In 1994, the JSRAE published 'HFCs and HCFCs', JAR Thermodynamic Tables, Vol.1, Version 1.0, providing the thermodynamic properties of 12 refrigerants with the software. At the time, experimental data for new alternative refrigerants were qualitatively and quantitatively limited. Many reliable experimental and theoretical information have been accumulated till present for pure HFCs. The ideal gas heat capacity values with an uncertainty of ±0.2 % and the transport properties are the good examples. New international standards on the molar gas constant or molar masses were defined very recently. As a review paper on the properties of HFCs, simple equations of the ideal-gas heat capacity, vapor pressures, saturated-liquid density, virial coefficients, surface tension, viscosity, thermal conductivity, and the information on the material compatibility and solubility with lubricants are summarized mainly for R32, R125, R134a, R143a, and R152a.

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In Japan, it is very effective for saving energy to develop highly efficient heat pumps for hot water supply. On the other hand, heat pumps with "natural working fluids" are being developed eagerly for environmental protection. After surveying the status of R&D relating to heat pumps with natural working fluids, CRIEPI focused on a CO₂ heat pump and started a basic study on it. We calculated COP of CO₂ heat pump cycle for hot water supply and studied the characteristics of the cycle. We verified that CO₂ cycle had unique characteristics and achieved higher COP than those of conventional working fluids.

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Environmental protection is becoming more important and heat pumps with natural working fluids are being developed eagerly. On the other hand, in Japan, the demand for hot tap water accounts for about one third of residential final energy consumption, but most of this demand is met by direct combustion of fossil fuel. So it is very effective for saving energy to develop highly efficient heat pumps for hot tap water supply. Under such a circumstance, the development of CO₂ heat pump water heater for residential use was started. The components, such as a compressor, heat exchangers etc. were developed. The prototype, which consists of these components, was designed and made. In this paper, we describe the outline of the prototype heat pump unit and its experimental results including its characteristic and performance. Also the yearly average COP on Tokyo condition was estimated from these studies and it was clarified that the average COP was over 3. The developed CO₂ heat pump water heater can achieve high efficiency and is very promising.

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Because of global environmental problems, the existing refrigerants are to be replaced with natural refrigerants. CO₂ is one of the natural refrigerants and environmentally safe, inflammable and non-toxic refrigerant. Therefore high efficiency compressor that can operate with natural refrigerants, especially CO₂, needs to be developed. We developed a prototype CO₂ hermetic compressor, which is able to use in carbon dioxide refrigerating systems for practical use. The compressor has two rolling pistons, and it leads to low vibrations, low noise. In additions, two-stage compression with two cylinders is adopted, because pressure difference is too large to compress in one stage. And inner pressure of the shell case is intermediate pressure to minimize gas leakage between compressing rooms and inner space of shell case. Intermediate pressure design enabled to make the compressor smaller in size and lighter in weight. As a result, the compressor achieved high efficiency and high reliability by these technology. We plan to study heat pump water heater, cup vending machine and various applications with CO₂ compressor.

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Theoretical cycle analysis was done on compression heat pump system, which uses water -ethanol mixture as a working fluid. Working temperature level was set below 100°C. At the low temperature region the pressure of the suction gas is low, and the influence of mechanical loss of the compressor on coefficient of performance (COP) will be large. Relations of COPs and mechanica1 loss of the compressor has been made clear on the ethanol mol fraction range (0 to 1). Water-ethanol mixture cycle can increase COP and lower the working temperature compared with a water cycle. Another effect of adding ethanol is to decrease the irreversible loss at the heat exchangers. As the water -ethanol mixture is a non-azeotropic mixture, temperature changes in two phase regions. This characteristic is valid when a second coolant is used.

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This paper deals with the heat exchange performance prediction of a counter flow type double-tube condenser for natural binary refrigerant mixtures composed of Propane/n-Butane or Propane/i-Butane. The local characteristics of heat transfer, mass transfer and pressure drop are calculated using a prediction method developed by the authors. The total pressure drop and the overall heat transfer coefficient are also evaluated on various heat exchange conditions. The calculated results of the natural refrigerant mixtures are compared with those of pure refrigerant HCFC22. In conclusion, natural binary refrigerant mixtures composed of Propane/n-Butane or Propane/i-Butane are appropriate candidates to replace HCFC22 from the viewpoint of heat transfer characteristics.

