Comparative analysis of R290 and R1234yf cooling performance in offset strip-fin plate heat exchanger for electric-vehicle battery thermal management

Abstract

This study compares the performances of two-phase refrigerant cooling (TPRC) using two refrigerants, namely R290 and R1234yf, in battery thermal management systems. A compact and energy-efficient brazed plate heat exchanger with an offset strip fin is employed as a cold-plate evaporator and experiments are conducted to examine its heat-transfer characteristics. Key performance parameters including the heat-transfer coefficient (HTC), pressure drop (PD), and wall temperature (Tw) are assessed at discharge rates (C-rates) of 1, 1.25, and 1.5C, saturation temperatures (Tsat) of 16 °C and 20 °C, the mass flux of 50 kg/m2s, and inlet vapor-quality values of 0.1–0.8. The results show that R290 offers a higher HTC and lower PD for all C-rates compared with R1234yf for Tsat = 16 °C and 20 °C. The HTC increases by 107%–113% for 1.5–1C at Tsat = 16 °C, and 84% (1.5 and 1C) and 70% (1.25C) at 20 °C. Similarly, the PD decreases by 6.7%–10.1% for 1–1.5C at Tsat = 16 °C and approximately 10% for all C-rates at 20 °C. Compared with R1234yf, R290 maintains a Tw that is 1.1 °C and 0.7 °C lower at Tsat = 16 °C and 20 °C, respectively. Results of critical heat transfer coefficient (CHTC) analysis confirm that R290 performs better than R1234yf at Tsat = 16 °C in terms of HTC increment and Tw reduction and that the critical HTC of R290 is higher than that of R1234yf by 80% and 40% for Tsat = 16 °C and 20 °C, respectively. Additionally, using R290 instead of R1234yf in the TPRC system yields a higher level of cooling efficiency at vapor-quality values of 0.4–0.5. In addition, an artificial neural network model is used to predict the experimental results, where a root-mean-square error of 2.3%–3.5% is indicated. Using this trained model, the HTC and PD are predicated at intermediate C-rates (1.1–1.4C) and the results are discussed.