KR100558212B1 - Refrigerant mixture for providing ultra-low temperature - Google Patents

Abstract

The present invention relates to an environment-friendly environment that can replace a freon-based refrigerant that destroys the earth's ozone layer, and to a mixed refrigerant that can achieve ultra low temperature of -60 ° C or less at a low discharge pressure of 15 kgf / cm 2 or less. The present invention provides a cryogenic mixed refrigerant containing 50 to 70% by weight of isobutane, 15 to 25% by weight of perfluoroethane, and 15 to 25% by weight of trifluoromethane. In addition, it provides a cryogenic mixed refrigerant containing tetrafluoromethane further 5 to 15% by weight based on the total weight of the mixed refrigerant.

Cryogenic, Mixed Refrigerant, Freon

Description

Refrigerant mixture for providing ultra-low temperature

1 is a schematic view showing a single stage refrigeration system used in the present invention.

<Brief description of symbols for the main parts of the drawings>

10 ... compressor 20 ... condenser

30.Dryer 40.Capillary tube

50 ... heat exchanger 60 ... evaporator

70 ... Freezer

The present invention relates to an ultra low temperature mixed refrigerant, and more particularly, it is environmentally friendly to replace the freon refrigerant that destroys the earth's ozone layer, and can achieve an ultra low temperature of -60 ° C. or less at a low discharge pressure of 15 kgf / cm 2 or less. It relates to a mixed refrigerant which can be.

Chlorofluorocarbon (CFC), commonly called Freon, is a compound composed of carbon, fluorine, and chlorine. Freon has high stability such as low corrosiveness, low toxicity, nonflammability, easy to change gas and liquid, dissolve organic matter, high permeability and electrical insulation, and low price. It has been used in various ways. However, production and use are regulated by the Montreal Protocol, as it is known that freon in the atmosphere reaches the stratosphere and decomposes due to light energy of short wavelength ultraviolet rays, and the chlorine atoms released from it combine with ozone to destroy the earth's protective ozone layer. have. HCFC-based compounds, including HCFC-22, are not as severe as CFC compounds, but they have a significant impact on the destruction of the ozone layer. Accordingly, research on alternative refrigerants continues in preparation for the regulation of CFCs and HCFCs worldwide.

The study of such alternative refrigerants has been conducted in two directions: the development of new refrigerants and the study of mixed refrigerants having the same performance as the regulated refrigerants by mixing existing refrigerants. However, the development of new refrigerants requires a lot of physical and human resources, and it is difficult to equip large-scale production facilities until commercialization of low-priced products. Is actively underway. However, even if it is mixed with only theoretically usable refrigerants out of the unregulated refrigerants, the number of combinations is over 100, and depending on each combination, the fractional substance when liquefaction or vaporization occurs between liquid and gas phase under a certain pressure. Some quasi-equilibrium temperatures do not change, while others change their temperature. The former is called an azeotropic refrigerant mixture, and the latter is a non-azeotropic refrigerant mixture. An azeotropic mixture exists only in a specific component ratio and exhibits thermodynamic properties such as pure substances. In the case of evaporation pressure and temperature are respectively changed according to the composition.

In particular, there are not many kinds of refrigerant gas capable of realizing the cryogenic freezer temperature of -60 ° C or less, which is being widely used in biotechnology, and the refrigerant which realizes ultra low temperature generally has a lower critical pressure as the standard boiling point is lower. Because of this high and low critical temperature, it cannot be easily liquefied under room temperature. For this reason, the binary refrigeration system is widely used for cooling the liquefaction process of the refrigerant having a lower boiling point than the refrigerant capable of liquefying at room temperature. However, such a dual refrigeration system is complex and difficult to maintain, and the two refrigeration cycles of the high temperature side and the low temperature side constitute a single refrigeration system, which is large and expensive.

Therefore, the present invention has been made to solve the above problems, in a single stage refrigeration cycle in which the heat exchange between the suction pipe, the capillary tube and the high-pressure liquid pipe is achieved to achieve a freezer temperature of -60 ℃ or less at a low discharge pressure of less than 15kgf / ㎠ It can be, and to provide an environment-friendly cryogenic mixed refrigerant that does not destroy ozone.

In order to achieve the above object, the present invention provides a mixed refrigerant containing 50 to 70% by weight of isobutane, 15 to 25% by weight of perfluoroethane, and 15 to 25% by weight of trifluoromethane.

According to another feature of the invention, the mixed refrigerant may further comprise 5 to 15% by weight of tetrafluoromethane relative to the total weight of the mixed refrigerant.

