the previous duration of the leak.

2. Use according to claim 1, characterized in that at least at one further point in the connecting chamber (6) a further temperature sensor (12) is arranged in an outer subregion (9) of the connecting chamber (6), which is in direct contact with the adsorbent (10) of the connecting chamber and is connected to an evaluation unit (14) via a measuring line (15), and wherein, at least the magnitude or the previous duration of the leak is inferred from the value of the measured temperature and / or the rate of an increase in temperature in the subregions (8, 9).

3. Use according to any one of claims 1 or 2, wherein a temperature sensor is arranged in the interior space (4) as a reference sensor (13) which is also connected to the evaluation unit (14).

4. Use according to any one of claims 1 to 3, wherein the evaluation unit (14) is configured to trigger at least a warning message or protective measures when an absolute threshold value of the temperature and / or a threshold value for the temperature increase per unit of time is exceeded.