JP2007085729A - Refrigerator system using non-azeotropic refrigerant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate trouble of a compressor by effectively condensing a low boiling point refrigerant, and making into a gaseous phase the refrigerant in the condensed state returned to the compressor in a refrigerator system using a non-azeotropic refrigerant. <P>SOLUTION: The single stage type refrigerator system is composed of a heat exchanger exchanging heat between a refrigerant circulated from the compressor to a condenser, an evaporator and back to the compressor, and a refrigerant in a process of reaching the evaporator from the condenser. The non-azeotropic refrigerant for use in the system is composed of the combination of a refrigerant having a standard boiling point near an ordinary temperature, and a refrigerant having a low standard boiling point of -60°C or lower. A dew point of the refrigerant at the pressure in a condensing process after compression is the ordinary temperature or higher, and the boiling point at that pressure is not lower than a dew point at low pressure in a process of reaching the compressor from the evaporator. As the combination of the above refrigerant components, butane or isobutane can be used as the refrigerant having a high boiling point near the room temperature and low steam pressure, and ethane, ethylene, or the like can be used as the refrigerant having a low boiling point suitable for ultra-low temperature. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention makes it possible to operate a single-stage refrigerator system composed of a single compressor and a condenser in a room temperature environment using a non-azeotropic refrigerant mixture and utilizing the characteristics of the non-azeotropic refrigerant, The present invention relates to a refrigerator system that realizes a system that realizes a low temperature of −40 ° C. or lower, particularly an ultralow temperature of −60 ° C. or lower.

Fluorocarbons, so-called chlorofluorocarbons, have been widely used as refrigerants for freezers and refrigerators. However, as chlorofluorocarbon-containing chlorofluorocarbons destroy ozone in the upper atmosphere, they do not contain chlorofluorocarbons or their substitutes. Development of a hydrocarbon-based refrigerant is desired.
In addition, many of the chlorofluorocarbons that do not contain chlorine have a high ability to absorb long-wavelength infrared rays and have an effect on global warming. It is necessary to devise as little as possible.
For this reason, a search for a gas that has a low-boiling hydrocarbon as a main component and satisfies the characteristics of a predetermined refrigerant has been made, but satisfying these conditions with a single gas is limited in the type of gas. It is difficult to adjust the characteristics by mixing two or more gases.
However, in the mixed refrigerant composed of these two or more components, the combination and composition of azeotropic refrigerants having a constant boiling point as in the case of conventional single component refrigerant gas, which are conventionally used, are limited. Many exhibit non-azeotropic properties.
Unlike non-azeotropic refrigerants and azeotropic refrigerants, these non-azeotropic refrigerants can have intermediate desirable characteristics by combining the properties of a single gas by selecting the gas composition as the component. On the other hand, because the boiling point and dew point are separated, the composition of the gas phase and the liquefied condensed phase is different under the conditions where the liquid phase and the gas phase coexist. Condensation did not occur and stable operation of the refrigeration system was difficult.

In order to deal with such problems, for example, those disclosed in Japanese Patent Application Laid-Open No. 51-83258 and Japanese Patent Publication No. 5-45867 include a non-azeotropic refrigerant mixture in a refrigeration system using a non-azeotropic refrigerant. Based on the relationship between the evaporation pressure and the corresponding saturation temperature, the temperature and pressure in the refrigeration system are controlled via the expansion valve, and the warning means is activated when these control conditions fall outside a certain range. In particular, the latter describes that heat exchange is performed between a low-temperature intake refrigerant in the process from the evaporator to the compressor and a high-pressure refrigerant from the compressor to the evaporator.
That is, the combination of the component refrigerants used is a low boiling point R-22 and a high boiling point refrigerant R-114, and the normal boiling points are -40.8 ° C and 3.85 ° C, respectively. The difference between the specific dew point and boiling point is large, which causes problems such as refrigerant suction in the liquid phase in the compressor, and avoids such a state by controlling the refrigerator system. Is.

On the other hand, in the thing of Unexamined-Japanese-Patent No. 8-166172, all the refrigerant components mentioned in the Example are fluorocarbons, and the normal boiling point is R-32: -51.7 degreeC, R- 125: −48.5 ° C., R-134a: −26.5 ° C. As a matter of course, a non-azeotropic refrigerant mixture composed of these is not liquefied unless the temperature is significantly lower than room temperature. A refrigeration system comprising a compressor, a condenser, a receiver, a decompressor, and an evaporator, and a heat exchanger that exchanges heat between the refrigerant flowing from the condenser to the receiver and the refrigerant flowing from the evaporator to the compressor It is a system.
In these refrigerants, the difference in boiling point is small, that is, the difference between the dew point and the boiling point as a mixed refrigerant is reduced to avoid the above problem, but the coexistence of the gas phase and the liquid phase in the system. For this condition, only the liquefied non-azeotropic refrigerant is separated by the receiver and sent to the evaporator, and liquid refrigerant enters the refrigerant gas entering the compressor to cause liquid compression. In order to prevent this, gas-liquid separation is also performed in the suction pipe.
However, such a system configuration is not only complicated, but, as described above, a non-azeotropic refrigerant has a gas-liquid coexistence state and the composition of the gas phase and the liquid phase is different. Makes it difficult to control to reach a stable steady state.
JP-A-51-83258 Japanese Patent Publication No. 5-45867 JP-A-8-166172

  In the refrigerator system using a non-azeotropic refrigerant, the characteristics of the non-azeotropic refrigerant obtained by combining a low boiling point refrigerant having a low standard boiling point that is difficult to condense or cannot condense in a room temperature environment with a refrigerant having a high standard boiling point. Condensed refrigerant in the low-temperature and low-pressure refrigerant returned to the compressor is effectively condensed, and the trouble of the compressor is solved.