Preferably, the mixed refrigerant according to the present invention may include 60% by weight of isobutane, 20% by weight of perfluoroethane, and 20% by weight of trifluoromethane.

Preferably, the mixed refrigerant according to the present invention may include 54% by weight of isobutane, 18% by weight of perfluoroethane, 18% by weight of trifluoromethane, and 10% by weight of tetrafluoromethane.

Hereinafter, the present invention will be described in more detail with reference to Examples, but it is obvious to those skilled in the art that the scope of the present invention is not limited by these Examples.

Isobutane not only destroys the ozone layer with a zero ozone depletion index, but also has a very low global warming index (GWP), which is recognized as an environmentally friendly refrigerant worldwide, and is named R-600a. It is used and flammable, but the resulting fire has not been reported. Trifluoromethane (CHF ₃ : hereinafter referred to as 'R-23') as an HFC refrigerant, perfluoroethane (C ₂ F ₆ : hereinafter referred to as 'R-116') and tetrafluoro as a FC refrigerant Methane (CF ₄ : hereafter referred to as 'R-14') does not have a chlorine component and thus has a low degree of destruction to the ozone layer.

Referring to Table 1, isobutane is easy to handle as a refrigerant of a refrigeration system operating at room temperature because of its high boiling point but low critical pressure and high critical temperature. R-116, R-23, and R-14 have very low boiling points and are suitable as cryogenic refrigerants, but are not easy to handle in a refrigeration system operating at room temperature. Therefore, these gases can be mixed and used as a refrigerant in a refrigeration system operating at room temperature, and the characteristics and composition ranges of mixed refrigerants that can realize ultra low temperatures of -60 ° C or less at low discharge pressures of 15 kgf / cm2 or less can be confirmed. Was completed.

Physical Properties of Isobutane, R-116, R-23, and R-14 Chemical formula Boiling point (℃) Critical temperature (℃) Critical pressure (MPa) Isobutane CH (CH ₃ ) ₃ -11.7 134.9 3.72 R-116 CF ₃ CF ₃ -78.2 19.7 2.98 R-23 CHF ₃ -82.2 25.6 4.837 R-14 CF ₄ -128 -45.5 3.743

1 is a schematic view showing a single stage refrigeration system used in the present invention. Referring to the drawings, the refrigerant compressed in the compressor 10 is radiated in the condenser 20 and sent to a dryer 30. The dryer 30 filters the various foreign substances such as acid, dust, wax, etc. contained in the refrigerant and absorbs moisture to protect the refrigeration system from the foreign substances. After passing through the dryer 30, the refrigerant is sent to the capillary tube 40 to depressurize, vaporizes in the evaporator 60 in the freezer 70, cools the inside of the freezer 70, and then passes through the heat exchange unit 50 again. 10) is returned. The heat exchange part 50 is configured to exchange heat between the suction pipe and the capillary and the high pressure liquid pipe. After the low-temperature refrigerant vaporized by the evaporator 60 and returned to the compressor passes through the heat exchange unit 50, the refrigerant of high pressure cools the high-pressure refrigerant, thereby lowering the temperature to promote the condensation process and lowering the pressure. The load can be reduced. In addition, energy efficiency can be improved by using sensible heat and latent heat of the refrigerant returned to the compressor.

Examples 1 to 7: Mixed refrigerant of isobutane / R-116 / R-23

The mixed refrigerant was prepared using a conventional method with the composition shown in Table 2, and the characteristics as a refrigerant were confirmed using the single stage refrigerator of FIG. The single stage freezer of FIG. 1 was charged with 350-437.5 g of mixed refrigerant of isobutane / R-116 / R-23 and operated at room temperature of 28 ° C. to measure the internal temperature of the freezer, the discharge pressure and the suction pressure of the compressor. The results are shown in Table 3. The discharge pressure and suction pressure are gauge pressures.

Mixed refrigerant (wt%) Isobutane R-116 R-23 Example 1 44 28 28 Example 2 50 25 25 Example 3 54 23 23 Example 4 60 20 20 Example 5 64 18 18 Example 6 70 15 15 Example 7 74 13 13

Freezer temperature (℃) Discharge pressure (kgf / ㎠) Suction pressure (kgf / ㎠) Example 1 -50 20 1.2 Example 2 -74.5 11 0.2 Example 3 -73 9.5 0.25 Example 4 -72 7 0.1 Example 5 -68 6.7 0 Example 6 -63 6 0 Example 7 -55 6 5 ^*

* Vacuum pressure (cmHg)

When operating a mixed refrigerant in a single stage refrigeration cycle, the freezer temperature can be achieved below -60 ° C, especially below -80 ° C. At the same time, the discharge pressure is 15kgf / cm2 or less to reduce the load on the compressor. Cryogenic mixed refrigerants are preferred.

