International Journal of Energy Research, Vol.45, No.4, 6333-6349, 2021
Hybrid heat sinks for thermal management of passively cooled battery chargers
Battery chargers are an important component in electric and plug-in hybrid vehicles and various other clean energy systems. The thermal management in battery charger is a crucial aspect that influences its overall performance and cyclic stability. Passive cooling technology using heat sinks is preferred in developing battery chargers due to its reliability, quietness, and efficiency (no parasitic power). In the present work, new hybrid passive heat sinks (HPHS) with various fin geometries, namely inclined interrupted fins, pin fins, and straight interrupted fins, have been developed by adding a phase change material (PCM) layer to passively cooled bare fin heat sinks (BFHS). The developed heat sinks have the same geometric footprint as that of the battery charger, IC650 built by the industrial partner of the project Delta-Q Technologies. Experimental investigations were carried out to analyze the effects of PCM quantities and continuous (80-120 W) and intermittent (duty cycle operation) thermal loads on the heating-cooling performance of the HPHS. Temperature contours obtained using infrared images show that the proposed HPHS provides a more uniform temperature with reduced hot spots compared to BFHS. The heating and cooling performances of straight interrupted fins-based HPHS were found better for all thermal loads and PCM quantities tested due to their smaller thermal resistance. Increasing the PCM volume fraction from 0.2 to 0.6 improves the load shedding capacity. However, the added thermal resistance requires optimal consideration. While conducting different cyclic operations for inclined interrupted fins-based HPHS, a maximum overall thermal management ratio of 0.45 was achieved. The proposed HPHS minimizes the temperature fluctuations more effectively while operating at high loads and shorter duty periods. This new passively cooled hybrid heat sink can notably improve the overall performance and reliability of battery chargers during both continuous and intermittent operations.