阅读说明：本技术 制冷剂 (Refrigerant ) 是由 克里斯蒂安·哈克 大卫·布劳费尔德 穆拉特·艾丁 于 2021-05-14 设计创作，主要内容包括：本发明涉及一种用于冷却装置(10)的制冷剂、一种用于调节空气的测试室以及制冷剂用于调节测试室的测试空间中的空气的用途。所述冷却装置(10)包括冷却回路(11),所述冷却回路(11)包括至少一个热交换器(12),所述冷却剂在所述热交换器中经历相变,所述制冷剂是包括一定分数的二氧化碳(CO-(2))、一定分数的1,1-二氟乙烯和一定分数的至少一种其他组分的制冷剂混合物,其中所述制冷剂混合物中二氧化碳的分数为45至90摩尔％,1,1-二氟乙烯的分数为5至40摩尔％。(The invention relates to a refrigerant for a cooling device (10), to a test chamber for conditioning air and to the use of a refrigerant for conditioning air in a test space of a test chamber. The cooling device (10) comprises a cooling circuit (11), the cooling circuit (11) comprising at least oneA heat exchanger (12) in which the coolant undergoes a phase change, the refrigerant being a refrigerant comprising a fraction of carbon dioxide (CO) 2 ) A refrigerant mixture of a fraction of 1, 1-difluoroethylene and a fraction of at least one other component, wherein the fraction of carbon dioxide in the refrigerant mixture is from 45 to 90 mole percent and the fraction of 1, 1-difluoroethylene is from 5 to 40 mole percent.)

1. Refrigerant for a cooling device (10, 23, 30, 36, 39, 44, 49, 55, 60), the cooling device (10, 23, 30, 36, 39, 44, 49, 55, 60) having a cooling circuit (11, 24, 42, 50), the cooling circuit (11, 24, 42, 50) comprising at least one heat exchanger (12, 25, 48, 54), the refrigerant undergoing a phase change in the at least one heat exchanger (12, 25, 48, 54), the refrigerant being a refrigerant comprising a fraction of carbon dioxide (CO)₂) A fraction of 1, 1-difluoroethylene (C)₂H₂F₂) And a fraction of at least one other component,

it is characterized in that the preparation method is characterized in that,

the fraction of carbon dioxide in the refrigerant mixture is from 45 to 90 mole percent and the fraction of 1, 1-difluoroethylene is from 5 to 40 mole percent.

2. The refrigerant as set forth in claim 1,

it is characterized in that the preparation method is characterized in that,

the fraction of carbon dioxide in the refrigerant mixture is from 50 to 80 mol%, preferably from 55 to 75 mol%, and the fraction of 1, 1-difluoroethylene is from 10 to 35 mol%, preferably from 15 to 30 mol%.

3. The refrigerant according to claim 1 or 2,

it is characterized in that the preparation method is characterized in that,

the other component is hexafluoroethane (C)₂F₆) Difluoromethane (CH)₂F₂) Pentafluoroethane (C)₂HF₅) And/or trifluoromethane (CHF)₃)。

4. The refrigerant according to claim 1 or 2,

it is characterized in that the preparation method is characterized in that,

the fraction of carbon dioxide in the refrigerant mixture is from 45 to 75 mol%, preferably from 50 to 70 mol%, particularly preferably from 55 to 65 mol%.

5. The refrigerant as set forth in claim 4,

it is characterized in that the preparation method is characterized in that,

the fraction of 1, 1-difluoroethylene is from 5 to 40 mol%, preferably from 10 to 35 mol%, particularly preferably from 20 to 30 mol%.

6. The refrigerant according to claim 4 or 5,

it is characterized in that the preparation method is characterized in that,

the other component is trifluoromethane (CHF)₃) Or hexafluoroethane (C)₂F₆) The fraction thereof is 1 to 30 mol%, preferably 5 to 25 mol%, particularly preferably 10 to 20 mol%.

7. The refrigerant as set forth in claim 4,

it is characterized in that the preparation method is characterized in that,

the fraction of 1, 1-difluoroethylene is from 1 to 30 mol%, preferably from 5 to 25 mol%, particularly preferably from 10 to 20 mol%, difluoromethane (CH)₂F₂) And pentafluoroethane (C)₂HF₅) Is a further component, and the fraction of difluoromethane is from 1 to 30 mol%, preferably from 3 to 23 mol%, particularly preferably from 8 to 18 mol%, and the fraction of pentafluoroethane is from 1 to 30 mol%, preferably from 1 to 20 mol%, particularly preferably from 2 to 12 mol%.

8. The refrigerant as set forth in claim 7,

it is characterized in that the preparation method is characterized in that,

the other component is trifluoromethane (CHF)₃) Or hexafluoroethane (C)₂F₆) The fraction thereof is 1 to 30 mol%, preferably 1 to 20 mol%, particularly preferably 1 to 10 mol%.

9. The refrigerant according to claim 5 or 6,

it is characterized in that the preparation method is characterized in that,

trifluoromethane (CHF)₃) The fraction (b) is from 1 to 30 mol%, preferably from 5 to 25 mol%, particularly preferably from 10 to 20 mol%.

10. The refrigerant according to claim 1 or 2,

it is characterized in that the preparation method is characterized in that,

the fraction of carbon dioxide in the refrigerant mixture is from 55 to 85 mol%, preferably from 60 to 80 mol%, particularly preferably from 65 to 75 mol%, and the fraction of 1, 1-difluoroethylene is from 5 to 35 mol%, preferably from 10 to 30 mol%, particularly preferably from 15 to 25 mol%.

11. The refrigerant as set forth in claim 10,

it is characterized in that the preparation method is characterized in that,

difluoromethane (CH)₂F₂) And pentafluoroethane (C)₂HF₅) Is a further component, and the fraction of difluoromethane is from 1 to 30 mol%, preferably from 1 to 20 mol%, particularly preferably from 5 to 15 mol%, and the fraction of pentafluoroethane is from 1 to 30 mol%, preferably from 1 to 20 mol%, particularly preferably from 1 to 10 mol%.

12. The refrigerant according to claim 10 or 11,

it is characterized in that the preparation method is characterized in that,

the other component is trifluoromethane (CHF)₃) Or hexafluoroethane (C)₂F₆) The fraction thereof is 1 to 30 mol%, preferably 1 to 20 mol%, particularly preferably 5 to 15 mol%.

13. The refrigerant according to claim 1 or 2,

it is characterized in that the preparation method is characterized in that,

the fraction of carbon dioxide in the refrigerant mixture is from 55 to 90 mol%, preferably from 65 to 80 mol%, particularly preferably from 70 to 74 mol%, and the fraction of 1, 1-difluoroethylene is from 5 to 35 mol%, preferably from 10 to 20 mol%, particularly preferably from 14 to 18 mol%.

14. The refrigerant as set forth in claim 13,

it is characterized in that the preparation method is characterized in that,

trifluoromethane (CHF)₃) And pentafluoroethane (C)₂HF₅) Is a further component, and the fraction of trifluoromethane is from 1 to 30 mol%, preferably from 1 to 20 mol%, particularly preferably from 5 to 10 mol%, and the fraction of pentafluoroethane is from 1 to 30 mol%, preferably from 1 to 20 mol%, particularly preferably from 2 to 6 mol%.

