Testing room and control method

Abstract

To provide a testing room for housing a test material, especially a testing room for air conditioning of a test space in an artificial weather room, and to provide a method.SOLUTION: A test space is sealed from a surrounding environment and thermally insulated. A cooling device 10 of a temperature control device in a testing room includes a cooling circuit 11 using carbon dioxide as a coolant, a heat exchanger 12 in the test space, a low pressure compressor 13, a high pressure compressor 14, a gas cooler 15, and an expansion valve 16 on the downstream of the low pressure compressor in a coolant flow direction, and is used for achieving the temperature in a temperature range of -20°C to +180°C in the testing room. The control device in the testing room is used for controlling the temperature and / or relative humidity in the test space. A dehumidifying bypass 20 in the cooling circuit is equipped with a second expansion valve 21 and a second heat exchanger 22, and is used for dehumidifying the air in the test space.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a test chamber, in particular a climatic chamber, for conditioning air and to a method for conditioning air in a test space of a test chamber, in particular a climatic chamber, for containing test materials, the test space being configured to be sealed and insulated from the surrounding environment, a cooling device of a temperature control device of the test chamber comprising a cooling circuit using carbon dioxide as a refrigerant, a heat exchanger in the test space, a low-pressure compressor, a high-pressure compressor, a gas cooler and an expansion valve downstream of the low-pressure compressor in the flow direction of the refrigerant, which is used to achieve a temperature in the test chamber within a temperature range of -20°C to +180°C, and a control device of the test chamber is used to control the temperature and / or relative humidity of the test space. [Background technology]

[0002] This kind of test chamber is usually used to test the physical and / or chemical properties of objects, in particular devices. For example, temperature test cabinets or climatic test cabinets are known in which temperatures can be set within the range of -70°C to +180°C. In the case of climatic test cabinets, the desired climatic conditions can additionally be set, to which the device or test material is then exposed for a defined period of time. The temperature of the test space containing the test material is usually controlled by means of an air circulation duct in the test space. The air circulation duct forms an air treatment space in the test space, in which a heat exchanger is arranged for heating or cooling the air flowing through the air circulation duct or the test space. A fan or a ventilation device draws air from within the test space and directs it through the air circulation duct to the respective heat exchanger. The test material can thus be temperature controlled or exposed to defined temperature changes. During the test period, the temperature can vary, for example, between the maximum and minimum temperatures of the test chamber. A test chamber of this kind is known, for example, from EP 0 344 397 A2.

[0003] The refrigerants used in the cooling circuits should have a relatively low carbon dioxide equivalent, i.e. the relative Global Warming Potential (GWP) should be as small as possible, to avoid indirect damage to the environment from the refrigerant upon release. It is therefore also known to use carbon dioxide (CO2) as a pure refrigerant. Carbon dioxide is available at low cost, is non-flammable and has a GWP of 1, making it practically environmentally neutral. Carbon dioxide has a freezing point temperature, or triple point, of -56.6°C, which makes it impossible to achieve lower temperatures with carbon dioxide alone.

[0004] Furthermore, cooling devices are known that are configured as what is called a booster system. In the cooling circuit of this cooling device, the high-pressure compressor is always connected in series downstream of the low-pressure compressor, so that the refrigerant is compressed in stages in the low-pressure compressor and then in the high-pressure compressor. Due to the high demands on temperature control within the temperature range of the test space, the load requirements fluctuate frequently during the operation of the test chamber. The cooling capacity realized by the compressor and the expansion valve must therefore vary infinitely. Nevertheless, in order to extend the compressor's service life, it is desirable that the compressor cannot be switched on and off frequently.

[0005] Carbon dioxide as a refrigerant has a very high volumetric cooling capacity, so that even when using compressors with a very small stroke volume flow rate, very high cooling capacity is provided by the cooling circuit. In addition, the pressure range of a cooling circuit with carbon dioxide as a refrigerant is very high (up to 120 bar) in supercritical operation, so that the components required to form the cooling circuit are relatively expensive. Furthermore, this type of cooling circuit has a complex configuration and requires a large installation space. Up to now, the use of this type of cooling circuit with carbon dioxide as a refrigerant was only suitable for systems or test chambers with a correspondingly high cooling capacity and, as a result, a relatively large test space or large equipment dimensions. Economical use in relatively small systems or test chambers with a small test space volume, for example only 25 liters, is still not possible.

[0006] There is also the problem that due to the very high cooling capacity, climatic tests can only be carried out to a limited extent. Defined relative humidity and temperature must be realized in the test space. In particular, if, for example, the air in the test space is cooled during the test cycle, this also requires dehumidification of the air in the test space. When the air is cooled, especially due to the high cooling capacity, condensation in the heat exchanger is difficult to control, which can lead to unnecessary dehumidification of the air in the test space. Furthermore, if, for example, only very slow, defined temperature changes are intended as part of the test cycle, the dehumidification power may also be too low. Thus, climatic test cycles cannot always be carried out with sufficient accuracy using this type of cooling device. Systems that require features for conditioning the air separated from the test space, for example air exchange within the test space, are costly, energy intensive and make the test room very large. Summary of the Invention

[0007] The object of the invention is therefore to propose a method for conditioning the air in the test space of a test chamber and a test chamber which allows climatic tests to be carried out in a relatively compact and technically simple test chamber configuration.

