Experimental investigation of start-up and transient thermal performance of pumped two-phase battery thermal management system

In this study, a pumped two-phase battery thermal management system was developed, and its start-up and transient thermal performances were experimentally evaluated. The start-up behavior was characterized, and the effects of the flow rate, heat flux, and cold-source temperature on the start-up and transient thermal performances were examined. Three start-up modes were observed: fluctuating growth, temperature overshoot, and smooth growth. The fluctuating growth start-up mode appears to be suitable for battery cooling. The transient performance was improved when the flow rate was decreased, which resulted in a quicker start-up and lower average temperature (t(avg)) and maximum temperature difference ( increment t(max)). Reducing the flow rate from 0.99 to 0.20 L/min significantly shortened the start-up time, loweredt(avg)and increment t(max), and increased the heat transfer coefficient (alpha) when the steady state was reached. Increasing the heat flux initially improved and then weakened the transient performance of the pumped two-phase system. Increasing the heat flux from 1.1 to 2.8 W/cm(2)initially reduced the start-up time andt(avg)to 350 seconds and 1.5 degrees C, respectively, but they then significantly increased to 360 seconds and 13.5 degrees C, respectively. The transientt(avg)and increment t(max)decreased with the cold-source temperature (t(cs)), while the start-up time was independent of changes int(cs).