Environmental simulation chamber and method for operating the same

Abstract

The environmental simulation chamber (100) comprises a refrigeration installation (1) including a refrigeration device (10) having a closed circuit (C) in which a refrigerant fluid circulates, said closed circuit (C) comprising at least one compressor (2), cooling means (3) for said refrigerant fluid, expansion means (4) for said refrigerant fluid and an evaporator (5), said chamber (100) further comprises an insulated space (20) in which a sample (21) to be tested is inserted, said evaporator (5) being configured to regulate the internal temperature of said insulated space (20), said simulation chamber comprising a refrigerant fluid (100) having a refrigeration unit (10) including a refrigerant fluid (100) and a cooling means (3) for said refrigerant fluid, said cooling means (3) for said refrigerant fluid, said expansion means (4) for said refrigerant fluid and an evaporator (5), said chamber (100) further comprises an insulated space (20) in which a sample (21) to be tested is inserted, said evaporator (5) being configured to regulate the internal temperature of said insulated space (20), said refrigerant fluid being carbon dioxide.

Description

Technical Field

[0001] The present invention relates to an environmental simulation chamber and its respective operating methods.

Background Art

[0002] The existence of an environmental simulation chamber equipped with refrigeration equipment including a refrigeration device having a closed circuit through which a refrigerant fluid circulates is known. This closed circuit is equipped with at least one compressor, means for cooling the refrigerant fluid, means for expanding the refrigerant fluid, and an evaporator. This chamber is further provided with a heat-insulated space into which a sample to be tested is inserted, and therein the evaporator cooperates with the expansion means to adjust the internal temperature of the heat-insulated space, and to test the behavior of the sample under various environmental conditions, even extreme conditions. Note that according to known techniques, the refrigerant fluid is usually known as R449.

[0003] However, this refrigerant fluid does not have no drawbacks. In fact, refrigeration equipment using this gas achieves very accurate and rapid temperature control within the heat-insulated space of the environmental simulation chamber, but it has been found that the GWP (Global Warming Potential) of R449 gas is quite high. The refrigerant needs to be specified to have a relatively low amount of CO 2 equivalent. In practice, in order to avoid indirect damage to the environment during refrigerant release, the relative Global Warming Potential (GWP) needs to be as low as possible. This GWP measures the regulated amount of the mass of greenhouse gases contributing to global warming. This value is set with carbon dioxide as the reference, and thus carbon dioxide becomes the reference value. Therefore, GWP represents the average warming effect of a specific gas or gas mixture over a specific period (100 years in this context).

[0004] CO 2For the definition of the equivalent amount or each GWP, in this book and hereinafter, reference is made to Regulation (EU) No. 517 / 2014 of the European Parliament and of the Council. Therefore, the higher the GWP value related to a gas, the greater the environmental risk when the gas is released into the atmosphere. Environmental simulation chambers operating with gases having a very low GWP are known. For example, Patent Document 1 in the name of ATT describes an environmental simulation chamber operating with a gas mixture having a very low GWP value of less than 38 over 100 years.

[0005] In any case, although the GWP value of the refrigerant mixture described in Patent Document 1 in the name of ATT is already extremely low, there is a tendency to identify a gas for an environmental control chamber having an even lower GWP value. Patent Document 2 in the name of Haack Christian describes an air-conditioning test chamber including a test space that can accommodate a test material, be blocked from the surrounding environment, and be insulated, and a temperature control device for controlling the temperature of this test space. This temperature control device can set the temperature in the test space within a temperature range of -80°C to +180°C, preferably -100°C to +200°C. Further, this temperature control device is equipped with a cooling circuit containing a refrigerant, a heat exchanger disposed in the test space, a compressor, a condenser, and a cooling device including an expansion element.

[0006] Patent Document 3 in the name of Dairikisha is related to an air-conditioning system. More specifically, it includes an air cooler for an air-conditioning area, and this air cooler functions as an evaporator in a refrigeration circuit, and controls system components including the air cooler to raise the air-conditioning area to a target temperature. This solution described in Patent Document 3 is related to an air-conditioning system particularly equipped with control means for adjusting humidity conditions.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0008] Accordingly, an object of the present invention is to provide an environmental simulation chamber that can operate with a refrigerant fluid having an extremely low GWP and tending to be almost zero. A further object of the present invention is to provide an environmental simulation chamber that consumes even less energy than those currently existing. Furthermore, an object of the present invention is to provide an environmental simulation chamber that can also enhance the safety level of the current chamber. Finally, an object of the present invention is to provide a method for operating the chamber according to the present invention, whereby the levels of efficiency and safety can be increased and, in any case, a method that can reach a higher level than the currently existing simulation chambers can be provided.

Means for Solving the Problems

[0009] These and other objects of the present invention are achieved by the environmental simulation chamber according to claim 1. In particular, this environmental simulation chamber includes refrigeration equipment having a refrigeration machine in which a refrigerant fluid circulates in a closed circuit. The closed circuit is provided with at least one compressor, means for cooling the refrigerant fluid, means for expanding the refrigerant fluid, and an evaporator. The chamber further includes a heat - insulated space into which a sample to be tested is inserted, and the evaporator is configured to adjust the internal temperature of the heat - insulated space. The simulation chamber is characterized in that the refrigerant fluid is carbon dioxide.

[0010] With this solution, the proposed objective can be achieved. In fact, since carbon dioxide is present as the refrigerant, it is possible to bring the GWP close to zero, that is, to 1 in 100 years.

[0011] Furthermore, this closed circuit further comprises an expansion reservoir for carbon dioxide operatively arranged along a first path arranged between the evaporator and the at least one compressor, and filling / discharging means enabling filling of the refrigerant fluid from the first path into the expansion reservoir and discharging of the refrigerant fluid from the expansion reservoir into the first path.

[0012] This solution will become apparent by the method described below, and it becomes possible to operate the compressor intermittently off as part of the operation of the simulation chamber. In particular, when the chamber operates partially, that is, when a non-excessive level of cooling is required, it is possible to operate the compressor intermittently, that is, to operate it off.

[0013] In fact, the compressor operates intermittently in the case of part load. The expansion reservoir is sized to suppress pressure fluctuations at the outlet of the evaporator to below a certain pressure, preferably below 8 bar, according to the part load opening of the expansion means for temperature control.

[0014] According to the proposed solution, this simulation chamber comprises a control unit that turns the compressor on or off based on the internal temperature regulated within the adiabatic space, and in this control unit, the refrigerant fluid present in the expansion reservoir is supplied to or filled by the closed circuit.