[0008] This object is achieved by a method having the features of claim 1 and by a test chamber having the features of claim 17.

[0009] In a method according to the invention for conditioning the air in a test chamber, in particular a test space of a climatic chamber, for containing test materials, the test space is configured to be sealed and insulated from the surrounding environment, a cooling circuit of the temperature control device of the test chamber comprises a cooling circuit using carbon dioxide as a refrigerant, a heat exchanger in the test space, a low-pressure compressor, a high-pressure compressor, a gas cooler and an expansion valve downstream of the low-pressure compressor in the flow direction of the refrigerant and is used to achieve a temperature in the test space within a temperature range from -20°C to +180°C, a control device of the test chamber is used to control the temperature and / or relative humidity of the test space, and a dehumidification bypass of the cooling circuit comprises a second expansion valve and a second heat exchanger in the test space and is used to dehumidify the air in the test space.

[0010] In the method according to the invention, heat exchange with the surrounding environment of the test space is largely avoided by insulating the side, floor and ceiling walls. The heat exchanger is connected to or integrated into the cooling circuit so that the refrigerant circulating in the cooling circuit flows through the heat exchanger. The heat exchanger of the cooling circuit is arranged in the test space or in the air handling space of the test space, so that the air in the test space is conditioned or temperature controlled by the heat exchanger. A gas cooler is also integrated into the cooling circuit and is formed by the heat exchanger. The gas cooler is arranged downstream of the high-pressure compressor in the cooling circuit, and the compressed refrigerant is under high pressure after compression and is substantially in gas or vapor state, i.e. wet vapor, and can condense in the gas cooler or condenser and then substantially in liquid state, namely condensation. It is also possible that the gas refrigerant does not condense in the gas cooler and leaves the gas cooler in a substantially gaseous state. The gas cooler or heat exchanger in question can comprise means for cooling the refrigerant, for example with air or water. In particular, the gas cooler can be a water- or air-cooled finned tube heat exchanger. In this case, the gas cooler can be particularly compact. The refrigerant flows from the gas cooler via an expansion valve, through which it expands again into a gaseous or vaporous state due to the pressure drop. In the process, the refrigerant flows through a heat exchanger, which consequently cools it. The gaseous refrigerant is then sucked back in and compressed by the low-pressure and high-pressure compressors.

[0011] According to the invention, the dehumidifying bypass of the cooling circuit is configured to dehumidify the air of the test space. This dehumidification can take place at any time during the test cycle, in particular whenever the temperature of the test space is within the temperature range from 0 to 100° C. If the temperature in the test space is lower or higher than this range, water will not condense in liquid phase on the second heat exchanger and the dehumidifying bypass will not function within this range. The cooling circuit of the cooling device is therefore designed in such a way that temperatures of -20° C. to +180° C. can be achieved in the test space during the test cycle, and the dehumidification of the air by the dehumidifying bypass takes place only within a partial range of this temperature range. The dehumidification is carried out by metering the refrigerant from the high-pressure side of the cooling circuit to the low-pressure side of the cooling circuit via the second expansion valve. This results in cooling of the second heat exchanger, which is arranged downstream of the second expansion valve of the dehumidifying bypass in the flow direction of the refrigerant. The control device can then meter the refrigerant via the second expansion valve such that a desired temperature difference between the temperature of the air of the test space and the temperature of the second heat exchanger is achieved. This temperature difference can be selected such that water from the air of the test space condenses in the second heat exchanger. This allows a targeted dehumidification of the air of the test space, substantially independent of the temperature realized in the test space. The expansion valve and the second expansion valve can thus be controlled independently of each other by means of the control device. The reduction in the temperature of the test space can furthermore be accompanied by, for example, more or less dehumidification, whereby the relative humidity can be set or controlled more precisely. Overall, the climatic test cycle can be performed more precisely with few components in a compact test chamber.

[0012] The dehumidifying bypass may be connected to the high-pressure side of the cooling circuit downstream of the gas cooler and upstream of the expansion valve, and to the low-pressure side of the cooling circuit downstream of the heat exchanger and upstream of the low-pressure compressor, so that refrigerant may be metered from the high-pressure side to the low-pressure side via the second expansion valve, so that the second heat exchanger is cooled. The second expansion valve may be an electronic expansion valve, for example a solenoid valve with a downstream restriction by a capillary tube, a nozzle or the like, or a thermostatic expansion valve. Optionally, the dehumidifying bypass may be connected downstream of any internal heat exchanger downstream of the gas cooler. The dehumidifying bypass is thus connected to the cooling circuit in parallel with the expansion valve and the heat exchanger. In this way, the dehumidifying bypass may be of a particularly simple design.