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The liquid dielectric constants of twelve fluorinated ethers, four fluorinated ketones and two fluorinated alcohols which are expected as promising candidates of CFC and HCFC alternatives were measured at temperatures from 278 K to 332 K and at atmospheric pressure. The liquid dielectric constants has been measured by an LCR-meter (Hewlett Packard, HP -4285A) within an error of 0.3 %. The relation between dielectric constant and temperature has been examined over the whole range of temperature.

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This paper reports experimental results of the vapor pressure for mixtures of HFC-134a and polyalkylene-glycol(PAG) oil. The vapor pressure has been measured for temperatures from 283.15 K to 333.15 K and pressures up to 1.68 MPa. The mass fraction of HFC-134a in liquid phase ranges from 0.1 to 1 HFC-134a. The uncertainty of the measurements is estimated as ±15mK in temperature, ±8kPa in pressure and ±1% in concentration, respectively. The correlation equation that interpolates the experimental vapor pressures as a function of temperature and concentration is also presented for practical use.

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Although a transition into several promising HFC alternative refrigerants and their mixtures from conventional CFC and/or HCFC refrigerants is steadily in progress, there still remains a niche to pursue a drop-in refrigerant in some limited engineering applications where the advantage of retrofitting can be emphasized.R-SP34E is one of such drop-in refrigerants to complement R-12 which is a ternary mixture refrigerant consisted of R-134a with minor fractions of propane and ethanol. In this paper, the fundamental thermodynamic properties such as VLE properties and gas-phase PVT properties of R-SP34E are presented. This paper reports the first sets of measured data including 7 dew-and bubble-point pressures and 73 gas-phase PVT properties in the extensive range of temperatures 300-380 K, pressures 0.1-5.2 MPa, and densities up to around the critical density, obtained by employing the Burnett apparatus. In order to complement and confirm the reliability of the measurements, thermodynamic models including a dew-point pressure correlation and a truncated virial equation of state were originally developed in this study. The models were confirmed to exhibit not only excellent reproducibility of the measurements but also the thermodynamic consistency regarding the temperature dependence of the second and third virial coefficients and derived properties such as specific heats or speed of sound. By presenting the reliable thermodynamic model, a systematic information about the thermodynamic properties of R-SP34E is provided in this paper.

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This paper introduces a new index to classify flammable refrigerants. A question on flammability indices that ASHRAE employs arose from combustion test results of R152a and ammonia. Conventional methods of not only ASHRAE but also ISO and Japanese High-pressure gas safety law to classify the flammability of refrigerants are evaluated to show why these methods conflict with the test results. The key finding of this paper is that the ratio of stoichiometric concentration to LFL concentration (R factor) represents the test results most precisely. In addition, it has excellent correlation with other flammability parameters such as flame speed and pressure rise coefficient. Classification according to this index gives reasonable flammability order of substances including ammonia, R152a and carbon monoxide. Theoretical background why this index gives good correlation is also discussed as well as the insufficient part of this method.

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A theoretical analysis is developed to predict the composition of zeotropic refrigerant mixtures circulating in a refrigeration cycle. The composition is calculated by considering the composition distribution in the cycle and mass conservation of the each component of the mixtures. The composition distribution in the gas-liquid two phase region is calculated with an assumption of local equilibrium in each phase. The predicted compositions are also compared with experimental results, which are obtained for R-407C (23wt% R-32/25wt% R-125/52wt% R-134a). The theoretical analysis shows that the composition distributions of the more volatile components, R-32 and R-125, in the two-phase regions are lower than the initial1y charged compositions. As a result, the circulating fractions of R-32 and R-125 are slightly larger than the charged fractions when appropriate amount of refrigerant is charged in the cycle. This difference increases with addition of more refrigerants, which results in the presence of liquid in the accumulator. The theoretical analysis shows good agreement with the experimental results.

