A Methodology for Simultaneously Measuring Thermal Conductivity and Viscosity of Refrigerant Mixtures

Properties, such as specific heat, viscosity, and thermal conductivity, are important thermophysical properties in any heat transfer study. Today, these properties are known for numerous fluids, however, there are still many fluids which have not been measured, especially those under the classification of refrigerant mixtures. This paper proposes a new approach for simultaneously measuring these properties. In this approach, thermal conductivity and specific heat are obtained by measuring the heat transfer charactertics of a heated test section, whereas viscosity is measured by a viscometer placed inline with the heated test section. A theoretical analysis and uncertainty analysis are also presented. The accuracy of the viscosity and thermal conductivity measurements was shown to be dependent upon the uncertainty of the equipment and heat transfer measurements. A; Ao a,b a" ,be c c· CF Cp D f h. ho k L m Nun Pr ~ l(net l{lou qtot q" Ren t To 'tw ':f.t T, Too &Twj Urdk Urpk Urgk v p J1. NOMENCLATURE inside tube heat transfer surface area, m 2 outer insulation surface area, m 2 exponential power constant for correlation curve fitting exponential power constant for measured data curve fitting coefficient of correlation curve fitting coefficient of measured data curve fitting calibration function specific heat, kJ /kg· I< inside tube diameter, m friction factor in-tube average heat transfer coefficient, W/m2 ·I< outer heat loss average heat transfer coefficient, Wfm2 • [( thermal conductivity, Wfm ·I< tube length, m mass flow rate, kg/s average N usselt number based on diameter D Prandtl number heat rate, W net heat input, W heat loss, W total heat input, W heat flux, Wfm 2 Reynolds number average inlet temperature of the test section, °C average outlet temperature of the test section, °C average wall temperature of the test section, °C average fluid temperature in the test section, °C average outer insulation surface temperature, °C average ambient temperature, °C average temperature difference between Tw and T1 , °C uncertainty percentage of k by the Dittus-Boelter correlation uncertainty percentage of k by the Petukhov and Popov correlation uncertainty percentage of k by the Gnielinski correlation velocity, m/s density, kgfm3 viscosity, kg/m · s ton leave from the Industrial Technology Research Institute(ITRI) in Taiwan .