JPH11158460A - Refrigerant composition and binary refrigerator using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a compsn. which has a sufficient refrigerant capability by mixing an azeotropic mixture of chlorodifluoromethane and octafluoropropane with n-pentane in a specified amt. based on the amt. of the azeotropic mixture. SOLUTION: This compsn. is prepd. by mixing an azeotropic mixture having an azeotropic point of -47 deg.C and comprising chlorodifluoromethane having a b.p. of -40 deg.C and octafluoropropane having a b.p. of -36.7 deg.C with n-pentane in an amt. of 14 wt.% or lower of the amt. of the azeotropic mixture. Though n-pentane has a high b.p. (36.0 deg.C), it is well compatible with a compressor oil; therefore, a specified amt. of n-pentane mixed enables the oil in the state of being dissolved in n-pentane to be returned to a compressor, thus enabling troubles such as locking of a compressor due to oil-up to be prevented. When a specified amt. of dichloromonofluoromethane is added to the azeotropic mixture, effects similar to one obtd. by n-pentane can be obtd. without the necessity for installing an oil separator for separating the oil.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerant composition used in a refrigeration system and having a low risk of destruction of the ozone layer.
It relates to a binary refrigeration system using the same.

[0002]

2. Description of the Related Art Conventionally, R12 (dichlorodifluoromethane) and R5
00 (azeotropic mixture of R12 and R152a (1,1-difluoroethane)). The boiling point of R12 is about -30
At 500C, the boiling point of R500 is about -33C, which is suitable for ordinary refrigeration equipment. Furthermore, even if the suction temperature into the compressor is relatively high, the discharge temperature will not be so high as to cause oil sludge in the compressor. Further, R12 has good compatibility with the oil of the compressor and plays a role of drawing the oil in the refrigerant circuit back to the compressor.

On the other hand, in order to obtain a lower temperature range of -45 ° C. or lower, R502 (azeotropic mixture of R22 and R115) is used. R503 has a boiling point of −45.4 ° C.
And is optimal for obtaining low temperatures.

[0004]

However, it is said that each of the above refrigerants may destroy the ozone layer, and the use of the refrigerant has been restricted. That is, R that composes R500
It has been elucidated that R115 constituting R12 and R502 is a so-called regulated refrigerant which is hardly decomposable, and there is a risk of destroying the ozone layer when it is released into the atmosphere and reaches the ozone layer.

At present, researchers around the world are researching and searching for alternative refrigerants to the above-mentioned restricted refrigerants.

The present invention has been made in view of the above points, and can achieve a low temperature of -45 ° C. or less without using a regulated refrigerant which has a large risk of destruction of the ozone layer, and has a refrigerating capacity and other performance aspects. It is an object of the present invention to provide a refrigerant composition that can be used as a substitute refrigerant for R502 and to provide a binary refrigeration apparatus that can actually achieve a low temperature.

[0007]

The present invention comprises a mixture of an azeotropic mixture of chlorodifluoromethane and propane octafluoride and n-pentane, wherein n-pentane is replaced by chlorodifluoromethane. And refrigerant at a ratio of 14% or less based on the total weight of octafluoropropane to form a refrigerant composition.

Further, as claimed in claim 2, the azeotropic mixture comprises an azeotropic mixture of chlorodifluoromethane and propane octafluoride and a mixture of dichloromonofluoromethane, wherein dichloromonofluoromethane is obtained by mixing chlorodifluoromethane and octafluoropropane. The refrigerant composition is obtained by mixing at a ratio of 20% or less with respect to the total weight.

In another aspect of the present invention, a high-temperature side refrigerant circuit and a low-temperature side refrigerant circuit are provided, and the refrigerant in the low-temperature side refrigerant circuit is condensed by the refrigerant passing through a cascade condenser in the high-temperature side refrigerant circuit. In the original refrigeration apparatus, the refrigerant sealed in the low-temperature side refrigerant circuit is a mixture of an azeotropic mixture of chlorodifluoromethane and octafluoropropane and n-pentane, and n-pentane is chlorodifluoromethane and octafluoromethane. This is a binary refrigeration apparatus using a refrigerant composition mixed at a ratio of 14% or less based on the total weight of activated propane.