[0013] The cooling circuit may be provided with a second bypass having at least a third expansion valve, the second bypass being connected to the high pressure side of the cooling circuit downstream of the gas cooler and upstream of the expansion valve, and the low pressure side of the cooling circuit downstream of the heat exchanger and upstream of the low pressure compressor, such that the refrigerant suction gas temperature and / or suction gas pressure in the low pressure side of the cooling circuit upstream of the low pressure compressor may be controlled by metering refrigerant to the low pressure side via the third expansion valve. Optionally, the second bypass may be connected to the high pressure side downstream of the internal heat exchanger and downstream of the gas cooler in the cooling circuit. The third expansion valve may be used to influence the suction gas temperature and / or suction gas pressure upstream of the low pressure compressor so that the final compression temperature of the low pressure compressor is within the intended operating range for the low pressure compressor. For example, if the temperature of the test space is reduced from, for example, 180° C. to a lower temperature, the temperature of the suction gas of the low-pressure compressor can rise particularly sharply. A heat exchanger is arranged in the test space so that refrigerant at the particularly high temperature in the test space of +180° C. can flow from the heat exchanger at this temperature to the low-pressure compressor. Before the highly superheated refrigerant is fed to the low-pressure compressor, it can be cooled by refrigerant metered in via a third expansion valve.

[0014] The cooling circuit may be provided with another bypass having at least one other valve, which is connected to the high-pressure side of the cooling circuit downstream of the high-pressure compressor and upstream of the gas cooler, and to the low-pressure side of the cooling circuit downstream of the heat exchanger and upstream of the low-pressure compressor, and by metering refrigerant to the low-pressure side via the other valve, the temperature and / or pressure of the refrigerant suction gas on the low-pressure side of the cooling circuit upstream of the low-pressure compressor can be controlled and / or the pressure difference between the high-pressure side and the low-pressure side of the cooling circuit can be equalized. The other bypass is thus configured so that refrigerant can be fed from the high-pressure side to the low-pressure side via the other valve. This refrigerant can be in a superheated or gaseous state. If the cooling circuit is operated in partial load operation, it is particularly advantageous to return the superheated refrigerant from the high-pressure side to the low-pressure side by means of the other bypass. In this case, the expansion valve is opened only a little or not often enough, so that there is a risk that the suction pressure upstream of the low-pressure compressor drops too much. When using carbon dioxide as refrigerant, dry ice is generated at pressures below 5.16 bar absolute, which may prevent the safe operation of the refrigeration circuit and may damage the low-pressure compressor. The generation of dry ice can be effectively prevented, since the highly superheated refrigerant can be fed directly from downstream of the high-pressure compressor to a point upstream of the low-pressure compressor via another bypass. In addition, it is also possible to equalize the pressure difference between the high-pressure side and the low-pressure side of the refrigeration circuit by means of another bypass, for example, when the cooling device is not in operation and the refrigerant heats up as a result of temperature equalization with the surrounding environment, so that there is a risk that undesirable high pressures will build up in the refrigeration circuit.

[0015] The rotational speed of the high pressure compressor and / or the low pressure compressor can be controlled. The high pressure compressor and / or the low pressure compressor can each be equipped with a frequency converter, which allows the rotational speed of the compressor to be adjusted. By reducing the rotational speed, the mass flow rate of the refrigerant can be further reduced in conditions of part-load operation of the cooling circuit, which further increases the efficiency of the cooling device in this operating condition. Furthermore, controlling the rotational speed of the low pressure compressor allows it to be increased or decreased by the control device, so that the pressure of the suction gas on the low pressure side of the cooling circuit can be changed and thus adjusted in a desired manner.

[0016] When the temperature in the test space is increased or kept constant, the pressure of the suction gas on the low-pressure side of the cooling circuit is reduced, making it possible to increase the temperature difference between the second heat exchanger and the test space. For example, the pressure of the suction gas on the low-pressure side can be realized in a corresponding manner if the cooling device has a second bypass of the cooling circuit, another bypass of the cooling circuit and / or a controllable rotation speed of the low-pressure compressor. Due to the fact that the boiling point of the refrigerant is dependent on the pressure of the suction gas on the low-pressure side, in particular, the temperature difference between the second heat exchanger and the test space is now increased. A reduction in the pressure of the suction gas thus leads to an increase in the temperature difference between the second heat exchanger and the temperature of the test space. This is particularly advantageous when a targeted dehumidification of the air of the test space is performed, for example, at a constant temperature of the test space. Overall, the cooling capacity of the dehumidification bypass or the second heat exchanger can be increased in this way.

[0017] Furthermore, the temperature difference between the heat exchanger and the test space can be increased so that the air in the test space can be dehumidified. In addition to the second heat exchanger or the dehumidification bypass, the heat exchanger can also be used to dehumidify the air in the test space. The cooling capacity that can be used for dehumidification can be maximized in this way without the need for complex additional components.