15. The refrigerant according to any one of the preceding claims,

it is characterized in that the preparation method is characterized in that,

the refrigerant mixture includes up to three components or four or more components.

16. The refrigerant according to any one of claims 1 to 14,

it is characterized in that the preparation method is characterized in that,

the refrigerant mixture contains fluoromethane (CH)₃F) Ethane (C)₂H₆) 2,3,3, 3-tetrafluoropropene (C)₃H₂F₄) Ethylene (C)₂H₄) Fluoroethylene (C)₂H₃F) Acetylene (C)₂H₂) Propane (C)₃H₈) Propylene (C)₃H₆) And/or fluoroethane (CH)₂FCH₃) As the other components, the amounts thereof are each up to 30 mol%, preferably each up to 20 mol%, particularly preferably each up to 10 mol%.

17. The refrigerant according to any one of the preceding claims,

it is characterized in that the preparation method is characterized in that,

the refrigerant has a temperature glide of ≦ 5K or > 5K.

18. The refrigerant according to any one of the preceding claims,

it is characterized in that the preparation method is characterized in that,

the refrigerant has the characteristics of having<Relative CO of 2500₂The equivalent weight and/or the refrigerant is non-flammable.

19. A test chamber for conditioning air, the test chamber comprising: a test space for containing a test material and which can be sealed with respect to the environment and thermally insulated; and a temperature control device for controlling the temperature of the test space, by means of which a temperature in the temperature range of-60 ℃ to +180 ℃, preferably-70 ℃ to +180 ℃, particularly preferably-80 ℃ to +180 ℃ can be established in the test space, having a cooling device (10, 23, 30, 36, 39, 44, 49, 55, 60), the cooling device (10, 23, 30, 36, 39, 44, 49, 55, 60) comprising a cooling circuit (11, 24, 42, 50), the cooling circuit (11, 24, 42, 50) having a refrigerant according to any of the preceding claims, a heat exchanger (12, 25, 48, 54), a compressor (13, 26, 51), a condenser (14, 27, 41, 52) and an expansion element (15, 28, 50), 53).

20. Use of a refrigerant consisting of a refrigerant mixture comprising a fraction of 45 to 90 mol% carbon dioxide (CO) for conditioning air in a test space of a test chamber₂) 5 to 40 mol% of 1, 1-difluoroethylene (C)₂H₂F₂) And a fraction of at least one other component, the test space being intended to contain a test material and being sealed and thermally insulated from the environment, the cooling device (10, 23, 30, 36, 39, 44, 49, 55, 60) of the temperature control device of the test chamber comprising a cooling circuit (11, 24, 42, 50), the cooling circuit (11, 24, 42, 50) having the refrigerant, a heat exchanger (12, 25, 48, 54), a compressor (13, 26, 51), a condenser (14, 27, 41, 52) and an expansion element (15, 28, 53) for establishing-60 ℃ to +180 ℃, preferably-70 ℃ to +180 ℃, within the test spaceTemperatures in the temperature range from-80 ℃ to +180 ℃ are particularly preferred.

21. The use according to claim 20, wherein,

it is characterized in that the preparation method is characterized in that,

-cooling the refrigerant of the high pressure side by means of an internal heat exchanger (19, 29, 47) of the cooling circuit (11, 24, 42) connected to the high pressure side (17) of the cooling circuit upstream of the expansion element (15, 28) and downstream of the condenser (14, 27, 41) and to the low pressure side (18) of the cooling circuit upstream of the compressor (13, 26) and downstream of the heat exchanger (12, 25, 48), the cooling of the refrigerant of the high pressure side being used to reduce the evaporation temperature at the expansion element by means of the internal heat exchanger.

22. The use according to claim 20 or 21,

it is characterized in that the preparation method is characterized in that,

only a portion of the refrigerant is evaporated in the heat exchanger (12, 25, 48, 54).

23. The use according to any one of claims 20 to 22,

it is characterized in that the preparation method is characterized in that,

the refrigerant is metered and evaporated in the heat exchanger (12, 25, 48, 54) in a timed manner during a time interval by means of the expansion element (15, 28, 53).

Technical Field

The invention relates to a refrigerant for a cooling device and to a test chamber for conditioning air having the refrigerant and to the use of the refrigerant for conditioning air in a test space of a test chamber.

Background

Such refrigerants are typically circulated within a closed cooling circuit of a chiller and undergo a series of different material state changes. The refrigerants should have the property that they can be used in the cooling circuit within a predetermined temperature difference. Single-component refrigerants and refrigerant mixtures of at least two components are known from the prior art. Before the priority date, the refrigerants were classified according to the latest version of section 6 of the german industrial standard DIN 8960.

As stipulated by law, refrigerants do not contribute significantly to the depletion of ozone in the atmosphere or to global warming. This means that essentially no fluorinated or chlorinated substances are used as refrigerants, which is why natural refrigerants or gases are optional. Furthermore, the refrigerant should be non-flammable so as not to complicate the filling, transport and operation of the cooling circuit due to any safety regulations that must be observed. Moreover, if flammable refrigerants are used, the production of the cooling circuit becomes more expensive due to the constructional measures required in this case. Flammability refers to the property of a refrigerant to react with ambient oxygen by releasing heat. The refrigerant is flammable, especially if it was classified before the priority date in the latest versions of the european standard EN2 fire class C and DIN 378 classes A2, A2L and A3.

In addition, the refrigerant should have a relatively low CO₂Equivalent weight; that is, the relative Global Warming Potential (GWP) should be as low as possible to avoid collateral damage to the environment in the event that the refrigerant is released. GWP indicates how much greenhouse gas of defined quality contributes to global warming, carbon dioxide as a reference value. This value describes the average warming effect over a certain period of time, set here for 100 years for purposes of comparability. With respect to relative CO₂The definition of equivalent weight or GWP, prior to the priority date, may be referenced to the inter-government climate change group (IPCC), assessment report, appendix 8.a, latest version of table 8. a.1.

Refrigerants with low GWP (such as <2500) have the following disadvantages: these refrigerants tend to have significantly lower cold capacities over the temperature range associated with the cooling circuit than refrigerants having relatively higher GWPs. Lower GWPs can be achieved using refrigerant mixtures with relatively high carbon dioxide fractions; however, due to the different substances being mixed, these refrigerant mixtures may have azeotropic properties, which is undesirable in many cooling circuits.

In azeotropic refrigerant mixtures, a phase change occurs in a temperature range known as temperature glide. Temperature glide refers to the difference between boiling temperature and dew point temperature at constant pressure. However, azeotropic refrigerant mixtures typically contain a high fraction of non-flammable components, which are characterized by a relatively high GWP. At first glance, carbon dioxide appears to be a suitable component of the refrigerant mixture because it is non-flammable and has a low GWP. However, in a mixture of carbon dioxide with another component, it is necessary that the fraction of carbon dioxide must be relatively large if the other component is flammable. However, this is disadvantageous because carbon dioxide has a freezing or freezing point of-56.6 ℃, which hardly allows achieving temperatures of-60 ℃ at high carbon dioxide concentrations.

