JPS606779A - Composition for absorption refrigerator - Google Patents

Abstract

PURPOSE:To provide a compsn. for absorption refrigerator, which has a low viscosity and is hardly crystallized out, by blending a specified imidazole compd. as an absorbent with a fluorinated alcohol as a refrigerant. CONSTITUTION:5-60wt% C2-C10 fluorinated alcohol (e.g. 2,2,2-trifluoroethanol) which is a liquid at room temp. and vaporizes by heating, is mixed with 40- 95wt% mixture of imidazole and 2-ethyl-4-methylimidazole in a weight ratio of 35-45:65-55.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a composition for an absorption refrigerator comprising a fluorinated alcohol as a refrigerant, and imidazole and an imidazole derivative as an absorbent.

←) Prior Art As compositions for conventional absorption refrigerators, compositions consisting of a refrigerant of water or methanol and an absorbent of a lithium halide salt have been mainly used.

This composition has a large latent heat of vaporization of water and methanol as refrigerants, so it has a high coefficient of performance for absorption refrigerators.
Although it has the advantage of being able to increase f performance, 0OP), it has the disadvantage that lithium halide salts generally have high viscosity and are corrosive to metals and prone to crystallization. Further, in order to liquefy the refrigerant of this composition, it is necessary to cool it to about 80 to 40°C, so the condenser and absorber of the absorption refrigerator are insufficiently cooled by air cooling, and it is necessary to use water cooling.

In addition, as a refrigerant, freons (halogenated hydrocarbons) such as R-22 (monochlorodifluoromethane) whose freezing point is below 0°C are used, and as an absorbent, an organic liquid that does not cause crystallization such as tetraethylene glycol dimethyl ether is used. Compositions are also known. This composition does not cause crystallization, has a low viscosity, and has the advantage that the condenser and absorber can be cooled by air cooling. However, since the refrigerant Freon has a small latent heat of vaporization, the OOP of the absorption refrigerator is low. Freon also has the disadvantage of poor heat resistance.

The reason for this is that in order to solve the above problems, as a refrigerant,
This was achieved as a result of research into compositions that use fluorinated alcohols, which have a large latent heat of vaporization.

(c) Purpose of the Invention The purpose of the present invention is to solve the drawbacks of the conventional compositions for absorption refrigerating machines as described above, and to provide a composition for absorption refrigerating machines that has a particularly low viscosity and has many advantages as described below. is to provide.

B) Structure of the Invention The refrigerant used in this invention has carbon atoms of 2-1 O (hereinafter in the margin, continued on the next page), is liquid at room temperature, and turns into vapor under normal pressure or reduced pressure when heated. Examples of the fluorinated alcohol include compounds described in JP-A-56-88485.

Among these, preferred is trifluoroethanol, and particularly preferred is 2.2.2-trifluoroethanol (hereinafter referred to as TFFj).

On the other hand, imidazole has two nitrogen atoms with unpaired electrons in its molecule, so fluorinated alcohols (such as T
Due to the electric attraction effect with FJC7j, etc., the degree of vapor pressure drop during absorption of fluorinated alcohol is large, and it is also chemically stable and has strong resistance to acids, alkalis, and reducing agents, making it suitable as an absorbent. has advantages. However, imidazoles are crystalline and have low solubility in the refrigerant fluorinated alcohol (for example, only 50% by weight dissolves in T'I!I at room temperature), and tend to have high viscosity and crystallization. be.

This invention focuses on the fact that a mixture of imidazole and 2-ethyl-4-methylimidazole has a low viscosity and a high boiling point.
This composition was developed based on the discovery that the composition has low viscosity, exhibits no crystallization, and is excellent as a composition for absorption refrigerators.

Thus, the present invention uses a fluorinated alcohol having 2>l O carbon atoms as a refrigerant and which is liquid at room temperature (61) and vaporized under normal pressure or reduced pressure when heated, imidazole as an absorbent, and 2- The present invention provides a composition for an absorption refrigerator comprising ethyl-4-methylimidazole.

