Pool boiling heat transfer of multi-scale composite copper powders fabricated by sintering-alloying-dealloying treatment

Abstract

Multi-scale composite copper powders (MCCP) were proposed and developed for pool boiling cooling system in this study. By means of sintering-alloying-dealloying technology, the nanostructures could be constructed on the surface of porous sintered copper powders, resulting in the formation of MCCP. The sizes of the ligaments and pores for nanostructures were less than 150 nm. Pool boiling heat transfer performance was systematically investigated in different subcooling conditions (ΔTsub= 0–30 °C) at atmospheric pressure, together with the bubble growth phenomenon. Sintered copper powders (SCP) were made and measured with pool boiling performance for comparison as well. The results showed that MCCP could significantly enhance the pool boiling heat transfer and reduce the wall temperature. The maximum boiling heat transfer coefficient of the MCCP was about 78.2 W/m2 K at heat flux 25.3 W/cm2, 3.1 times higher than that of the sintered copper powders at saturation case. Besides, the heat transfer curves and visualization results both revealed that MCCP went into the fully developed nucleate boiling stage quickly. The above enhancement was due to the existence of nanostructures on the powder surface, which considerably increased the active nucleation sites.