Flow Boiling of R134a and R134a/Propane Mixtures at Low Saturation Temperatures Inside a Plain Horizontal Tube

摘要

Local heat transfer coefficients for flow boiling of pure 1,1,1,2-tetrafluoroethane (R134a) and binary mixtures of propane (R290) and R134a were measured. The experimental setup employed a vapor heated plain horizontal tube (d_i= 10 mm, d_o=12mm, L = 500 mm). The measurements covered a wide range of saturation temperatures (233 ≤ T_s ≤ 278K), mass fluxes (100 ≤ m ≤ 300 kg/m~2 s), qualities (0 ≤ x ≤ 1), and concentrations (0 ≤ z ≤ 0.65). In the zeotropic region of R134a/R290 mixtures, the measured local heat transfer coefficient was found to show a maximum decrease by a factor of 2 relative to that for pure Rl34a. At the azeotropic point (65% R290), it was found to increase by a factor of 1.2. The measured local heat transfer coefficients for both R134a and R134a/R290 were compared with a number of correlations.