JPS6040183A - Refrigerant composition for absorption refrigerator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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, an evaporator, and an 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 refrigerating composition containing a high concentration of absorbent sent from the generator in the absorber, and is turned into a refrigerating composition containing a low concentration of absorbent and flowing into the generator. . 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 (H20) as a refrigerant and lithium bromide (L i Br) as an absorbent, and ammonia (NH3) as an absorbent. Freezing compositions using a refrigerant and water (H, 20) as an absorbent have been put into practical use.

However, since H2O-LiBr-based refrigeration compositions use water as a refrigerant, the evaporation temperature cannot be set below 0°C, and therefore they cannot be used for purposes other than air conditioning. Air cooling of the condenser is difficult due to limited solubility, vapor pressure is too low and a significant negative pressure must be maintained in the equipment, and corrosion inhibitors are added due to the corrosive nature of the solution. There are disadvantages such as restrictions on the materials used for the device.

In addition, N143H2O-based refrigeration compositions have a fairly high vapor pressure, so the equipment must be designed to withstand high pressure, and ammonia gas is explosive and toxic, making it dangerous, so it cannot be used in absorption refrigerators. is currently hardly used. Therefore, methanol is used as a refrigerant that can obtain a temperature of 0°C or less.
Systems using alcohols such as ethanol as a refrigerant and halides such as lithium bromide (LiBr) and zinc bromide (ZnBr2) as absorbents have been proposed and studied.

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. Disadvantages have been pointed out, such as the liquid film of the concentrated absorbent solution in the absorber becoming thicker and the alcohol absorption rate decreasing.

In view of the above-mentioned problems with refrigeration compositions, studies have recently been conducted on systems that use various fluorocarbon compounds as refrigerants and various organic solvents that dissolve these fluorocarbon compounds as absorbents. Part of it is published in Japanese Unexamined Patent Publication No. 54-5
This method has been proposed in Japanese Patent Application Laid-Open No. 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 NH3
Like the H2O type, it has the disadvantage of being expensive.

In view of the problems of the refrigeration compositions used in conventional absorption refrigerators, the present invention has developed a refrigeration composition that is particularly safe to handle, has too high a vapor pressure (and is less corrosive to the equipment). As a result of intensive research, the refrigerant is chlorotrifluoroethane, and N,
The inventors have discovered that a refrigeration composition containing N'-dimethylbormamide as an absorbent is an excellent refrigeration composition that is well suited to the above-mentioned purpose, leading to the present invention. That is, in the present invention, chlorotrifluoroethane is used as a refrigerant, and N , N'
- A refrigeration composition for an absorption refrigerator using dimethylbormamide as an absorbent.

Chlortrifluoroethane used as a refrigerant in the present invention has three isomers with different structural formulas, namely CH
C2F-CHF2 ('R133), CH2Cj! −
CF3 (R133a) and CC7! F2-CH2F
(R133b) exists, but since their physical properties are almost similar, any isomer can be used.

Therefore, in the following explanation, the case where R133a is used as chlorotrifluoroethane will be exemplified and explained.

In Figure 1, R133a is used as a refrigerant, and N, N'
- A temperature-vapor pressure diagram using the absorbent concentration as a parameter of the refrigeration composition of the present invention using dimethylformamide as an absorbent 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 accomplished by repeating processes such as vaporization) and absorption of fluorocarbon gas into a concentrated absorbent solution (a solution with a low concentration of fluorocarbons).
The concentrations of the above dilute absorbent solution and 'a/8 solution are determined by the operating conditions of the refrigerator, that is, the heating temperature of the dilute absorbent solution (temperature inside the generator).
, is arbitrarily set according to the evaporation temperature of liquefied fluorocarbon (temperature inside the evaporator) and the absorption temperature of fluorocarbon gas (temperature inside the absorber). In a refrigeration cycle using CFC as a refrigerant, when R133a is used as the refrigerant and N2,N'-dimethylbormamide is used as the absorbent as in the present invention, the evaporation temperature of the liquefied R133a is approximately θ°C, and the absorption temperature is approximately at about 40 to 53°C, and the absorbent dilute solution concentration is about 50°C.
% by weight (hereinafter, in this specification, % represents weight % unless otherwise specified), and it is appropriate to set the concentration of the concentrated solution to about 60%.