As can be seen from Table 3, as the concentration of isobutane increases, the discharge pressure decreases but the temperature in the freezer tends to increase, and as the concentration of R-116 and R-23 increases, the temperature in the freezer decreases but the discharge The pressure tended to increase.

The discharge pressure is kept low in the region where the mixing ratio of isobutane, R-116 and R-23 is around 70:15:15, but the temperature lowering effect is lowered. In the region around 50:25:25, the discharge pressure is significantly higher and the temperature is The deterioration effect also fell. Therefore, the mixing ratio of isobutane, R-116, and R-23 is preferably in the range of 70:15:15 to 50:25:25. More preferably, the mixed refrigerant including 60% by weight of isobutane, 20% by weight of R-116, and 20% by weight of R-23 may achieve ultra low temperature of −72 ° C. at a discharge pressure of 7 kgf / cm 2.

Examples 8 to 5: Mixed refrigerant of isobutane / R-116 / R-23 / R-14

The mixed refrigerant was prepared using a conventional method with the composition shown in Table 4, and the characteristics as the refrigerant were confirmed using the single stage refrigerator of FIG. The single stage refrigerator of FIG. 1 was charged with 350-437.5 g of a mixed refrigerant of isobutane / R-116 / R-23 / R-14 and operated at room temperature of 28 ° C. Was measured, and the results are shown in Table 5. The discharge pressure and suction pressure are gauge pressures.

Mixed refrigerant (wt%) Isobutane R-116 R-23 R-14 Example 8 58.8 19.6 19.6 2 Example 9 57 19 19 5 Example 10 54 18 18 10 Example 11 51 17 17 15 Example 12 48 16 16 20

Freezer temperature (℃) Discharge pressure (kgf / ㎠) Suction pressure (kgf / ㎠) Example 8 -74 7.3 0.15 Example 9 -76 8.5 0.25 Example 10 -89 11.5 0.33 Example 11 -92 17.5 0.4 Example 12 -78 20 0.45

As shown in Table 5, the mixed refrigerant consisting of 50 to 70% by weight of isobutane, 15 to 25% by weight of R-116, and 15 to 25% by weight of R-23 was tested with different amounts of R-14. As the concentration of 14 increased, the effect of lowering the temperature in the freezer increased, but the discharge pressure also increased. When the concentration of R-14 exceeds 15% by weight, the effect of lowering the temperature in the freezer is remarkably reduced and the discharge pressure is also increased. Therefore, in order to achieve an ultra-low temperature of -80 ° C at a low discharge pressure, it is preferable to include 5 to 15% by weight of R-14 based on the total weight of the mixed refrigerant. More preferably, the mixed solvent containing 54% by weight of isobutane, 18% by weight of R-116, 18% by weight of R-23, and 10% by weight of R-14 is in a freezer at -89 ° C at a discharge pressure of 11.5 kgf / cm 2. Temperature can be achieved.

 As described above, the cryogenic mixed refrigerant according to the present invention has a temperature in the freezer of -60 ° C. or less, especially -80 ° C., at a low discharge pressure of 15 kgf / cm 2 or less in a single stage refrigeration cycle in which heat exchange between the suction tube, the capillary tube and the high pressure liquid tube is performed. It can achieve and can provide an environmentally friendly refrigerant without the risk of ozone layer destruction.

Although the present invention has been described with reference to the above embodiments, it is merely illustrative, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. . Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (4)

A cryogenic mixed refrigerant containing 50 to 70% by weight of isobutane, 15 to 25% by weight of perfluoroethane, and 15 to 25% by weight of trifluoromethane. The cryogenic mixed refrigerant according to claim 1, comprising 60% by weight of isobutane, 20% by weight of perfluoroethane, and 20% by weight of trifluoromethane. The cryogenic mixed refrigerant according to claim 1 or 2, further comprising 5 to 15% by weight of tetrafluoromethane based on the total weight of the mixed refrigerant. The cryogenic mixed refrigerant according to claim 3, comprising 54% by weight of isobutane, 18% by weight of perfluoroethane, 18% by weight of trifluoromethane, and 10% by weight of tetrafluoromethane.

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