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A composition sensing circuit (CS circuit) which detects the circulating composition of the ternary zeotropic refrigerant mixture R-407C in a refrigeration cycle has been developed. The CS circuit consists of a heat exchanger, a capillary tube, two temperature detectors and one pressure detector. The circulating composition is calculated from the temperature and pressure in the circuit and the vapor-liquid equilibria for R-32/R-125/R-134a mixtures together with the approximated relation between mass fractions of R-32 and R-125. The experiments were also carried out to evaluate the accuracy of calculation. The results indicated that the difference between the calculated and measured composition was within 1% f or R-32 and R-125 and within 2% for R-134a in the circulating composition range from 17/20/63 wt% to29/30/41 wt% This difference corresponds to less than 0.5°C in the saturation temperature. This method is therefore applicable to performance stabilization and reliability improvement of the refrigeration cycle with R-407C.

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A dynamic model is developed for a vapor compression refrigeration cycle with zeotropic refrigerant mixtures. In this model, the refrigeration cycle is represented by elements, such as a compressor and heat exchangers and connecting points of each element. The continuity equation of pressure and the conservation equation of mass and energy at each connecting point are used as the equations of the refrigeration cycle. To solve the equations, inlet pressure, inlet mass flow rate or outlet pressure of each element, enthalpy and the circulating composition of each connecting point are modified. In this way, a versatile modeling of refrigeration cycles is realized. In addition, including conservation of mass of each composition of zeotropic refrigerant mixtures in this model, dynamic characteristics of compositions are calculated.

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In order to prove the effectiveness of the developed model, reported in the first report, about dynamics of a vapor compression refrigeration cycle with zeotropic refrigerant mixtures, simulation results are compared with the experimental results obtained for R-407C (R-32/R-125/R-134a=23/25/52wt%).The simulation results are consistent well with the experimental results. As a result of the numerical analysis of dynamic characteristics of composition changing, the variation of compositions in the refrigeration cycle is caused by the variation of the existing compositions of accumulator. The time constant of the composition is approximately equal to the time constant of the pressure and the mass distribution.

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R407C and R410A have been widely used as alternative refrigerants for air conditioners. This paper reports the noise characteristics of a scroll compressor with a discharge check valve when R410A is applied. Since a scroll compressor has a fixed compression ratio, the excessive motion of a check valve occurs under the over compression and under-compression conditions. Moreover, the velocity of the motion is higher in case of using R410A than in case of using R22 or R407C. In this paper, we measured the motion of a check value (a reed valve) by using a gap sensor and also measured the noise of a compressor under various operating conditions. The relationship between the noise and each condition has been investigated. Consequently we have found that we can reduce the noise of a scroll compressor by the optimization of compression ratio.

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This paper deals with an experimental study on the performance evaluation of a room air conditioner using R32. The test room air conditioner is a product developed for the R410A use. The COP, cooling and heating capacities, charge amount of refrigerant, electric power input, refrigerant thermodynamic states in the air conditioner etc. were measured for both refrigerant R410A and R32, based on JIS-C9612 standard. The experimental results of R32 are evaluated in comparison with the results of R410A, and the following are confirmed :(1) The performance of R32 is higher than R410A. This reason is mainly due to the pressure drop and heat exchange characteristics (in the evaporator and the condenser), (2) The charge amount of R32 is less than that of R410A. From the above results, the further improving the performance and saving the refrigerant amount are expected when refrigerant R410A is replaced with R32. The effects of the performance of components on the COP are also analyzed based on the measured thermodynamic states at both ends of components in the system. Then, it's clarified that the most effective factor is irreversibility of the compressor and the following is the pressure drop in low pressure side including the evaporator and the suction pipe in the system.

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A new refrigerant HFE-245mc (CF₃CF₂OCH₃) is expected being a possible candidate to replace CFC-114 especially for waste heat recovery heat pump systems. HFE-245mc has zero ozone depletion potential and also much smaller global warming potential. In the present study, experiments were made on boiling and condensation heat transfer for HFE-245mc flowing inside a horizontal smooth tube. Measured local heat transfer coefficients agreed well with the values estimated from the respective correlations for boiling and condensation of conventional refrigerants. There was found no peculiar difference from conventional refrigerants in the characteristics of boiling and condensation heat transfer. Comparing the values calculated from the correlations, the heat transfer for HFE-245mc showed to be better than or equal to that of CFC-114 in boiling and condensation, and therefore, from the standpoint of heat transfer, there was no problem in the use of HFE-245mc as the alternative refrigerant to CFC-114.

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