Investigations of partial flow behavior on R290 condensation under variable heat loads in a plate heat exchanger for battery thermal management

This study offers an innovative battery thermal management system for electric vehicles (EV-BTMS) that uses R290 refrigerant with mass flow separation to regulate battery heating. In this work, the refrigerant flow has been split between a cabin condenser and an offset-strip-fin plate heat exchanger (OSF-PHE) to simplify system structure and enhance cold-start performance. It evaluates system stability under variable heat flux (q) which replicate real driving conditions, unlike earlier studies. The experiments were conducted at refrigerant saturation temperature (T sat ) of 55 °C, with variations in mass flux (G) of 30, 40 & 50 kg/m 2 s, inlet vapor quality (X inl ) of 0.1–0.9, and coolant flow rates of 1.5, 2.5 & 3.5 Liter Per Minute (LPM). The refrigerant-side heat transfer coefficient (h ref ) reached 8057.2 W/m 2 K at 1.5 LPM and G = 30 kg/m 2 s, while the maximum q enhanced to 25.18 kW/m 2 at 3.5 LPM and G = 50 kg/m 2 s. The OSF-PHE achieved a peak effectiveness (εPHE) of 0.81 at 1.5 LPM and G = 50 kg/m 2 s, with an Energy Performance Index (EPI) of 93.2 % and a frictional pressure drop (ΔP fri ) of 5.10 kPa. Moreover, the coolant flow analysis demonstrated that 1.5 LPM offers the highest thermal effectiveness but greater-pressure losses, 3.5 LPM improves heat transfer but reduces efficiency, and 2.5 LPM ensures stable and balanced thermal operation. Finally, thermal evaluation of a 200 Ah LiFePO₄ battery reveals significant heat generation of 25.18 kW/m 2 at 1C and highlighting the need for precise thermal management to ensure safe, efficient, and reliable operation of battery modules. • An innovative R290 mass split boosts battery heating and cold-start stability. • Maximum heat transfer coefficient of 8057.2 W/m 2 K (G = 30 kg/m 2 s) gained at 1.5 LPM. • Highest heat flux of 25.2 kW/m 2 attained at 3.5 LPM with G = 50 kg/m 2 s operation. • Condenser effectiveness peaked at 0.81 with 1.5 LPM and G = 50 kg/m 2 s flow. • Optimum 2.5 LPM yield best trade-off between heat transfer and pressure drop.