[0015] According to a first variant of the invention, the filling / discharging means comprise a connecting conduit. Thus, the expansion reservoir does not control the inflow and outflow of carbon dioxide inside it, and depends on the pressure along the first path of the closed circuit, and thus the pressure of the refrigerant fluid upstream of the same compressor.

[0016] In a further embodiment of the present invention, this connecting conduit is provided with a first shut-off valve, and preferably, the control unit permits or prohibits the inflow / outflow of the refrigerant fluid to / from the expansion reservoir according to the pressure at the outlet of the evaporator.

[0017] Alternatively, the filling / discharging means comprises a bypass circuit arranged along the first path between the evaporator and the at least one compressor, and the bypass circuit comprises a first inlet branch from the first path to the expansion reservoir and a second outlet branch from the expansion reservoir to the first path. The filling / discharging means further comprises a first shut-off valve arranged along the first inlet branch, a second shut-off valve arranged along the second outlet branch, and at least one third shut-off valve arranged along the first path between the first inlet branch and the second outlet branch. According to the second embodiment of the present invention, the filling / discharging of the expansion reservoir can be more finely controlled, and thus the environmental simulation chamber can be operated more accurately.

[0018] Furthermore, the circuit further comprises a storage reservoir for the liquid refrigerant fluid arranged in the second path of the closed circuit between the cooling means and the expansion means. According to a further embodiment of the present invention, the closed circuit comprises at least one auxiliary line that directly or indirectly connects the closed circuit to the adiabatic space, and the auxiliary line is provided with an inlet section of the refrigerant fluid arranged along the first path of the closed circuit between the evaporator and the at least one compressor and an outlet section of the refrigerant fluid. This outlet section is connected to the adiabatic space, and gaseous carbon dioxide flows into the adiabatic space.

[0019] In certain embodiments of the present invention, this solution can exist even in the absence of an expansion reservoir and enables carbon dioxide, which can extinguish a fire when a fire occurs, to be introduced into the insulated space. In particular, the auxiliary line is provided with an on-off valve arranged along the auxiliary line, which permits or prevents the passage of the refrigerant fluid along the auxiliary line.

[0020] Furthermore, according to a preferred embodiment of the present invention, the simulation chamber further comprises detection means for detecting the ignition of a fire within the insulated space, and the detection means is operatively connected to the on-off valve to control its opening and closing. With this solution, a fire that may exist within the insulated space can be automatically extinguished without the need for an operator to intervene and control.

[0021] In a further embodiment of the present invention, the refrigeration equipment comprises further refrigeration devices having a further closed circuit through which a further refrigerant fluid circulates, and this further closed circuit is equipped with at least one further compressor, further cooling means for cooling the refrigerant fluid, further expansion means for the refrigerant fluid, and a further evaporator configured to operate in cooperation with the cooling means of the refrigeration devices. This further refrigeration device operates in a temperature range higher than the temperature range in which the refrigeration device operates. In this case, the refrigerant fluid circulating within the closed circuit, namely carbon dioxide, operates in a subcritical state.

[0022] In another embodiment of the present invention, the refrigerant fluid can also operate in a supercritical state, but in this case, there is no further refrigeration device in the closed circuit, and furthermore, the cooling means no longer operates as a condenser. In this embodiment, the closed circuit includes, in addition to the at least one compressor, a second high-pressure compressor connected in series with the at least one compressor, a bypass circuit for the cooling means, and this bypass circuit has at least one control valve for operating the bypass circuit, an intermediate throttle valve downstream of the storage reservoir, and a condensing pressure control valve.

[0023] In particular, the closed circuit further comprises a heat exchanger operatively connected to a third path of the closed circuit between the at least one second compressor downstream of the bypass circuit and the refrigerant fluid storage reservoir, and means for regulating the flow rate of the refrigerant fluid entering the heat exchanger. The heat exchanger is arranged within the insulated space, and preferably, the heat exchanger and the evaporator are arranged in two separate compartments existing within the insulated space. Thus, the same refrigeration equipment can be used to cool and heat the insulated space.

[0024] The object of the present invention is also achieved by a method of operating an environmental simulation chamber according to one or more of claims 1 to 12, the method comprising the following steps: a) setting at least one temperature, or at least one temperature range, to be achieved within the insulated space; b) operating the at least one compressor to circulate the refrigerant fluid within the closed circuit of the refrigeration equipment; c) adjusting the opening and closing of the expansion means so as to vary the flow rate of the refrigerant fluid passing through the evaporator according to the at least one temperature, or the temperature range, required within the insulated space. Here, the refrigerant fluid is carbon dioxide. In particular, the method further comprises step d) of at least partially filling the expansion reservoir with the refrigerant fluid.

[0025] Furthermore, in step c), when the expansion means operates at part load and the at least one expansion reservoir is sized to accommodate fluctuations in the pressure at the outlet of the evaporator (lower than a specific pressure, preferably lower than 8 bar), the method comprises step e) of operating the compressor intermittently. In practice, the operating method of the environmental simulation chamber operates advantageously especially when the expansion means operates at part load, i.e., when the flow rate of the refrigerant passing through the expansion means decreases compared to the flow rate sucked in by the compressor. This occurs when the refrigeration load in the insulated space has not reached the limit of the capacity of the refrigeration equipment, but the user requests a temperature higher than -20°C. This occurs when the cooling load in the insulated space has not reached the limit of the capacity of the refrigeration equipment, but the user requests a temperature higher than -20°C. In these situations, due to the presence of the expansion reservoir, the compressor can be operated intermittently, i.e., turned off and then on again, while maintaining the cooling control in the insulated space at a very efficient level. For example, in a simulation chamber of known technology such as the patent document WO2020 / 012348A1 in the name of the applicant, the compressor is always kept on, and a significant amount of electrical energy is consumed for its operation.

[0026] Furthermore, step e) includes step e1) of reducing the flow rate of the refrigerant fluid passing through the expansion means to a value less than the flow rate sucked in by the at least one compressor and reducing the suction pressure of the at least one compressor to a pressure value at which the at least one compressor stops, step e2) of supplying the expansion reservoir with the fluid flowing out of the evaporator until the pressure of the expansion reservoir rises to a first pressure value equal to the suction pressure at which the at least one compressor starts sucking refrigerant fluid from the expansion reservoir in step e1), where the pressure of the expansion reservoir is determined according to the temperature or temperature range required in the insulated space, in step e1), starting to suck refrigerant fluid from the expansion reservoir, step e3) is a step of restarting the operation of the compressor when the first pressure value in the reservoir is exceeded, and steps e1), e2), and e3) are repeated periodically. This solution has the advantage that it can operate with an intermittently operating compressor while maintaining an excellent temperature control function within the insulated space.

