JP2003013049A - Three component-based refrigerant for ultra low temperature - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a refrigerant for ultra low temperature in which an amount of fluorocarbon used is reduced as much as possible and environmental loading is minimized and which is inexpensive and readily handled. SOLUTION: This non-azeotropic mixed refrigerant is characterized by comprising a butane-ethylene mixed gas and R-14 and having improved characteristics in which especially the butane/ethylene mixed ration of the butane-ethylene mixed gas is 90/10-70/30 and the amount of R-14 added based on the mixed gas is >0% and <=7.5%. The non-azeotropic mixed refrigerant of the composition is used for a refrigerator system for ultra low temperature in which a return gas from an evaporator is used to cool a compressed gas in a condensation process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerant for ultra-low temperature, which has a hydrocarbon-based gas as a main component and a fluorocarbon that does not contain chlorine to improve its characteristics.

[0002]

2. Description of the Related Art Conventionally, so-called CFCs have been widely used as refrigerants for refrigerators and freezers. However, since CFCs containing chlorine destroy ozone in the upper atmosphere layer, CFCs containing no CFCs or those Development of a hydrocarbon-based refrigerant as an alternative is desired. In addition, most of CFCs that do not contain chlorine have a high ability to absorb long-wavelength infrared rays and have an effect on global warming, so it is possible to use these substances with a small so-called greenhouse effect and the amount used. It is necessary to devise to reduce it as much as possible. For this reason,
Gases containing low-boiling hydrocarbons as the main component and satisfying the characteristics of a given refrigerant are being searched for, but it is difficult to satisfy these conditions with a single gas because the type of gas is limited. Yes, two or more kinds of gases are mixed to adjust their characteristics.

However, in order to switch from a conventional refrigerating system using a single component refrigerant gas to a refrigerating system using these mixed refrigerants, the composition and boiling point of the refrigerant gas are vaporized and condensed. Although an azeotropic refrigerant that does not change its physical characteristics and can be handled like a single-component refrigerant is often used, the types and combinations of refrigerant gases that have such characteristics are limited. ,
It has been difficult to obtain a refrigerant gas having desired properties. In particular, there are few types of refrigerant gas that can realize an ultra-low internal temperature of −60 ° C. or less that the present inventors aim to achieve, and a low boiling point gas that achieves such an ultra-low temperature is under extremely high pressure in a room temperature environment. Since it cannot be condensed at room temperature, it is not possible to condense it at room temperature.Therefore, a multi-source refrigeration system in which condensation is performed using a cooling system that combines an evaporator of a refrigeration system that uses a liquefiable gas at room temperature as a refrigerant is the mainstream It was

However, the conventional multi-source refrigeration system is not only complicated in structure, expensive and large in size, but also heavy in maintenance. On the other hand, since most cryogenic freezers cannot withstand temperature changes such as medical living tissue, deterioration or interruption of the refrigeration function is not allowed during maintenance. In addition, the refrigeration equipment for ultra-low temperature, as described above,
Since it is necessary to preserve living tissues for a long period of time, it is essential to maintain a stable operating state.
In the event of a failure, it will cause enormous and irreversible loss, so there is a demand for an ultra-low temperature refrigerant applicable to a simple refrigerator system similar to a conventional refrigerator.

In view of these circumstances, the present inventors can handle the same as a single-component refrigerant, and realize a super low temperature inside the chamber of −60 ° C. or less, a non-azeotropic mixed refrigerant. Is intended to be provided. Further, the present inventors previously used the return gas from the evaporator (evaporator) for cooling the compressed gas in the condensation process as a refrigerator system that uses a non-azeotropic mixed gas as these refrigerant gases. According to the above, it has been filed earlier that the handling of these non-azeotropic mixed refrigerant gases is facilitated, and the refrigerating capacity can be dramatically improved, but the present invention is particularly preferable in these refrigerator systems. Provided is a non-azeotropic mixed refrigerant which exhibits various characteristics.

[0006]

DISCLOSURE OF THE INVENTION The present invention is a non-azeotropic mixed refrigerant for ultra-low temperature in which R-14 is added together with a butane-ethylene mixed gas to improve the characteristics, and, in particular, a butane-ethylene mixed gas. Butane-ethylene mixture ratio of 90 /
The non-azeotropic mixed refrigerant is characterized in that it is in the range of 10 to 70/30, and the amount of R-14 added to this mixed gas is more than 0% and 7% or less. Furthermore, it is a non-azeotropic mixed refrigerant of the above composition used in an ultra-low temperature refrigerator system in which the return gas from an evaporator (evaporator) is used to cool the compressed gas in the condensation process.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Butane has a high boiling point, but since it has a low vapor pressure and a high critical temperature, it is a gas that is easy to handle as a refrigerant in a refrigerator system operating at room temperature. on the other hand,
On the contrary, ethylene has an extremely low boiling point and has properties suitable as an ultra-low temperature refrigerant, but has an extremely high vapor pressure 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 are confirmed, and the range usable as the refrigerant of the refrigerator system operating at room temperature is searched for.
By adding (perfluoromethane) to improve the characteristics as a refrigerant for ultra-low temperature, the refrigerator system operating at room temperature, which is the aim of the present inventors, without using a complicated binary refrigerator system- Over 60 ℃, -8
The characteristics and composition range of the mixed refrigerant that achieves an ultralow temperature of 0 ° C. or less were confirmed.

