冷媒R1234ze(E),R1234ze(Z),R134a およびR245fa の水平平滑円管上の自由対流凝縮およびプール沸騰熱伝達特性

In this study, condensation and pool boiling heat transfer characteristics of R134a, R1234ze(E), R245fa and R1234ze(Z) are investigated experimentally on a horizontal plane tube. The test tube of outer diameter and heat transfer length are 19.12 mm and 400 mm, respectively. For the condensation at saturation temperatures from 20 to 60 °C and the degrees of wall subcool from 0.77 to 28.81 K, the measured condensation heat transfer coefficient of R1234ze(Z) agree with that of Nusselts filmwise condensation theory within approximately ±11 %. The condensation heat transfer coe_officient of R1234ze(Z) is slightly higher than _-2other refrigerants. For pool boiling at saturation temperatures from 10 to 60 C and heat fluxes from 0.73 to 80.13 kWm , the measured pool boiling heat transfer coefficients reasonably agree with that predicted by Stephan-Abdelsalam correlation. The pool boiling heat transfer coefficie_onts of R1234ze(E) and R134a _-2are significantly higher than those of R1234ze(Z) and R245fa at saturation temperature 20 C and heat flux 15 kWm . However, the pool boiling heat transfer coefficient of R1234ze(Z) becomes larger with increasing the reduced pressure.