JPH0617040A - Refrigerant for refrigerator - Google Patents

Abstract

PURPOSE:To obtain economically a refrigerant for a refrigerator having a refrigerative capacity superior to that of a fluorocarbon refrigerant, dispensing with high pressure and being free from the problem in flammability by mixing propane with a specified gas in a specified ratio. CONSTITUTION:The refrigerant is prepared by mixing propane with liquefied carbon dioxide in an amount to give an ignitability limit value or larger, desirably in a mixing ratio of the propane to the liquefied carbon dioxide in the liquid phase of 8:2-6:4 (by mole). Namely, propane is used as the principal component to be mixed with liquefied carbon dioxide in an amount to give a concentration in the liquid phase of 30-35mol%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerant used in a refrigerator, and more particularly to a useful refrigerant which can substitute for a chlorofluorocarbon refrigerant.

[0002]

2. Description of the Related Art Generally, the cooling action of a refrigerator is represented by a refrigeration cycle of a dry vapor compression cycle as shown in FIG. In FIG. 1, 1 to 2 are evaporation processes, 2 to 3
Is a compression process, 3 to 4 is a condensation process, and 4 to 1 is a free expansion process. One cycle in this direction results in a temperature T ₁ (K)
At a low temperature of 1 kg, 1 kg of the refrigerant absorbs the heat quantity q ₁ from the surroundings, and the condenser discharges the heat quantity q ₂ at the normal temperature of T ₂ .

The refrigerant used in the refrigeration cycle is required to satisfy the following conditions. First, the boiling point is low, that is, the temperature reached by cooling is low. Secondly, the critical temperature is room temperature, that is, it can be condensed at room temperature. Third, the latent heat of vaporization is large, that is, refrigerant 1
That is, the cooling heat amount per Kg is large. Fourthly, the vapor density is high, that is, the device volume is small. Fifth, the compression ratio is small, that is, the compression power is small. Sixth is that it is not degradable, corrosive, or toxic.

As a typical refrigerant satisfying the above conditions,
CFC 12, CFC 22, propane, and liquefied carbon dioxide gas can be used. Of these, propane is flammable and liquefied carbon dioxide gas needs to be used under high pressure. Therefore, except for a special case, the CFC type has been widely used until now.

[0005]

However, recently, CFCs have been severely regulated in their emission into the atmosphere as they lead to the destruction of the earth's ozone layer, and are used in a closed environment like refrigerators. However, even in the case where there is a leak, it is becoming an era where it is necessary to deal with the leakage and disposal.

The present invention has been made in view of the above circumstances, and provides an excellent refrigerant that replaces a fluorocarbon refrigerant in a refrigeration cycle.

[0007]

The refrigerating machine refrigerant of the present invention comprises propane as a main component and a mixed system in which liquefied carbon dioxide gas is mixed to form a mixed system.

[0008]

In general, when an inactive gas is mixed with a flammable gas such as propane in excess of the ignition limit value, explosion of the flammable gas can be prevented. In the present invention, liquefied carbon dioxide gas, which is an excellent refrigerant in itself, is used as the inert gas.
Further, such a mixed system has an advantage that the condensation pressure can be reduced as compared with the case of using liquefied carbon dioxide gas alone.

[0009]

The present invention will be described in detail below. Table 1 shows the characteristics of the respective refrigerants calculated by using the approximation formula of the physical property values created by the present inventors and comparing the characteristics thereof. However, the total actual efficiency of the cycle was uniformly set to η = 0.5 and the compression ratio was Z = 6. In Table 1, the coefficient of performance ε is the freezing effect q (Kc
al) and the work W (Kcal) of the compressor, which is expressed as ε = q / W in FIG. This coefficient of performance ε is generally an important index for the structure of the refrigeration cycle and the selection of the refrigerant. The freezing heat quantity q _v represents the amount of heat absorbed per 1 m ^{3 of} freezing steam and serves as a measure of the size of the device.