In a single-stage refrigerator system comprising a compressor, a condenser, an evaporator, and a heat exchanger that exchanges heat between the refrigerant from the evaporator to the compressor and the refrigerant in the process from the condenser to the evaporator ,
Using a non-azeotropic refrigerant consisting of a combination of a refrigerant having a normal boiling point near room temperature and a refrigerant having a normal boiling point of −60 ° C. or lower,
In a condenser under compression conditions, heat is dissipated into the room temperature atmosphere by condensing and liquefying high-boiling components,
Endothermic cooling by vaporizing the condensed phase rich in low boiling point components in the evaporator under reduced pressure conditions,
Depending on these compression and decompression conditions,
Achieving a phase change between the condensation of the gas phase rich in the low boiling point component on the high pressure side and the vaporization of the condensed phase rich in the high boiling point component on the low pressure side in the heat exchanger;
A control method of a refrigerator system, characterized in that
Also, a single stage refrigeration comprising a compressor, a condenser, an evaporator, and a heat exchanger that exchanges heat between the refrigerant from the evaporator to the compressor and the refrigerant in the process from the condenser to the evaporator. A non-azeotropic refrigerant used in the machine system,
A combination of a refrigerant having a normal boiling point near room temperature and a refrigerant having a low normal boiling point of −60 ° C. or lower,
The dew point under high pressure from the compressor through the heat exchanger to the evaporator is above room temperature and the boiling point is higher than the dew point under low pressure from the evaporator through the heat exchanger to the compressor. Is a non-azeotropic refrigerant characterized by
Furthermore, the high boiling point gas having a boiling point near the room temperature is butane or isobutane,
The low boiling point gas of −60 ° C. or lower is ethane or ethylene, and is a non-azeotropic refrigerant whose characteristics are improved by adding R-14 (perfluoromethane) thereto.
It is characterized by
Moreover, the butane-ethane mixing ratio of the mixed gas in which the high boiling point gas is butane and the low boiling point gas is ethane is in the range of 90/10 to 60/40, and R-14 (perfluoromethane) with respect to this mixed gas. Addition amount exceeds 0% and 9% or less,
The high boiling point gas is butane and the low boiling point gas is ethylene, butane / ethylene mixing ratio is in the range of 90/10 to 70/30, and R-14 (perfluoromethane) to this mixed gas. Addition amount exceeds 0% and 0.7% or less,
The mixed gas in which the high boiling point gas is isobutane and the low boiling point gas is ethane has an isobutane-ethane mixing ratio in the range of 90/10 to 70/30, and R-14 (perfluoromethane) relative to this mixed gas. Addition amount exceeds 0% and 15% or less,
Further, the mixed gas in which the high-boiling gas is isobutane and the low-boiling gas is ethylene has an isobutane-ethylene mixing ratio in the range of 90/10 to 80/20, and R-14 (perfluoromethane to this mixed gas) ) Is a non-azeotropic refrigerant mixture for ultra-low temperature with improved characteristics by exceeding 0% and not more than 10%.

In the process of searching for a hydrocarbon ultra-low temperature azeotropic refrigerant that does not contain chlorine, the present inventors have developed a hydrocarbon-based refrigerant gas that realizes an ultra-low temperature of −60 ° C. or lower, that is, a hydrocarbon having an extremely low standard boiling point. On the other hand, an attempt was made to realize a non-azeotropic refrigerant that can be used in a room temperature environment by combining hydrocarbons having a high normal boiling point, a normal boiling point near room temperature, and a low vapor pressure.
That is, if it can be condensed by the compression process near room temperature, or if it can be condensed by cooling by heat exchange with the refrigerant from the evaporator as described above, even in non-azeotropic refrigerants, such as gas-liquid separation We focused on the fact that a complicated mechanism is unnecessary, the configuration can be simplified, and the above-described instability of the refrigerator caused by the characteristic of the non-azeotropic refrigerant separating the boiling point and the dew point can be eliminated.
The characteristics of the non-azeotropic refrigerant and a system using the characteristics will be described below.
FIG. 20 schematically shows a state diagram by taking butane and ethylene as an example of the non-azeotropic refrigerant mixture.