Furthermore, the use of the refrigerant should be as simple as possible, i.e. without extensive technical modifications of the cooling device. In particular, for refrigerants having a temperature glide of more than 3K, the expansion element and the heat exchanger or evaporator of the cooling circuit in question must be adjusted to the evaporation temperature of the refrigerant and a corresponding control must be provided. Furthermore, it is necessary to distinguish between refrigerants designed for static operation of a cooling device (i.e. a cooling device where the temperature at the heat exchanger or evaporator is substantially constant over a longer period of time) and refrigerants designed for dynamic cooling devices, which exhibit relatively rapid temperature changes at the heat exchanger. This type of dynamic cooling device is integrated in, for example, a test chamber, which means that the refrigerant used must be used over a large temperature range.

Test chambers are commonly used for testing physical and/or chemical properties of objects, in particular devices. For example, temperature test chambers or climate test chambers are known, wherein temperatures in the range of-60 ℃ to +180 ℃ can be set. In a climatic test chamber, the desired climatic conditions can additionally be set and the device or the test material is then exposed to the climatic conditions for a defined period of time. Test rooms of this type are usually or sometimes implemented as mobile devices which are connected to the building only via the required supply lines and which comprise all the modules required for controlling the temperature and climate. The temperature of the test space holding the material to be tested is usually controlled in a circulating air pipe within the test space. The circulating air pipe forms an air processing space in the test space, and a heat exchanger for heating or cooling air flowing through the circulating air pipe and the test space is disposed in the air processing space. A fan or ventilator draws air located in the test space and directs it to a corresponding heat exchanger in the circulating air duct. In this way, the test material can be temperature controlled or exposed to a defined temperature change. During the test interval, the temperature may be repeatedly varied between the highest and lowest temperatures of the test chamber. A test chamber of this type is known, for example, from EP 0344397 a 2.

The refrigerant circulating in the cooling circuit must have such properties that it can be used in the cooling circuit within the aforementioned temperature difference. In particular, the dew point temperature of the refrigerant cannot be higher than the lowest temperature of the temperature range of the cooling circuit to be realized, since otherwise the lowest temperature would not be realized when the refrigerant is evaporated in the heat exchanger for cooling the test space. The dew point temperature of the azeotropic refrigerant is reached in the heat exchanger immediately after the expansion element. The straight cooling circuit for the test space requires a very high temporal temperature stability of ≦ 0.5K to precisely control the temperature of the test chamber, which cannot be achieved at all or only to a limited extent with azeotropic refrigerants. High temperature stability cannot be achieved in this case because due to the temperature difference, the dew point temperature or dew point of the azeotropic refrigerant may move locally in the heat exchanger area in the test space as a function of the temperature in the test space. Thus, the temperature may change during evaporation, and different temperatures may occur at the heat exchanger. When using azeotropic refrigerants, it is difficult to maintain a space temperature profile of ≦ 2K, since the described temperature stratification at the heat exchanger may also occur in the test space.

Refrigerants R23 and R469A are used in particular as cryogenic refrigerants for test chambers having temperatures up to-70 ℃. However, R23 has a GWP of 14,800, which excludes this refrigerant from use in the future. Although R469A does have a significantly lower GWP of 1347, it must be adapted to the cooling circuit of the test chamber in order to be able to compensate for the lower performance compared to R23 and the relatively higher temperature slip compared to R23.

Furthermore, cooling devices are known in which an azeotropic refrigerant mixture is continuously evaporated. This means that the components of the refrigerant are successively evaporated by the expansion element. This type of cooling device is also referred to as a mixed fluid cascade system and is suitable for achieving a substantially static low temperature.

WO 2017/157864 a1 discloses refrigerants comprising carbon dioxide and pentafluoroethane, as well as other components. For example, refrigerants having carbon dioxide in the range of 30 to 70 wt% and pentafluoroethane in the range of 20 to 80 wt% are indicated. Difluoromethane as a mixing partner is also disclosed.

DE 4116274 a1 relates to refrigerants containing carbon dioxide and difluoromethane as a mixed formulation. For example, a fraction of 5 to 50 wt% of carbon dioxide and a fraction of 25 to 70 wt% of difluoromethane are indicated.

Disclosure of Invention

It is therefore an object of the present invention to propose a refrigerant for a cooling device, a test chamber with a refrigerant and the use of a refrigerant, which remedy the disadvantages known from the prior art.

This object is achieved by a refrigerant having the following features, a test chamber having the following features and the use of a refrigerant having the following features.

In one aspect, a refrigerant for a cooling device is provided. The cooling device has a cooling circuit comprising at least one heat exchanger in which the refrigerant is presentUndergoing a phase change, the refrigerant being a refrigerant comprising a fraction of carbon dioxide (CO)₂) A fraction of 1, 1-difluoroethylene (C)₂H₂F₂) And a fraction of at least one other component. The fraction of carbon dioxide in the refrigerant mixture is from 45 to 90 mole percent and the fraction of 1, 1-difluoroethylene is from 5 to 40 mole percent.

In another aspect, a test chamber for conditioning air is provided. The test chamber includes: a test space for containing a test material and which can be sealed with respect to the environment and thermally insulated; and a temperature control device for controlling the temperature of the test space, by means of which a temperature in the temperature range of-60 ℃ to +180 ℃, preferably-70 ℃ to +180 ℃, particularly preferably-80 ℃ to +180 ℃ can be established in the test space, having a cooling device comprising a cooling circuit with a refrigerant according to any one of the preceding claims, a heat exchanger, a compressor, a condenser and an expansion element.

In yet another aspect, there is provided the use of a refrigerant consisting of a refrigerant mixture comprising a fraction of 45 to 90 mole% carbon dioxide (CO) for conditioning air in a test space of a test chamber₂) 5 to 40 mol% of 1, 1-difluoroethylene (C)₂H₂F₂) And a fraction of at least one other component, the test space being intended to contain a test material and being sealed and thermally insulated from the environment, the cooling device of the temperature control device of the test chamber comprising a cooling circuit with the refrigerant, the heat exchanger, the compressor, the condenser and the expansion element for establishing a temperature in the temperature range-60 ℃ to +180 ℃, preferably-70 ℃ to +180 ℃, particularly preferably-80 ℃ to +180 ℃ within the test space.

In some embodiments, in the refrigerant for a cooling device according to the present invention, the cooling device has a cooling circuit having at least one heat exchanger in which the refrigerant undergoes a phase change, the refrigerant being a refrigerant mixture consisting of a fraction of carbon dioxide, a fraction of 1, 1-difluoroethylene and a fraction of at least one other component, wherein the fraction of carbon dioxide in the refrigerant mixture is from 45 to 90 mol%, and the fraction of 1, 1-difluoroethylene is from 5 to 40 mol%.

The terms fraction and mol% refer to mass fraction. The range expressed in mol% may also be interpreted as a range expressed in mass%.

