Thermal conductivity of refrigerants in the liquid state: A comparison of estimation methods

The thermal conductivity of refrigerants in the liquid phase is an open issue: the continuous generation of new refrigerants implies the necessity of determining new thermal conductivity values. Because experimental data usually do not cover the whole temperature range of industrial interest, estimation methods are generally requested. The lack of rigorous and consistent theories for the liquid state makes empirical estimation the most used way to produce thermal conductivity values at different temperatures. In this paper, a comparison of three different methods used to estimate thermal conductivity is presented; the database used for this comparison contains all of the common refrigerants belonging to the methane, ethane and propane series (almost all those included in ASHRAE Standard 34), and a wide temperature range (reduced temperatures from 0.30 to 0.95) is considered. Conclusions are drawn regarding the accuracy of these methods and possible improvements.