Condensation heat transfer of R1234ze(E) and R134a inside a brazed plate heat exchanger: experimental data and model assessment

Condensation from superheated vapour is an essential process widely encountered in energy applications, mostly for refrigeration and heat pump technologies and for power production systems. This paper presents and analyses the experimental results obtained during partial condensation inside a brazed plate heat exchanger (BPHE) of the HydroFluoroCarbon R134a and of one of its replacements, the HydroFluoroOlefin R1234ze(E). Tests have been conducted considering different values of the outlet vapour quality, mass flux, and a saturation temperature that ranges between 34.6°C and 42.3°C. Partial condensation tests revealed that the heat transfer coefficients collected with R134a are 4-8% higher than those with R1234ze(E). Experimental tests of complete condensation of R1234ze(E) with different degrees of superheating and subcooling have also been performed to investigate how these parameters affect the thermal performance in real operating conditions. The experimental results, in terms of condensation heat transfer coefficient, have been compared with the predictions of some existing correlations, highlighting those that provide the best accuracy when designing brazed plate condensers.