For example, when butane (boiling point: −0.5 ° C.) and ethylene (boiling point: −103.7 ° C.) are taken as an example, the dew point and the vapor phase line representing the boiling point and the liquid phase line are divided into upper and lower parts as shown in the figure.
In addition to the phase diagram at atmospheric pressure, the phase diagram under high pressure sent from the compressor and in the condensation process and the phase diagram under low pressure in the evaporation process are almost parallel to each other as shown by the dashed line and the broken line, respectively. The relationship moved to.
The combination of component gases with significantly different boiling points such as butane and ethylene results in a state diagram that is remarkably inclined from high to low boiling points as shown in the figure, and the characteristic that the boiling point and dew point change greatly due to slight changes in composition. can get.
In the figure, when the room temperature range (R), which is the operating environment of the refrigerator, is about 35 ° C. to 20 ° C. as shown by hatching, the range that can be operated under this temperature condition is the high-pressure side liquid phase. It is necessary that the line be above this temperature range. At the same time, in order not to cause liquid compression in the compressor, the low-pressure side gas line must be equal to or lower than the temperature of the refrigerant when the compressor is sucked.
In the figure, the range that satisfies the former condition is a composition of E0% or less represented by the perpendicular line passing through the point A ′ where the horizontal line passing through 35 ° C. intersects with the high-pressure side liquidus line. It is necessary to operate in the temperature range above the gas phase line on the left side of the crossing A ″.
When operating with a single-stage refrigeration system consisting of a single (one unit) compressor, condenser, and evaporator using a non-azeotropic refrigerant, if the above conditions are met, exceptional control conditions and gas-liquid A separation device is not necessary, and the refrigerator system can be configured with a simple configuration.

However, the range satisfying these conditions is extremely narrow for the former as shown in the figure, and the latter cannot be achieved in a room temperature environment.
Therefore, in order to achieve these conditions, it is difficult to operate in the temperature range above the gas phase line on the low pressure side, because the refrigerant after the evaporation process is low temperature, as described above. Heat is exchanged with the refrigerant on the high pressure side, and in addition, condensation on the high pressure side is promoted.
The present inventors have found that the problem arising from these characteristics, which has been a drawback, can be solved by utilizing the characteristics of the heat exchange conditions that are different from the dew point and boiling point of the non-azeotropic refrigerant.
In the figure, it can be seen that the composition range of the refrigerant having a dew point equal to or higher than the room temperature is relatively wide when the refrigerant contains a high boiling point component. Therefore, in this range, the refrigerator system can release heat outside the system, that is, to the room temperature atmosphere.
On the other hand, in the system system, it is only necessary to achieve a condition in which all of the high-pressure side gas is condensed and liquefied by heat exchange and at the same time, all of the low-pressure side refrigerant is vaporized.
In other words, the above-described single-stage refrigerator system can be achieved if the amount of heat taken into the system system can be pumped out of the condenser at the ambient temperature from the viewpoint of heat exchange with the outside of the system. The lowest possible refrigeration temperature is determined by the boiling point of the refrigerant that can be condensed during the condensation process, and if the conditions for condensation / liquefaction of the high-pressure refrigerant and evaporation / vaporization of the low-pressure refrigerant are met, A refrigerator system is established.
Therefore, this problem can be solved if conditions of such condensation / liquefaction and evaporation / vaporization can be achieved by heat exchange between these refrigerants together with a refrigerant having a dew point equal to or higher than the environmental temperature.

When this condition is seen from the above-described state diagram of the non-azeotropic refrigerant, it is understood that the high-pressure side liquidus line should be above the low-pressure side gas line.
In other words, in the figure, the relationship between the temperature of the refrigerant having a composition of ethylene E% whose high-pressure side vapor line is above room temperature and the temperature is perpendicular to the point E and The intersection points are A, B, C, and D from the top, but it is understood that the above condition can be achieved if the point A is equal to or higher than the atmospheric temperature and the point B is equal to or higher than the point C. If heat loss is ignored, the point D is the lowest temperature that can be achieved.
Of course, in order to establish these systems, it is necessary to consider the loss from ideal conditions, and although the relationship with the heat balance outside the system system is not mentioned, the amount of heat released by latent heat in the condenser is It is necessary to be sufficiently large and have a large interval between the points B and C and to be able to transfer a sufficient amount of heat, and this amount of heat is determined by the component composition rich in high-boiling refrigerants. In order to achieve the above, it is necessary to determine the optimum range in combination with these conditions.
Since the characteristics of these non-azeotropic refrigerants have not been fully elucidated, no quantitative relationship has been established, and there are few available data to determine specific conditions. What is necessary is just to determine empirically and experimentally from the characteristic of each refrigerant | coolant.
As a high boiling point gas having a normal boiling point near room temperature that can be used in such a system, butane, isobutane, isomers of various butenes (C ₄ H ₈ ), ethyl acetylene (C ₄ H ₆ ), R-134a (CH ₂ FCF ₃ ) and the like, and examples of the low boiling point gas realizing the ultra-low temperature aimed by the present invention include ethane, ethylene, or fluorocarbon R-14 (perfluoromethane) containing no chlorine.
In order to achieve an ultra-low temperature with these mixed gases, the gas composition must contain a considerable amount of low-boiling gas, and thus the pressure in the condensation process is considerably high. As a feature, the gas phase and the liquid phase coexist over a wide temperature range and pressure range, so that a substantial amount of the liquid phase rich in high-boiling components remains after the evaporation process. By cooling the high-pressure refrigerant from the compressor, the condensation process within the range of 15 atm (maximum 20 atm) or less, which is the practical capacity of the compressor, is promoted, and operation with a single-stage refrigerator system becomes possible.
Examples of the refrigerant gas suitable for the present invention and characteristics as these refrigerants are given below.

