Condensation of R290 + R13I1 zeotropic mixture in a plate heat exchanger with offset-strip fin geometry

Energy-efficient refrigerants with a low global-warming potential (GWP) is becoming increasingly popular, particularly in the automobile sector. In this sense, despite its higher flammability, R290 can meet environmental regulations with outstanding thermal properties. Studies have been conducted to reduce the flammability of R290 by combining it with flame retarding agents, and it has been discovered that the use of R13I1 has good control over R290's flammability and offering good thermal performance. However, research into the two-phase behavior of R290 + R13I1 combinations is extremely important for building compact heat-pumps. Therefore, this study experimentally investigated the condensation behavior of a new low-GWP R290 + R13I1 refrigerant mixture in a plate heat exchanger with an offset-strip fin flow passage. The effects of the heat flux (HF), mean vapor quality (x_m), saturation temperature (T_s), and mass flux (MF) on the condensation heat transfer coefficient (HTC) and two-phase frictional pressure drop were explored. The results show that the peak condensation HTC increased by 66.2% and 19.7% with an increase in HF and MF, respectively, although it deteriorated by 26.7% in the case of T_s. Moreover, the dominance of the mass transfer resistance (MTR) and surface tension was observed at lower x_m values, whereas the shear force dominated at higher x_m values. The MTR was estimated with Silver–Bell–Ghaly (SBG) approximation, and the values were in the range of 0.0000342 K.m⁻².W⁻¹ and 0.000067 K.m⁻².W⁻¹. Moreover, the Nusselt number (Nu) predicted using the SBG approximation correlations was lower than the experimental value. Hence, two types of new Nu correlation were made with and without SBG approximation, and they showed reasonably good Nu prediction with 9.6% and 10.8% mean absolute deviation.