Further, a high temperature side refrigerant circuit and a low temperature side refrigerant circuit are provided, and the refrigerant in the low temperature side refrigerant circuit is condensed by the refrigerant passing through a cascade condenser in the high temperature side refrigerant circuit. In the original refrigeration apparatus, the refrigerant sealed in the low-temperature side refrigerant circuit is an azeotropic mixture of chlorodifluoromethane and octafluoropropane, and a mixture of dichloromonofluoromethane, and dichloromonofluoromethane is chlorodifluoromethane. This is a binary refrigeration apparatus using a refrigerant composition mixed at a ratio of 20% or less to the total weight of octafluoropropane.

[0011]

According to the present invention, according to the first aspect, chlorodifluoromethane (R22) contains HC but also contains hydrogen.
FC, and octafluoropropane (R218) is an FC consisting only of fluorine and carbon, and n-pentane also does not contain chlorine, and neither is subject to regulation on the problem of depletion of the ozone layer. The boiling points thereof are -40 ° C for chlorodifluoromethane (R22) and -36.7 ° C for propane octafluoride (R218), and the azeotropic point of both mixtures is about -47 ° C. As a substitute refrigerant for R502, sufficient refrigeration capacity can be exhibited.

Incidentally, chlorodifluoromethane (R22)
Has a relatively high specific heat ratio of 1.18. Therefore, when sealed in a refrigerant circuit, there is a concern that the discharge temperature will rise. However, propane octafluoride (R21
Since 8) is mixed in a predetermined amount, an increase in the discharge temperature can be suppressed. As a result, a desired refrigeration capacity can be realized, and deterioration of oil sludge and oil can be suppressed.

Further, chlorodifluoromethane (R22)
The azeotropic mixture of propane and octafluoride (R218) has poor compatibility with conventional compressor oils such as mineral oil and alkylbenzene oil. However, by mixing a predetermined amount of n-pentane, Oil can be returned to the compressor. That is, n-pentane has a high boiling point of + 36.07 ° C., but has good compatibility with the oil of the compressor.
By mixing a predetermined amount of pentane, it is possible to return to the compressor in a state where oil is dissolved in n-pentane, and it is possible to prevent adverse effects such as lock due to oil rising of the compressor. Here, since n-pentane has a high boiling point, if it is mixed in a large amount, the evaporation temperature rises, so that a desired low temperature cannot be obtained, and there is a danger of explosion because it is flammable. For this reason, by mixing n-pentane at a ratio of 14% by weight or less, the oil can be returned to the compressor without increasing the evaporation temperature and ensuring the non-flammable region of n-pentane.

According to the second aspect of the present invention, it is possible to provide a refrigerant composition that returns oil to the compressor without particularly providing an oil separator to separate oil. That is,
Dichloromonofluoromethane (R21) also has good compatibility with the oil of the compressor, and the oil is dissolved in dichloromonofluoromethane (R21) by mixing a predetermined amount of dichloromonofluoromethane (R21). To return to the compressor, and it is possible to prevent adverse effects such as lock caused by oil rising of the compressor. Here, the boiling point of dichloromonofluoromethane (R21) is + 8.9 ° C.
The cooling performance is impaired if the amount is too large. However, by keeping the amount of dichloromonofluoromethane (R21) at a predetermined amount, the cooling performance does not decrease, and since the boiling point is high, the compression performance is reduced. After returning to the compressor, it can be evaporated in the compressor, and the compressor can be cooled.

According to the third and fourth aspects of the present invention, in an actual refrigerant circuit, the oil return is improved without using an oil separator, and the temperature is reduced to -60 ° C. in an evaporator without danger such as explosion. A low temperature of the order can be achieved, and it can be put to practical use as a medical freezer such as blood cooling without using a regulated refrigerant.

[0016]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. FIG. 1 is a refrigerant circuit diagram of a binary refrigeration apparatus in which the refrigerant composition of the present invention is sealed. S1 represents the high-temperature side refrigerant cycle, and S1
2 indicates a low-temperature side refrigerant cycle.