As the high boiling point gas component in the non-azeotropic refrigerant of the present invention, the above butane and isobutane are both hydrocarbons widely used as fuels and the like, but the boiling points are −0.5 ° C. and −11. Since it is 7 ° C. and near room temperature and its vapor pressure is extremely low, it can be liquefied at a relatively low pressure. Butenes, ethylacetylene, and R-134a have similar characteristics.
In addition, as a low boiling point component that realizes an ultra-low temperature, R-14 has a standard boiling point of −60 ° C. or less as a component added to ethane, ethylene, and a mixed refrigerant composed of these in the above table. Although effective in achieving this, it is difficult to condense in a room temperature environment because of its low critical temperature and high vapor pressure.In particular, R-14 cannot be used alone in a single-stage refrigeration system, but it has a low vapor pressure. Combined with high boiling point components, it raises the liquefaction condensation temperature and lowers the vapor pressure, allowing the high-temperature and high-pressure refrigerant from the compressor to the evaporator to exchange heat with the low-temperature refrigerant from the evaporator to the compressor. By cooling, the refrigeration system can be operated by condensing and liquefying in a range of 15 atm or less and a maximum of 20 atm (1.5 to 2.0 MPa) which is a commonly used compression function force range.
Since the exchange of heat energy by these heat exchanges is merely exchange of heat in the refrigerator system, in order to operate the entire refrigeration system, the heat in the system must be effectively released to the external environment at room temperature. In the present invention, the refrigeration power of the system is maintained by releasing the latent heat of the refrigerant rich in the high boiling point component having a low vapor pressure from the condenser.
Therefore, it is necessary for the high boiling point component to be liquefied in a room temperature environment, and to have a refrigerant charge amount and a condenser capacity for releasing latent heat sufficient to maintain the refrigeration system.

In FIG. 1, the outline | summary of the refrigerator system used for the Example of this invention is shown.
In the figure, 1 is a compressor, and the refrigerant gas discharged from the compressor is decompressed by a throttle valve (capillary tube) 6 through an outlet pipe 10 through a condenser 2 and a heat exchanger 50 and is stored in a freezer 8. It vaporizes in the evaporator 7 and cools the inside of the freezer. The return gas from the evaporator cools the refrigerant in the forward path by the heat exchanger 50 through the return pipe 12, and then returns to the compressor.
In a refrigeration system using a non-azeotropic refrigerant, the composition of the refrigerant decompressed in the evaporator includes a gas phase rich in low-boiling components and a condensed liquid phase rich in high-boiling components as the pressure drops. The so-called wet gas is sent to the compressor suction side. However, since the suction of the condensed liquid is not preferable for the compressor, in the above prior art, the return refrigerant is accompanied by a condensed phase. It was operated under no conditions, or was gas-liquid separated by an accumulator.
In the present invention, the characteristics of these non-azeotropic refrigerants, which have conventionally caused troubles in the operation of the refrigerator, are used in reverse, and in heat exchange between the return refrigerant and the high-pressure side refrigerant. By condensing all of the high-pressure side gas with the latent heat of the condensed liquid phase of the return refrigerant, while vaporizing the entire liquid phase of the return refrigerant, the refrigerant gas composition surrounding the system is maintained at the initial set value and stable operation is achieved. The condition is realized.
The function of the heat exchanger is important for this purpose, but the type itself can be of any structure, but its heat exchange capacity needs to be large.
The heat exchanger used in the present invention has the structure shown in FIG. 2 and is formed by brazing 15 the forward pass 10 from the compressor and the return pass 12 from the evaporator. In order to satisfy the heat exchange conditions, the total length L of the heat exchanger was 3 m.

The operating conditions and results of this heat exchanger are shown below.
The refrigerator system used for the experiment is as follows.
Refrigerator model: Model name SC-15CNX manufactured by Danfors, capacity: 213 liter throttle valve use experiment 1 is filled with 250 g of butane-ethylene mixed non-azeotropic refrigerant mixed with 15% ethylene, experiment 2 Further, 10 g (4%) of R-14 (fluoromethane) was added thereto for operation.
The measurement points are as follows in FIG.
All temperatures are piping temperatures, and pressure is gauge pressure.
Low pressure side inlet: A, High pressure side outlet: B
Low pressure side outlet: E, High pressure side inlet: F

In the data of Table 2, the high-pressure side inlet temperature is below room temperature because the temperature of the wall of the heat exchanger is measured. The temperature is slightly higher than this, and above room temperature. The temperature at the outlet on the high-pressure side is the same, which is lower than the measured temperature, and a similar temperature difference occurs on the low-pressure side.
As a result, the return gas on the compressor suction side is about room temperature, while the refrigerant on the high pressure side toward the evaporator is below the boiling point under the pressure, and thus it is understood that the above condition is satisfied.
Further, in Tables 3 and 4 below, R-14 was added in the range of 0 to 3.85% to a refrigerant having a butane-ethylene mixing ratio of 90/10 and a butane-ethylene mixing ratio of 85/15, respectively. The relationship between the pressure and temperature of the refrigerant on the high-pressure side and low-pressure side that can be achieved in the heat exchanger in this case will be described. The refrigerator system used for the experiment has the same conditions as in (1) above.