[0018] While lowering the temperature of the test space, the pressure of the intake gas on the low pressure side of the cooling circuit can be increased, and the temperature difference between the second heat exchanger and the test space can be reduced. In this way, the pressure of the intake gas can be increased significantly, especially in the case of low cooling load requirements. The low pressure compressor then normally maintains the pressure of the intake gas as low as possible at the operating temperature. This can be done, for example, by a second bypass or by controlling the rotation speed of the low pressure compressor. The pressure of the intake gas can then be increased to such an extent that it allows for dehumidification that is as minimal as possible. As a result, the second heat exchanger is less prone to freezing at temperatures of the intake gas below 0°C, whereby the formation of an insulating layer of ice on the second heat exchanger can be completely prevented or reduced. The same applies to the heat exchanger, which is also less prone to freezing due to the increase in the temperature of the intake gas. It is also possible to reduce the temperature difference between the heat exchanger and the second heat exchanger in the test space by increasing the effective surface area of ​​the heat exchanger or the second heat exchanger, but this is disadvantageous if high dehumidification capacity or rapid dehumidification of the air in the test space is required.

[0019] The cooling circuit may have a medium pressure bypass, which is connected to the high pressure side of the cooling circuit downstream of the gas cooler and upstream of the expansion valve, and to the medium pressure side of the cooling circuit upstream of the high pressure compressor and downstream of the low pressure compressor, in which case refrigerant can be metered from the high pressure side to the medium pressure side by another expansion valve. The medium pressure bypass can then be used to perform a so-called medium pressure injection of refrigerant into the line connecting the low pressure compressor to the high pressure compressor or into the medium pressure side. The refrigerant supplied via the medium pressure bypass can then be mixed at this point with the refrigerant circulating in the cooling circuit.

[0020] The cooling circuit may have an internal heat exchanger, which is connected to the high-pressure side of the cooling circuit downstream of the gas cooler and upstream of the expansion valve, and the internal heat exchanger may be coupled to an intermediate pressure bypass of the cooling circuit, which may be connected to the high-pressure side downstream of the internal heat exchanger upstream of the gas cooler and upstream of the expansion valve, and may be connected to the intermediate pressure side of the cooling circuit upstream of the high-pressure compressor and downstream of the low-pressure compressor, and refrigerant may be metered from the high-pressure side to the intermediate pressure side by the other expansion valve via the internal heat exchanger. Immediately downstream of the internal heat exchanger and upstream of the expansion valve, an intermediate pressure bypass with another expansion valve may be connected to the circuit as a result. The refrigerant already passed through the internal heat exchanger may then also be fed and expanded via the other expansion valve. The internal heat exchanger may be connected in the intermediate pressure bypass downstream of the other expansion valve. The refrigerant expanded in the other expansion valve flows through the internal heat exchanger and is cooled as a result. Thus, on the medium pressure side, the internal heat exchanger is cooled, and as a result the refrigerant on the high pressure side of the internal heat exchanger is cooled. In principle, however, the medium pressure bypass may also be connected to the cooling circuit downstream of the gas cooler and upstream of the internal heat exchanger, so that the refrigerant then flows via a further expansion valve and an internal heat exchanger. Downstream of the internal heat exchanger, the medium pressure bypass may be connected between the low pressure compressor and the high pressure compressor, so that the refrigerant sent via the medium pressure bypass can be mixed at this point with the refrigerant circulating in the cooling circuit. By using a medium pressure bypass with an internal heat exchanger, it is also possible to bypass the refrigerant via the medium pressure bypass, so that less refrigerant flows via the expansion valve, depending on the cooling load requirements of the control device. At the same time, the refrigerant flowing via the medium pressure bypass can be used by the internal heat exchanger to control the temperature of the refrigerant on the high pressure side. When only a lower cooling capacity is required in the test space, the very high volumetric cooling capacity of carbon dioxide is thus bypassed upstream of the heat exchanger and used to cool the refrigerant on the high pressure side. This also allows the test space to be more compact and the carbon dioxide powered cooling circuits to be used in smaller test chambers.

[0021] The intermediate pressure side of the cooling circuit may be connected to a gas cooler upstream of the high pressure compressor and downstream of the low pressure compressor, and the refrigerant may be sent from the low pressure compressor to the high pressure compressor via the gas cooler. This allows the refrigerant, compressed and heated by the low pressure compressor, to be cooled by the gas cooler before it reaches the high pressure compressor. Since the gas cooler may be used to cool the refrigerant, no additional heat exchanger is required.

[0022] Alternatively, the medium pressure side of the cooling circuit may be connected to a medium pressure chiller upstream of the high pressure compressor and downstream of the compressor, and the refrigerant may be sent from the low pressure compressor to the high pressure compressor via the medium pressure chiller, which may in particular be used to cool the refrigerant compressed and heated by the low pressure compressor before it reaches the high pressure compressor.

[0023] The gas cooler and / or the medium pressure cooler may be designed as air-cooled or water-cooled. Alternatively, an external cooling device may be used to cool the gas cooler and / or the medium pressure cooler.