[Table 1]

From Table 1, the coefficient of performance ε is maximum for liquefied carbon dioxide, followed by Freon 22 and Freon 12, and slightly smaller for propane. The freezing heat quantity q _v is 21 times that of chlorofluorocarbon 12 and 13 times that of chlorofluorocarbon 22, and propane is almost equal to that of fluorocarbon 22. As described above, liquefied carbon dioxide has a large coefficient of performance ε and a large amount of freezing heat q _v , and is excellent in refrigerating capacity, but it has a practical drawback that the condensing pressure P ₂ is extremely large. Therefore, in the refrigerant of the present invention, propane is used as a main component.

Therefore, the mixing ratio of propane and liquefied carbon dioxide in the liquid phase is 8: 2, 7: 3, 6: 4 in terms of molar ratio, and the coefficient of performance ε and the amount of heat of freezing when these mixtures are used as a refrigerant. Table 2 shows q _v calculated in the same manner as in Table 1. However, in Table 2, the evaporation temperature T ₁ , the condensation temperature T ₂ , and the total actual efficiency η of the cycle were uniformly set to 50%.

[Table 2] As is clear from the results in Table 2, all of the above-mentioned mixtures have a coefficient of performance ε and a freezing heat quantity q _v higher than those of the CFC type. Further, the condensation pressure P ₂ of the mixture is reduced as compared with liquefied carbon dioxide gas alone.

Next, the ignition limit value of propane will be described. FIG. 2 shows the ignition control range of propane-carbon dioxide-air (see the physical property constants, Vol. 6, page 11, edited by Chemical Society of Japan). Therefore, if the concentration of liquefied carbon dioxide mixed with propane in the liquid phase is set to 30 mol% or more, even if the propane-liquefied carbon dioxide mixture leaks, it will always be outside the ignition limit. Can be taken safely. On the other hand, increasing the concentration of liquefied carbon dioxide is not preferable from the viewpoint of pressure, as already described. Therefore, it can be said that the optimum concentration of liquefied carbon dioxide mixed with propane in the liquid phase is in the range of 30 to 35 mol%.

The refrigerant of the present invention is a mixture of liquefied carbon dioxide and propane. Carbon dioxide and propane are
It is considered that the polarities are zero, there is no obstacle in the mixing of the two, and normal vapor-liquid equilibrium is exhibited. However, in general, a low temperature liquid has a small entropy, and therefore a uniform mixed state cannot be obtained by simply mixing liquid and liquid. Therefore, it is necessary to mix high-pressure carbon dioxide gas with a low-pressure (eg, 25 ° C., 10 atm) liquid phase of propane by a method of bubbling it or by expanding a high-pressure gas-gas to liquefy it.

The composition change in gas-liquid equilibrium is a problem in an open system, but since the refrigerant of the present invention is used in a closed system, it is considered that no extreme composition change occurs.

[0015]

As described above, the refrigerant for a refrigerator of the present invention is one in which liquefied carbon gas is mixed with propane at an ignition limit value or more, preferably, the mixing ratio of propane and liquefied carbon gas in the liquid phase is The molar ratio is in the range of 8: 2 to 6: 4. Therefore, it is not necessary to use high pressure like liquefied carbon dioxide alone, and in particular, in the former case, the problem of flammability of propane can be solved, and the refrigerating capacity is higher than that of CFCs. In addition, 1 kg of industrial CFC refrigerant
Since the price per unit is ten times that of propane and liquefied carbon dioxide, the refrigerant of the present invention is much more economical than the chlorofluorocarbon type.

[Brief description of drawings]

FIG. 1 is a diagram showing a refrigeration cycle based on a dry vapor compression cycle.

FIG. 2 is a diagram showing an ignition control range of propane-carbon dioxide-air.

Claims (2)

[Claims] 1. A refrigerating machine refrigerant, characterized in that liquefied carbon gas is mixed with propane at an ignition limit value or more. 2. A refrigerating machine refrigerant, wherein the mixing ratio of propane and liquefied carbon gas in the liquid phase is 8: 2 to 6: 4 in molar ratio.