(1) Characteristic confirmation of non-azeotropic refrigerant with R-14 added to butane-ethane and butane-ethane mixed gas Experiment 1
Using the refrigeration system shown in Fig. 1, the characteristics of the butane and ethane mixed gas refrigerants were confirmed as basic data by actual operation.
The results are shown in Table-5 and FIG.

Note: The pressure value is the differential pressure (gauge pressure) from the atmospheric pressure, and the following actual machine operation data is the same.
From the graph of FIG. 3, there is a very gradual peak that achieves an internal temperature of around −60 ° C. with the ethane concentration near 20-30% as an apex, while the pressure on the high-pressure side, that is, the compressor side, increases with the amount of ethane added It rises, and when the ethane content exceeds 30%, it rises rapidly.
As a refrigerator for ultra-low temperature, it aims to achieve an internal temperature of -60 ° C or lower and further -80 ° C or lower. Although the effect gradually decreases toward ethane 10% or less and 40% or more, it is still around -55 ° C. Moreover, although the inside temperature falls again from the vicinity of the ethane addition amount exceeding 40%, the high pressure side pressure also rises rapidly, which is not preferable.
Therefore, in order to improve the refrigerant characteristics in a region where these internal temperatures are kept around −60 ° C. and become almost flat, the components of butane-ethane type refrigerant gas are ethane corresponding to these ranges: 10, 20, The results of confirming the change in characteristics with respect to the amount of addition of R-14 gas at 30 and 40%, that is, the mixing ratios of 90/10, 80/20, 70/30, and 60/40 are shown below. Shown in
The experimental conditions are the same as described above, and the results are shown in Tables 6, 7, 8, and 9 and FIGS.

Experiment-2
R-14 was added in increments of 5 g to a total of 250 g of mixed gases having a butane-ethane mixing ratio of 90/10, and the effect of the addition was confirmed.

According to the graph of FIG. 4 in which the data in Table 6 is plotted, R-14: 0% at a temperature in the range of −50 ° C., and there is almost no change even if R-14 is added thereafter. From this, there is a tendency for the internal temperature to rise. On the other hand, the high-pressure side pressure suddenly rises nevertheless, reaching the practical limit when the R-14 addition amount is around 9%.
Experiment-3
R-14 was added in increments of 5 g to a total of 250 g of mixed gas with a butane-ethane mixing ratio of 80/20, and the effect of the addition was confirmed.

According to the graph of FIG. 5 in which the data in Table 7 are plotted, the internal temperature is reduced to −60 ° C. or less with the addition of R-14: 1% or less, and the effect of lowering the internal temperature is obtained with the increase in the amount added. Yes. In particular, the temperature inside the chamber is remarkably lowered from around R-14: 8% and becomes -80 ° C. or lower. However, the pressure on both the high pressure side and the low pressure side rises, and the practical limit is reached around R-14: 9%. .
Experiment-4
R-14 was added in increments of 5 g to a total of 250 g of mixed gas having a butane-ethane mixing ratio of 70/30, and the effect of the addition was confirmed.

According to the graph of FIG. 6 in which the data of Table 8 is plotted, R-14 is 0% or less at −60 ° C., but the effect of lowering the internal temperature is obtained with an increase in the amount of R-14. The pressure on the high-pressure side and the low-pressure side increases with the increase in the amount of R-14 added. R-14: The internal temperature is -85 ° C or lower at 9-10%, but the pressure on the low pressure side is 1.0. This is almost its practical limit.
Experiment-5
R-14 was added in increments of 5 g to a total of 250 g of mixed gas having a butane-ethane mixing ratio of 60/40, and the effect of the addition was confirmed.

According to the graph of FIG. 7 in which the data of Table 9 is plotted, the internal temperature achieves −60 ° C. when the addition amount of R-14 is 4% or more, but thereafter, the increase in the addition amount of R-14 The temperature drop in the refrigerator is very gradual and not effective.
On the other hand, the pressure increases on both the high-pressure side and the low-pressure side, and in particular, the low-pressure side pressure is near the practical limit from when R-14 is not added.
From the above, the characteristics of the refrigerant aimed at by the present invention are the regions where the ethane content of the butane-ethane mixed component exceeds 10% and less than 40%, that is, the mixing ratio exceeds 90/10 and less than 60/40, and R- It can be seen that it can be achieved in the range exceeding 14: 0% and 9% or less.
In this range, these three-component non-azeotropic refrigerants were able to maintain stable conditions over a wide range of high pressure side pressure, low pressure side pressure and internal temperature.

