Flow thermohydraulic characterization of open diverging microchannel heat sink for high heat flux dissipation

The future fusion reactor puts forward higher demand for the heat dissipation capability of the divertor, which requires to withstand ultra-high heat flux of up to 20 MW/m2. Our previous study demonstrated that microchannel cooling technology is a promising strategy to remove high heat loads on the target plate of the divertor. However, the high pressure drop of the straight rectangular microchannel limits its practical implementation. In this study, we propose an open diverging microchannel heat sink (ODMHS) to reduce the pressure drop under high heat flux and high flow rate conditions. The effects of the width and height of expanding channel on the heat transfer performance and pressure drop were first studied numerically. The results indicated that expanding channel width resulted in a reduction of heat transfer coefficient, whereas the expansion of the channel height led to the enhancement of heat transfer performance. Regardless of the divergence of channel width or height, the enlargement of the channel dimension can effectively reduce the pumping power. Subsequently, experimental tests were carried out in ODMHS with a width ratio and a height ratio of 1.33 and 1.30, respectively. The results demonstrated that the ODMHS can withstand heat flux of up to 15.6 MW/m2 at 3 L/min. This study provides important insights for high heat flux dissipation on the target plate of the divertor by rational design of microchannel structures.