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

Next, an example of the operation of a suction delta-type 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 Figure 3 is based on the temperature-vapor pressure diagram of the R133a-N,N'-dimethylformamide-based refrigeration composition in Figure 1, and the concentration of pure R133a and N,N'-dimethylformamide is 50%. This is an excerpt of the 60% line diagram.

First, a 50% dilute solution of N,N'-dimethylformamide (point A in Figure 3) in which R133a was dissolved as a refrigerant was heated at a temperature of about 96°C and a pressure of 2500+u+Hg (absolute pressure is shown).
The same applies hereinafter), the 50% dilute solution is heated to about 113°C using the external heat source 3 in the generator 1, and the 50% dilute solution is concentrated to a 60% concentrated solution (point B in Figure 3).
R133a gas corresponding to Dragon Hg is generated. Next, this R133a 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 the point where the extended line of B-A intersects with the R133a line). Then liquid R133a
is introduced into the evaporator 3 after being reduced in pressure by the pressure reducing valve 5. When the temperature in the absorber 4 is set at about 40 to 53°C, the pressure inside the evaporator 3 is reduced to about 6001 mHg, which corresponds to the vapor pressure, and liquid R133a is sprayed from the nozzle 6 at about O
It evaporates at a temperature of 0.degree. C., and the brine flowing through the tube 7 takes away the heat of evaporation to cool it and use it for freezing.

Next, the evaporated R133a gas is introduced into the absorber 4, and N,N'-dimethylborumamide 60 at about 53°C is cooled from the generator 1 through the heat exchanger 8 and sprayed from the nozzle 9.
% concentrated solution (point C in Figure 3). 10 is absorber 4
This is a cooling pipe for adjusting the internal temperature within a predetermined range. The concentrated solution that absorbed R133a gas was diluted to a 50% dilute solution of N,N'-dimethylformamide (
3rd target point) and exchanges heat with the table FG liquid sent from the generator 1 to the absorber 4 via the heat exchanger 8. : After being removed, it is introduced into the generator 1 by the pump 11 (Fig. 3A).
point), repeat the same cycle thereafter.

In the above example, the case where the evaporation temperature of liquid R133a 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 chlorotrifluoroethane as a refrigerant and N,N'-dimethylbormamide as an absorbent, The highest vapor pressure in the generator is approximately 2,500 mHg, 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.

Moreover, N,N'-dimethylformamide 9 of R133a
5 m of melt each for steel, stainless steel,
A small piece of copper and a small piece of copper were immersed separately and heated under reflux at 180°C for 3 days, but in both cases, almost no coloration was observed in the solution, and no change in quality was observed. The refrigeration composition of the invention was also found to be excellent in corrosion resistance and thermal stability, and was demonstrated to have extremely desirable characteristics as a refrigeration composition for absorption refrigerators.

[Brief explanation of drawings]

Figure 1 shows temperature-vapor pressure curves with various concentrations of the absorbent as parameters for the refrigeration composition of the present invention using R133a as chlorotrifluoroethane as the refrigerant and N,N'-dimethylformamide as the absorbent. 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. 1... Generator, 2... Condenser, 3... Evaporator, 4
...Absorber, 5...Reducing valve, 8...Heat exchanger, 1
1...Pump. Patent applicant Yazaki Sogyo Co., Ltd. Figure 1 degree ↑ (0C)

Claims (1)

[Claims] A refrigeration composition for an absorption refrigerator, characterized in that chlorotrifluoroethane is used as a refrigerant and N,N'-dimethylformamide is used as an absorbent.