[0024] The cooling circuit can be operated in a thermodynamically subcritical or supercritical operating state. Depending on the cooling load requirements in the test space, the operating state can be changed accordingly by using the control device. In a subcritical operation of the cooling circuit, the refrigerant is liquefied in the gas cooler below the critical point of the refrigerant and expanded in the expansion valve and converted to gas phase or wet steam. The high pressure and low pressure compressors can be operated at least in a subcritical operating state. The subcritical operating state of the cooling circuit corresponds to a part-load operation. In a supercritical operating state, the refrigerant circulates in the cooling circuit in a substantially gaseous state. This means that the temperature difference is reduced to such an extent that the refrigerant is not liquefied in the gas cooler. Also, in a supercritical operating state, a pressure above the critical point of the refrigerant is reached in the gas cooler. If the cooling load requirement is high or if cooling from +180°C to -20°C is required, for example, the cooling circuit can be operated in supercritical. If the cooling load requirement in the test space is low, for example if the temperature is to be kept constant or if the ambient temperature is low, the cooling circuit can be operated subcritically. This allows an increase in efficiency to be achieved, especially in the case of low cooling load requirements, as opposed to only supercritical operating conditions. The change between subcritical and supercritical operating conditions is made possible in particular by the intermediate pressure bypass and the internal heat exchanger.

[0025] Advantageously, pure carbon dioxide can be used as the refrigerant. Pure carbon dioxide has a GWP of 1, is non-flammable, non-hazardous and is available at low cost. In addition, carbon dioxide is a pure substance or azeotropic, which allows for advantageous implementation of the method and its variants in the first place. On the other hand, a refrigerant with a non-azeotropic nature would hardly be able to provide a sufficient amount of gaseous refrigerant at very small temperature differences, and as a result, the operation of the high-pressure compressor would be hardly controlled.

[0026] The temperature control device may be used to achieve a temperature in the test space within the temperature range of -40°C to +180°C, preferably -50°C to +180°C, particularly preferably -55°C to +180°C.

[0027] The temperature control device may be used to achieve a relative humidity within the test space of 10% to 95%, preferably 5% to 99%, at a temperature within the temperature range of +10°C to +90°C, preferably +5°C to +98°C.

[0028] A test chamber, in particular a climate chamber, according to the invention for conditioning air comprises a test space for accommodating a test material and a temperature control device for controlling the temperature of the test space, the test space being configured to be sealed and insulated from the surrounding environment, the temperature control device being configured to achieve a temperature in the test space within a temperature range of -20°C to 180°C, the temperature control device comprising a cooling device with a cooling circuit using carbon dioxide as a refrigerant, a heat exchanger in the test space, a low-pressure compressor, a high-pressure compressor, a gas cooler and an expansion valve downstream of the low-pressure compressor in the flow direction of the refrigerant, the test chamber being equipped with a control device for controlling the temperature and / or relative humidity in the test space, the cooling circuit comprising a dehumidification bypass with a second expansion valve and a second heat exchanger in the test space for dehumidifying the air in the test space. Regarding the advantages of the test chamber according to the invention, reference is made to the description of the advantages of the method according to the invention.

[0029] In a similar cooling circuit operated with carbon dioxide as refrigerant, an additional valve containing a throttling element is required in parallel to the expansion valve in order to make it possible to operate the cooling device in the defined temperature range. By using a dehumidification bypass, this valve or the corresponding pipe section of the cooling circuit can be omitted, so that the cooling circuit is simplified in manufacture. In this case, the effective surface area of ​​the heat exchanger for cooling the air of the test space is increased, since a large part of the effective surface area of ​​the heat exchanger can also be used to cool the air of the test space when the temperature control device is in air conditioning mode. To achieve an equivalent cooling capacity, the temperature difference between the temperature of the heat exchanger and the temperature of the air of the test space may be smaller if the effective surface area of ​​the heat exchanger is increased. The cooling capacity (W) is determined by the surface area of ​​the heat exchanger (m 2 ) and the heat transfer coefficient (W / m 2 The dehumidification bypass is obtained by multiplying the refrigerant flow rate (K) by the temperature difference (K). The smaller temperature difference when the effective surface area of ​​the heat exchanger is large has the effect that the control accuracy can be improved since unwanted dehumidification, for example by condensation on the cold surface of the heat exchanger, is reduced when the temperature drops below the dew point temperature. In the dehumidification bypass, a check valve can be arranged downstream of the second heat exchanger. The check valve can be used to prevent the refrigerant from moving in the opposite direction to the flow direction to the second heat exchanger when the second expansion valve is closed.

[0030] The high-pressure and low-pressure compressors may share a compressor housing. In principle, the high-pressure and low-pressure compressors may have two separate compressor housings. The use of the low-pressure and high-pressure compressors in a shared compressor housing significantly reduces the installation space required for the compressors. The compressors can be designed as rolling piston compressors or as fully hermetic reciprocating piston compressors of the encapsulated type. Furthermore, an oil separator can be installed in the cooling circuit downstream of the high-pressure compressor. Since in the test space temperatures can reach up to 180° C., this temperature is then also transferred by the heat exchanger to the refrigerant contained therein. This can lead to an accelerated deterioration of the oil in the cooling circuit, which can result in damage to the compressor. By means of the oil separator, the amount of oil inside the heat exchanger can be kept as small as possible, so that only a small amount of oil is exposed to very high temperatures. This may further extend the useful life of the compressor.

[0031] The heat exchanger and the second heat exchanger may have separate heat exchanger bodies or may share a heat exchanger body. In this sense, a heat exchanger body is understood here to be, for example, a body through which the refrigerant flows, which may consist of one or more parts. This also includes a line arrangement provided with fins for better heat transfer. The fins then form the heat exchanger body together with the line arrangement(s). The exchanger body then has an effective surface area for heat transfer.

