JPS6040185A - Refrigerant composition for absorption refrigerator - Google Patents

Abstract

PURPOSE:To provide the titled composition having safe handleability, relatively low vapor pressure, low corrosiveness to the apparatus, and excellent heat stability, by using dichlorotrifluoroethylene as the refrigerant and diethylene glycol dimethyl ether as the absorbent. CONSTITUTION:The objective composition is obtained by using dichlorotrifluoroethane (any isomers of CHCl2-CF3, CHClF-CClF2 or CHF2-CCl2F meet the purpose) as the refigerant and diethylene glycol dimethyl ether as the absorbent.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a refrigeration composition used in an absorption refrigerator.

In general, absorption refrigerators include a generator containing a refrigeration composition,
It is formed by a closed cycle consisting of a condenser, evaporator, and absorber, and when the liquid refrigerant evaporates in the evaporator, heat is taken from the outside, and this heat of evaporation is used for refrigeration. The refrigerant vapor evaporated in the evaporator is contacted and absorbed by the refrigeration composition containing a high concentration of absorbent sent from the generator in the absorber, and is returned to the generator as a refrigeration composition containing a low concentration of absorbent. . The refrigeration composition containing a low concentration of absorbent is heated in a generator with an external heat source to release refrigerant vapor, which is condensed in a condenser and sent back to the evaporator.

Conventionally, refrigeration compositions used in absorption refrigerators having such a cycle include refrigeration compositions using water (H2O) as a refrigerant and lithium bromide (L i Br) as an absorbent, and ammonia (NH3) as an absorbent. A refrigeration composition using a refrigerant and water (H'20) as an absorbent has been put into practical use.

However, since HzOLiBr-based refrigeration compositions use water as a refrigerant, the evaporation temperature cannot be set below θ°C, and therefore cannot be used for anything other than air conditioning. Due to the limited solubility, it is difficult to air-cool the condenser; the vapor pressure is too low, so it is necessary to maintain a considerable negative pressure in the equipment; and the corrosive nature of the solution makes it difficult to air-cool the condenser. There are drawbacks such as restrictions on the addition of agents and materials for equipment.

In addition, since the steam pressure of NH3-H2O-based refrigeration compositions is quite high, the equipment must be designed to withstand high pressure, and since ammonia gas is explosive and toxic, it is dangerous to absorb it. Currently, it is hardly used for type refrigerators.

Therefore, a system in which alcohols such as methanol and ethanol are used as refrigerants to obtain temperatures below 0°C and halides such as lithium bromide (LiBr) and zinc bromide (ZnBr2) are used as absorbents has been proposed and researched. has been done.

However, in this system, the solubility of halides in alcohol is low, and halide crystals tend to precipitate in low concentration ranges, resulting in a narrow operating concentration range.The viscosity of the solution is high, which increases the power required for liquid circulation. It has been pointed out that there are drawbacks such as the thickening of the warm solution film of the absorbent 'a in the absorber, which reduces the absorption rate of alcohol.

In view of the above-mentioned problems with refrigeration compositions, recently research has been carried out on systems that use various fluorocarbon compounds as refrigerants and various Nu-containing solvents that dissolve these fluorocarbon compounds as absorbents. Some of them are published in Japanese Unexamined Patent Application Publication No. 1983-
This method has been proposed in Japanese Patent Publication No. 5.5849, Japanese Patent Application Laid-open No. 79175/1980, and the like. However, there are many possible combinations of systems in which a fluorocarbon compound is used as a refrigerant and an organic solvent is used as an absorbent. Refrigeration compositions that use methane-based fluorocarbons such as R-22) as a refrigerant and tetraethylene glycol dimethyl ether as an absorbent are attracting attention, but their vapor pressure is N
Like the H3H2O system, it has the disadvantage of being expensive.

In view of the problems of the refrigeration compositions used in conventional absorption refrigerators, the present invention provides a refrigeration composition that is particularly safe to handle, does not have a very high vapor pressure, and is less corrosive to equipment. As a result of intensive research, it was discovered that a refrigeration composition using dichlorotrifluoroethane as a refrigerant and diethylene glycol dimethyl ether as an absorbent is well suited to the above purpose and is an excellent refrigeration composition. This led to the present invention. That is, the present invention is a refrigeration composition for an absorption refrigerator that uses dichlorotrifluoroethane as a refrigerant and diethylene glycol dimethyl ether as an absorbent.

Dichlorotrifluoroethane used as a refrigerant in the present invention has three isomers with different structural formulas, namely CH
Cj! 2 CF3 (R123), CHCffF-CC
j! F2 (R123a) and CHF2 CCj22F
(R123b) exists, but since their physical properties are almost similar, any isomer can be used. Therefore, in the following explanation, the case where R123a is used as dichloro-1-lifluoroethane will be exemplified and explained.

FIG. 1 shows the temperatures at which the absorbent concentration of the refrigeration composition of the present invention using R123a as a refrigerant and diethylene glycol dimethyl ether as an absorbent is varied.
A vapor pressure diagram is shown.