The discharge side pipe 2 of the compressor 1 constituting the high temperature side refrigerant cycle S1 is connected to the evaporating pipe 3 and the frame pipe 4, and the frame pipe 4 is connected to the oil cooler 5, the condenser 6, and the dryer of the compressor 1. 7. Capillary tube 8
Are sequentially connected to the cascade condenser 9, and connected to the compressor 1 by the suction side pipe 10. Reference numeral 11 denotes a cooling fan for the condenser 6.

The discharge pipe 13 of the compressor 12 of the low-temperature side refrigerant cycle S2 is connected to an auxiliary condenser 14, and the compressor 1
2, a pipe 16 in the cascade condenser 9, a dryer 17, and a capillary tube 1 via an oil cooler 15.
8, flows into the evaporator 20 from the inlet pipe 19,
This is a configuration that exits from 1 and returns to the compressor 12 from the suction side pipe 23 of the compressor 12 via the accumulator 22.

The high-temperature side refrigerant cycle S1 includes chlorodifluoromethane (R22), 1-chloro-1,1-difluoroethane (R142b) and propane octafluoride (R21).
8) is sealed. R22 has a boiling point of −40.75 ° C. at atmospheric pressure, R142b has a boiling point of −9.8 ° C.,
The boiling point of R218 is -36.7 ° C. Then, this mixture is condensed in the condenser 6, reduced in pressure in the capillary tube 8, flows into the cascade condenser 9, and evaporates. Here, the temperature of the cascade capacitor 9 is about −25 ° C.

The low-temperature side refrigerant cycle S2 includes chlorodifluoromethane (R22) and propane octafluoride (R218).
And an azeotrope of n-pentane. Here, chlorodifluoromethane (R22) and 8
The mixing ratio of propane fluoride (R218) is 43.8: 5
6.2, and n-pentane is formed by mixing chlorodifluoromethane (R22) and propane octafluoride (R218) at a ratio of 14% or less based on the total weight.
As a result, a refrigerant composition having a considerably low azeotropic point of −47 ° C. is enclosed. The refrigerant and compressor oil discharged from the compressor 6 flow into the pipe 16 in the cascade condenser 9 via the auxiliary condenser 14 and the oil cooler 15, and are cooled by evaporation of the refrigerant in the high-temperature side refrigerant cycle S1. Be condensed. Thereafter, the pressure is reduced in the capillary tube 18 and then flows into the evaporator 20 to evaporate. The evaporator 20 is attached to a wall of a freezer (not shown) in a heat exchange relationship to cool the inside of the freezer. Here, the evaporation temperature in the evaporator 20 reaches −60 ° C.

In the binary refrigeration system configured as described above, chlorodifluoromethane (R22), which is a refrigerant composition sealed in the low-temperature side refrigerant cycle S2, is an HCFC containing chlorine but also hydrogen, and octafluoride. Propane (R21
8) is an FC consisting only of fluorine and carbon, n-pentane does not contain chlorine, neither is subject to regulation on the ozone depletion problem, and its boiling point is chlorodifluoromethane ( R22) is -40 ° C,
Octafluoropropane (R218) at -36.7 ° C.
Since the azeotropic point of the mixture of the two is about -47 ° C., the refrigeration ability can be sufficiently exhibited as a substitute refrigerant for R502.

Incidentally, chlorodifluoromethane (R22)
Has a relatively high specific heat ratio of 1.18. Therefore, when sealed in a refrigerant circuit, there is a concern that the discharge temperature will rise. However, propane octafluoride (R21
Since 8) is mixed in a predetermined amount, an increase in the discharge temperature can be suppressed. As a result, a desired refrigeration capacity can be realized, and deterioration of oil sludge and oil can be suppressed.