The absorbent used in the composition of this invention has a weight ratio of imidazole and 2-ethyl-4-methylimidazole of 85 to 45:65 to 55, and 40:60.
Preferably. Furthermore, the content ratio of the fluorinated alcohol of the refrigerant and the absorbent in the composition of this invention can vary within a wide range. That is, based on the weight of the composition, the refrigerant is usually 5 to 60% by weight, preferably 10 to 60% by weight, and the absorbent is usually 40 to 95% by weight, preferably 5% by weight.
Compositions ranging from 0 to 90% by weight are used.

The composition of the present invention is generally used in an absorption refrigerator having a configuration as shown in FIG.

(1) is a generator that absorbs refrigerant and heats and separates the refrigerant from the diluted absorption liquid; (2) is a condenser that cools the gaseous refrigerant flowing from the generator (1) into a liquid refrigerant; (3) ) is an evaporator that reduces the pressure of the liquid refrigerant in the condenser (2) with a pressure reducer (4) and sprays it under low pressure conditions to vaporize it to achieve the desired cooling; (5)
(6) is an absorber that absorbs the refrigerant vaporized in the evaporator (3) with an absorption liquid so that the evaporator (3) can continuously cool the refrigerant; A heat exchanger (7) exchanges heat between the concentrated absorbent liquid that is separated and sent to the absorber (5) and the diluted absorbent liquid that returns from the absorber (5) to the generator [1]. Liquid circulation pump, (
8) and (9) are an analyzer and a rectifier.

(e) Experimental Examples and Examples This invention will be explained by the following experimental examples and examples, but they are not intended to limit the invention.

Experimental example Composition viscosity: 40% by weight imidazole and 60% by weight 〇2-ethyl-
The mixture with 4-methylimidazole has a viscosity of about 100 centivoise at room temperature, which is significantly lower than that of 2-ethyl-4-methylimidazole, which has a high viscosity of about 8000 centivoise. It was also observed that a composition consisting of 70% by weight of this mixture and 80% by weight of TFFi had a viscosity of about 60 centipoise at room temperature and was free of crystallization.

The boiling point of the above composition is 154°C, and the refrigerant T
This shows an increase in the boiling point of 79.5°C compared to the boiling point of FB of 74.5°C, which indicates that the refrigerant (TFE) absorbency of the absorbent is large and therefore the degree of vapor pressure drop is large.

Further, the boiling point of the mixture (400ff of imidazole and 60% by weight of 2-ethyl-4-methylimidazole) is approximately 278, as is clear from the vapor pressure temperature diagram in Figure 2 below.
℃adeshi, TF1! It can be seen that the boiling point of i is extremely high at 745° C., so it is easy to separate the FB from the absorbent.

Example 8 A composition consisting of 80% by weight of a refrigerant (TFFi) and 70% by weight of an absorbent (a mixture of imidazole and 2-ethyl-4-methylimidazole) was
FIG. 2 shows a vapor pressure diagram when the gas is enclosed in the absorption refrigerator shown in the figure and is operated.

That is, TFB flows into the generator (1) (point a in Fig. 2), and the weight percent ratio of the collected agent is 8 o/7.

An absorbent liquid (dilute liquid) with a low absorbent concentration is generated, and this is
It is heated to 74°C to vaporize and separate TFK (point shown in Figure 2) and sent to a condenser (2). On the other hand, the absorbent liquid (concentrated liquid) with a high absorbent concentration concentrated to approximately 85% by weight is cooled via the heat exchanger (6) and flows into the absorber (5) (
Point C in Figure 4), the amount of TFK flowing into the condenser (2) is approximately 5
It is cooled to 7.5°C and liquefied, and is supplied to the evaporator (3) at a pressure of approximately 10.5ff) via a pressure reducing device (4), and when vaporized here, the evaporator (3) The surrounding object is cooled to about -8°C. The vaporized TFB is transferred to the absorber (5
), the evaporator <
3) The dilute liquid generated by absorbing the TFR gas (point d in Figure 4), which is maintained at approximately 1 G and 5 m 11 g, is mixed with the concentrated liquid flowing into the absorber (5) in the heat exchanger (6). After exchanging heat and raising the temperature, it flows into the generator (1) again (point a in Figure 4).