[0032] The temperature control device may have a heating device having a heater and a heating heat exchanger in the test space. For example, the heating device may be an electric resistance heater that heats the heating heat exchanger so that the heating heat exchanger can increase the temperature of the test space. If the heat exchanger and the heating heat exchanger can be targeted and controlled by the control device to cool or heat the air circulating in the test space, a temperature within the above-mentioned temperature range can be achieved in the test space by the temperature control device.

[0033] Further embodiments of the test chamber are evident from the characterizing claims which are dependent on method claim 1. [Brief description of the drawings]

[0034] In the following, preferred embodiments of the invention will be described in more detail with reference to the accompanying drawings. [Figure 1] FIG. 1 is a schematic diagram of a first embodiment of a cooling device. [Diagram 2] FIG. 2 is a schematic diagram of a second embodiment of a cooling device. [Diagram 3] FIG. 3 is a schematic diagram of a third embodiment of a cooling device. [Figure 4] FIG. 4 is a schematic diagram of a fourth embodiment of a cooling device. [Diagram 5] FIG. 5 is a schematic diagram of a fifth embodiment of a cooling device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035] FIG. 1 shows a possible embodiment of a cooling device 10 of a test chamber (not shown). The cooling device 10 comprises a cooling circuit 11 using carbon dioxide (CO2) as a refrigerant, a heat exchanger 12, a low-pressure compressor 13, a high-pressure compressor 14, a gas cooler 15 and an expansion valve 16. In this case, the gas cooler 15 is configured as a heat exchanger or condenser and is cooled by a heat transfer medium such as air or water. The heat exchanger 12 is arranged in an air handling duct (not shown) of a test space of the test chamber, so that the air in the test space circulated by the air handling duct can be cooled by the heat exchanger 12. Furthermore, the cooling circuit 11 has a low-pressure side 17, an intermediate-pressure side 18 and a high-pressure side 19. In the low-pressure side 17, the pressure of the refrigerant is relatively lower than the pressure of the refrigerant in the intermediate-pressure side 18. In the intermediate-pressure side 18, the pressure of the refrigerant is relatively lower than the pressure of the refrigerant in the high-pressure side 19.

[0036] Furthermore, a dehumidifying bypass 20 with a second expansion valve 21 and a second heat exchanger 22 is also arranged in the test space and is arranged in the cooling circuit 11. The air in the test space can be dehumidified by the second heat exchanger 22, i.e. by the dehumidifying bypass 20. For this purpose, the test chamber has a control device (not shown) by means of which the temperature and / or the relative humidity in the test space can be controlled. To this end, the control device can actuate in particular the expansion valve 16 and the second expansion valve 21. This allows the cooling device 10 to be used for carrying out climatic tests in which the dehumidification or the relative humidity in the test space can be realized very precisely, even with a constant or even falling temperature in the test space.

[0037] The cooling circuit 11 further comprises an internal heat exchanger 23 downstream in the flow direction of the refrigerant and an intermediate pressure bypass 24 upstream of the expansion valve 16, which ends downstream of the low pressure compressor 13 and upstream of the high pressure compressor 14. A further expansion valve 25 is arranged in the intermediate pressure bypass 24. The further expansion valve 25 is connected upstream of the internal heat exchanger 23. Essentially, liquid refrigerant is now fed from the gas cooler 15 through the high pressure side 19 of the internal heat exchanger 23 and, if necessary, metered via the further expansion valve 25 to the intermediate pressure side 18 of the internal heat exchanger 23. In the process, the refrigerant on the high pressure side 19 is subcooled to such an extent that an even lower temperature can be achieved in the expansion valve 16 or the heat exchanger 12. At the same time, the refrigerant flowing via the intermediate pressure bypass 24 can be used to keep the temperature of the suction gas of the high pressure compressor 14 relatively low.

[0038] In addition, the cooling circuit 11 comprises a second bypass 26 with a third expansion valve 27. The second bypass 26 is connected to the cooling circuit 11 downstream of the internal heat exchanger 23 and upstream of the expansion valve 16, and downstream of the heat exchanger 12 and upstream of the low-pressure compressor 13 in the flow direction of the refrigerant. By means of the third expansion valve 27, liquid refrigerant can be fed through the expansion valve 16 and the heat exchanger 12 to the low-pressure side 17. This makes it possible to control the temperature of the suction gas and / or the pressure of the suction gas on the low-pressure side 17 upstream of the low-pressure compressor 13.

[0039] Furthermore, the cooling circuit 11 comprises a further bypass 28 with a further valve 29, which is connected to the cooling circuit 11 downstream of the high-pressure compressor 14 and upstream of the gas cooler 15 in the flow direction of the refrigerant, and downstream of the heat exchanger 12 and upstream of the low-pressure compressor 13. By means of the further bypass 28, i.e. the further valve 29, depending on the operating state of the cooling circuit 11, refrigerant, in particular superheated refrigerant or refrigerant in gaseous state, can be fed from the high-pressure side 19 to the low-pressure side 17 upstream of the low-pressure compressor 13. This also makes it possible to control the temperature of the suction gas and / or the pressure of the suction gas on the low-pressure side 17 upstream of the low-pressure compressor 13. This can be done by a control device (not shown) in the test chamber and by sensors, in particular pressure and temperature sensors, arranged in the cooling circuit 11.