Further, chlorodifluoromethane (R22)
Azeotrope of octafluoropropane (R218) is poorly compatible with conventional compressor oil, but by mixing a predetermined amount of n-pentane, the oil can be returned to the compressor in the refrigerant circuit. Can be. That is, n-pentane has a high boiling point of + 36.07 ° C., but has good compatibility with the oil of the compressor, and the oil is dissolved in n-pentane by mixing a predetermined amount of n-pentane. To return to the compressor, and it is possible to prevent adverse effects such as lock caused by oil rising of the compressor. Here, since n-pentane has a high boiling point, if it is mixed in a large amount, the evaporation temperature rises, so that a desired low temperature cannot be obtained, and there is a danger of explosion because it is flammable. For this reason, n-pentane is
By mixing at a ratio of 14% by weight or less, the oil can be returned to the compressor without increasing the evaporation temperature and ensuring the non-flammable region of n-pentane. As a result, the oil can be returned to the compressor 12 without having to provide an oil separator or the like to separate the oil in the refrigerant.

Here, the value of the specific heat ratio K (Cp / Cv) has a great effect on the discharge gas temperature of the compressor in adiabatic compression as shown by the following equation (1), and the molecular weight of the composition is Larger values indicate smaller values.

[0025]

(Equation 1)

Since n-pentane has a high boiling point, if it is mixed too much, the evaporation temperature rises and the desired low temperature cannot be obtained. However, it is necessary to mix n-pentane at a ratio of 14% by weight or less. Thereby, the oil can be returned to the compressor without increasing the evaporation temperature and while maintaining n-pentane in the non-combustible region.

[0027] Specifically, the results were confirmed by the following experiments.

Using a binary refrigeration system incorporating a refrigerant circuit shown in FIG. 1, chlorodifluoromethane (R22), 1-chloro-1,1-difluoroethane (R142b) and octafluoride were added to the high-temperature side refrigerant cycle S1. Propane (R218)
And 300 g of a non-azeotropic mixed refrigerant obtained by mixing at a ratio of 70: 25: 5% by weight with the low-temperature side refrigerant cycle S2
240 g of a mixed refrigerant of chlorodifluoromethane (R22), propane octafluoride (R218) and n-pentane, which is a mixed refrigerant of the present invention, is sealed in the mixed refrigerant of the present invention.
The weight and the n-pentane were changed from 0 to 15%, and the temperature and pressure change in each part of the apparatus were observed. The outside air temperature was 35 ° C. FIG. 2 shows the results of this experiment.

In FIG. 2, A is the temperature of the discharge pipe 13 on the low temperature side,
B is the temperature of the compressor 12 on the low temperature side, C is the discharge pressure on the high temperature side, D is the temperature of the suction pipe 23, E is the outlet temperature of the pipe 16 on the low temperature side in the cascade condenser 9, F is the discharge pressure on the low temperature side, G indicates the high-side suction pressure, H indicates the internal temperature, I indicates the inlet temperature of the evaporator 20, J indicates the outlet temperature of the accumulator 22, and K indicates the measurement result of the low-side suction pressure.

From this experimental result, it can be inferred that when the proportion of n-pentane exceeds 14% by weight, the inlet temperature I of the evaporator 20 increases, and that oil is stagnant in the refrigerant circuit. Further, it was confirmed that the ratio of n-pentane was appropriately in the range of 4 to 14% by weight from the stability of the internal temperature. When oil remains in the refrigerant circuit, the refrigerant passage is narrowed and the amount of circulating refrigerant is reduced.
, The heat exchange rate is lowered, so that the cooling performance is deteriorated.

As described above, according to the binary refrigeration apparatus of the present embodiment, it is possible to achieve a low oil temperature of about -60 ° C. in the evaporator without causing a danger of explosion or the like, with good oil return. It can be put to practical use as a medical freezer for blood cooling etc. without using a regulated refrigerant.

Also, since n-pentane is not produced in a factory, it can be easily obtained when used in a freezer or the like.
It is practical.

