SUPERHYDROPHILIC COMPOSITE STRUCTURE OF COPPER MICRO-CHANNEL AND NANO-FOREST FOR ENHANCING BOILING HEAT TRANSFER

Nanostructures are then made on the micro-pin-fins through a simple one-step electrodeposition process, which looks like a natural forest structure with rich branch-like grooves. Capillary rise tests were performed with ethanol to characterize the capillary force of the wick structure. An efficient boiling heat transfer (BHT) interface based on a superhydrophilic copper micro-pin-fins and nano-forest composite structure is reported. In principle, these micro-pin-fins are efficient nucleation sites, helping to reduce the surface superheat required for the onset of nucleate boiling (ONB) and enhance the heat transfer coefficient (HTC). Disperse nanoforest contribute to bubbles detachment from the heated wall rapidly. Micro-pin-fins with a depth of a few hundreds of microns can avoid excessive interface thermal resistance, the superwetting effect of the micro-nano composite structure helps to increase the critical heat flux (CHF). By studying the morphology, wettability, liquid subcoolings and heat transfer characteristics of the micro-pin-fins and nano-forest composite structure as a function of growth time, an optimal interface was obtained, with a maximum HTC enhancement of 243%, CHF enhancement of 204%, and the superheat corresponding to the ONB compared to the flat copper surface is reduced by 50%. At the same time, the combination of experimental and theoretical analysis also clarified why the micro-pin-fins and nano-forest composite structure on the copper surface can effectively enhance boiling heat transfer.