[0027] It should be noted that when the compressor is turned off, the flow of the refrigerant is prevented from passing through the same compressor. Therefore, the refrigerant fluid that continues to pass through the expansion means and thus the evaporator accumulates downstream of these, and the pressure in the expansion reservoir increases. By the above operation of the simulation chamber, energy can be saved in the operation of the entire environmental simulation chamber. This operating mode is realized by the solution shown in FIG. 1.

[0028] As an alternative to the above-described operating method, a solution in which the filling / discharging means includes a first shut-off valve arranged along the first inlet branch, a second shut-off valve arranged along the second outlet branch, and at least one third shut-off valve arranged along a first path between the first inlet branch and the second outlet branch, that is, using the embodiment shown in FIG. 2, Said step e) comprises a step e1') of reducing the flow rate of the refrigerant fluid passing through said expansion means to a value less than the flow rate sucked in by said at least one compressor, a step e2') of closing, opening or leaving open said third shut-off valve and said first shut-off valve, Said at least one second shut-off valve is determined according to the temperature or temperature range required within said insulated space, and when the at least one compressor reaches a first suction pressure of said compressor equal to the pressure at which the at least one compressor starts to suck refrigerant fluid from said expansion reservoir in said step e1'), said at least one second shut-off valve is actuated, and when a pressure value is reached at which the at least one compressor is stopped, said at least one compressor is stopped, including step e3').

[0029] This method further includes the following steps. During the said step e2’) and / or e3’), when the pressure of the refrigerant fluid between the said first shut-off valve or the said third shut-off valve and the evaporator is higher than the second suction pressure of the compressor 2 which is higher than the said first suction pressure, a step e4’) of reopening the said first shut-off valve, and During step e2’) and / or e3’), when the pressure of the refrigerant fluid between the first shut-off valve or the third shut-off valve and the evaporator drops to a value lower than the first suction pressure of the compressor, a step e5’) of closing the first shut-off valve, and A step e6’) of restarting the compressor when at least the pressure in the said expansion reservoir is higher than the said first pressure. Finally, steps e1’) to e6’) are periodically repeated.

[0030] This solution ensures a higher level of control than can be achieved with a closed circuit without the said expansion reservoir and bypass circuits for the three shut-off valves described above.

[0031] Furthermore, even in the case of a solution where the said filling / discharging means includes a first shut-off valve arranged along the said first inlet branch, a second shut-off valve arranged along the said second outlet branch, and at least one third shut-off valve arranged along the said first path between the said first inlet branch and the said second outlet branch, The said method includes a step f) of keeping the said second shut-off valve and the said third shut-off valve open and keeping the said first shut-off valve closed. At least when the flow rate sucked by the said at least one compressor is equal to the flow rate passing through the said expansion means (i.e., when the simulation chamber is at full load), or when the environmental simulation chamber is off (no load), The refrigerant fluid present in the said expansion reservoir can offset the increase in the specific volume of the refrigerant gas present in the said closed circuit and / or reduce the undesirable pressure increase in the said closed circuit.

[0032] Furthermore, in the case of a solution where the filling / discharging means includes a first shut-off valve arranged along the first inlet branch, a second shut-off valve arranged along the second outlet branch, and at least one third shut-off valve arranged along the first path between the first inlet branch and the second outlet branch, Step a) includes step a1) of rapidly increasing the requirement of the required refrigeration load (i.e., booster operating conditions); In this case, the method further includes step h) of reducing the pressure in the expansion reservoir to a minimum pressure value preferably equal to the minimum suction pressure value of the at least one compressor.

[0033] Furthermore, in the case of a solution where the filling / discharging means includes a first shut-off valve arranged along the first inlet branch, step a) includes step a1) of rapidly increasing the requirement of the required refrigeration load (i.e., booster operating conditions). In this case, the method further includes step h) of reducing the pressure in the expansion reservoir to a minimum pressure value preferably equal to the minimum suction pressure value of the at least one compressor. Step h) is before step a1), after step h), and at the same time as step a1), the method includes step r) of keeping the first shut-off valve and the expansion means open.

[0034] Furthermore, step r) continues until the temperature in the adiabatic space reaches a value higher than the evaporation temperature of the refrigerant fluid in the evaporator, preferably until the temperature in the chamber is 10 K (Kelvin) higher than the evaporation temperature, or until the suction pressure of the at least one compressor reaches the maximum operating condition expected for the operating conditions of the at least one compressor and the at least one first shut-off valve and / or the at least one second shut-off valve is closed or is being closed. The storage reservoir and the expansion reservoir of the refrigerant fluid are sized so that the liquid-phase refrigerant fluid does not run out during step r). In the case of a circuit in which the refrigerant fluid circulates under supercritical conditions, step l) of flowing the refrigerant fluid along the heat exchanger is performed simultaneously with, or independently of, step h).

[0035] Furthermore, this method further includes step m) of controlling the opening degree of the on-off valve to allow the refrigerant fluid to pass along the auxiliary line, and step n) of fluidly connecting the closed circuit to the adiabatic space by the auxiliary line, The auxiliary line is provided with an inlet section of the refrigerant fluid arranged along a first path of the closed circuit between the evaporator and the at least one compressor, and an outlet section of the refrigerant fluid, The outlet section is connected to the adiabatic space, and gaseous carbon dioxide flows into the adiabatic space.

[0036] Furthermore, before step m), step o) of detecting the ignition of a fire in the adiabatic space is performed.

Brief Description of the Drawings

[0037]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0038] Some specific embodiments of the present invention will be described by way of non-limiting examples only with reference to the accompanying drawings. Figure 1 is a simplified view showing an environmental simulation chamber 100, and this environmental simulation chamber is provided with a refrigeration facility 1 having a refrigeration device 10 including a closed circuit C through which a refrigerant fluid circulates. This closed circuit C includes, in particular, a compressor 2 having a piston, a cooling means 3 for the refrigerant fluid, an expansion means 4 for the refrigerant fluid, and an evaporator 5. In addition, embodiments in which two or more compressors are arranged in series or stepwise are also included in the protection scope of the present invention.

[0039] The chamber 100 further includes a heat-insulated space 20 into which a sample 21 to be tested is inserted. In this heat-insulated space 20, the evaporator 5 is configured to cooperate with the expansion means 4 to adjust the internal temperature of the heat-insulated space 20. Preferably, the refrigerant fluid used in the refrigeration facility 1 is carbon dioxide.

