摘要
Visualization experiments are performed for horizontal mesh-wick flat-plate heat pipes with the evaporator and condenser sections chemically treated to manifest different surface wettabilities. Deionized water is used as the working fluid. The static contact angles (θ 0 s) examined include θ 0,e = 0° and 13° (untreated) and θ 0,c = 0°, 13°, 80°, and 120°. The measured evaporator resistances are similar for θ 0,e = 0° and 13°. The condenser resistances for θ 0,c = 0° are the highest as the liquid in the condenser levels up to the wick top. The condensation for θ 0,c = 13° or larger exhibits cyclic dropwise condensation on the islands of exposed wire sections. With θ 0 as large as 120°, the water level in the condenser was lowest but numerous large round drops may sustain a while, along with other rapidly growing drops of different sizes, before they rupture and drain away. These large round drops act as heavy thermal barrier so that condenser resistances for θ 0,c = 80° and 120° are higher than for θ 0,c = 13°. Hydrophilic treatment on the evaporator fails to enlarge Q max , because while the capillarity increases slightly from θ 0 = 13° to θ 0 = 0°, the liquid flow is hindered by the deposited nanostructures. Among all the surface conditions tested, the untreated wick (θ 0 = 13°) exhibits the best performances in both Q max and total thermal resistance.