Before the priority date of the present application, as refrigerant or component carbon dioxide (CO) according to the latest version of German Industrial Standard DIN 8960₂) Also named R744, pentafluoroethane (C)₂HF₅) Is named as R125, difluoromethane (CH)₂F₂) Is named as R32, 2,3,3, 3-tetrafluoropropene (C)₃H₂F₄) Is named as R1234yf, fluoromethane (CH)₃F) Is named as R41, trifluoromethane (CHF)₃) Under the name R23, 1, 1-difluoroethylene (C)₂H₂F₂) Is named as R1132a, ethylene (C)₂H₄) Under the name R1150, fluoroethylene (C)₂H₃F) Is named as R1141, propane (C)₃H₈) Is named as R290, propylene (C)₃H₆) Is named as R1270, hexafluoroethane (C)₂F₆) Is named R116 and fluoroethane (CH)₂FCH₃) Is named as R161.

The present invention provides refrigerant mixtures of carbon dioxide and one or more fluorinated refrigerants that have low GWP and are non-flammable or flammable only to a limited extent. The fraction of carbon dioxide must be as low as possible, since otherwise the freezing point of the refrigerant mixture will increase with increasing carbon dioxide fraction. However, a lower carbon dioxide fraction reduces the GWP reducing effect of carbon dioxide. This is why partially fluorinated refrigerants have a significantly higher GWP than carbon dioxide, while also having an improved flame retardant effect.

It has surprisingly been found that sufficiently low GWPs can be achieved using refrigerant mixtures containing a fraction of 45 to 85 mole% carbon dioxide, a fraction of 5 to 40 mole% 1, 1-difluoroethylene and at least one other component. In addition, the negative properties of 1, 1-difluoroethylene and carbon dioxide can be reduced by adding a third component of the refrigerant mixture. In particular, the use of 1, 1-difluoroethylene in a specified mixing ratio with carbon dioxide allows the refrigerant to be flexibly adapted to different applications in the test chamber by mixing it with at least one other component. For example, to accommodate existing cooling circuits, to achieve a particular cryogenic temperature or to maintain a desired temperature stability.

Advantageously, the fraction of carbon dioxide in the refrigerant mixture is from 50 to 80 mol%, preferably from 55 to 75 mol%, and the fraction of 1, 1-difluoroethylene is from 10 to 35 mol%, preferably from 15 to 30 mol%. In this case the GWP of the refrigerant mixture can be reduced even further.

The other component may be hexafluoroethane, difluoromethane, pentafluoroethane and/or trifluoromethane. It has been found that these components are particularly advantageous for adapting the refrigerant to different requirements.

The fraction of carbon dioxide in the refrigerant mixture may be 45 to 75 mol%, preferably 50 to 70 mol%, particularly preferably 55 to 65 mol%.

Advantageously, the fraction of 1, 1-difluoroethylene can be from 5 to 40 mol%, preferably from 10 to 35 mol%, particularly preferably from 20 to 30 mol%.

The other component may be trifluoromethane or hexafluoroethane, wherein the fraction thereof may be from 1 to 30 mol%, preferably from 5 to 25 mol%, in particular from 10 to 20 mol%.

Particularly preferably, the fraction of 1, 1-difluoroethylene may be from 1 to 30 mol%, preferably from 5 to 25 mol%, in particular from 10 to 20 mol%, wherein difluoromethane and pentafluoroethane may be other components, and the fraction of difluoromethane may be from 1 to 30 mol%, preferably from 3 to 23 mol%, particularly preferably from 8 to 18 mol%, and the fraction of pentafluoroethane may be from 1 to 30 mol%, preferably from 1 to 20 mol%, particularly preferably from 2 to 12 mol%. It has been found that the flame retardant effect of pentafluoroethane is relatively large compared to carbon dioxide. Meanwhile, difluoromethane and trifluoromethane or hexafluoroethane and carbon dioxide exhibit lower freezing temperatures than pentafluoroethane. Although pentafluoroethane does not lower the freezing point of refrigerant mixtures as difluoromethane does with trifluoromethane or hexafluoroethane, it has a greater flame retardant effect than carbon dioxide, which is advantageous. One disadvantage is that pentafluoroethane has a GWP of 3150 and therefore may be higher than the GWP of the other components of the refrigerant mixture.

The other component may be trifluoromethane or hexafluoroethane, wherein the fraction thereof may be 1 to 30 mol%, preferably 1 to 20 mol%, particularly preferably 1 to 10 mol%.

Advantageously, the fraction of trifluoromethane may be from 1 to 30 mol%, preferably from 5 to 25 mol%, particularly preferably from 10 to 20 mol%.

According to another embodiment, the fraction of carbon dioxide in the refrigerant mixture may be from 55 to 85 mol%, preferably from 60 to 80 mol%, particularly preferably from 65 to 75 mol%, and the fraction of 1, 1-difluoroethylene may be from 5 to 35 mol%, preferably from 10 to 30 mol%, particularly preferably from 15 to 25 mol%.

In this case, difluoromethane and pentafluoroethane may be other components, and the fraction of difluoromethane may be 1 to 30 mol%, preferably 1 to 20 mol%, particularly preferably 5 to 15 mol%, and the fraction of pentafluoroethane may be 1 to 30 mol%, preferably 1 to 20 mol%, particularly 1 to 10 mol%.

The other component may be trifluoromethane or hexafluoroethane, wherein the fraction thereof may be from 1 to 30 mol%, preferably from 1 to 20 mol%, in particular from 5 to 15 mol%.

According to another embodiment, the fraction of carbon dioxide in the refrigerant mixture may be from 55 to 90 mol%, preferably from 65 to 80 mol%, particularly preferably from 70 to 74 mol%, and the fraction of 1, 1-difluoroethylene may be from 5 to 35 mol%, preferably from 10 to 20 mol%, particularly preferably from 14 to 18 mol%.

In this case, trifluoromethane and pentafluoroethane may be other components, and the fraction of trifluoromethane may be 1 to 30 mol%, preferably 1 to 20 mol%, particularly preferably 5 to 10 mol%, and the fraction of pentafluoroethane may be 1 to 30 mol%, preferably 1 to 20 mol%, particularly preferably 2 to 6 mol%.

The refrigerant mixture may include up to three components or four or more components. Thus, the refrigerant mixture may be a ternary refrigerant mixture or a five-membered refrigerant mixture. It may be provided that the refrigerant mixture does not contain any further components beyond this.

The refrigerant may contain fluoromethane, ethane, 2,3,3, 3-tetrafluoropropene, ethylene, fluoroethylene, acetylene, propane, propylene and/or fluoroethane as additional components in amounts of up to 30 mol% each, preferably up to 20 mol% each, particularly preferably up to 10 mol% each. Even with this relatively low fraction of the one or more components, improved performance of the refrigerant may be achieved.

In the following table, examples of the refrigerant according to the above-described embodiment are shown.