[0008]

[Table-1]

FIG. 1 shows an outline of a refrigerator system used in an embodiment of the present invention. In the figure, 10 is a compressor, and the refrigerant gas discharged from the compressor is decompressed by the throttle valve 15 through the condenser 20, the dryer 30, and the heat exchanger 35 by the outward pipe 11, and evaporated in the freezer 40. Bowl 4
It vaporizes in 5 and cools the inside of a freezer. The return gas from the evaporator is returned to the compressor after cooling the outward refrigerant in the heat exchanger 35 through the return pipe 12. When a non-azeotropic mixed refrigerant is used, this heat exchanger is arranged and the high-pressure gas from the compressor is cooled by the low-temperature return gas to lower its temperature and accelerate the condensation process to improve cooling efficiency. Can be improved. Moreover, energy efficiency can be improved by effectively utilizing the sensible heat and latent heat of the return gas. For reference, see Tables 2 and 3 below.
Compressed gas that could be achieved in a heat exchanger when R-14 was added to a refrigerant having a butane-ethylene mixing ratio of 90/10 and a butane-ethylene mixing ratio of 85/15 in the range of 0 to 3.85%, respectively. The relationship among the temperature, the pressure, and the temperature inside the chamber is shown below. The refrigerator system used in the experiment is as follows. Refrigerator model: Danforce, capacity: 213 liters Measurement point: Compressed gas pressure (high pressure side pressure), heat exchanger outlet temperature measurement point: A Return gas pressure (low pressure side pressure), heat exchanger outlet as shown Temperature measurement point: B Capillary tube 50 cm (0.9 mm as a throttle valve)
φ) As the heat exchanger, use the one in which the forward pipe and the return pipe are brazed for 3 m. The experiment was performed under the same conditions below. The use of such a heat exchanger is for lowering the temperature of the compressed gas to advance the condenser process, and when the heat exchanger is not used, other well-known cooling means are used to compress the compressed gas. Can be cooled to these temperature ranges to promote the desired condensation process.

[0010]

[Table-2]

[0011]

[Table-3]

[0012]

[Experiment] Experiment 1: Confirmation of characteristics of butane / ethylene mixed gas as a refrigerant The characteristics of butane / ethylene mixed gas as a refrigerant were confirmed as basic data by actual operation using the refrigerator system shown in FIG. The results are shown in Table 4 and FIG.

[0013]

[Table-4]

From the graph of FIG. 2 in which the results of Table 4 are plotted, it can be seen that the temperature inside the freezer significantly decreases as the ethylene concentration increases, but the pressure on the compressor side also increases accordingly. As an ultra-low temperature refrigerator, we aim to easily achieve an internal temperature of -60 ° C or below and to achieve an internal temperature of -80 ° C or below. Although it can be achieved, even if the concentration is higher than that, it tends to become almost flat when the temperature exceeds -70 ° C, and the internal temperature exceeds -70 ° C again near the concentration of 30%. It became unstable during driving, and it was not possible to confirm at more than 35%. Therefore, in order to improve the refrigerant characteristics in a region where the inside temperature becomes -60 ° C or lower and becomes even more flat, the components of the butane-ethylene refrigerant gas are ethylene corresponding to these ranges: 10, 15, 20 , 30%, that is, butane-ethylene mixing ratio: 90/10, 85/15, 80/20, 70
5 to 20 g of R-14 gas was added to a mixed gas of 250 g in total in each range of / 30, and the characteristic change with respect to the added amount was confirmed. In addition, in the experiment in which R-14 was added to the mixed gas having a butane-ethylene mixing ratio of 95/5, the inside temperature was -60 at R-14: 1.96%.
The experiment was terminated because the temperature did not drop below ℃ and the expected effect could not be expected. The experimental conditions are the same as above, and the results are shown in Tables 5, 6, 7, and 8 and FIGS.
6 shows.

Experiment-2 A total of 2 mixed gases having a butane-ethylene mixing ratio of 90/10
R-14 was added to 50 g in 5 g increments, and the effect of the addition was confirmed.

