Abstract:

Saturated flow boiling experiments were conducted to investigate the influence of surface wettability on the hydraulic and thermal transport performance in a large width-to-height aspect ratio, one-sided heated rectangular microchannel with deionized water as the working fluid. The superhydrophilic surface is fabricated through the Plasma Enhanced Chemical Vapor Deposition (PECVD) method on the originally smooth hydrophilic silicon wafer. The contact angles of the silicon wafer and superhydrophilic surface deposited with 100 nm-thickness silicon dioxide thin film are 65° ±3° and less than 5° respectively. Effects of heat flux and mass flux on the heat transfer characteristics for the superhydrophilic and silicon wafer surface are discussed through experimental measurements, which are further explained by flow patterns observed through high speed visualization. The local heat transfer coefficient decreases first until approaching a minimum value and then increases towards the exit along the flow direction. Severe heat transfer deterioration is obtained for the bare silicon wafer surface with increased heat flux, resulting from the local dryout phenomenon as can be verified by the flow visualization. Improved heat transfer performance is obtained on the superhydrophilic surface for relatively low mass fluxes and high heat fluxes as a result of latish occurrence of the local dryout phenomenon.