JP2007155193A - Refrigerating cycle device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigerating cycle device using a non-azeotropic mixed coolant of dimethyl ether and carbon dioxide, and improving safety. <P>SOLUTION: In the refrigerating cycle device, the mixed coolant of dimethyl ether and carbon dioxide is used as a coolant, and as refrigerating machine oil of a compressor, refrigerating machine oil is used having a characteristic of K1<K2 when a weight ratio of a dissolution amount with respect to an initial charged amount of the carbon dioxide during operation is K1, and a weight ratio of a dissolution amount with respect to an initial charged amount of the dimethyl ether is K2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a refrigeration cycle apparatus, and more particularly to a refrigeration cycle apparatus suitable for using a mixed refrigerant composed of dimethyl ether and carbon dioxide.

Conventionally, an R22 refrigerant, which is an HCFC refrigerant, has been generally used as a refrigerant in a refrigeration cycle apparatus such as a heat pump hot water supply system, but in recent years, a carbon dioxide (CO ₂ ) refrigerant, which is a natural refrigerant, has been used.

Since this CO ₂ refrigerant has a high pressure, measures such as proof pressure enhancement are required for the refrigeration cycle apparatus and its components in order to ensure safety against high pressure, and non-azeotropic mixing of dimethyl ether (referred to as DME) and CO ₂ . Development has been made to realize a highly efficient refrigeration cycle that uses refrigerant and can reduce the working pressure.

  On the other hand, refrigeration oil is enclosed in the compressor in order to maintain lubricity and ensure the sealing performance of the compression part.

Depending on the characteristics of the refrigerating machine oil, since the refrigerant is a mixed refrigerant, there may be a difference in the solubility of the refrigerant in the refrigerating machine oil. For example, if the solubility in the refrigeration oil on the CO ₂ side is unilaterally high, the mixing ratio of DME in the mixed refrigerant increases, and there is a problem that the risk of combustibility increases.

Patent Document 1 describes a refrigeration cycle apparatus using a CO ₂ refrigerant, and Patent Document 2 describes a refrigeration cycle apparatus using a mixed refrigerant composed of specific hydrocarbons and CO _2. .
JP 2001-201177 A JP 2005-15633 A

  The present invention has been made in consideration of the above-described circumstances, and an object thereof is to provide a refrigeration cycle apparatus using a non-azeotropic refrigerant mixture of dimethyl ether and carbon dioxide and improving safety.

  In order to achieve the above-described object, a refrigeration cycle apparatus according to the present invention uses a mixed refrigerant of dimethyl ether and carbon dioxide as a refrigerant in a refrigeration cycle apparatus including a compressor, a condenser, an expansion device, and an evaporator. When the weight ratio of the amount of penetration with respect to the initial amount of carbon dioxide during operation is K1, and the weight ratio of the amount of penetration with respect to the initial amount of dimethyl ether is K2, The refrigeration oil which has is used.

  The refrigeration cycle apparatus according to the present invention can provide a refrigeration cycle apparatus that uses a non-azeotropic refrigerant mixture of dimethyl ether and carbon dioxide to improve safety.

  Hereinafter, a refrigeration cycle apparatus according to a first embodiment of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a configuration diagram of a refrigeration cycle apparatus according to an embodiment of the present invention.

  As shown in FIG. 1, the refrigeration cycle apparatus 1 of the present embodiment includes a compressor 3 provided with an accumulator 2, a condenser 4 as a radiator, an expansion device 5, and an evaporator 6.

  In the refrigeration cycle apparatus 1, as indicated by arrows in FIG. 1, the high-temperature and high-pressure refrigerant discharged from the compressor 3 is condensed by the condenser 4, then decompressed by the expansion device 5, and flows into the evaporator 6. The air that evaporates and exchanges heat with the evaporator 6 is cooled.

The refrigeration cycle apparatus 1 uses a mixed refrigerant of DME and CO _{2 as} a refrigerant. The compressor 3 includes a rotary compressor unit 3b accommodated in a casing 3a and an electric motor unit 3c that drives the rotary compressor unit 3b. Furthermore, in the casing 3a, the refrigerating machine oil O for maintaining the lubricity of the movable part of the rotary compressor section 3b and ensuring the sealing performance is sealed and stored in the bottom.

Hereinafter, the DME / CO ₂ mixed refrigerant will be described in detail.

FIG. 2 shows the relationship between the DME concentration and the combustibility in the DME / CO ₂ mixed refrigerant. When DME is less than 12% by weight, it is an incombustible region, and when it is 12% by weight or more and less than 35% by weight, it is a weakly combustible region. If it is 35% by weight or more, it indicates a strong combustion region.

FIG. 3 shows the relationship between the CO ₂ concentration in the DME / CO ₂ mixed refrigerant and the mixed refrigerant pressure, and the pressure in the refrigeration cycle apparatus 1 increases as the initial concentration of CO ₂ when the mixed refrigerant is sealed increases. It is shown that.

There may be a difference in the amount of the DME / CO ₂ mixed refrigerant dissolved in the refrigeration oil after being sealed in the compressor 2.

When the weight ratio of the amount dissolved in the refrigerating machine oil with respect to the initial charged amount of the CO ₂ refrigerant is larger than that ratio of the DME refrigerant, the concentration of DME in the mixed refrigerant remaining without being dissolved is increased. As can be seen from FIG. 2, when the concentration of DME in the residual mixed refrigerant exceeds 35% by weight, it becomes a highly flammable gas, and the risk of combustion and explosion increases.

