DE102021102722A1 - Method and arrangement for detecting refrigerant leaks in a refrigeration circuit which is arranged in a closed housing - Google Patents

Abstract

The invention relates to a method and an arrangement for detecting a leak in a refrigeration circuit (1) filled with a refrigerant (2), which is arranged in an interior (4) of a tight housing (3) which is connected to an external environment (5). is only connected via a connecting chamber (6) provided with an adsorbent filling (7) for the refrigerant (2), with refrigerant (2) escaping from the refrigeration circuit (1) being adsorbed into the interior (4) in the adsorbent filling (7) with the development of heat The temperature is measured at at least one point in the adsorbent filling (7) and a leak is concluded when an absolute threshold value is exceeded and/or a threshold value for the temperature rise per unit time is exceeded. The connecting chamber (6) preferably has at least one inner section (8) and one outer section (9), with a temperature sensor (11, 12) being arranged in each section (8, 9). In addition, a temperature sensor can be arranged in the interior (4) as a reference sensor (13), which is also connected to the evaluation unit (14). The present invention allows leaks in refrigerant (2) to be reliably detected and appropriate measures to be taken using simple, robust and largely maintenance-free instrumentation consisting of one or more temperature sensors (11, 12) in an adsorbent filling (7).

Description

The invention relates to a method and an arrangement for detecting refrigerant leaks in a refrigeration cycle.

Modern heating systems are often equipped with heat pumps that extract heat from the environment in order to heat buildings and/or water. This requires a refrigeration circuit in which a refrigerant circulates, which is mostly gaseous at ambient temperature and pressure and therefore escapes as a gas if there is a leak in the refrigeration circuit. Usual refrigerants, e.g. B. the so-called R290, for which the present invention is particularly suitable, should not get into buildings uncontrolled for various reasons. Some refrigerants are also flammable, so uncontrolled distribution must be avoided for this reason alone. Therefore, if a refrigeration circuit cannot be placed outside buildings, it is placed in an interior space of a sealed housing, which e.g. B. is placed in a basement or an adjoining room of a building. Escaping refrigerant can initially only escape into the interior, from where it can be routed out of the building into the open air. Since one often wants to avoid a discharge of refrigerant into the environment or a discharge into the free environment is sometimes difficult, it is also known to install a connection chamber in a connection between the interior and the environment, which is filled with an adsorbent, which exiting refrigerant binds. Depending on the dimensioning of such an adsorbent filling, it can be sufficient to bind the entire refrigerant content of a refrigeration circuit, so that it cannot get into the open air or into a building.

On the other hand, for the operation of a heat pump it is not enough to just prevent an uncontrolled escape of refrigerant, but it is also important to detect leaks of any size as early as possible in order to be able to initiate countermeasures (warning, maintenance, shutdown, fault reporting). Various types of detectors for refrigerants are known for this purpose, which can be arranged in the interior of the housing, in particular electrochemical sensors. However, such sensors have various disadvantages, in particular they are expensive, prone to failure (e.g. due to possible contamination, e.g. by siloxanes or cross-sensitivities, e.g. to water vapor), have a limited service life and/or are maintenance-intensive.

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 create a method and an arrangement for determining and/or quantitatively determining the presence of a refrigerant leak in a refrigeration circuit, the arrangement being simple and suitable for everyday operation of a refrigeration circuit and requiring little maintenance, if possible for its entire service life.

A method and an arrangement as well as a computer program product according to the independent claims serve to solve this task. Advantageous refinements and developments of the invention are specified in the respective dependent claims. The description, in particular in connection with the drawing, illustrates the invention and specifies further exemplary embodiments.

Contributing to this is a method for detecting a leak in a refrigeration circuit filled with a refrigerant, which is arranged in an interior space of a tight housing which is connected to an external 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, with the development of heat, the temperature being measured at at least one point in the adsorbent filling. If an absolute threshold value of the temperature is exceeded and/or if a threshold value for the temperature rise per unit of time is exceeded, a leak is then concluded.

When a substance is adsorbed on a suitable adsorber material, adsorption enthalpy is released, which heats the adsorber material with the adsorbed substance. With a refrigerant such as R290 and, for example, activated carbon as an adsorbent, this is an amount of energy per adsorbed mass unit that can easily be measured as a temperature increase. With a temperature measurement in the innermost area of the adsorbent filling, where escaping refrigerant is first adsorbed, even small leaks can be detected by an increase in temperature. If it is determined directly from a measurement and/or recorded or stored measured values of the temperature measurement(s) that a specifiable absolute threshold value has been exceeded and/or that a specifiable threshold value for a temperature rise per unit of time has been exceeded, this can (automatically) be interpreted as an indication of a leak where necessary countermeasures (e.g. warning message, maintenance, shutdown, error message) can be initiated automatically.