In this embodiment, a mixture of chlorodifluoromethane (R22), propane octafluoride (R218) and n-pentane has been described. However, dichloromonofluoromethane (R21) is used instead of n-pentane. The same effect can be obtained by mixing at a predetermined ratio. That is, dichloromonofluoromethane (R21) also has good compatibility with compressor oil, and by mixing propane at a ratio of not more than 20% by weight, dichloromonofluoromethane (R21) can be obtained without impairing the cooling performance. Can be returned to the compressor 12 in a state where the oil is dissolved in the
It is possible to prevent adverse effects such as lock due to oil rising. Here, the boiling point of dichloromonofluoromethane (R21) is +
Since the temperature is as high as 8.9 ° C., if it is added in an excessively large amount, the evaporation temperature increases, and since it is toxic, there is a problem that the working environment is deteriorated. However, by setting the proportion of dichloromonofluoromethane (R21) to 20% by weight or less, the oil can be returned while solving these problems.

Specifically, the results were confirmed by the following experiments.

Using a binary refrigeration system having a built-in refrigerant circuit shown in FIG. 1, chlorodifluoromethane (R22), 1-chloro-1,1-difluoroethane (R142b) and octafluoride were added to the high-temperature side refrigerant cycle S1. Propane (R218)
And 300 g of a non-azeotropic mixed refrigerant obtained by mixing at a ratio of 70: 25: 5% by weight with the low-temperature side refrigerant cycle S2
242 g of a mixed refrigerant of chlorodifluoromethane (R22), propane octafluoride (R218) and dichloromonofluoromethane (R21), which is a mixed refrigerant of the present invention, is sealed therein. By changing the weight percentage of (R21) from 0 to 25%, changes in temperature and pressure in each part of the apparatus were observed. The outside air temperature is 3
The condition was 5 ° C. FIG. 3 shows the results of this experiment.

In FIG. 3, L is the temperature of the discharge pipe 13 on the low temperature side,
M is the temperature of the compressor 12 on the low temperature side, N is the discharge pressure on the high temperature side, O is the temperature of the suction pipe 23, P is the outlet temperature of the pipe 16 on the low temperature side in the cascade condenser 9, Q is the discharge pressure on the low temperature side, R indicates the high-side suction pressure, S indicates the inside temperature, T indicates the inlet temperature of the evaporator 20, U indicates the outlet temperature of the accumulator 22, and V indicates the measurement result of the low-side suction pressure.

From the results of this experiment, when the proportion of dichloromonofluoromethane (R21) exceeds 20% by weight, the inlet temperature T of the evaporator 20 rises, and it is presumed that oil is stagnant in the refrigerant circuit. it can. In addition, it was confirmed that the ratio of dichloromonofluoromethane (R21) was appropriately in the range of 5 to 20% by weight from the stability of the internal temperature.

In this embodiment, the case where the refrigerant composition of the present invention is sealed in a binary refrigeration apparatus has been described. However, the present invention is not limited to this. The same effect can be exerted in a simple refrigeration cycle including the device and the evaporator.

[0039]

As described above, according to the present invention, chlorodifluoromethane (R22) contains H but also contains hydrogen.
CFC, propane octafluoride (R218) is an FC consisting of only fluorine and carbon, and n-pentane does not contain chlorine, and neither is subject to regulations on the problem of depletion of the ozone layer. The boiling points thereof are -40 ° C. for chlorodifluoromethane (R22) and -36.7 ° C. for propane octafluoride (R218), and the azeotropic point of both mixtures is about −47 ° C. As a substitute refrigerant for R502, sufficient refrigeration capacity can be exhibited.

Incidentally, chlorodifluoromethane (R22)
Has a relatively high specific heat ratio of 1.18. Therefore, when sealed in a refrigerant circuit, there is a concern that the discharge temperature will rise. However, propane octafluoride (R21
Since 8) is mixed in a predetermined amount, an increase in the discharge temperature can be suppressed. As a result, a desired refrigeration capacity can be realized, and deterioration of oil sludge and oil can be suppressed.

Further, chlorodifluoromethane (R22)
An azeotrope of propane and octafluoride (R218) has poor compatibility with oil. However, by mixing a predetermined amount of n-pentane, the oil can be returned to the compressor in the refrigerant circuit. That is, n-pentane has a boiling point of +36.0.
Although it is as high as 7 ° C., the compatibility with the oil of the compressor is good, and by mixing a predetermined amount of n-pentane, the oil can be returned to the compressor in a state where the oil is dissolved in n-pentane, It is possible to prevent adverse effects such as locking caused by oil rising of the compressor. Here, since n-pentane has a high boiling point, if it is mixed in a large amount, the evaporation temperature rises, so that a desired low temperature cannot be obtained, and there is a danger of explosion because it is flammable. For this reason. n-pentane at 14 ° C.
By mixing at the following ratio, the oil can be returned to the compressor without increasing the evaporation temperature and while ensuring the non-flammable region of n-pentane.