  Therefore, the refrigeration cycle apparatus 1 of the present invention regulates the solubility characteristics of the refrigeration oil in order to avoid such danger.

That is, the refrigerating machine oil has a characteristic that K1 ≦ K2 when the weight ratio of the amount of penetration relative to the initial amount of CO ₂ during operation is K1 and the weight ratio of the amount of penetration relative to the initial amount of DME is K2. It is

  If a specific example is shown, the refrigerating machine oil which has the solubility characteristic used as K1 = 5% and K2 = 10% is mentioned.

The mixing ratio of CO ₂ and DME at the time of initial sealing into the cycle device 1 is 8: 2 which is a weak combustion region (20% DME weight ratio enters the weak combustion region of FIG. 2), and 1 kg of mixed refrigerant as a whole When used in the refrigeration cycle apparatus 1, the amount of CO ₂ dissolved in the refrigerator oil is 1 kg × 0.8 × 0.05 = 0.04 kg, and the amount of DME dissolved in the refrigerator oil is 1 kg × 0.2 × 0. 1 = 0.02 kg.

Therefore, among the mixed refrigerant in the cycle apparatus 1, CO ₂ is 1 kg × 0.8−0.04 kg = 0.76 kg, and DME is 1 kg × 0.2−0.02 kg = 0.18 kg.

The mixing ratio of CO ₂ and DME at this time is
[Equation 1]
(0.76 / (0.76 + 0.18)) :( 0.18 / (0.76 + 0.18))
≒ 8.09: 1.91
When this CO ₂ : DME≈8.09: 1.91 is applied to FIG. 2, the DME weight ratio at the initial encapsulation is reduced from 20% to 19.1%, and the risk of flammability is It has been shifted to the non-combustible side from the position, and it can be seen that it is safer after melting into the refrigerating machine oil.

Preferably, the difference between K1 and K2 is 10% or less. Thereby, the change in the characteristics of the mixed refrigerant and the pressure can be kept within a predetermined range. When the difference between K1 and K2 exceeds 10%, the composition and characteristics of the mixed refrigerant change, and it becomes impossible to obtain a predetermined performance as a refrigeration cycle apparatus. Also, as shown in FIG. 3, DME / CO ₂ mixed refrigerant, as the CO ₂ concentration in the mixed refrigerant becomes high, because it has a higher becomes properties pressure, CO ₂ concentration in the mixed refrigerant pressure becomes higher becomes higher, the refrigeration cycle device and its components In addition, a large pressure resistance is required.

  Further, as can be seen from FIG. 2, by using a mixed refrigerant having an initial ratio of DME in the mixed refrigerant of less than 35% by weight, it is possible to prevent a constantly inflammable region and improve safety. . When the initial ratio exceeds 35% by weight, the region is always in a highly flammable region, increasing the danger.

  In this way, the refrigeration cycle apparatus is a refrigeration unit in order to prevent the weight ratio of DME in the mixed refrigerant from exceeding 35% during operation and becoming a highly flammable gas, thereby increasing the risk of combustion and explosion. The solubility characteristic of machine oil is regulated so that K1 ≦ K2.

  According to the refrigeration cycle apparatus of the present embodiment, a refrigeration cycle apparatus that uses a non-azeotropic refrigerant mixture of dimethyl ether and carbon dioxide and has improved safety is realized.

  In the above embodiment, the high-pressure side refrigerant discharged from the compressor has been described as being condensed by a condenser as a radiator, but the present invention is not limited to the case where the high-pressure side refrigerant is in a condensed state. However, the supercritical state at a higher pressure, that is, the state of the refrigerant discharged from the compressor becomes equal to or higher than the pressure and temperature at the intersection of the saturated liquid line and the saturated vapor line on the Mollier diagram (pressure-enthalpy diagram). It may be a thing.

The block diagram of the refrigerating-cycle apparatus which concerns on one Embodiment of this invention. Correlation diagram of DME concentration and flammability in DME / CO ₂ mixed refrigerant used refrigeration cycle apparatus according to an embodiment of the present invention. Correlation diagram of the CO ₂ concentration and mixed refrigerant pressure of the refrigeration cycle apparatus DME / CO ₂ mixed refrigerant used according to an embodiment of the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Refrigeration cycle apparatus, 3 ... Compressor, 4 ... Condenser, 5 ... Expansion apparatus, 6 ... Evaporator.

Claims (3)

In a refrigeration cycle apparatus equipped with a compressor, a radiator, an expansion device, and an evaporator, a mixed refrigerant of dimethyl ether and carbon dioxide is used as a refrigerant, and an initial amount of carbon dioxide during operation as a refrigeration oil for the compressor A refrigeration cycle apparatus using a refrigerating machine oil having a characteristic of K1 ≦ K2, where K1 is a weight ratio of a penetration amount to K2 and K2 is a weight ratio of a penetration amount to an initial amount of dimethyl ether encapsulated. The refrigeration cycle apparatus according to claim 1, wherein the refrigerating machine oil has a difference between K1 and K2 of 10% or less. The refrigeration cycle apparatus according to claim 1 or 2, wherein an initial weight ratio of dimethyl ether in the mixed refrigerant is less than 35%.

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