[0016]

[Table-5]

According to the graph of FIG. 3 in which the data of Table-5 are plotted, the temperature inside the refrigerator reaches -60 ° C at R-14: 0%, but at -80 ° C near R-14: 2%. Below, it can be seen that the effect of adding R-14 is remarkable. However, the effect is saturated at about R-14: 5.0%, while the pressure on the high-pressure side tends to rise sharply.
When it exceeds 7.4%, the practical limit is gradually approached, and it tends to be difficult to achieve more stable operation in actual operation.

Experiment-3 A total of 2 mixed gases having a butane-ethylene mixture ratio of 85/15
R-14 was added to 50 g in 5 g increments, and the effect of the addition was confirmed.

[0019]

[Table-6]

According to the graph of FIG. 4 in which the data of Table 6 are plotted, the effect of lowering the temperature inside the chamber can be obtained by increasing the R-14 concentration, but the effect of lowering the temperature becomes mild from around 4%, and the same as above. R-14: The pressure on the high-pressure side increased remarkably from around 7.4%, and it became difficult to operate the actual machine.

Experiment-4 Total gas mixture with a butane-ethylene mixture ratio of 80/20 2
R-14 was added to 50 g in 5 g increments, and the effect of the addition was confirmed.

[0022]

[Table-7]

According to the graph of FIG. 5 in which the data of Table 7 is plotted, the effect of lowering the temperature inside the chamber is obtained by increasing the amount of R-14, but the effect by increasing R-14 is 6.
There is a tendency to reach a peak in the vicinity of 0%, and the effect gradually declines. At the same time, there is a rise in high-pressure side pressure,
It will gradually become difficult to operate the actual machine in the area exceeding 7.4%.

Experiment-5 A total of 2 mixed gases having a butane-ethylene mixture ratio of 70/30
R-14 was added to 50 g in 5 g increments, and the effect of the addition was confirmed.

[0025]

[Table-8]

According to the graph of FIG. 6 in which the data of Table-8 is plotted, the temperature inside the chamber rises conversely with the addition of R-14, and the initial effect cannot be obtained. On the other hand, the high pressure side is R-
It sharply increases with the concentration of 14 and becomes close to the practical limit of the actual operation in the vicinity of R-14: 6%. Further, the pressure increase on the low pressure side is remarkable, and R-14 exceeds 1% and exceeds 1 atm, and the effect as a refrigerant cannot be expected. From the above, it is understood that the characteristics of the refrigerant aimed at by the present invention can be achieved when the butane-ethylene-based mixed component butane is 10% to 30% and R-14 is more than 0% to 7.5%. In this range, the three-component non-azeotropic mixed refrigerant can maintain stable conditions over a wide range in the high-pressure side pressure, the low-pressure side pressure, and the internal cold storage temperature. Therefore, according to the present invention, in the ultra-low temperature refrigerator, stable operation is possible for a long period of time, and also because of its simple structure and low cost in terms of maintenance, it is low cost and frozen. Maintenance and maintenance work can be performed without causing a large change in the temperature conditions of the machine.

[0027]

The ultra-low temperature non-azeotropic mixed refrigerant of the present invention comprises:
It is possible to easily achieve an ultra-low temperature of -60 ° C or less by an inexpensive gas component, and particularly to stably maintain an ultra-low temperature of -80 ° C or less, so that not only conventional foods but also biological tissues, especially sperm, etc. It can also be widely used for long-term storage of rice, and contributes to the development of these industries in response to the demands of these bio industries. Also,
The amount of CFC used is extremely small, and the effect on environmental destruction such as the Greenhouse effect is extremely small.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a refrigerator system of the present invention.

FIG. 2 shows characteristics of butane-ethylene mixed refrigerant.

FIG. 3: Butane-ethylene mixing ratio: at 90/10
Effect of adding R-14.

[Fig. 4] Butane-ethylene mixing ratio: at 85/15
Effect of adding R-14.

FIG. 5: Butane-ethylene mixing ratio: at 80/20
Effect of adding R-14.

FIG. 6: Butane-ethylene mixing ratio: at 70/30
Effect of adding R-14.

[Explanation of symbols]

10 compressor 11 Outward piping 12 Return piping 15 Throttle valve (capillary) 20 Condenser 30 dryer 35 heat exchanger 40 freezer 45 Evaporator A High pressure side, heat exchanger outlet compressed gas temperature measurement point B Low pressure side pressure measurement point

Claims (3)

[Claims] 1. A R but with a butane-ethylene mixed gas
A super-low temperature non-azeotropic mixed refrigerant with improved properties by adding -14. 2. The butane-ethylene mixing ratio of the butane-ethylene mixed gas is in the range of 90/10 to 70/30,
R-14 (perfluoromethane) for this mixed gas
The non-azeotropic mixed refrigerant according to claim 1, wherein the added amount is more than 0% and 7.5% or less. 3. The non-azeotropic mixed refrigerant for a cryogenic refrigerator according to claim 1 or 2, wherein the return gas from the evaporator is used for cooling the compressed gas in the condensation process.