Fluctuations in ASHRAE Refrigerant Physical Properties and the Effect on Single and Two Phase Flow
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Throughout the course of the American Society of Heating Refrigeration and Air Conditioning, data of refrigerant physical properties have been published in their Handbooks. However, this information is not constant, rather varying as each subsequent handbook edition is released. Thirteen properties (liquid and vapor viscosity, thermal conductivity, specific heat, enthalpy, surface tension, density and specific volume) from five widely used refrigerants (R-22, R-134a, R-410a, R-152a, R-600a) are examined at temperatures of 100 and 40 degrees Fahrenheit. Also, standard correlations to design variables such as effect on Reynolds number are obtained using these properties. Mass flux rates of 100 and 300 lbm/ft^2-s are considered with pipe diameter of 8.52mm. The resultant values are compared to 2013, the most recent ASHRAE Handbook edition, as well as between editions beginning in 1981 in a standard percent change format. It is seen that physical properties can vary by nearly 30% with respect to edition 2013 and up to 25% between editions with a stabilizing effect appearing near more current editions. Additionally, design variables showed a similar trend however, as equations became a function of more physical properties, percent change became more erratic. With regards to mass flux rate, percent change was not affected for the selected single phase design variables as mass flux increased due to a scaling factor response, yet at lower mass flux pipe friction factor could be affected. Two phase flow calculations resulted in R-600a showing discrepancies of nearly plus and minus 50 percent through the quality range of 0.2 to 0.8 for condensation and plus 15 percent to negative 20 percent for qualities of 0.2 and 0.8, respectively. R-22 showed the lowest error with R-152a revealing at times negative 40 percent error for condensation and plus 7 percent error for evaporation.
Single Phase Flow
Two Phase Flow
Nagy, Paul (2014). Fluctuations in ASHRAE Refrigerant Physical Properties and the Effect on Single and Two Phase Flow. Master's thesis, Texas A & M University. Available electronically from