Watch (A)

In other embodiments, the refrigerant may have a temperature glide of ≦ 5K or < 5K. The temperature glide is related to an evaporation pressure of 1 bar and may be between 0.5K and 25K. Particularly low temperature glide of ≦ 5K may be achieved using refrigerants 1, 3, 5, and 7 shown in the table. Temperature glide of >5K can be achieved using refrigerants 2, 4, 6 and 8 shown in the table. Using refrigerant 9, a temperature glide of >5K can be achieved in examples with R744 using 70-74 mole%, and a temperature glide of <5K can be achieved in other examples with R744 using 65-80 mole% and 55-90 mole%. For refrigerants with temperature glide >5K, an internal heat exchanger or recuperator may be needed for safe operation and to achieve temperatures in the cooling circuit of < -55 ℃. In contrast, for refrigerants with a temperature glide of ≦ 5K, no internal heat exchanger is needed to achieve high cold capacity. However, due to the low density of the respective refrigerant at low evaporation temperatures, the piping and the compressor of the cooling circuit have to be changed. With these refrigerants, it is only possible to achieve relatively high temperatures compared to refrigerants with a temperature glide of > 5K.

The refrigerant may have a relative CO of 2500 for 100 years₂The equivalent weight, and/or the refrigerant may be flammable. Therefore, the refrigerant is less harmful to the environment.

Furthermore, the refrigerant can be particularly safe, which makes it possible in particular for the cooling circuit and the test chamber to be designed more cost-effectively, since special safety measures in respect of the flammability of the refrigerant do not have to be observed.

In this case, the refrigerant may not be classified at least in fire class C and/or refrigerant safety group a 1. Furthermore, the transport and transport of the cooling circuit is easier, since the cooling circuit can be filled with refrigerant before transport, irrespective of the mode of transport. If flammable refrigerants are used, filling cannot be done until startup at the installation site. In addition, a non-flammable refrigerant may be used in the presence of an ignition source.

The test chamber for conditioning air according to the present invention comprises: a test space for containing a test material and being sealable with respect to the environment and thermally insulating; and a temperature control device for controlling the temperature of the test space, by means of which a temperature in the temperature range of-60 ℃ to +180 ℃, preferably-70 ℃ to +180 ℃, particularly preferably-80 ℃ to +180 ℃ can be established in the test space, the temperature control device having a cooling device comprising a cooling circuit with a refrigerant according to the invention, a heat exchanger, a compressor, a condenser and an expansion element. With regard to the advantages of the test chamber according to the invention, reference is made to the description of the advantages of the refrigerant according to the invention.

Unlike in a mixed fluid cascade system, refrigerant with all components contained in the refrigerant can be vaporized simultaneously by the expansion element. Since the freezing point of carbon dioxide is-56.6 ℃, in principle, refrigerant mixtures containing a large fraction of carbon dioxide are no longer suitable for achieving temperatures below-56.6 ℃. However, the use of the refrigerant according to the invention allows to achieve a dew point temperature of the refrigerant below-70 ℃.

The cooling circuit may have an internal heat exchanger, and the internal heat exchanger may be connected to a high pressure side of the cooling circuit upstream of the expansion element and downstream of the condenser and to a low pressure side of the cooling circuit upstream of the compressor and downstream of the heat exchanger. By using an internal heat exchanger and cooling the liquefied refrigerant at the high pressure side by means of the internal heat exchanger, temperatures below-56 c can be easily reached. The evaporation temperature of the refrigerant cooled by the internal heat exchanger may be reduced at the expansion element relative to the evaporation temperature of the uncooled refrigerant. The cold capacity transferred from the low pressure side to the high pressure side via the internal heat exchanger can thus be used at least partially, preferably exclusively, for reducing the evaporation temperature of the refrigerant at the expansion element. Furthermore, it is possible to use a refrigerant with a temperature glide of >5K first, since in this case the location of the dew point temperature of the refrigerant or the dew point of the refrigerant can be moved into the internal heat exchanger. As a result of the temperature glide of the azeotropic refrigerant, the dew point temperature of the obtained refrigerant may be relatively high, thereby preventing further cooling of the heat exchanger.

Thus, only part of the refrigerant may evaporate in the heat exchanger and an unusable part of the wet vapour fraction of the refrigerant may be transferred to the internal heat exchanger. Overall, this allows refrigerants that contain a fraction of carbon dioxide and that are environmentally friendly while having azeotropic properties to be used to establish low temperatures in the test space. Furthermore, if part of the temperature of the refrigerant slips or part of the wet vapor is transferred from the heat exchanger in the test space into the internal heat exchanger, a relatively improved temperature stability can be achieved with the azeotropic refrigerant. In this case, the cold capacity output via the heat exchanger can be generated only in a part of the temperature glide, which means that the movement of the dew point of the refrigerant in the cooling circuit has hardly any effect on the temperature stability of the heat exchanger. Furthermore, in this case, a single heat exchanger may be used to cool the fluid, i.e. the air in the test space.

The heat exchanger may be sized such that only a portion of the refrigerant may evaporate in the heat exchanger. This results in the advantage that the location of the dew point or dew point temperature of the refrigerant can be moved out of the heat exchanger into the internal heat exchanger. Due to the temperature glide of the azeotropic refrigerant, a partial evaporation of the refrigerant in the heat exchanger achieves a lower temperature in the heat exchanger than the subsequent remaining evaporation of the refrigerant in the internal heat exchanger.

In one embodiment of the test chamber, a heat exchanger may be disposed in the test space. In this case, the heat exchanger may also be provided in the air-handling space of the test space, so that the air circulated by the fan can come into contact with the heat exchanger. In this way, the circulating volume of air of the test space can be cooled directly in the test space by the cooling device via the heat exchanger. The test chamber may have the cooling circuit as a single, separate cooling circuit. In this case, the cooling circuit is directly connected to the test space.

In a further embodiment of the test chamber, the condenser can be realized as a cascade heat exchanger of a further cooling circuit of the cooling device. Thus, the test chamber may have at least two cooling circuits, in which case a cooling circuit may form the second stage of the cooling device, while another cooling circuit arranged upstream of the cooling circuit may form the first stage of the cooling device. In this case, the condenser is used as a cascade heat exchanger or as a heat exchanger for a cooling circuit. This embodiment of the test chamber allows a particularly low temperature to be established in the test space.

The temperature control device may have a heating device including a heater and a heating heat exchanger in the test space. The heating device may be an electrical resistance heater which heats the heating heat exchanger such that the temperature in the test space may be raised by the heating heat exchanger. If the heat exchanger and the heating heat exchanger can be specifically controlled by the control device to cool or heat the air circulating in the test space, a temperature in the above-mentioned temperature range can be established in the test space by the temperature control device. A time-dependent temperature stability of ± 1K, preferably ± 0.3K to ± 0.5K or less than ± 0.3K, can be established in the test space during the test interval, irrespective of the test material or the operating state of the test material. The test interval is a segment of the entire test cycle in which the test material is exposed to substantially constant temperature or climatic conditions. The heating heat exchanger can be combined with the heat exchanger of the cooling circuit in such a way that a common heat exchanger body can be realized, through which the refrigerant can flow and which has the heating elements of the electric resistance heater. The condenser may be cooled with air, water or another coolant. In principle, the condenser may be cooled using any suitable fluid. The main aspect is that the heat load generated at the condenser is discharged via cooling air or cooling water, so that the refrigerant can condense until it is completely liquefied.

