Thermo-physical behavior of an oscillating heat pipe developed for thermal management of 21,700 cylindrical cells in electric vehicles: Towards a deeper understanding

A novel examination of thermo-physical behavior in vertical oscillating heat pipes (V-OHP) developed for the electric vehicle battery thermal management system (BTMS) was performed. The V-OHP was designed based on the geometric characteristics of a 21,700 cylindrical Li-ion battery. This analysis aims to provide detailed information derived under different conditions, thereby enhancing the BTMS. R-410 A refrigerant was identified as the working fluid, utilizing a filling volume of 50% and 60%. This research focuses on thermo-physical dynamics of a V-OHP, such as the onset of nucleation boiling (bubbles formation duration), slug-plug motion start time, condenser's horizontal section inflow, circulation motion start time (start-up time), and circulation duration. Results were analyzed for the heating power of 10 W to 80 W in the evaporator (10 W almost reflects the heat from a 21,700 battery cell discharging with 1C), and also convective coefficient varying from 700 W/m 2 K to 1400 W/m 2 K in the condenser at T in = 288 K. An increase in the FV from 50% to 60% leads to a longer duration required for the start of oscillatory motion and a reduction in the time required to transition from oscillation to circulation motion. Maximum value for circulation duration obtained for 20 W, FV = 60% and CC = 1000 W/m 2 K.