[0040] With this solution, the GWP value of such an environmental simulation chamber 100 can be reduced to 1, thereby realizing a great advantage in terms of the environment. According to the first embodiment shown in the figure, the closed circuit C further includes an expansion reservoir 30 for carbon dioxide operatively arranged along a first path T located between the evaporator 5 and the compressor 2, and a filling / discharging means 6 for filling the expansion reservoir 30 with the refrigerant fluid from the first path T and discharging the refrigerant fluid from the expansion reservoir 30 to the first path T.

[0041] In particular, due to the presence of this expansion reservoir 30, the compressor 2 operates intermittently in the case of partial load. This expansion reservoir 30 is actually sized to suppress pressure fluctuations at the outlet of the evaporator 5 below a specific pressure, preferably less than 8 bar, according to the partial load opening of the expansion means 4 for temperature control.

[0042] In particular, the chamber 100 is provided with a control unit that switches the compressor 2 on and off based on the internal temperature to be adjusted within the heat-insulated space 20. Therefore, the refrigerant fluid present in the expansion reservoir 30 is filled by the expansion means 5 during the intermittent operation of the compressor 2, and thus is supplied to the closed circuit C or is supplied by the closed circuit C. According to the embodiment described in FIG. 1, the filling / discharging means 6 includes a connecting conduit 61 between the expansion reservoir 30 and the aforementioned first path T located between the evaporator 5 and the compressor 2.

[0043] Due to the presence of the expansion reservoir 30, the compressor 2 can operate intermittently in the case of partial load. Therefore, if the size of the compressor is specially designed to limit the pressure fluctuations of the evaporator 4 and preferably be 8 bar or less, it can operate intermittently up to a maximum of 50% without exceeding the number of operating times per minute permitted by the manufacturer of the compressor 2 according to the partial load opening of the expansion means 4 for temperature control. In a conventional environmental simulation chamber using a conventional refrigerant, due to load limitations, the compressor is always running, and the operation of the refrigeration equipment is carried out through a so-called high-temperature gas bypass conduit or line (see also the following description).

[0044] It should be emphasized here that the "compressor 2 operating at partial load" means that within the heat-insulated space 20, it is not the maximum minimum limit achievable by the refrigeration equipment 10, but rather a use temperature such that, for example, the maximum opening of the expansion means 4 is 50%.

[0045] The expansion means 4 is provided with, for example, a throttle valve. The opening of this throttle valve controls the flow rate of the refrigerant fluid reaching the evaporator 5, enabling the temperature within the heat-insulated space 20 to be finally adjusted. Therefore, the partial load operation means an operation that reaches a temperature higher than the achievable minimum limit. On the one hand, when there is a refrigerant fluid such as carbon dioxide, an expansion reservoir 30 with limited dimensions can be used compared to an expansion reservoir used in a closed circuit in which a known refrigerant such as R449 circulates. In fact, in these systems using R449, the refrigerant has a much higher specific gas volume than when using carbon dioxide, so the expansion reservoir occupies a very large space to guarantee the same operating conditions. For this reason, in known techniques, that is, refrigeration equipment operating with R449, such an expansion reservoir is never used.

[0046] Furthermore, in FIG. 1, along the closed circuit C, a high-temperature gas bypass line 35 with a corresponding valve 36 is also shown, so that in the case of partial load operation of the refrigeration facility 1, the refrigerant fluid can pass through this line 35 without passing through the expansion means 4 and the evaporator 5. In this case, the compressor 2 operates continuously without interruption, and the temperature in the adiabatic space 20 approaches the minimum value. Referring further to FIG. 1, the chamber comprises at least one auxiliary line 50 that directly connects the closed circuit C to the adiabatic space 20. This auxiliary line 50 is provided with an inlet section 51 of the refrigerant fluid arranged along the first path T of the closed circuit C between the evaporator 5 and the compressor 2, an outlet section 52 of the refrigerant fluid, and an on-off valve 55 that permits or prohibits the passage of carbon dioxide along the auxiliary line 50. The outlet section 52 is connected to the adiabatic space 20, and gaseous carbon dioxide flows into the adiabatic space 20. Therefore, with this solution, an actual fire extinguisher constantly connected within the adiabatic space 20 can be formed.

[0047] It should be noted that this auxiliary line 50 can also be indirectly connected to the circuit C, for example, when it is connected to the expansion reservoir 30. In another embodiment not shown here, the chamber 100 may comprise the auxiliary line 50, but the refrigeration equipment 1 may not comprise the expansion reservoir 30, without departing from the protection scope of the present invention.

[0048] The chamber 100 further includes a detection means 80 for detecting the ignition of a fire within the heat-insulated space 20. Specifically, these detection means 80 are operatively connected to the on-off valve 55 and control its opening and closing. In this way, when a fire or the occurrence of a fire is detected within the heat-insulated space 20, the opening degree of the valve 55 is immediately controlled so that a part of the flow rate of the carbon dioxide circulating within the closed circuit C reaches the heat-insulated space 20 to extinguish the fire.

[0049] Furthermore, according to this first embodiment, the refrigeration facility 1 includes a further refrigeration device 10' having a further closed circuit C' through which a further refrigerant fluid circulates. This further closed circuit C' is equipped with a further compressor 2', a further cooling means 3' for the refrigerant fluid, a further expansion means 4' for the refrigerant fluid, and a further evaporator 5' configured to operate in cooperation with the cooling means 3 of the refrigeration device 10 in the closed circuit C of the refrigeration facility 1. This further refrigeration device 10' operates in a temperature range higher than the temperature at which the refrigeration device 10 operates. Furthermore, the refrigerant fluid used in this further refrigeration device 10' is R449.

[0050] In this situation, the refrigerant fluid of the refrigeration device 10, that is, carbon dioxide, operates in a subcritical state, and typically the temperature of the refrigerant fluid is less than 20°C. In this case, the cooling means 3 operates in the same manner as the condenser normally operates.

[0051] In the embodiment of FIG. 2, the only difference from the embodiment of FIG. 1 is that the filling / discharging means 6 includes a bypass circuit C1 arranged along a first path T between the evaporator 5 and the compressor 2. This bypass circuit C1 includes a first inlet branch 41 from the first path T to the expansion reservoir 30 and a second outlet branch 42 from the expansion reservoir 30 to the first path T. The filling / discharging means 6 further includes a first shut-off valve 43 arranged along the first inlet branch 41, a second shut-off valve 44 arranged along the second outlet branch 42, and a third shut-off valve 45 arranged along the first path T between the first inlet branch 41 and the second outlet branch 42. Due to the presence of this bypass circuit C1 and the shut-off valves 43, 44, and 45, the operation of the refrigeration device 10 can be finely controlled according to the temperature control requirements within the adiabatic space 20, which is clear from the operation method of the chamber 100 shown below.

