Experimental study on flow boiling characteristics in a long minichannel under low pressure

To cope with the challenge of instantaneous high heat flux of high-speed aircraft, a novel minichannel flow boiling thermal management method based on open system is proposed, in which the heat is dissipated by directly draining the high temperature medium to low pressure environment. To test its feasibility, the experiment on the thermal performance is conducted based on a long heat sink consisting of four long parallel mini channels. The evolution mechanism of flow boiling pattern under various back pressure conditions is investigated. The heat transfer coefficient (HTC) changes along the channel is compared, and the flow pattern evolution is obtained by visualization method with different pressure. The results indicate that flow boiling exhibits different heat transfer characteristics at different heat flux densities, and the decrease in pressure has a certain effect on the evolution of convective two-phase flow patterns. With the increase in heat flux, the wall thermal uniformity does not increase monotonically. In addition, we are surprised to discover that under the same heat flux, the wall temperature of the channel wall significantly decreases under low pressure. In our experiments, the obtained maximum temperature drop reached 20 K. Accompanied by the advantages of simple in structure, avoiding the introduction of large volume and weight cooling equipment, the proposed thermal management method provides a new idea to deal with the short-time high heat flux problem that may occur in hypersonic aircraft.