In addition, in Fig. 2, the straight line (4) represents the saturated vapor pressure of TFB at each temperature.
4) has a TFI/absorbent weight ratio of 4'/60. ”/7
The straight line (0) shows the saturated vapor pressure of the composition of 0°''/80.10/90 at each temperature, and the straight line (0) shows the saturated vapor pressure of the absorbent at each temperature.

In the absorption refrigeration cycle described above, TFE and the absorbent do not undergo azeotropy, and the difference in boiling point between the two is extremely large as described above, so the analyzer (8) and rectifier (9) of the absorption refrigeration machine have a simple structure. That's fine.

Furthermore, when the above composition is used, the operating pressure of the absorption refrigerator is about 850 ff on the high pressure side where the generator (1) is located, and about 10 ff on the low pressure side where the evaporator (3) is located, both of which are at atmospheric pressure. Unlike the conventional 7 leone-tetraethylene glycol dimethyl ether system, which has an operating pressure of 10 to 20 kg/d on the high pressure side and about 5 kg/cd even on the low pressure side, which operates under high pressure conditions, The composition of this example shows no crystallization phenomenon under normal absorption chiller operating conditions and has a low viscosity. It is. In addition, since air cooling is sufficient for cooling the condenser (2) and absorber (3), there is no need for a water cooling mechanism or cooling tower like in conventional water-lithium bromide systems, making it ideal for areas with poor water conditions. It is also possible to operate an absorption refrigerator.

(f) Effects of the Invention The composition for absorption refrigerators of the present invention has the following advantages.

(1) When separating the refrigerant from the composition in the generator, the temperature does not need to be very high.

(i) The refrigerant absorbency of the absorbent is high and the degree of vapor pressure drop during absorption is large.

(1) Air cooling is sufficient for cooling the condenser and absorber since the temperature does not need to be very low when condensing the refrigerant.

Wholesale: A high coefficient of performance (COP) can be obtained.

(V) Since the refrigerant and the absorbent do not azeotrope and the difference in boiling point between them is extremely large, the analyzer and rectifier of the absorption refrigerator may be of simple structure.

(vl) Since it can be operated at low pressure, there is no risk of leakage of liquid or gas from inside the machine, and it is possible to reduce the strength of the device and simplify maintenance management.

輔）Since the composition has low viscosity, circulation power can be reduced.

(4) Since the composition does not have crystallization properties, circulating power is reduced and heat transfer resistance is reduced. It can also be used in cold regions.

QX) The composition has low corrosivity to iron and copper.

(X) The composition is non-toxic.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an example of an absorption refrigerator using the composition of this invention, and FIG. 2 is a vapor pressure temperature diagram of an example of the composition of this invention. (1 generator, (2) --- condenser, (3) --- evaporator, (4) --- pressure reducer, (5) --- absorber, (6
)--heat exchanger, (7)... absorption liquid circulation pump,
(8) --- Analyzer, and (9) --- Rectifier.

Claims (1)

[Scope of Claims] 1. A fluorinated alcohol having 2 to 1O carbon atoms as a refrigerant and which is liquid at room temperature and turns into vapor under normal pressure or reduced pressure when heated, and imidazole as an absorbent. and 2-
A composition for an absorption refrigerator comprising ethyl-4-methylimidazole. 2. The composition according to claim 1, wherein the fluorinated fluorinated fluorinated fluoroethanol is 2+L2- fluoroethanol.