The adsorbent filling in the connecting chamber preferably has at least one inner section and one outer section, with the temperature being measured in each of these sections. More than two partial areas can be provided. The partial areas do not have to be structurally delimited from one another, for example by a collar, a lattice or the like. The sub-areas can include different volumes of the adsorbent filling, it being preferable for them to be defined with approximately the same volume fraction, depending on the number. The “inner” or first sub-area is usually closest to the interior space, while the “outer” sub-area (or further sub-areas) is further away from the interior space or consists of more interior sub-areas from the interior space. If more than two sub-areas are provided, temperature measurements do not have to be provided or carried out in all sub-areas. It is possible that a (direct) temperature measurement is taken at one point in each sub-area.

At the beginning of a leak, refrigerant gets into the inner part and triggers a temperature increase there, while no refrigerant can be detected in the outer part. Over time and/or in the case of very large leaks, the temperature also increases in the outer partial area, while the temperature in the inner partial area drops again the more it is saturated with adsorbed refrigerant. A subdivision into more partial areas can increase the measurement accuracy. In any case, not only can the presence of a leak be determined in this way, but the magnitude of a leak can also be determined more precisely than with just one temperature measurement. Since the temperature in the connecting chamber can vary depending on the time of year and environmental or operating conditions, it makes sense to establish a reference temperature that will not be affected by a leak and only determine the difference in temperatures measured in the adsorbent filling from this reference temperature and to be used for further evaluation. The reference temperature can be measured in the interior or in the environment.

In particular, the size and/or the previous duration of the leak is inferred from the value (or the level) of the measured temperature and/or the speed of a temperature rise in the partial areas or in each partial area.

The currently determined temperature values and/or the rate of change of the temperature can be related to previous and/or stored values from the same and/or another sub-area. From this, characteristic values and/or correlations can be determined (automatically) which characterize the propagation area of the leak, the amount of refrigerant that has occurred and/or the behavior of the leak over time. This information can be used to initiate further actions, such as targeted notifications for maintenance, shutdown or malfunction.

The task is also solved by an arrangement for detecting a refrigerant leak in a refrigeration circuit, which is arranged in an interior of a tight housing, which is connected to an external environment only via a connecting chamber provided with an adsorbent filling for the refrigerant, wherein in the adsorbent filling in at least one temperature sensor is arranged in the connecting chamber, which is connected to an evaluation unit via a measuring line.

Temperature sensors are robust and require little maintenance and have a very long service life as does a typical adsorbent, so the arrangement can have a service life similar to that of a refrigeration cycle. In particular, 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 connection chamber at the side. The evaluation unit can include a computer and a (data) memory.

The connecting chamber preferably has at least one inner partial area and one outer partial area, with a temperature sensor being arranged in each of the partial areas. If more than two subareas are provided, at least one temperature sensor can be provided in each subarea, but it is also possible for at least one subarea to be designed without a temperature sensor.

Refrigerant escaping in the event of a leak first reaches the inner section and only later - when the absorption capacity of the adsorbent filling in this area has been reached - the (further) outer section, so that temperature sensors in both sections (or even other sections) provide additional information about the Magnitude of the leak and / or the amount of refrigerant that has already leaked can be obtained.

In a special embodiment, a temperature sensor is arranged as a reference sensor in the interior, which is also (via an electronic or electrical measuring line) with the evaluation tea unit is connected. This reference sensor provides a temperature unaffected by a leak, which essentially corresponds to the temperature in the connection chamber, so that only the difference of temperatures measured in the connection chamber from the reference temperature has to be considered when interpreting the data.

Preferably, in particular for the refrigerant R290, the adsorbent filling comprises or contains activated carbon and/or another adsorbent which heats up when the refrigerant is adsorbed.

The evaluation unit can be set up in such a way that if an absolute threshold value for the temperature and/or a threshold value for the temperature rise per unit of time (or the respective difference to a reference temperature) is exceeded, a warning message and/or protective measures are (automatically) triggered. This can be an indication on a display, a message to a remote maintenance center or a shutdown of the refrigeration cycle.

The size (e.g. the volume or the dimensions) of the connecting chamber and the amount of adsorbent in it is particularly preferably designed such that, in the event of leaks below a tolerance value, no refrigerant escapes into the external environment within a specifiable time interval. This can even go so far that everything can be adsorbed even if all the refrigerant escapes. This means additional security for a building or the environment. Nevertheless, a leak is quickly detected and reported.

A further aspect also relates to a computer program product comprising instructions which cause the arrangement described to carry out the method described. The evaluation of the data measured by the sensors and their further use require a program and data, both of which must be updated from time to time.

The explanations for the method can be used for a more detailed characterization of the arrangement, and vice versa. The arrangement can also be set up in such a way that the method is carried out with it.

• 1: einen Kältekreislauf in einem dichten Gehäuse mit zugehöriger Sensorik für Leckagen.

A schematic embodiment of the invention, to which it is not limited, and the way the method works will now be explained in more detail with reference to the drawing. It shows:

• 1 : a refrigeration circuit in a sealed housing with associated sensors for leaks.