The first bypass with the at least one controllable second expansion element can be implemented in the cooling circuit, in which case the first bypass can be connected to the cooling circuit upstream of the interior heat exchanger and downstream of the condenser, and the first bypass can be implemented as a controllable additional interior cooling system. Thus, the first bypass may form a re-injection device of the refrigerant. Thus, the refrigerant can be recirculated from the controllable second expansion element in the internal heat exchanger on the low pressure side. In this case, the first bypass may be connected to the low pressure side of the cooling circuit upstream of the internal heat exchanger and downstream of the heat exchanger. The refrigerant cooled or reduced in its temperature level by the second expansion element may be led through the internal heat exchanger and enhance the cooling of the refrigerant on the high pressure side of the internal heat exchanger. Moreover, the cooling capacity of the internal heat exchanger can be controlled even more precisely in this way.

A second bypass comprising at least one third expansion element may be formed in the cooling circuit, in which case the second bypass bypasses the expansion elements downstream of the condenser and upstream of the internal heat exchanger, and the refrigerant may be metered through the third expansion element in such a way that the suction gas temperature and/or the suction gas pressure of the refrigerant may be controlled at the low pressure side of the cooling circuit upstream of the compressor. In this way, potential overheating and damage of the compressor, which may be for example a compressor device, may be prevented in particular. Thus, gaseous refrigerant upstream of the compressor can be cooled via the second bypass by actuating the third expansion element by adding refrigerant that is still liquid. The third expansion element, which may be actuated by a control device, is itself coupled to a pressure and/or temperature sensor in the cooling circuit upstream of the compressor. Particularly advantageously, a suction gas temperature of ≦ 30 ℃ may be set via the second bypass. Also, the refrigerant may be metered in such a manner that the operation time of the compressor can be controlled. In principle, it is disadvantageous for the compressor or the compressor device to be repeatedly switched on and off. The service life of the compressor can be extended if the compressor is operated for a longer period of time. The refrigerant may be directed through an expansion element or condenser via a second bypass, for example, to delay automatic deactivation of the compressor and extend the operating time of the compressor.

A further bypass comprising at least one further expansion element may be formed in the cooling circuit, the further bypass bypassing the compressor downstream of the compressor and upstream of the condenser in such a way that the suction gas temperature and/or the suction gas pressure of the refrigerant can be controlled upstream of the compressor at the low pressure side of the cooling circuit and/or the pressure difference between the high pressure side and the low pressure side of the cooling circuit can be equalized. The second bypass may additionally be equipped with a settable or controllable valve, for example a solenoid valve. Connecting the high pressure side and the low pressure side via the further expansion element ensures that the gaseous refrigerant thus compressed flows gradually from the high pressure side to the low pressure side of the cooling circuit in the event of a system shutdown. This also ensures a gradual pressure balance between the high pressure side and the low pressure side even when the expansion element is closed. The cross-section of the further expansion element may be dimensioned such that the refrigerant flowing from the high pressure side to the low pressure side has only a minor influence on the normal operation of the cooling device. At the same time, the gaseous refrigerant upstream of the compressor may be cooled by adding liquid refrigerant via another bypass.

Furthermore, the internal heat exchanger can be realized as a supercooling section or as a heat exchanger, in particular as a plate heat exchanger. The supercooling section can be realized simply by two line sections of the cooling circuit which are in contact with one another.

The expansion element may have a throttle valve and a solenoid valve, in which case the refrigerant may be metered via the throttle valve and the solenoid valve. The throttle valve can be a settable valve or a capillary tube via which the refrigerant is guided through a solenoid valve. The solenoid valve itself may be actuated by the control means.

Furthermore, the temperature control means may comprise control means comprising at least one pressure sensor and/or at least one temperature sensor in the cooling circuit, in which case the solenoid valve may be actuated by the control means depending on the measured temperature and/or pressure. The control means may comprise means for data processing which processes the data sets from the sensors and controls the solenoid valves. In this case, the function of the cooling device can also be adjusted to the refrigerant used, for example, by means of a suitable computer program. In addition, if desired, the control device may signal a fault and initiate a shutdown of the test chamber to protect the test chamber and test material from damage due to critical or undesired operating conditions of the test chamber.

When a refrigerant is used according to the invention, which refrigerant consists of a refrigerant mixture comprising a fraction of 45 to 90 mol% carbon dioxide, a fraction of 5 to 40 mol% 1, 1-difluoroethylene and a fraction of another component, the refrigerant being used for conditioning the air in a test space of a test chamber, which test space is intended to contain a test material and is sealable and thermally insulated with respect to the environment, the cooling device of the temperature control device of the test chamber comprising a cooling circuit with the refrigerant, the heat exchanger, the compressor, the condenser and the expansion element, the cooling device being used to establish a temperature in the temperature range from-60 ℃ to +180 ℃, preferably from-70 ℃ to +180 ℃, particularly preferably from-80 ℃ to +180 ℃ within the test space.

By means of the internal heat exchanger of the cooling circuit, which may be connected to the high pressure side of the cooling circuit upstream of the expansion element and downstream of the condenser and to the low pressure side of the cooling circuit upstream of the compressor and downstream of the heat exchanger, the refrigerant of the high pressure side may be cooled, and the cooling by means of the refrigerant of the high pressure side of the internal heat exchanger may be used to reduce the evaporation temperature at the expansion element.

The suction pressure of the refrigerant on the low pressure side may be kept constant during the period in which the evaporation temperature of the refrigerant on the high pressure side is lowered. In this case, no greater system complexity is necessary, for example in the form of additional control of the suction pressure and control of the expansion element as a function of the suction pressure. In particular, the compressor can also be operated at constant output, irrespective of the operating state of the cooling circuit. In particular, when the piston pump is used as a compressor, the piston pump must be operated for a long time and at a constant speed in order to obtain a long service life.

The refrigerant of the high pressure side may be cooled by the refrigerant of the low pressure side at a constant suction pressure at the low pressure side by the internal heat exchanger. Thus, the refrigerant can evaporate at a constant suction pressure on an evaporation portion of the cooling circuit from the expansion element to and including the internal heat exchanger. If the suction pressure or the evaporation pressure of the refrigerant is constant, the refrigerant can be evaporated from the expansion element at the low evaporation temperature to the internal heat exchanger at the high evaporation temperature according to the temperature glide of the refrigerant. The dew point temperature resulting from the temperature glide may be higher than the temperature of the fluid to be cooled or the air in the test space. Once the evaporation temperature of the refrigerant is equal to the temperature of the air in the test space cooled at the same suction pressure, the air cannot be cooled further. However, the dew point temperature reached in the other heat exchanger is lower than the liquid temperature of the refrigerant on the high pressure side of the inner heat exchanger, which means that the liquid temperature of the refrigerant can be further reduced. Thus, the evaporation temperature downstream of the expansion element can be reduced without changing the suction pressure, allowing a further cooling of the air in the test space to be achieved.