According to the configuration of the second aspect, the refrigerant composition can return the oil to the compressor without particularly providing an oil separator to separate the oil. That is,
Dichloromonofluoromethane (R21) also has good compatibility with the oil of the compressor, and the oil is dissolved in dichloromonofluoromethane (R21) by mixing a predetermined amount of dichloromonofluoromethane (R21). To return to the compressor, and it is possible to prevent adverse effects such as lock caused by oil rising of the compressor. Here, the boiling point of dichloromonofluoromethane (R21) is + 8.9 ° C.
The cooling performance is impaired if the amount is too large. However, by keeping the amount of dichloromonofluoromethane (R21) at a predetermined amount, the cooling performance does not decrease, and since the boiling point is high, the compression performance is reduced. After returning to the compressor, it can be evaporated in the compressor, and the compressor can be cooled.

According to the third and fourth aspects of the present invention, in the actual refrigerant circuit, the oil return is improved without using an oil separator, and the temperature is reduced to -60 ° C. in the evaporator without danger such as explosion. A low temperature of the order can be achieved, and it can be put to practical use as a medical freezer such as blood cooling without using a regulated refrigerant.

[Brief description of the drawings]

FIG. 1 is a refrigerant circuit diagram of a binary refrigeration apparatus in which a refrigerant composition of the present invention is sealed.

FIG. 2 is a graph showing experimental results of a binary refrigeration apparatus in which the refrigerant composition of the present invention is sealed.

FIG. 3 is a graph showing experimental results of a binary refrigeration apparatus in which another refrigerant composition of the present invention is sealed.

[Explanation of symbols]

 S1 High temperature side refrigerant cycle S2 Low temperature side refrigerant cycle 1,12 Compressor 9 Cascade condenser 20 Evaporator

Claims (4)

[Claims] An azeotropic mixture of chlorodifluoromethane and propane octafluoride and a mixture of n-pentane,
A refrigerant composition obtained by mixing n-pentane at a ratio of 14% or less based on the total weight of chlorodifluoromethane and octafluoropropane. 2. An azeotropic mixture of chlorodifluoromethane and propane octafluoride and a mixture of dichloromonofluoromethane, wherein dichloromonofluoromethane is added in an amount of 2 to the total weight of chlorodifluoromethane and octafluoropropane.
A refrigerant composition mixed at a ratio of 0% or less. 3. A two-stage refrigeration apparatus comprising a high-temperature side refrigerant circuit and a low-temperature side refrigerant circuit, wherein the refrigerant in the low-temperature side refrigerant circuit is condensed by a refrigerant passing through a cascade condenser in the high-temperature side refrigerant circuit. The refrigerant sealed in the low-temperature side refrigerant circuit is a mixture of azeotropic mixture of chlorodifluoromethane and octafluoropropane, and n-pentane, and n-
A binary refrigerating apparatus using a refrigerant composition obtained by mixing pentane at a ratio of 14% or less based on the total weight of chlorodifluoromethane and propane octafluoride. 4. A binary refrigeration apparatus comprising a high-temperature side refrigerant circuit and a low-temperature side refrigerant circuit, wherein the refrigerant in the low-temperature side refrigerant circuit is condensed by a refrigerant passing through a cascade condenser in the high-temperature side refrigerant circuit. The refrigerant sealed in the low-temperature side refrigerant circuit is an azeotropic mixture of chlorodifluoromethane and octafluoropropane, and a mixture of dichloromonofluoromethane, and the dichloromonofluoromethane is a total of chlorodifluoromethane and octafluoropropane. 20% by weight
A binary refrigeration apparatus using a refrigerant composition mixed at the following ratio.