In general, a refrigeration cycle that uses fluorocarbons as a refrigerant involves the generation of fluorocarbon gas from a dilute absorbent solution (a solution with a high concentration of fluorocarbons), the condensation of the generated fluorocarbon gas, and the evaporation of liquefied fluorocarbons.
This is achieved by repeating the steps of evaporation) and absorption of the fluorocarbon gas into an absorbent a solution (a solution with a low concentration of fluorocarbons).
Above absorbent l@solution and? (a) The concentration of the molten liquid depends on the operating conditions of the refrigerator, the heating temperature of the absorbent dilute solution (temperature inside the generator), the evaporation temperature of liquefied chlorofluorocarbon (temperature inside the evaporator), and the absorption temperature of fluorocarbon gas (temperature inside the absorber). (temperature)). In a refrigeration cycle using CFC as a refrigerant, R123a is used as a refrigerant as in the present invention,
When diethylene glycol dimethyl ether is used as an absorbent, the evaporation temperature of liquefied R1,23a is approximately 0°C,
The absorption temperature is about 42 to 54 ° C., and the concentration of the dilute absorbent solution is about 52% by weight (hereinafter, % is not specified in this specification and represents weight%), and the concentration of the concentrated solution is about 62%. It is appropriate to set it to .

In addition, when operating conditions are set to other than the above, the absorbent dilute solution concentration and a solution concentration conditions can be changed accordingly. Furthermore, the refrigeration composition of the present invention uses a refrigeration cycle similar to the above, and a heat pump cycle (not shown) configured in a system in which an evaporator absorbs heat from outside air and a condenser or absorber releases heat. ) can also be applied as is.

Next, an example of the operation of an absorption refrigeration cycle using the refrigeration composition of the present invention will be explained based on the flow sheet of FIG. 2 and the operating cycle diagram of FIG. 3. The operating cycle diagram in FIG. 3 is an excerpt from the temperature-vapor pressure diagram of the R123a-diethylene glycol dimethyl ether based refrigeration composition in FIG. It is something that

First, a 52% dilute solution of diethylene glycol dimethyl ether in which R123a was dissolved as a refrigerant (point A in Figure 3) was prepared.
When heated to about 102°C using external heat source 3 in generator 1 at a temperature of about 88°C and a pressure of 1100 rnmHg (absolute pressure; the same applies hereinafter), the 52% dilute solution becomes 62%
% concentrated solution (point B in Figure 3), during which time the pressure was 11%.
R123a gas corresponding to 00 mmHg is generated. Next, this R123a gas is introduced into the condenser 2 and cooled by the cooling pipe 4, whereupon it is condensed and liquefied at about 40° C. (the temperature at which the extended line of B-A intersects the R123a line). Then liquid R1
23a is reduced in pressure by the pressure reducing valve 5 and introduced into the evaporator 3.

When the temperature in the absorber 4 is set at approximately 42 to 54°C, the pressure inside the evaporator 3 is reduced to approximately 230 mm1 (H) corresponding to its vapor pressure, and liquid R123a is sprayed from the nozzle 6 at approximately 0°C. The brine is evaporated and the heat of evaporation is taken away from the brine flowing through the pipe 7 to cool it and use it for freezing.

Next, the evaporated R123a gas is introduced into the absorber 4, cooled from the generator 1 through the heat exchanger 8, and turned into a 62% concentrated solution of diethylene glycol dimethyl ether at about 54°C (point C in Figure 3), which is sprayed from the nozzle 9. Let it absorb. 10 is a cooling pipe for adjusting the temperature inside the absorber 4 within a predetermined range.

The concentrated solution that has absorbed the R123a gas is diluted to become a 52% dilute solution of diethylene glycol dimethyl ether (third point), and the fM/8 liquid is sent from the generator 1 to the absorber 4 via the heat exchanger 8. After being heated through heat exchange, it is introduced into the generator 1 by the pump 11 (point A in Figure 3).
, and then repeat the same cycle.

In the above example, the case where the evaporation temperature of liquid R123a in the evaporator 3 was 0°C was explained, but the above operating conditions may be selected and implemented as appropriate depending on the degree or speed of freezing or cooling required. be able to.

As explained above, according to the refrigeration composition of the present invention which uses dichlorotrifluoroethane as a refrigerant and diethylene glycol dimethyl ether as an absorbent, as is clear from the above-mentioned operation cycle, the vapor pressure during operation is the highest. The vapor pressure inside the container is about 1100 mmHg, which is considerably lower than the vapor pressure when using methane-based fluorocarbons, and the pressure-resistant structure of the refrigerator can be significantly relaxed.

In addition, small pieces of steel, stainless steel, and copper were separately added to 5 m R of a 95% diethylene glycol dimethyl ether concentrated solution of R123a. M and 10 at 180℃
Although heated under reflux for several days, almost no coloration of the solution was observed in any case, and no deterioration of the /8 solution was observed at all, indicating that the freezing composition of the present invention also has excellent corrosion resistance and thermal stability. It turns out that absorption type cold/! It was demonstrated that the composition had extremely favorable properties as a refrigeration composition for aircraft.

[Brief explanation of the drawing]

Figure 1 shows R123a as dichlorotrifluoroethane.
Temperature-vapor pressure diagram with parameters of various concentrations of the absorbent of the refrigeration composition of the present invention using as a refrigerant and diethylene glycol dimethyl ether as an absorbent,
FIG. 2 is a flow sheet of an absorption refrigeration cycle, and FIG. 3 is an operating cycle diagram using the refrigeration composition of the present invention. ■... Generator, 2... Condenser, 3...
...Evaporator, 4...Absorber, 5...
・Pressure reducing valve, 8...Heat exchanger, 11...
pump. Patent applicant Yazaki Sogyo Co., Ltd. Figure 1 1 Watari 1 ('C) Figure 2

Claims (1)

[Claims] A refrigeration composition for an absorption refrigerator, characterized in that dichlorotrifluoroethane is used as a refrigerant and diethylene glycol dimethyl ether is used as an absorbent.