Only a portion of the refrigerant may be evaporated in the heat exchanger. Thus, a first portion of the refrigerant directed via the expansion element may be evaporated in the heat exchanger and a second portion of the refrigerant may be evaporated in the internal heat exchanger. The evaporation portion of the cooling circuit, in which the refrigerant evaporates, may extend from the expansion element to the internal heat exchanger. The evaporation section may pass through an internal heat exchanger, in which case the dew point of the refrigerant may be located at the outlet of the internal heat exchanger upstream of the compressor. The first portion/second portion ratio may be varied during operation of the cooling circuit as a function of the temperature in the test space or at the heat exchanger. For example, a relatively large temperature difference between the temperature of the heat exchanger and the temperature in the test space may result in accelerated heating of the refrigerant in the heat exchanger, which results in the dew point of the refrigerant moving towards the inlet of the internal heat exchanger or the outlet of the heat exchanger upstream of the compressor. This type of movement of the dew point can be tolerated as long as a relatively low or target temperature has not been established in the test space. As the temperature of the heat exchanger approaches the temperature in the test space, the dew point moves, and thus the second portion increases relative to the first portion of refrigerant.

During certain time intervals, the refrigerant may be metered and evaporated in a timed manner in the heat exchanger. For example, the expansion element may be a solenoid valve, which is configured to be controlled by means of the control device. The timed operation of the solenoid valve (i.e., expansion element) allows only a small amount of refrigerant to be purposefully fed into the heat exchanger. In particular, maintaining low temperatures generally requires only a low cold capacity. The latter can be produced by metering the amount of refrigerant evaporated at the heat exchanger. By opening and closing the expansion element periodically during a certain time interval, the metering can be achieved in a particularly simple manner. The timed opening and closing refers in particular to a constant periodic sequence.

The evaporation temperature of the refrigerant on the high pressure side can be lowered in a self-controlled manner. Depending on the temperature at the heat exchanger, the refrigerant which is no longer evaporating can be discharged from the heat exchanger in the flow direction, since in this case the temperature at the heat exchanger is no longer sufficient to cause a phase change of the refrigerant. Thus, the wet vapour or liquid refrigerant is re-evaporated in the internal heat exchanger, since here the temperature difference between the high pressure side and the low pressure side is always larger than the temperature difference at the heat exchanger. If the temperature of the liquid refrigerant upstream of the expansion element is reduced by means of the internal heat exchanger by heat exchange at the internal heat exchanger, the energy density of the refrigerant upstream of the expansion element and thus the temperature difference achievable at the heat exchanger increases. It is in principle not necessary to control the interaction of the expansion element, the heat exchanger and the internal heat exchanger.

In particular, a constant suction pressure can also be maintained during the lowering of the evaporation temperature of the refrigerant on the high pressure side by the internal heat exchanger. Thus, the cooling of the refrigerant on the high pressure side via the internal heat exchanger can also be used, partly or exclusively, to reduce the evaporation temperature of the refrigerant at the expansion element.

The dew point temperature of the refrigerant may be higher than the lowest temperature of the temperature range. In the test cells known from the prior art, in this case, the lowest temperature of the temperature range can no longer be established with this type of refrigerant, but rather a relatively high lowest temperature, which essentially corresponds to the dew point temperature of the refrigerant. However, in the test chamber according to the invention, it is possible to use a refrigerant with a dew point temperature above the lowest achievable temperature of the temperature range, since the liquefied refrigerant on the high pressure side can be cooled by the internal heat exchanger, which means that the evaporation temperature of the refrigerant at the expansion element can be relatively low.

The refrigerant may be completely evaporated at a suction pressure or an evaporation pressure in the pressure range of 0.3 to 5 bar. The use of a refrigerant in this pressure range allows a cost-effective production of the cooling circuit, since no special pressure-resistant modules and components have to be used to construct the low-pressure side of the cooling circuit.

Furthermore, the refrigerant may be completely condensed at a condensation pressure in the range of 5 to 35 bar. Here, the high pressure side can also be constructed using modules and components that are not necessarily adapted to relatively high pressures.

Other embodiments of the use will be apparent from the description of the features above.

Drawings

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

FIG. 1 is a schematic view of a first embodiment of a cooling apparatus;

FIG. 2 is a pressure-enthalpy diagram of the refrigerant;

FIG. 3 is a schematic view of a second embodiment of a cooling apparatus;

FIG. 4 is a schematic view of a third embodiment of a cooling apparatus;

FIG. 5 is a schematic view of a fourth embodiment of a cooling apparatus;

FIG. 6 is a schematic view of a fifth embodiment of a cooling apparatus;

FIG. 7 is a schematic view of a sixth embodiment of a cooling apparatus;

FIG. 8 is a schematic view of a seventh embodiment of a cooling apparatus;

FIG. 9 is a schematic view of an eighth embodiment of a cooling apparatus;

FIG. 10 is a schematic view of a ninth embodiment of a cooling apparatus;

figure 11 is a pressure-enthalpy diagram of the refrigerant;

FIG. 12 is a cycle-time diagram of an expansion element;

fig. 13 is a temperature-surface diagram for a cooling circuit.

Detailed Description

Fig. 1 shows a first embodiment of a cooling device 10 of a test chamber (not shown). The cooling device 10 comprises a cooling circuit 11 with a refrigerant, a heat exchanger 12, a compressor 13, a condenser 14 and an expansion element 15. In this case, the condenser 14 is cooled by a further cooling circuit 16. The heat exchanger 12 is disposed in a test space (not shown) of the test chamber. Furthermore, the cooling circuit 11 has a high pressure side 17 and a low pressure side 18, and an internal heat exchanger 19 is connected to the high pressure side 17 and the low pressure side 18.

Fig. 2 shows a pressure-enthalpy diagram (log p/h diagram) of the refrigerant circulating in the cooling circuit 11, which refrigerant is an azeotropic refrigerant. According to the combined view of fig. 1 and 2, starting from position a, the refrigerant upstream of the compressor 13 is sucked and compressed, whereby the pressure is obtained downstream of the compressor 13 according to position B. The refrigerant is compressed by a compressor 13 and then liquefied according to the position C in a condenser 14. The refrigerant passes through the internal heat exchanger 19 on the high pressure side 17, where it is further cooled and thus reaches a location C' upstream of the expansion element 15. By means of the internal heat exchanger 19, the part of the wet vapour zone (positions E to E ') which is not available in the heat exchanger 12 can be used to further reduce the temperature of the refrigerant (positions C' to C). At the expansion element 15, the refrigerant relaxes (positions C ' to D ') and is partially liquefied (positions D ' to E) in the heat exchanger 12. The wet vapor of the refrigerant then enters the internal heat exchanger 19 at the low pressure side 18, where the refrigerant is re-evaporated until the dew point temperature or dew point of the refrigerant is reached at location E'. Thus, a first sub-portion 20 of the evaporation portion 22 of the refrigerant passes through the heat exchanger 12 and a second sub-portion 21 of the evaporation portion 22 passes through the internal heat exchanger 19. The main aspect is that the suction pressure of the compressor 13 on the low pressure side 18 remains constant over the evaporation portion 22 even if the evaporation temperature at the expansion element 15 changes.

