Replacement of R22 in tube-and-shell condensers: experiments and simulations

An investigation of the change in condenser overall heat transfer coefficient when replacing R22 with one of the three mixtures R407C, R404A and R410B was made, both experimentally and theoretically. Measurements have been carried out on a full-scale test plant consisting of a horizontal shell-side condenser. According to the measurements the decrease in overall heat transfer coefficient for the non-azeotropic mixture R407C was very large, up to 70% compared to R22, while for the near-azeotropic mixture R404A the decrease was less than 15%. Simulations of the condenser were done with a comprehensive computer program, calculating the condensation heat transfer with an approximate method including a correction for mass resistance. The calculation model was not able to predict this large degradation for the non-azeotropic mixture, while the predictions agreed rather well with the measurements for the pure fluid and the near-azeotropic mixtures.