Numerical study on hot spot minimization and heat transfer enhancement of narrow rectangular channel with slit elliptic dimples

Both arrangement and modification of dimples have significant effects on flow and heat transfer performance and the local high-temperature spots (hot spots) risk on the channel walls, which could potentially cause irretrievable damages to the high-power heat source, due to the negative effect on heat transfer of low velocity "dead zone" in the wake region for traditional dimples. To this end, the narrow rectangular channel with elliptic dimples with different rotated angles ranging from 0 degrees to 90 degrees are firstly systematically studied to explore the mechanism of balance of average and local heat transfer performance and flow resistance to figure out the most appropriate rotated angle. In order to further minimize the hot spot risk, novel dimples with streamwise/inclined slit are proposed and numerically studied to explore the dissipation of recirculation region or low velocity "dead zone" through the slit inducing a stream of flow from the front region to the wake region. In evaluation of the hot spot risk, the new indicator of high temperature probability (HTP) is proposed as a critical indicator. Compared to the channel with traditional dimples, slit can effectively reduce local high temperature and pressure loss by inducing a stream of flow from the front region to the wake region. Compared with the streamwise slit, the inclined slit performs better both in heat transfer performance and HTP. Compared with the smooth channel, the average heat transfer coefficient of the channel with inclined slit dimples with rotated angle of 75 degrees can be the improved by up to 14%, the maximum temperature of the channel wall can be decreased by up to 6.78 K and HTP of the channel wall can be decreased by up to 14.21%.