Calculations of transport properties of CO2-HCs mixtures based on semi-empirical potential energy surface

F. Yang1, B. Song1, X. Wang1 and Z. Liu1

1Key Laboratory of Thermal Fluid Science and Engineering of MOE, Xi'an Jiaotong University, P.R. China

Keywords: new invert potential energy surface; kinetic theory
property: transport properties
material: CO2-HCs refrigerants

Due to the environmental issues of ozone depletion and climate change, recent research was focused on finding and developing new alternative refrigerants. Natural fluids, like ammonia, carbon dioxide and hydrocarbons (HCs), were a kind of environmentally friendly substances with zero ODP (ozone depletion potential) and low GWP (global warming potential) [Int. J. Refrig. 18, 190 (1995)]. Carbon dioxide could reduce the flammability of hydrocarbons while hydrocarbons could reduce the problems occurring due to high pressure of carbon dioxide. Therefore, mixtures of CO2 and HCs were proposed as ideal potential working fluids in refrigeration, air condition and heat pump. Accurate transport property for CO2-HCs refrigerants had to be known when designing and operating refrigeration systems. In order to obtain transport properties of CO2-HCs mixtures in present work, potential energy surface for interactions between CO2 and HCs molecules were determined by a semi-empirical method based on the principle of corresponding states. A new correlation of reduced collision integrals proposed by Najafi et al. [Int. J. Thermophys. 21, 1011 (2000)] was used in the inversion method to study eight interacting systems, consisting of CO2-methane, CO2-ethane, CO2-propane, CO2-butane, CO2-isobutane, CO2-pentane, CO2-isopentane and CO2-neopentane. From the invert intermolecular potentials, transport properties of the eight binary mixtures of CO2-HCs were calculated at low-density over temperature ranges of 273.15 K to 973.15 K, including viscosity coefficient, thermal conductivity coefficient, thermal diffusion coefficient and thermal diffusion factor. Present results were in good agreements with that of literature values. The estimated uncertainties were 2 % for viscosity coefficient, 10 % for thermal conductivity coefficient and 15 % for thermal diffusion coefficient, respectively. It was indicated that the effective potentials determined in present work could be applied to predict accurate transport properties of CO2-HCs refrigerants for wide temperature ranges. This work has been supported by the National Natural Science Foundation of China (Grant 51006083) and the Fundamental Research Funds for the Central Universities.

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