[0052] In the embodiment of FIG. 4, the difference from the embodiment of FIG. 1 is that the filling / discharging means 6 includes a connection conduit 61, and this connection conduit 61 includes the first shut-off valve 43. This control unit is configured to open and close the first shut-off valve 43 to permit or prohibit the inflow / outflow of the refrigerant fluid to the expansion reservoir 30 according to the pressure at the outlet of the evaporator 5.

[0053] In the embodiments shown in FIGS. 1, 2, and 4 described above, the circuit C further includes a storage reservoir 70 for the liquid refrigerant fluid (operatively) arranged in the second path T2 of the closed circuit C between the cooling means 3 and the expansion means 4.

[0054] However, when the refrigerant fluid circulating within the circuit C operates in a supercritical state, there is no additional refrigeration device 10', and the cooling means 3 no longer operates like a condenser. In this embodiment shown in FIG. 3, as additional components to the circuit C shown in FIGS. 1, 2, and 4, there are a second high-pressure compressor 110, a bypass circuit 112 for the cooling means 3, a control valve 113 for operating this bypass circuit 112, an intermediate throttle valve 114 arranged downstream of the storage reservoir 70, and a condensing pressure control valve 115. It is also preferable that the second high-pressure compressor 110 is also of the piston type.

[0055] The intermediate throttle valve 114 is operatively disposed between the storage reservoir 70 and the second high-pressure compressor 110, and like the high-temperature gas bypass line 35 and each valve 36, enables the refrigerant flow to pass through this line without passing through the expansion means 4 and the evaporator 5 in the case of partial load operation of the refrigeration facility 1.

[0056] Furthermore, upstream of the storage reservoir 70 and downstream of the cooling means and the bypass circuit 112, a condensing pressure control valve 115 is disposed, which has the function of enabling throttling of the refrigerant fluid and as a result adjusting the condensing pressure in the storage reservoir 70. The bypass circuit 112 enables bypassing of the cooling means 3, so that the refrigerant fluid is not cooled and is kept at a temperature required for other applications, as will become apparent in the following paragraphs.

[0057] In this embodiment, the closed circuit C further comprises a heat exchanger 200 operatively connected to a further third path T3 of the closed circuit C between the second high-pressure compressor 110, which is downstream of the bypass circuit 112, and the storage reservoir 70. The closed circuit C further comprises means (three-way valve 205, check valve 206) for regulating the flow rate of the refrigerant fluid entering the heat exchanger 200. This heat exchanger 200 is disposed within the adiabatic space 20.

[0058] These regulating means include a three-way valve 205 that deflects the flow of refrigerant gas, i.e., carbon dioxide, coming from the direction of the second high-pressure compressor 110 towards the heat exchanger 200, and a check valve 206 that exits from the heat exchanger 200. The three-way valve 205 is operatively disposed downstream of the bypass circuit 112. When the three-way valve 205 for passing the high-temperature refrigerant fluid through the heat exchanger 200 is actuated, the control valve 113 for actuating the bypass circuit 112 is simultaneously actuated and the cooling means 3 is bypassed. Furthermore, in the embodiment shown in FIG. 3, the heat exchanger 200 and the evaporator 5 are disposed within two separate compartments existing within the adiabatic space 20.

[0059] In the embodiment of the simulation chamber 100 shown in FIG. 3, a bypass circuit C1 of the type shown in FIG. 2, i.e., a bypass circuit C1 arranged along a first path T between the evaporator 5 and the compressor 2, is provided. This bypass circuit C1 includes a first inlet branch 41 and a second outlet branch 42 from the expansion reservoir 30 to the first path T. The filling / discharging means 6 further includes a first shut-off valve 43 arranged along the first inlet branch 41, a second shut-off valve 44 arranged along the second outlet branch 42, and a third shut-off valve 45 arranged between the first inlet branch 41 and the second outlet branch 42 along the first path T. The filling / discharging means 6 is of the type shown in the embodiment of FIG. 1, and these filling / discharging means 6 are of the type shown in FIG. 1, and a conduit 61 is provided. However, embodiments in which these filling / discharging means 6 are of the type provided with a conduit 61 as shown in FIG. 1, or embodiments in which the conduit 61 is of the type provided with a first shut-off valve 43 as shown in FIG. 4, are included within the scope of protection of the present invention in any case.

[0060] The operation modes of the chamber 100 shown in FIGS. 1 to 4 will be described below. In particular, the operation method of the environmental simulation chamber 100 includes the following steps. a) Set the temperature or temperature range to be achieved within the adiabatic space 20. b) Operate the compressor 2 to circulate the refrigerant fluid within the closed circuit C of the refrigeration device 10. c) Adjust the opening and closing of the expansion means 4 to change the flow rate of the refrigerant fluid passing through the evaporator 5 according to the required temperature or temperature range within the adiabatic space 20. Here, the refrigerant fluid circulating within the circuit C is carbon dioxide.

[0061] In particular, this method includes a step d) of at least partially filling the expansion reservoir 30 with the refrigerant fluid so as to compensate for the user's rapid demand for temperature change or to be able to operate the chamber 100 while keeping the compressor 2 in an idle state during a part of its operation. This operation cannot be performed using a refrigerant fluid of known art such as R449. This is because, as described above, the gas of this known art has a specific volume much larger than that of carbon dioxide, so the expansion reservoir is too large to be used.

[0062] Furthermore, when the expansion means 4 operates at part load in step c) and the expansion reservoir 30 is sized to suppress pressure fluctuations at the outlet of the evaporator 5 below a specific pressure, preferably less than 8 bar, this method includes a step e) of intermittently operating the compressor. That is, the compressor 2 is continuously turned off and on when specific thermodynamic conditions of the refrigerant fluid are reached. Therefore, the expansion reservoir 30 is filled and emptied according to the temperature maintained in the adiabatic space 20, the characteristics of the compressor 2, i.e., the minimum operating pressure that the compressor can reach, and the number of start / stop cycles per minute that this compressor can withstand without the risk of failure.

[0063] It should be emphasized that "the expansion means 4 operating at part load" means that in the adiabatic space 20, a use temperature is required such that the maximum opening degree of the expansion means 4, for example, is 50%, rather than the maximum minimum limit achievable by the refrigeration equipment 10. The expansion means 4 is provided with, for example, a throttle valve. By the opening degree of this throttle valve, the flow rate of the refrigerant fluid reaching the evaporator 5 is controlled, and as a result, the temperature in the adiabatic space 20 can be finally adjusted.

