Enhanced flow boiling heat transfer study on EDM-modified aluminum surface

Heat transfer surface of evaporator is crucial for the heat transfer efficiency of self-circulating evaporative cooling system. A novel modified Al alloy profile plate surface is prepared via electrical discharge machining. The modified surface with multifarious microstructures exhibits superior heat transfer properties, which has a higher heat flux and lower wall temperature. The experiments indicated that the surface temperature of the Al6 modified surface is 8.7 degrees C lower than the smooth surface when the heat flux is 300 kW/m2. The maximum heat flux of the liquid box with modified surface can still reach the thermal equilibrium state at 500 kW/m2, while the maximum heat flux of the liquid box with smooth surface can only reach 300 kW/m2. To clarify the heat transfer properties, the macroscopic morphology of the Al alloy profile plates was investigated. The surface roughness of the modified plate is between 2.26 mu m-3.73 mu m, and the contact angles range from 82 degrees-95 degrees. The wettability of the modified surface has similar variation with the surface roughness. The modified surface with capillary action of the micro-structure can form a local hydrophilic region, which can easily inflow the liquid to generate more bubbles and recede wall temperature. As an effective method to improve the heat transfer performance of heat exchangers, surface modification technology is an important research trend with considerable application potential.