(2) Confirmation of characteristics of non-azeotropic refrigerant by addition of butane-ethylene and butane-ethylene mixed gas and R-14 Ethylene has a very low boiling point and is suitable as an ultra-low temperature refrigerant. Is extremely high and cannot be handled by a refrigerator system operating at room temperature (see Table 1).
Therefore, the characteristics of the refrigerant gas in which these gases are mixed by adding butane as described above are checked, and a range that can be used as a refrigerant in a refrigerator system that operates at room temperature is searched. By adding fluoromethane) to improve the characteristics as a refrigerant for ultra-low temperature, a refrigeration system operating at room temperature is aimed at -60 ° C by the present inventors without using a complicated binary refrigeration system. The characteristics and composition range of the mixed refrigerant that achieves an extremely low internal temperature of −80 ° C. or lower were confirmed.
The operating conditions such as the refrigerator system are the same as above.

Experiment-1: Confirmation of characteristics of butane and ethylene mixed gas as refrigerants Using the refrigerator system shown in FIG. 1, the characteristics of butane and ethylene mixed gas as refrigerants were confirmed as basic data by actual operation.
The results are shown in Table 10 and FIG.

From the graph of FIG. 8 in which the results of Table-10 are plotted, it can be seen that the freezer temperature decreases markedly as the ethylene concentration increases, and the pressure on the compressor side increases accordingly.
As an ultra-low temperature freezer, it aims to easily achieve an internal temperature of -60 ° C or lower and to achieve -80 ° C or lower. Although it can be achieved, even if the concentration is higher than −70 ° C., it tends to become almost flat, and the temperature inside the chamber exceeds −70 ° C. again in the vicinity of 30%. Operation became unstable, and confirmation at 35% or more was not possible.
Therefore, in order to improve the refrigerant characteristics in a region where the internal temperature becomes −60 ° C. or less and becomes substantially flat, the components of the butane-ethylene-based refrigerant gas are ethylene corresponding to these ranges: 10, 15, 20 30%, that is, a butane-ethylene mixing ratio: 90-20, 85/15, 80/20, 70/30 in total, 250 g of the mixed gas is added to 5 to 20 g of R-14 gas. The characteristic change with respect to the added amount was confirmed. In addition, the experiment of adding R-14 to a mixed gas of butane-ethylene mixing ratio: 95/5 shows that the internal temperature does not decrease to −60 ° C. or lower at R-14: 1.96%, The experiment was terminated because the effect was not expected.
The experimental conditions are the same as described above, and the results are shown in Tables 11, 12, 13, and 14 and FIGS.
Experiment-2
R-14 was added in increments of 5 g to a total of 250 g of mixed gas of 90/10 butane-ethylene mixture ratio, and the effect of the addition was confirmed.

According to the graph of FIG. 9 in which the data of Table-11 is plotted, the internal temperature of −60 ° C. is achieved at R-14: 0%, but it is −80 ° C. or less at around R-14: 2%, It turns out that the addition effect of R-14 is remarkable.
However, the effect is almost saturated at about R-14: 5.0%, while the high-pressure side pressure tends to increase rapidly, reaching about the practical limit at about 7.4%. Further stable operation became difficult.
Experiment-3
R-14 was added in increments of 5 g to a total of 250 g of mixed gas having a butane-ethylene mixing ratio of 85/15, and the effect of the addition was confirmed.

According to the graph of FIG. 10 in which the data of Table-12 is plotted, an increase in the R-14 concentration provides an effect of lowering the internal temperature, but the temperature decrease effect becomes moderate from around 4%. : Around 7.4%, the pressure on the high-pressure side increased significantly, making operation difficult.
Experiment-4
R-14 was added in increments of 5 g to a total of 250 g of mixed gas having a butane-ethylene mixing ratio of 80/20, and the effect of the addition was confirmed.

According to the graph of FIG. 11 in which the data of Table-13 is plotted, the effect of decreasing the internal temperature is obtained by increasing the amount of R-14, but the effect of increasing R-14 peaks around 6.0%. The effect tends to decline more slowly than that.
At the same time, there is an increase in the high-pressure side pressure, and the effect of actual machine operation at 7.4% or more cannot be expected.
Experiment-5
R-14 was added in increments of 5 g to a total of 250 g of mixed gas having a butane-ethylene mixing ratio of 70/30, and the effect of the addition was confirmed.

According to the graph of FIG. 12 in which the data of Table-14 is plotted, the internal temperature rises conversely with the addition of R-14, and the desired effect cannot be obtained. On the other hand, the high-pressure side pressure rises rapidly with the concentration of R-14, and approaches the practical limit in actual machine operation in the vicinity of R-14: 6%.
Also, the gauge pressure on the low pressure side is large, and R-14: 1 is slightly above practical limit, and the effect as a refrigerant cannot be expected.
From the above, it can be seen that the characteristics of the refrigerant aimed at by the present invention can be achieved when the butane-ethylene mixed component has an ethylene content of 10 to 30%, R-14: 0% and 7.5% or less.
In this range, these three-component non-azeotropic mixed refrigerants can maintain stable conditions over a wide range of high pressure side pressure, low pressure side pressure, and internal temperature.