[0040] Figure 2 shows a cooling device 30 with a cooling circuit 31, which differs from the cooling circuit of Figure 1 in that the intermediate pressure side 32 of the cooling circuit 31 is connected to a gas cooler 33 upstream of the high pressure compressor 14 and downstream of the low pressure compressor 13. In this way, refrigerant can be fed from the low pressure compressor 13 to the high pressure compressor 14 via the gas cooler 33 and cooled therein. The cooling circuit 31 therefore does not have an internal heat exchanger.

[0041] Figure 3 shows a cooling device 34 with a cooling circuit 35, which differs from the cooling circuit of Figure 2 in that a second expansion valve 37, a second heat exchanger 38 and a dehumidification bypass 36 with a check valve 39 are formed. The check valve 39 is arranged downstream of the second heat exchanger 38 in the dehumidification bypass 36 in the refrigerant flow direction. This prevents refrigerant on the low-pressure side 40 of the cooling circuit 31 next to the dehumidification bypass 36 from flowing in the opposite direction to the normal flow direction and moving to the second heat exchanger 28.

[0042] Figure 4 shows a cooling device 41 with a cooling circuit 42, which differs from the cooling circuit of Figure 3 in that a water-cooled gas cooler 43 is used. Here, on the medium pressure side 44, a medium pressure cooler 45 is formed, which is also water-cooled. The medium pressure cooler 45 is used to cool the refrigerant, which flows from the low pressure compressor 13 to the high pressure compressor 14 via the medium pressure side 44.

[0043] Figure 5 shows a cooling device 46 with a cooling circuit 47, which differs from the cooling circuit of Figure 4 in that it has an intermediate pressure bypass 48. The intermediate pressure bypass 48 is connected to a high pressure side 49 of the cooling circuit 47 downstream of the gas cooler 43 and upstream of the expansion valve 16 in the flow direction of the refrigerant, and to an intermediate pressure side 50 of the cooling circuit 47 upstream of the high pressure compressor 14 and downstream of the low pressure compressor 13. By means of a further expansion valve 51, the refrigerant can be metered from the high pressure side 49 to the intermediate pressure side 50.

Claims

1. A method for conditioning the air in a test chamber, in particular a test space of a climatic chamber, intended to contain test materials, comprising the steps of: The test space is configured to be sealed and insulated from the surrounding environment; The cooling device (10, 30, 34, 41, 46) of the temperature control device of the test chamber Carbon dioxide (CO ２ a cooling circuit (11, 31, 35, 42, 47) using a refrigerant gas, a heat exchanger (12) in the test space, a low-pressure compressor (13), a high-pressure compressor (14), a gas cooler (15, 33, 43), and an expansion valve (16) downstream of the low-pressure compressor in the flow direction of the refrigerant, used to achieve a temperature in the test space within a range of −20° C. to +180° C.; the test chamber control device is used to control the temperature and / or relative humidity of the test space; The dehumidification bypass (20, 36) of the cooling circuit is A second expansion valve (21, 37) and a second heat exchanger (22, 38) are provided in the test space, used to dehumidify the air in the test space; method.

2. the dehumidification bypass (20, 36) is connected to a high pressure side (19, 49) of the cooling circuit (11, 31, 35, 42, 47) downstream of the gas cooler (15, 33, 43) and upstream of the expansion valve (16), and is connected to a low pressure side (17, 40) of the cooling circuit downstream of the heat exchanger (12) and upstream of the low pressure compressor (13); The refrigerant is metered and supplied from the high pressure side to the low pressure side via the second expansion valve (21, 37) so as to cool the second heat exchanger (22, 38). The method of claim 1.

3. a second bypass (26) having at least a third expansion valve (27) is formed in the cooling circuit (11, 31, 35, 42, 47); the second bypass is connected to the high pressure side (19, 49) of the cooling circuit downstream of the gas cooler (15, 33, 43) and upstream of the expansion valve (16), and is connected to the low pressure side (17, 40) of the cooling circuit downstream of the heat exchanger (12) and upstream of the low pressure compressor (13); metering the refrigerant to the low pressure side via the third expansion valve to control a suction gas temperature and / or a suction gas pressure of the refrigerant on the low pressure side of the refrigeration circuit upstream of the low pressure compressor; The method according to claim 1 or 2.

4. a further bypass (28) having at least one further valve (29) is formed in said cooling circuit (11, 31, 35, 42, 47); the other bypass is connected to the high pressure side (19, 49) of the cooling circuit downstream of the high pressure compressor (14) and upstream of the gas cooler (15) and is connected to the low pressure side (17, 40) of the cooling circuit downstream of the heat exchanger (12) and upstream of the low pressure compressor (13); Metering the refrigerant to the low pressure side via the other valve, The refrigerant suction gas temperature and / or suction gas pressure on the low pressure side of the refrigeration circuit upstream of the low pressure compressor is controlled; and / or the pressure differential between the high pressure side and the low pressure side of the cooling circuit is equalized; The method according to any one of claims 1 to 3.