[0064] In particular, in the case of the embodiment of FIG. 1, since there is no bypass circuit C1, step e) of the method includes the following steps. Step e1): Reduce the flow rate of the refrigerant fluid passing through the expansion means 4 to a value less than the flow rate value of the refrigerant fluid sucked in by the compressor 2, and reduce the suction pressure of the compressor 2 to the pressure value Ps at which the compressor 2 stops. Step e2): The pressure of the expansion reservoir 30 is determined according to the temperature or temperature range required in the adiabatic space 20, and the fluid flowing out of the evaporator 5 is supplied to the expansion reservoir 30 until the pressure rises to a first pressure value P1 equal to the suction pressure at which the compressor 2 starts to suck the refrigerant fluid from the expansion reservoir 30 in step e1). Step e3): When the pressure in the expansion reservoir 30 exceeds the first pressure value P1, restart the operation of the compressor 2. Steps e1), e2) and e3) can be repeated periodically.

[0065] By turning off the compressor 2 and operating the chamber 100 normally in any case, the energy cost of the chamber 100 can be significantly saved. Also, since the operation of the compressor 2 is significantly less than normal, the wear of this component is also reduced. In practice, when the temperature in the adiabatic space 20 is determined / set / selected to be, for example, -15 °C (almost corresponding to the evaporation temperature of -25 °C of the refrigerant fluid in the evaporator 4), it operates under partial load, that is, under non-extreme conditions, whereby the operating step e1) of the method is implicitly determined. At this point, since the flow rate of the refrigerant fluid passing through the expansion means 4 is less than the flow rate supplied by the compressor 2, the pressure of the refrigerant fluid begins to decrease more and more downstream of the evaporator 4. In this step, the refrigerant fluid coming out of the evaporator 4 reaches the compressor 2 at a constant pressure. In fact, when the test temperature is set in the adiabatic space 20, it should be remembered that the thermodynamic pressure value of the refrigerant fluid of the entire circuit C, particularly the pressure P1 at the inlet (during suction) of the compressor 2, can be known. Therefore, the pressure P1, that is, the first pressure, is uniquely determined by the temperature required in the adiabatic space 20. For example, in the example shown here, when the temperature of the adiabatic space 20 is -15 °C, the first pressure P1 corresponds to 17 bar.

[0066] When the same compressor is selected, the pressure value Ps for stopping the compressor 2 is determined. In this case, for example, the suction pressure for stopping the compressor 2 is 8.5 bar. Therefore, during step e1), when the pressure of the refrigerant fluid upstream of the compressor 2 further drops below the value of the first pressure P1 (as determined above, the pressure is set within the adiabatic space 20 and thus varies according to this value), the compressor 2, at this point, continues to draw refrigerant gas from the expansion reservoir 30, which is at a pressure higher than the gas pressure at the outlet of the evaporator 5, rather than from the outlet of the evaporator 5. The compressor 2 does not stop when the pressure drops below the pressure value Ps for stopping (for example, 8.5 bar). When the pressure of the compressor 2 reaches the stop value Ps, the chamber 100 can continue to operate with excellent adjustment characteristics in the state where the compressor 2 has stopped until the pressure of the expansion reservoir 30 gradually rises to the value of the first pressure P1 by the action of the opening of the expansion means 4, and an obvious energy saving of more than 50% is achieved compared with the conventional chamber.

[0067] However, the expansion reservoir 30 of the refrigerant fluid is sized according to the dimensions of the liquid refrigerant fluid storage reservoir 70 to prevent insufficient supply of the liquid refrigerant fluid to the expansion means 4 when the compressor 2 is turned off. As soon as the pressure in the expansion reservoir 30 exceeds the first pressure P1 (step e3), the compressor 2 restarts. Thereafter, the on / off cycle continues to be repeatedly performed. Obviously, the number of on / off cycles of the compressor 2 cannot exceed the limit value specified by the manufacturer. Otherwise, the compressor 2 may malfunction.

[0068] In the case of the embodiment of FIG. 2, the filling / discharging means is composed of a first shut-off valve 43 arranged along the first branch 41, a second shut-off valve 44 arranged along the second outlet branch 42, and a third shut-off valve 45 arranged along the first path T between the first inlet branch 41 and the second outlet branch 42. In this situation, the pressure P1, Ps, and temperature within the heat-insulated space 20 are maintained at the same values as in the previous example, namely 17 bar, 8.5 bar, and -15 °C. Step e) of this method is Step e1’): a step of reducing the flow rate of the refrigerant fluid passing through the expansion means 4 to a value less than the value sucked in by the compressor 2; Step e2’): when the first suction pressure P1’ of the compressor 2 (corresponding to the same first pressure P1 as in the previous case, i.e., 17 bar) is reached, closing the third shut-off valve 45 and the first shut-off valve 43, and opening or leaving open the second shut-off valve 44; This is determined according to the temperature or temperature range required within the heat-insulated space 20 and is equal to the pressure at which the compressor 2 starts to suck the refrigerant fluid from the expansion reservoir 30 (instead of the expansion means 5) during step e1’). And, Step e3’: stopping the compressor 2 when the pressure value Ps at which the compressor 2 is to be stopped is reached.

[0069] This method further includes Step e4’: a step of reopening the first shut-off valve 43 during step e2’) and / or e3’), The pressure of the refrigerant fluid between the first shut-off valve 43 or the third shut-off valve 45 and the evaporator 5 is Higher than the second suction pressure P2’ of the compressor 2 (e.g., 17.5 bar) and higher than the first suction pressure P1’ of the compressor 2 (i.e., 17 bar). Step e5: closing the first shut-off valve 43 when the pressure of the refrigerant fluid between the first shut-off valve 43 or the third shut-off valve 45 and the evaporator 5 drops to a value lower than the first suction pressure P1’ of the compressor 2 during step e2’) and / or e3’). And, step e6’: includes at least restarting the compressor 2 when the pressure within the expansion reservoir 30 is higher than the first pressure P1’, i.e., 17 bar. Finally, steps e1’) to e6’) are repeatedly performed periodically.

[0070] Furthermore, in the embodiment of FIG. 2, in the steady state, i.e., in the case of full load operation, this method is Step f: When the flow rate sucked by at least the compressor 2 is equal to the flow rate passing through the expansion means 4, or when the environmental simulation chamber 100 is off (therefore, when the compressor 2 is off), keep the second shut-off valve 44 and the third shut-off valve 45 open and keep the first shut-off valve 43 closed. The refrigerant fluid present in the expansion reservoir 30 includes steps that enable compensating for the increase in the specific volume of the refrigerant gas present in the closed circuit C and / or reducing an undesirable pressure increase in the closed circuit C. This operation is performed when step e) of the method described above is not necessary, i.e., when the required load of the refrigerant fluid flow rate is partial and the required temperature in the adiabatic space 20 is not extreme (i.e., less than -20°C), so there is no need to intermittently operate the compressor 2.

