I have a problem in finding the heat transfer coefficient of a heat exchanger in which Ethane undergoes a phase transition. I would like to find the Prandtl number of Ethane in the phase transition region. So far I thought I would use the following: Pr_av = x * Pr_g + (1-x) Pr_l Pr_av = The Prandtl number of the mixture Pr_g = The Prandtl number of the vapor (found in table) Pr_l = The Prandtl number of the liquid (found in table) x = the vapor quality of the mixture However, I do not know whether this is correct. Should I calculate the Prandtl number from the (average Specific heat * average dynamic viscosity)/(average thermal conductivity) If so, how do I calculate these properties for my g/l mixture? Right now I don't even know how to calculate the specific heat at the boiling point.