FR2792944A1 - REFRIGERANT - Google Patents

Abstract

The invention concerns a mixture in specific proportions enabling to obtain thermodynamic properties close to those of R22 (chlorodifluoromethane) while exhibiting a lower GWP (Global Warming Potential). Said novel mixture consists of three refrigerant fluids: CO2, R32 (difluorodihydromethane-CH2F2) and R134a (tetrafluorodihydromethane-CHF2CHF2). Its composition, expressed in volume fraction (kg/kg), is between the following ranges: CO2 0.05 +/- 0.02; R32 0.20 +/- 0.05; R134a 0.70 +/- 0.05.

Description

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Refrigerant.

  The present invention relates to a new refrigerant.

  The Montreal Protocol (European Regulation 3093/94) has resulted in the cessation of production of chlorinated refrigerants such as CFCs (chloro-fluorocarbons) or HCFCs (hydro-chloro-fluorocarbons) which were widely used in refrigeration and air conditioning systems. These substances destroy the stratospheric ozone layer (protective layer against hard UV (B) radiation). We know the energy benefits they present. They allow to obtain a high level of energy efficiency of the refrigeration systems in which they are

  used and they are neither toxic nor flammable.

  A third family of fluorinated refrigerants, called HFC (hydrofluoro-

  carbides) was developed to replace CFCs and HCFCs. It is often necessary to use these fluids in mixture to have thermodynamic properties suitable for the use of refrigeration systems whose

  evaporation temperatures are highly variable, typically from - 40 to + 10 C.

  With the implementation of the Kyoto Protocol targeting greenhouse gases, new constraints appear for the use of HFC type refrigerants. Indeed these gases are part of the greenhouse gases whose emissions are limited by the Kyoto Protocol. Greenhouse gases are gases whose production is linked to human activity and which modify the ability of the atmosphere to trap thermal radiation. They cause an increase in the

  temperature of the earth and consequently climatic instabilities.

  An index called GWP (Global Warming Potential) makes it possible to assess the impact of a given gas in relation to global warming. This evaluation scale is expressed in kg of C02 equivalent. By definition, the GWP index of C02 is equal to 1. Typically HFCs have

  GWP values which vary between 100 and 10,000 kg of C02 per kg of these gases.

  It is therefore quite useful to develop mixtures preferably using HFCs with low GWP or mixtures containing both such HFCs and other molecules which also have low GWP. The objective is to produce refrigerant mixtures with suitable thermodynamic properties while reducing, as far as possible, their GWP index. A particular HCFC, R22 (chlorodifluoromethane CHCIF2), the use of which will soon be stopped by the Montreal protocol, is used in a large number of applications, both refrigeration and air conditioning. Figure 1

  presents the Mollier diagram (enthalpy - pressure) of this well known fluid.

  The object of the invention is a mixture in defined proportions making it possible to obtain thermodynamic properties close to those of R22 while having a lower GWP. This new mixture is composed of three refrigerants: C02, R32 (difluorodihydromethane CH2F2) and R134a (tetrafluorodihydroethane - CHF2CHF2). Its composition, expressed as a mass fraction (kg / kg) is included in the following ranges:

C02 0.05 + 0.02

R32 0.20 0.05

  R134a 0.70 0.05 Preferably, the composition of the mixture called ARMIX01 is included in the following ranges:

C02 0.04 + 0.005

R32 0.23 - 0.005

  R134a 0.73 0.005 Figure 2 presents the Mollier diagram of the ARMIX01 mixture established according to the

usual methods.

  Table 1 gives the essential thermodynamic characteristics and the GWP for R22 and for ARMIX01. The latter were calculated from the data relating to the constituents of the mixture and their consistency was verified by experimental tests. Table I - Essential thermodynamic characteristics of R22 and ARMIXO I Pressure Temperature Temperature Qv GWP critical critical boiling point at (kJ / m3) (kg (MPa) (C) atmospheric pressure C02) (C)

  R22 4.99 96.2 - 40.8 3,061.7 1,590.6 I 500

(1) (2)

  ArmixO0 4.92 89.6 - 43 2,786.2 1,391.9 1,100

(C02 / R32 / R134 (-51.3 / -34.7) (1) (2)

  a, 4/23/73 in (3) weight) (1) Condensation temperature / Evaporation temperature, 55 C / 2 C (2) Condensation temperature / Evaporation temperature, 40 C / -20 C (3 ) The temperature of - 43 C is the average phase change temperature over the entire plateau, the lowest temperature being the bubble temperature and the

  higher being the dew temperature.

  FIG. 3 is a pressure / temperature diagram which makes it possible to verify that the saturation curve 2 of R22 is located inside the two saturation curves (bubble curve I for the saturating liquid, dew curve 3 for the saturating vapor ) of the ARMIX01 mixture. The thermodynamic data of the ARMIX01 mixture were calculated from the data relating to the constituents of the

  mixture and their consistency was verified by experimental tests.

  The proportions of the various fluids composing the ARMIXOI mixture have been chosen so that the properties of use, as a refrigerant, are close to those of R22. The mixture, although comprising R32 which is a low flammable fluid, is non-flammable, even in the case of fractionation the

  more critical, either in the vapor phase or in the liquid phase.

  The toxicology studies of these three fluids are already done and they are classified

as non-toxic.

  The ARMIX01 mixture is therefore a safety refrigerant.

  This fluid can be advantageously used in refrigeration systems and

  air conditioning or both fixed and mobile.

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Claims (3)

  1. Refrigerant characterized in that it comprises a mixture of the following three chemical compounds: - C02, - difluorodihydromethane (CH2F2), otherwise known under the code R32,   - tetrafluorodihydroethane (CHF2CHF2), otherwise known by the code Rl 134a.   2. Refrigerant according to claim 1 characterized in that its composition, expressed in mass fraction (kg / kg), is included in the following ranges: C02 0.05 0.02 R32 0.20 + 0.05 Rl34a 0.70 + 0.05.   3. Refrigerant according to claim 1 characterized in that its composition expressed in mass fraction (kg / kg), is included in the following ranges: C02 0.04+ 0.005 R32 0.23 + 0.005 Rl34a 0.73 + 0.005.