[0071] Therefore, in the specific operating mode of the chamber 100 shown in FIG. 2, the filling / discharging means includes a second shut-off valve 44 arranged along a second outlet branch 42 including a first shut-off valve 43 arranged along a first inlet branch 41, and a third shut-off valve 45 arranged along a first path T between the first inlet branch 41 and the second outlet branch 42. Step a) of the method is defined to include step a1) of rapidly increasing the requirements of the required refrigeration load, in a so-called state known to those skilled in the art as a "booster", and this method further includes step h) of reducing the pressure in the expansion reservoir 30 to a minimum pressure value, preferably equal to the minimum suction pressure value Ps of the compressor 2, and then step h) of opening and keeping the first shut-off valve 43 and the expansion means 4 fully open.

[0072] Furthermore, since the further operating mode of the chamber 100 shown in FIG. 4 includes a first shut-off valve 43 arranged along the connecting conduit 61 of the filling / discharging means, step a) of the method includes step a1) of rapidly increasing the required refrigeration load requirement (a state called the so-called "booster"), and this method further Step h: including the step of reducing the pressure in the expansion reservoir 30 to a minimum pressure value preferably equal to the minimum suction pressure value Ps of the compressor 2. This step h) is before step a1), that is, the step of preparing the "booster" step, that is, the step that rapidly requires a temperature drop in the adiabatic space 20. Subsequent to step h), simultaneously with step a1), this method Step r: including the step of keeping the first shut-off valve 43 and the expansion means 4 open.

[0073] According to this "booster" operating mode, step r) is preferably until the temperature in the adiabatic space 20 reaches a value higher than the evaporation temperature of the refrigerant fluid in the evaporator 5, or until this temperature in the adiabatic space 20 is 10 °C higher than the evaporation temperature, or until the suction pressure of the compressor 2 reaches the maximum operating condition defined by the same operating conditions of the compressor 2, and the first shut-off valve 43 (in the case of the embodiment shown in FIG. 4) is closed, or until the first shut-off valve 43 and the second shut-off valve 44 (in the case of the embodiment shown in FIG. 2) are closed. In this case, to perform this step r), it is necessary to determine the sizes of the liquid refrigerant storage reservoir 70 and the expansion reservoir 30 so that the liquid refrigerant fluid does not run out during the booster effect and the liquid refrigerant fluid is not insufficient in the expansion means 4 during the booster effect.

[0074] In the case of the embodiment shown in FIG. 3, and in the case of a booster requirement by the refrigeration device 10, step l) of flowing the refrigerant fluid along the heat exchanger 200 is performed simultaneously with step h) or independently of step h). In any of the embodiments shown in the above specification and FIGS. 1 to 4, this method includes step m) of controlling the opening of the on-off valve 55 for passing a refrigerant fluid, i.e., carbon dioxide, along the auxiliary line 50, and step n) of fluidly connecting the closed circuit C to the heat-insulated space 20 via the auxiliary line 50. This auxiliary line 50 is provided with an inlet section 51 of the refrigerant fluid arranged along the first path T of the closed circuit C between the evaporator 5 and the compressor 2, and an outlet section 52 of the refrigerant fluid. This outlet section 52 is connected to the heat-insulated space 20, and gaseous carbon dioxide flows into this heat-insulated space 20.

[0075] Furthermore, before step m), step o) of detecting the occurrence of a fire in the heat-insulated space 20 is performed as a condition for executing step m). It should be noted that these steps m), n), and o) can be executed independently of steps e) to h), and in combination with steps a) to d) of the method.

Explanation of Reference Numerals

[0076] 1 Refrigeration equipment 2 Compressor 3 Cooling means 4 Expansion means 5 Evaporator 6 Filling / discharging means 10 Refrigeration equipment 10’ Refrigeration equipment 20 Heat-insulated space 21 Sample 30 Expansion reservoir 35 High-temperature gas bypass line 41 First inlet branch 42 Second outlet branch 43 First shut-off valve 44 Second shut-off valve 50 Auxiliary line 51 Inlet section 52 Outlet section 55 On-off valve 61 Connection conduit 80 Detection means 100 Environmental simulation chamber C Closed loop C’ Closed loop T First path T2 Second path

Claims

1. An environmental simulation chamber (100) comprising a refrigeration facility (1) including a refrigeration device (10) having a closed circuit (C) through which a refrigerant fluid circulates, said closed circuit (C) comprising at least one compressor (2), cooling means (3) for said refrigerant fluid, expansion means (4) for said refrigerant fluid, and an evaporator (5), said chamber (100) further comprising a heat-insulated space (20) into which a sample (21) to be tested is inserted, said evaporator (5) being configured to adjust the internal temperature of said heat-insulated space (20), said simulation chamber being characterized in that said refrigerant fluid is carbon dioxide.

2. The chamber (100) according to claim 1, wherein said closed circuit further comprises an expansion reservoir (30) for said carbon dioxide, said expansion reservoir (30) being operatively arranged along a first path (T) between said evaporator (5) and said at least one compressor (2), and further characterized by filling / discharging means (6) enabling filling of said refrigerant fluid from said first path (T) into said expansion reservoir (30) and discharging of said refrigerant fluid from said expansion reservoir (30) into said first path (T).

3. The chamber according to claim 2, wherein said compressor (2) operates intermittently in the case of part load.

4. The chamber according to claim 2, comprising at least one control unit for turning said compressor (2) on or off based on said internal temperature adjusted within said heat-insulated space, said refrigerant fluid present within said expansion reservoir (30) being supplied to and / or filled by said closed circuit (C).

5. The chamber (100) according to claim 2, characterized in that said filling / discharging means (6) comprises a connecting conduit (61).

6. The chamber (100) according to claim 5, wherein said connecting conduit (61) comprises a first shut-off valve (43), and said control unit opens and closes said first shut-off valve (43) to permit or prohibit inflow / outflow of said refrigerant fluid into / from said expansion reservoir (30) according to the pressure at the outlet of said evaporator (5).

7. The chamber (100) according to claim 2, characterized in that the closed circuit (C) further comprises a storage reservoir (70) of the liquid refrigerant fluid, arranged in a second path (T2) of the closed circuit between the cooling means (3) and the expansion means (4).

8. The chamber (100) according to claim 1, comprising at least one auxiliary line (50) connecting the closed circuit (C) directly or indirectly to the adiabatic space (20), wherein the auxiliary line (50) is provided with an inlet section (51) of the refrigerant fluid arranged along the first path (T) of the closed circuit (C) between the evaporator (5) and the at least one compressor (2), an outlet section (52) of the refrigerant fluid, and an on-off valve (55) for permitting or preventing passage of the refrigerant fluid along the auxiliary line, the outlet section (52) being connected to the adiabatic space (20) and configured such that gaseous carbon dioxide flows into the adiabatic space (20).