5. The rotation speed of the high pressure compressor (14) and / or the low pressure compressor (13) is controlled; The method according to any one of claims 1 to 4.

6. While the temperature in the test space is increased or kept constant, the pressure of the intake gas in the low pressure side (17, 40) of the cooling circuit (11, 31, 35, 42, 47) is reduced; The temperature difference between the second heat exchanger (22, 38) and the test space is increased. The method according to any one of claims 1 to 5.

7. The temperature difference between the heat exchanger (12) and the test space is increased so that the air in the test space is dehumidified. The method according to any one of claims 1 to 6.

8. While the temperature in the test space is being reduced, the pressure of the intake gas in the low pressure side (17, 40) of the cooling circuit (11, 31, 35, 42, 47) is increased, The temperature difference between the second heat exchanger (22, 38) and the test space is reduced. The method according to any one of claims 1 to 5.

9. the cooling circuit (47) has an intermediate pressure bypass (48) connected to a high pressure side (49) of the cooling circuit downstream of the gas cooler (43) and upstream of the expansion valve (16), and connected to an intermediate pressure side (50) of the cooling circuit upstream of the high pressure compressor (14) and downstream of the low pressure compressor (13); The refrigerant is metered and supplied from the high pressure side to the intermediate pressure side via another expansion valve (51). The method according to any one of claims 1 to 8.

10. the cooling circuit (11) comprises an internal heat exchanger (23) connected to the high pressure side (19) of the cooling circuit downstream of the gas cooler (15) and upstream of the expansion valve (16); the internal heat exchanger is coupled to a medium pressure bypass (24) of the cooling circuit; the intermediate pressure bypass is connected to the high pressure side downstream of the internal heat exchanger or the gas cooler and upstream of the expansion valve, and is connected to the intermediate pressure side (18) of the cooling circuit upstream of the high pressure compressor (14) and downstream of the low pressure compressor (13); The refrigerant is metered and supplied from the high pressure side to the intermediate pressure side via the internal heat exchanger by another expansion valve (25). The method according to any one of claims 1 to 8.

11. the intermediate pressure side (32) of the cooling circuit (31, 35) is connected to the gas cooler (33) upstream of the high pressure compressor (14) and downstream of the low pressure compressor (13); The refrigerant is supplied from the low pressure compressor to the high pressure compressor via the gas cooler. The method according to any one of claims 1 to 8.

12. the intermediate pressure side (44) of the cooling circuit (42) is connected to an intermediate pressure cooler (45) upstream of the high pressure compressor (14) and downstream of the low pressure compressor (13); The refrigerant is supplied from the low pressure compressor to the high pressure compressor via the intermediate pressure cooler. The method according to any one of claims 1 to 8.

13. the cooling circuit (11, 31, 35, 42, 47) is operated in a thermodynamic subcritical or supercritical operating state; The method according to any one of claims 1 to 12.

14. Pure carbon dioxide (CO ２ ) is used as the refrigerant; The method according to any one of claims 1 to 13.

15. The temperature control device is used to achieve a temperature in the test space within a temperature range of −40° C. to +180° C., preferably −50° C. to +180° C. The method according to any one of claims 1 to 14.

16. the temperature control device is used to achieve in the test space a relative humidity in the range of 10% to 95%, preferably 5% to 99%, at a temperature in the range of +10° C. to +90° C., preferably +5° C. to +98° C., The method according to any one of claims 1 to 15.

17. A test chamber, in particular a climatic chamber, for conditioning air, comprising: The test chamber comprises: A test space for containing a test material, The test space is configured to be sealed and insulated from the surrounding environment; A test space; A temperature control device for controlling a temperature of the test space, The temperature control device is configured to achieve a temperature in the test space within a temperature range of −20° C. to +180° C. A temperature control device, the temperature control device comprises a cooling device (10, 30, 34, 41, 46) with a cooling circuit (11, 31, 35, 42, 47) using carbon dioxide as a refrigerant, a heat exchanger (12) in the test space, a low pressure compressor (13), a high pressure compressor (14), a gas cooler (15, 33, 43) and an expansion valve (16) downstream of the low pressure compressor in the flow direction of the refrigerant, the test chamber includes a control device for controlling the temperature and / or relative humidity within the test space; the cooling circuit comprises a dehumidification bypass (20, 36) having a second expansion valve (21, 37) and a second heat exchanger (22, 38) in the test space for dehumidifying air in the test space; Examination room.

18. A check valve (39) is disposed in the dehumidification bypass (36) downstream of the second heat exchanger (38).

18. The test chamber of claim 17.

19. The high pressure compressor (14) and the low pressure compressor (13) share a compressor housing.

19. A test chamber according to claim 17 or 18.

20. The heat exchanger (12) and the second heat exchanger (22, 38) have separate exchanger bodies or share a common exchanger body. A test chamber according to any one of claims 17 to 19.

21. The temperature control device includes a heating device having a heater and a heating heat exchanger in the test space. A test chamber according to any one of claims 17 to 20.

Images