Condensation of Halogenated Refrigerants Inside Smooth Tubes

TLDR

The authors develop a new predictive model for heat‑transfer coefficient and pressure drop during condensation of pure or blended halogenated refrigerants, including high‑pressure HFCs, in smooth tubes, addressing inadequacies of existing methods. The model derives from a flow‑pattern analysis of condensation, incorporating experimental data for R‑22, R‑134a, R‑125, R‑32, R‑236ea, R‑407C, and R‑410A in an 8 mm tube at 30–50 °C and 100–750 kg m⁻² s⁻¹, and applies Silver and Bell‑Ghaly corrections for zeotropic blends. Comparisons with the authors’ measurements and a broad independent data bank show excellent agreement in almost all cases.

Abstract

The paper presents a new predicting model to compute the heat transfer coefficient and pressure drop during condensation inside smooth tubes when operating with pure or blended halogenated refrigerants, including the new high-pressure HFC fluids, for which the existing predicting methods are inadequate. The suggested model is based on a predictive study of the flow patterns occurring during the condensation process. Predictions from this new procedure are compared both with the authors' experimental data and with a wide experimental data bank from independent authors; excellent agreement is demonstrated in almost all cases. Heat transfer coefficients were obtained during condensation of refrigerants R-22, R-134a, R-125, R-32, R-236ea, R-407C, and R-410A in an 8 mm inside diameter plain tube, carried out at a saturation temperature ranging between 30 and 50°C, and mass velocities varying from 100 to 750 kg/(m2·s), over the entire vapor quality range. For zeotropic blended refrigerants, such as R-407C, the Silver (1947) and Bell and Ghaly (1973) correction has been implemented in the prediction.