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 nano-forest 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.