9. The chamber (100) according to claim 8, further comprising detection means (80) for detecting the occurrence of a fire in the adiabatic space (20), the detection means (80) being operatively connected to the on-off valve (55) and controlling the opening and closing of the on-off valve.

10. The chamber (100) according to claim 1, characterized in that the refrigeration equipment (1) comprises further refrigeration equipment (10') having a further closed circuit (C') through which a further refrigerant fluid circulates, wherein the further closed circuit (C') is equipped with at least one further compressor (2'), further cooling means (3') for the refrigerant fluid, further expansion means (4') for the refrigerant fluid, and a further evaporator (5') configured to operate in cooperation with the cooling means (3) of the refrigeration equipment (10), the further refrigeration equipment (10') being operative in a temperature range higher than the temperature range in which the refrigeration equipment (10) operates.

11. The chamber (100) according to claim 7, wherein the closed circuit (C) further comprises at least one second high-pressure compressor (110) arranged in series with the at least one compressor (2), a bypass circuit (112) for the cooling means (3) having at least one control valve (113) for operating the bypass circuit (112), an intermediate throttle valve (114) downstream of the storage reservoir (70), and a condensation pressure control valve (115). The chamber is characterized in that the intermediate throttle valve (114) is operatively arranged between the storage reservoir (70) and the second compressor (110).

12. The chamber (100) according to claim 11, wherein the closed circuit further comprises a heat exchanger (200) operatively connected to a third path (T3) of the closed circuit (C) between the at least one second compressor (110) downstream of the bypass circuit (112). The storage reservoir of the refrigerant fluid (70) and means (205, 206) for regulating the flow rate of the refrigerant fluid entering the heat exchanger are provided. The heat exchanger (200) is arranged within the adiabatic space (20). The chamber is characterized in that the heat exchanger (200) and the evaporator (5) are arranged in two separate compartments existing within the adiabatic space (20).

13. A method of operating an environmental simulation chamber according to claim 1, the method comprising the following steps. a) Setting at least one temperature or at least one temperature range obtained within the adiabatic space; b) Operating the at least one compressor (2) to circulate the refrigerant fluid within the closed circuit (C) of the refrigeration apparatus (10); c) Controlling the opening and closing of the expansion means (4) so as to change the flow rate of the refrigerant fluid passing through the evaporator (5) according to the at least one temperature or the temperature range required within the adiabatic space; wherein the refrigerant fluid is carbon dioxide.

14. A method of operating an environmental simulation chamber according to claim 13, characterized by comprising step d) of at least partially filling the expansion reservoir (30) with the refrigerant fluid.

15. The method according to claim 14, wherein in step c), the expansion means operates at part load, and when the at least one expansion reservoir (30) is of a size capable of accommodating fluctuations in the pressure at the outlet of the evaporator, the method includes a step e) of intermittently operating the compressor. A method of operating an environmental simulation chamber, characterized in that it comprises this.

16. The method according to claim 15, wherein step e) comprises step e1) of reducing the flow rate of the refrigerant fluid passing through the expansion means (4) to a value less than the flow rate sucked in by the at least one compressor (2), and reducing the suction pressure of the at least one compressor to a pressure value (Ps) at which the at least one compressor is stopped; step e2) of supplying the fluid flowing out of the evaporator to the expansion reservoir (30) until the pressure of the expansion reservoir (30) is determined according to the temperature or temperature range required in the adiabatic space and the at least one compressor (2) in step e1) rises to a first pressure value (P1) equal to the suction pressure at which it starts to suck refrigerant fluid from the expansion reservoir (30); step e3) of restarting the operation of the compressor when the first pressure value (P1) in the reservoir is exceeded, and steps e1), e2) and e3) are periodically repeated. A method of operating an environmental simulation chamber, characterized in that it comprises this.

17. The method according to claim 13, wherein the chamber is provided with filling / discharging means (6) enabling filling of the refrigerant fluid from the first path (T) into the expansion reservoir (30) and discharging of the refrigerant fluid from the expansion reservoir (30) into the first path (T), the filling / discharging means (6) includes a first shut-off valve (43) arranged along the connecting conduit (61), step a) includes step a1) of rapidly increasing the requirement of the required refrigeration load, the method further includes a step h) of reducing the pressure in the expansion reservoir (30) to a minimum pressure value, preferably equal to the minimum suction pressure value (Ps) of the at least one compressor (2), step h) is before step a1), and is carried out simultaneously with step a1) following step h), The method further includes step r) of leaving the first shut-off valve (43) and the expansion means (4) open, and is a method for operating an environmental simulation chamber characterized thereby.

18. The method according to claim 17, wherein step r) is continued until the temperature in the adiabatic space reaches a value higher than the evaporation temperature of the refrigerant fluid in the evaporator, and the temperature in the chamber is higher than 10 K with respect to the evaporation temperature, or when the suction pressure of the at least one compressor (2) reaches the maximum operating condition expected for the operating conditions of the at least one compressor (2), the first shut-off valve (43) is closed, the refrigerant fluid storage reservoir (70) and the expansion reservoir (30) are sized so that the liquid-phase refrigerant fluid does not run out during step r), and is a method for operating an environmental simulation chamber characterized thereby.

19. The method according to claim 13, at least in the simulation chamber according to claim 12, the refrigerant fluid circulates in the closed circuit under supercritical conditions, and step l) of flowing the refrigerant fluid along the heat exchanger (200) is performed simultaneously with or independently of step h), and is a method for operating an environmental simulation chamber characterized thereby.

20. The method according to claim 13, including step m) of controlling the opening degree of the on-off valve (55) to allow the refrigerant fluid to pass along the auxiliary line, and step n) of fluidly connecting the closed circuit (C) to the adiabatic space (20) by the auxiliary line (50), the auxiliary line (50) is provided with an inlet section (51) of the refrigerant fluid arranged along the first path (T) of the closed circuit (C) between the evaporator (5) and the at least one compressor (2), and an outlet section (52) of the refrigerant fluid connected to the adiabatic space (20) and allowing carbon dioxide in gaseous form to flow into the adiabatic space (20), and is a method for operating an environmental simulation chamber characterized thereby.

21. The method according to claim 20, characterized in that, before step m), step o) of detecting the ignition of a fire in the adiabatic space (20) is performed, and is a method for operating an environmental simulation chamber characterized thereby.

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