(3) Characteristic confirmation of non-azeotropic refrigerant by addition of isobutane-ethane and isobutane-ethane mixed gas and R-14 Even if isobutane is an isomer instead of butane, as shown in the data in Table 1 above, Since the physical properties are substantially the same, a non-azeotropic refrigerant having similar characteristics can be obtained.
The configuration of the refrigerator system is the same as (1) and (2) above, but as a refrigerator, Danforth NLE6F, product name: FB-75 was used. The refrigerant gas filling amount was reduced by half to 100 g to 125 g, and the capacity was small, so that the refrigerating capacity such as the freezer temperature was slightly inferior.

According to FIGS. 13 to 15 in which the data of Tables 15 to 17 are plotted, the internal temperature is slightly higher due to the small capacity as described above compared with the characteristics of the butane-ethane mixed refrigerant, and the pressure in the system However, the high pressure side and the low pressure side tend to be slightly higher, but it is understood that the characteristics as the refrigerant are almost common.
From these data, as in the case of the butane-ethane mixed gas, the mixing ratio of isobutane and ethane gradually shows an effect from 90/10, but when ethane is 40%, the high pressure side pressure is almost the practical limit.
In addition, when the mixing ratio of isobutane-ethane gas mixture is 90/10 to 70/30, the effect of addition of R-14 is effective even in a small amount, but the high pressure increases rapidly with this. In particular, since there is a tendency to be linked to an increase in ethane concentration, isobutane-ethane 70/30 is almost the limit, and the amount of R-14 added is also about 15%, which is a practical limit.

(4) Characteristic confirmation of non-azeotropic refrigerant by addition of isobutane-ethylene and isobutane-ethylene mixed gas and R-14 The configuration of the refrigerator system is the same as (1) to (3), but the isobutane-ethylene mixed gas For confirmation of characteristics, Unidart GL-99EJ, product name: F-14L (refrigerant filling amount: 120 g to 160 g):
In other experiments, Danforth NLE6F, product name: FB-75 was used. The refrigerant filling amount was reduced to half as 100 g to 125 g, and since the capacity was small, a result that the refrigerating capacity such as the temperature inside the freezer was slightly inferior was obtained.

The data of Tables 18-21 are plotted and shown in FIGS.
According to Fig.16, the capacity is small, for example, the refrigerant charge is halved, so there are differences such as slightly higher internal temperature compared to the characteristics of butane-ethylene mixed gas, and when the ratio of ethylene increases. The effect of the characteristic that the vapor pressure is high appears, the pressure on the high-pressure side increases rapidly, and the pressure including the low-pressure side tends to be unstable, which appears at a lower concentration.
The reason for this is considered to be due to the small capacity of the refrigerator as in the case of the experiment of (3), and the basic characteristics of the refrigerant are the same characteristics as the butane-ethylene mixed gas. I understand.
Moreover, according to FIGS. 17-19, compared with the case where it is based on a butane-ethylene mixed gas, the inside temperature is slightly higher, and the pressure appears higher on both the high pressure side and the low pressure side. Although the pressure on the deep low-pressure side tends to be high, it can be understood that the refrigerant gas can be handled in the same manner as the butane-ethylene mixed refrigerant in consideration of the small refrigerator capacity as in the case of (3).
From these data, as in the case of the butane-ethylene mixed gas, the characteristics of isobutane and ethylene as a cryogenic refrigerant can be evaluated from the mixing ratio 90/10, but the pressure condition becomes unstable in the vicinity of 20% ethylene, Although there is a side due to the capacity of the refrigerator, it is almost the practical limit.

In addition, in the mixing ratio 90/10 to 80/20 of the isobutane-ethylene mixed gas, the effect of the addition of R-14 is effective even in a very small amount, but the high pressure increases with it. On the other hand, the internal temperature does not decrease as much as the left, and is substantially saturated around 10%.
As is clear from the above experimental examples, a non-azeotropic refrigerant composed of a combination of a low-vapor pressure gas having a boiling point near room temperature and a low-boiling gas necessary for achieving ultra-low temperature is used in a single stage at room temperature. By using the refrigerator system, an extremely low temperature of −40 ° C., particularly −60 ° C. or less can be realized.
In order to achieve the target ultra-low temperature with this non-azeotropic refrigerant, it is necessary to use the non-azeotropic characteristics of the refrigerant as a refrigerator system, and the high-boiling gas rich gas component of the compressed refrigerant gas High-pressure refrigerant gas due to the evaporation heat of the liquid phase component rich in high-boiling point gas by heat exchange between the refrigerant gas after exhaust heat in the condenser and the refrigerant from the evaporator, along with heat exhaustion due to condensation in the condenser The heat exchange in the system accompanied by the condensation of the low-boiling component gas is performed by cooling the gas.
That is, the present invention is a refrigeration system that maximizes the refrigerating capacity of a non-azeotropic refrigerant composed of a combination of these heat exchange systems and the characteristics of the non-azeotropic refrigerant, and is a refrigerant suitable for the system. From the properties of these gases and the behaviors observed in the experiments, it is clear that there are regions that can be similarly applied even when two or more of high-boiling gas and low-boiling gas are combined.
In addition to these experimental examples as refrigerants that can be employed in the present invention, in the mixed refrigerant of 1-butene and ethylene listed in Table 1, the mixed refrigerant of 70 parts of 1-butene and 30 parts of ethylene is -74. The internal temperature of 5 ° C. (high pressure side pressure: 1.2 MPa, low pressure side pressure: 0.1 MPa, gauge pressure, respectively, the same shall apply) is achieved, and further, 5-10 parts of R-14 are added, The internal temperature of 77 ° C. (high pressure side pressure: 1.4 MPa, low pressure side pressure: 0.13 MPa) and −88 ° C. (high pressure side pressure: 2.0 MPa, low pressure side pressure: 0.17 MPa) was achieved.
In addition, butenes, ethylacetylene, and R-134a listed in Table 1 can be similarly applied due to their properties, and are not limited to these examples, and substances having similar high boiling point and low vapor pressure characteristics. The present invention can be applied in combination with a low boiling point substance.