1 shows schematically a refrigeration circuit 1, filled with refrigerant 2, which is arranged in an interior 4 of a housing 3. The refrigeration circuit 1 typically contains components that are not explained in more detail here, such as a compressor, an expansion element, an evaporator and a condenser, which in turn can also have supply lines that are guided through the housing in a sealed manner. There are other measuring systems for internal leaks in such supply lines, which are not the subject of the considerations here. The following only deals with leaks of refrigerant 2, which lead to refrigerant 2 escaping into the interior 4, where the refrigerant spreads quickly through diffusion and, because of the resulting overpressure in the interior, through a connecting chamber 6 into an environment 5 (free environment or building) wants to escape. This is achieved by an adsorbent, e.g. B. activated carbon prevented, which the refrigerant 2 adsorbed. There are suitable adsorbent fillings 7 for R290 and other natural refrigerants, some of which can also be flammable. These are porous and have a large surface area, so that effective adsorption can take place, with heat being released. In the event of a leak, refrigerant 2 first reaches an inner partial area 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, it is already possible to monitor for leaks. Over time (when the adsorbent in the first section is increasingly saturated), the adsorption zone 10, in which mainly the heat is released, moves further outwards and then also reaches an outer section 9, in which the temperature is also measured by a second temperature sensor 12 can be measured. By evaluating the temperature measurements from the first 11 and second 12 temperature sensor, not only can a leak be detected, but its size and duration can also be estimated. With a third temperature sensor 13 as a reference, temperature fluctuations that are not due 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 considered. The evaluation unit 14 determines that a definable absolute threshold value has been exceeded and/or that a definable threshold value 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 be used in the latter to send warning signals, warning displays, messages to a remote maintenance center and/or to take direct action men to trigger a shutdown of the refrigeration circuit 1. By using adsorbents in a suitable amount, the arrangement can also be designed to be inherently safe against the escape of refrigerant 2 into the environment 5 at the same time.

The present invention makes it possible to reliably detect refrigerant leaks and to initiate appropriate measures with a simple, robust and largely maintenance-free instrumentation consisting of one or more temperature sensors in an adsorbent filling.

Reference List

1

refrigeration cycle

2

refrigerant

3

Housing

4

inner space

5

external environment

6

compound chamber

7

adsorbent filling

8th

inner section

9

Outer Section

10

adsorption zone

11

First temperature sensor

12

Second temperature sensor

13

Third temperature sensor (reference sensor)

14

evaluation unit

15

Measurement line

Claims (10)

Method for detecting a leak in a refrigeration circuit (1) filled with a refrigerant (2), which is arranged in an interior (4) of a tight housing (3) which is connected to an external environment (5) only via an adsorbent filling ( 7) is connected to the connecting chamber (6) provided for the refrigerant (2), with refrigerant (2) escaping from the refrigeration circuit (1) into the interior (4) being adsorbed in the adsorbent filling (7) with the development of heat, the temperature being at least measured at a point in the adsorbent filling (7) and a leak is concluded when an absolute threshold value is exceeded and/or a threshold value for the temperature rise per unit of time is exceeded. procedure after claim 1 , wherein the adsorbent filling (7) in the connecting chamber (6) has at least one inner section (8) and one outer section (9) and the temperature is measured in each of these sections (8, 9). procedure after claim 2 , wherein at least the size or the previous duration of the leak is inferred from the value of the measured temperature and/or the speed of a temperature rise in the partial areas (8, 9). Arrangement for detecting a refrigerant leak in a refrigeration circuit (1), which is arranged in an interior (4) of a tight housing (3), which is connected to an external environment (5) only via an adsorbent filling (7) for the refrigerant (2 ) provided connecting chamber (6), wherein in the adsorbent filling (7) in the connecting chamber (6) at least one temperature sensor (11) is arranged, which is connected via a measuring line (15) to an evaluation unit (14). arrangement according to claim 4 , wherein the connecting chamber (6) has at least one inner partial area (8) and one outer partial area (9), wherein a temperature sensor (11, 12) is arranged in each partial area (8, 9). Arrangement according to one of Claims 4 or 5 , wherein in the interior (4) a temperature sensor is arranged as a reference sensor (13), which is also connected to the evaluation unit (14). Arrangement according to one of Claims 4 until 6 , wherein the adsorbent filling (7) comprises activated carbon and/or another adsorbent which heats up during the adsorption of refrigerant (2). Arrangement according to one of Claims 4 until 7 , wherein the evaluation unit (14) is set up to initiate at least one warning message or protective measures when an absolute threshold value of the temperature and/or a threshold value for the temperature rise per unit of time is exceeded. Arrangement according to one of the claims, wherein the size of the connecting chamber (6) and the amount of adsorbent filling (7) in it are designed such that, in the event of leaks below a tolerance value, no refrigerant (2) escapes into the external environment (5) within a specifiable time interval . Computer program product comprising instructions that cause the arrangement according to one of the Claims 4 until 9 the procedure according to one of the Claims 1 until 3 executes

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