The refrigerant may be refrigerant 2, 4, 6, 8 or 9 from the above table. These refrigerants do not contain more than three components and have a high temperature glide of >5K, which is why the internal heat exchanger 19 is necessary for safe operation and to achieve temperatures of < -55 ℃. As described in connection with fig. 1, with these refrigerants, the cold capacity available at heat exchanger 12, i.e. at the test space (not shown), is used in heat exchanger 19 to subcool the liquid refrigerant upstream of expansion element 15. This effect is particularly pronounced when refrigerants with a temperature glide >5K are used, and the improvement in performance is therefore correspondingly high. Control via a sophisticated sensor system is not necessary. However, dynamic load variations (i.e. temperature variations) are only possible to a limited extent due to the inertia of the cooling circuit 16 and the cooling device 10. Further, the refrigerant located in the test space may be evaporated by heating the heat exchanger 12.

Fig. 3 shows a schematic view of the simplest embodiment of the cooling device 23, the cooling device 23 being self-controlled. The cooling device 23 comprises a cooling circuit 24 with a heat exchanger 25, a compressor 26, a condenser 27, an expansion element 28 and an internal heat exchanger 29. Depending on the temperature at the heat exchanger 25, incompletely evaporated refrigerant escapes from the heat exchanger 25, because the temperature at the heat exchanger 25 or in the test space (not shown) is no longer high enough to cause a phase change. In this case, the still liquid refrigerant is re-evaporated in the internal heat exchanger 29, since the temperature difference there must always be greater than the temperature difference at the heat exchanger 25. Once the temperature of the liquid refrigerant upstream of the expansion element 28 has been reduced by heat exchange in the internal heat exchanger 29, the energy density and the temperature difference achievable at the heat exchanger 25 with it increase. The cooling device 23 does not require fine control by a sensor or the like.

Fig. 4 shows a cooling device 30 which differs from the cooling device of fig. 3 in that it has a first bypass 31 and a second bypass 32. A controllable second expansion element 33 is arranged in the first bypass 31, the first bypass 31 being configured as an additional internal cooling system 34. The first bypass 31 is connected to the cooling circuit 24 immediately downstream of the condenser 27 and upstream of the internal heat exchanger 29 and downstream of the heat exchanger 25 and upstream of the internal heat exchanger 29. The first bypass 31 thus bypasses the expansion element 28 and the heat exchanger 25, and the internal heat exchanger 29 can be supplied with evaporated refrigerant via the second expansion element 33. In the case of high suction gas temperatures, which may be caused by the heat exchanger 25, the suction gas mass flow introduced into the internal heat exchanger 29 may additionally be cooled by means of a first bypass 31. In this way, the refrigerant upstream of the expansion element can be prevented from evaporating. The first bypass 31 can thus be used to react to changing load conditions of the cooling device 30. The second bypass 32 has a third expansion element 35 and is connected to the cooling circuit 24 downstream of the condenser 27 and upstream of the internal heat exchanger 29 and downstream of the internal heat exchanger 29 and upstream of the compressor 26. This allows the suction gas mass flow upstream of the compressor 26 to be reduced sufficiently via the second bypass 32 to avoid unacceptably high final compression temperatures.

Fig. 5 shows a cooling device 36 which differs from the cooling device of fig. 4 in that it has a further bypass 37. The other bypass 37 has a further expansion element 38 and is connected to the cooling circuit 24 downstream of the condenser 27 and upstream of the internal heat exchanger 29 and downstream of the internal heat exchanger 29 and upstream of the compressor 26.

The first bypass 31 makes it possible to cope with changing load situations. Thus, in case of high suction gas temperatures, which may be caused by the heat exchanger 25, the suction gas mass flow may be introduced into the internal heat exchanger 19 and additionally cooled by re-injection via the first bypass 31. It is thus ensured that no evaporation is possible upstream of the expansion element 28. In addition, the re-injection via the other bypass 37 may reduce the suction gas temperature upstream of the compressor 26 sufficiently low to avoid excessive compression end temperatures. This makes it possible to use refrigerants with a temperature glide of >5K for low temperature applications even in the case of highly dynamic load variations.

Fig. 6 shows a cooling device 39 which differs from the cooling device of fig. 5 in that it has a further cooling circuit 40. The further cooling circuit 40 serves for cooling a condenser 41 of a cooling circuit 42. The condenser 41 is realized in this case as a cascade heat exchanger 43.

Fig. 7 shows a cooling device 44, which cooling device 44 has a cooling circuit 45 and a further cooling circuit 46, and in particular an internal heat exchanger 47 in the cooling circuit 45. In this case, the heat exchanger 48 is disposed in an insulated test space of a test chamber (not shown).

Fig. 8 shows a schematic view of the simplest embodiment of a cooling device 49 without an internal heat exchanger. The cooling circuit 50 of the cooling device 49 is realized with a compressor 51, a condenser 52, an expansion element 53 and a heat exchanger 54 in an insulated test space of a test chamber (not shown).

The refrigerant circulating in the cooling circuit 50 may be one of the refrigerants 1, 3, 5, 7 and 9 from the above table. These refrigerants have a temperature glide of ≦ 5K, which is why no internal heat exchanger is needed for safe operation and to achieve temperatures <55 ℃. The low density of the respective refrigerant necessitates a corresponding change in the compressor 51 and the pipes of the cooling circuit 50 in the case of low evaporation temperatures.

Fig. 9 shows a cooling device 55 which differs from the cooling device of fig. 8 in that a first bypass 56 with a first expansion element 57 and a second bypass 58 with a second expansion element 59 are provided. The first bypass 56 and the second bypass 58 may be used as described in connection with fig. 4. Thus, the suction temperature and the evaporation pressure of the compressor 51 can be set or controlled by means of the first expansion element 57 and the second expansion element 59.

Fig. 10 shows a cooling device 60 which differs from the cooling device of fig. 9 in that it has a further bypass 61 comprising a further expansion element 62. By means of the further expansion element 62, the suction gas temperature and thus indirectly the compression end temperature can be reduced even further.

Furthermore, based on the cooling devices shown in fig. 3 and 8, the effective temperature glide of the refrigerant used can be advantageously reduced in all cooling devices. As can be seen from the line graph of fig. 11, the temperature slip is not linear, mainly in refrigerants with a temperature slip > 5K. In fig. 11, arrows 63 mark the pipe sections of the cooling circuit that pass through the heat exchanger in the test space. The reduction of the effective temperature glide in the heat exchanger stabilizes the test space temperature. For example, complete evaporation is achieved by utilizing superheat of the refrigerant in the compressor suction line. Furthermore, by the targeted reheating of the refrigerant or by the use of a liquid separator, the energy contained in the refrigerant can be utilized ideally in order to increase the installation efficiency.

The diagram shown in fig. 12 shows, as a further advantageous measure, the timed opening and closing of the expansion element during a certain time interval. In this way, a small amount of refrigerant evaporating on the heat exchanger can be fed to the heat exchanger when only a relatively low cold capacity is required to maintain the temperature.

The diagram shown in fig. 13 illustrates the superheat with the refrigerant in the suction line 66 of the compressor. The arrow 64 marks the heat exchanger, more precisely the course of the temperature increase as the refrigerant passes through the heat exchanger surface 65 upstream of the suction line, more precisely its surface 66. By means of the electronic expansion element, the temperature is reduced downstream of the heat exchanger, while ensuring overheating in the suction line.