The present invention is capable of stable operation over a long period of time in a refrigerator system having a simple configuration as described above, and is low in cost because of its simple structure and inexpensive materials used for maintenance. In addition, maintenance and maintenance work can be performed without causing large fluctuations in the temperature conditions of the refrigerator.
The ultra-low temperature non-azeotropic refrigerant mixture of the present invention can easily achieve an ultra-low temperature of −60 ° C. or less with an inexpensive gas component, and in particular, can stably maintain an ultra-low temperature of −80 ° C. or less. Can be widely used for long-term preservation of biological tissues, especially valuable biological tissues used for transplantation and tissue culture, in response to the demands of these bio industries. It contributes.
In addition, by using fluorocarbon as a refrigerant in combination with hydrocarbon refrigerants, it is possible to effectively improve refrigeration capacity and minimize the use of chlorofluorocarbons, thereby destroying the environment such as the green house effect. The effect on is very small.

It is a conceptual diagram of the refrigeration system of this invention. The example of the heat exchanger used for this invention is shown. Characteristics of butane-ethane mixed gas, Butane-ethane: 90/10 mixed gas + R14 characteristics, Butane-ethane: 80/20 mixed gas + R14 characteristics, Butane-ethane: 70/30 mixed gas + R14 characteristics, Butane-ethane: 60/40 mixed gas + R14 characteristics, Characteristics of butane-ethylene mixed gas, Characteristics of butane-ethylene: 90/10 mixed gas + R-14, Butane-ethylene: 85/15 mixed gas + R-14 characteristics, Butane-ethylene: 80/20 mixed gas + R-14 characteristics, Butane-ethylene: 70/30 mixed gas + R-14 characteristics, Characteristics of isobutane-ethane mixed gas, Isobutane-ethane: 90/10 mixed gas + R-14 characteristics, Isobutane-ethane: 70/30 mixed gas + R-14 characteristics, Characteristics of isobutane-ethylene mixed gas, Properties of isobutane-ethylene: 90/10 mixed gas + R-14, Characteristics of isobutane-ethylene: 80/20 mixed gas + R-14, Characteristics of isobutane-ethylene: 70/30 mixed gas + R-14, The gas / liquid phase state (schematic diagram) of the non-azeotropic refrigerant (butane-ethylene) is shown.

Explanation of symbols

1 Compressor 2 Condenser
6 Throttle valve (capillary)
7 Evaporator (Evaporator)
8 Freezer,
10 Compressed gas forward passage 12 Return gas pipe 50 Heat exchanger 15 Joint (brazing)

Claims (2)

In a single-stage refrigerator system comprising a compressor, a condenser, an evaporator, and a heat exchanger that exchanges heat between the refrigerant from the evaporator to the compressor and the refrigerant in the process from the condenser to the evaporator ,
Using a non-azeotropic refrigerant consisting of a combination of a refrigerant having a normal boiling point near room temperature and a refrigerant having a normal boiling point of −60 ° C. or lower,
In a condenser under compression conditions, heat is dissipated into the atmosphere at room temperature by condensing and liquefying a composition rich in high-boiling components,
Endothermic cooling by evaporation of the low-boiling component rich composition in the evaporator under reduced pressure conditions,
These compression and decompression pressure conditions are
In the heat exchanger, the high pressure side liquid phase line in the phase diagram is the low pressure side gas line in the phase diagram by the condensation of the gas phase rich in the low boiling point component on the high pressure side and the vaporization of the condensed phase rich in the high boiling point component on the low pressure side. Achieved as a higher pressure condition,
A control method of a refrigerator system, characterized in that. Single stage refrigerator system comprising a compressor, a condenser, an evaporator, and a heat exchanger that exchanges heat between the refrigerant from the evaporator to the compressor and the refrigerant in the process from the condenser to the evaporator A non-azeotropic refrigerant used for
A combination of a refrigerant having a normal boiling point near room temperature and a refrigerant having a low normal boiling point of −60 ° C. or lower,
The dew point under high pressure from the compressor through the heat exchanger to the evaporator is above room temperature and the boiling point is higher than the dew point under low pressure from the evaporator through the heat exchanger to the compressor. A non-azeotropic refrigerant characterized by

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