A Study of Thermodynamic Properties of Next Generation Mixture Refrigerants Including Hydrocarbons

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A series of precise measurements of vapor pressures and gas-phase PVT properties of isobutene (R-600a), a hydrocarbon refrigerant, being an important component of the next generation mixture refrigerants with low environmental impact have been conducted by means of the improved Burnett apparatus, since reliable thermodynamic property information about this substance were not available. Sixteen vapor pressure data at temperatures 300-370 K have been obtained, while 48 gas-phase PVT data at 300-380 K. In addition, 9 vapor-pressure data at temperatures down to 260 K were recently obtained, whereas the measurement of temperature dependence of the cell constant of this apparatus is in progress.A density-measuring system with an aid of the vibrating-tube densimeter was newly designed and constructed, and it was then confirmed that the measurement system could provide us a satisfactory performance with rapid and precise measurements as expected. Measurements for pure water, methanol and 3 dif … More ferent MFC alternative refrigerants such as R-134a, R-125 and R-143a have been completed throughout the present research project. Additionally, similar precise density measurements have been carried out for compressed-liquid phases of HFE-245mc and HFE-143m, promising alternative candidates recently developed as next generation refrigerants, as well as for those or natural hydrocarbon refrigerants including propane (R-290) and R-600a.Concerning the analytical studies, on the other hand, a series of thermodynamic properly model with the Helmholtz-energy type equation of state which is effective for the entire fluid phase of typical natural refrigerants including R-290, R-600a and n-butane (R-600), have been developed with a universal functional form. These models developed have been published in one of the leading international journals. A significant success has also been confirmed in developing the mixing rule which does play an important role to formulate the thermodynamic property models for hydrocarbon (HC) mixtures so as to lead to those for the HC + HFC refrigerant mixtures.It should be noted that the thermodynamic property models developed by the present study for 3 HCs mentioned above have been accepted with international qualification for their forthcoming inclusion to the next version of the REFPROP, a thermodynamic property package developed by the U.S. National Institute of Standards and Technology (NIST) and being widely used on the international basis. Less