Experimental Study of Evaporative Heat Transfer in Sintered Copper Bidispersed Wick Structures

Abstract

An experiment has been carried out on evaporative heat transfer in rectangular bidispersed wick structures heatedbya groovedblock from thetop. Threebidispersedwick structures,havinglarge/smallpore-diameterratios of 200/80, 400/80, and 800/80 πm, were formed by sintering copper powder. For comparison, two monodispersed wick structures having pore diameters of 80 and 800 πm, respectively, were also tested. It was found that the heat transfer coefe cient and the critical heat e ux of a bidispersed wick are much higher than that of a monodispersed wick having its pore diameter equal to the smaller pore diameter of the bidispersed wick. It is also found that for bidispersed wicks with the same small-pore diameter there exists an optimal large-pore diameter that gives both the highest heat transfer coefe cient and the highest critical heat e ux. Finally, the effect of the adverse hydrostatic head on the heat transfer performance in the wick is shown. Nomenclature Ah = heating surface area, m 2 a = length of heating block, m h = heat transfer coefe cient, W/m 2 K K = permeability, m 2 P m = mass e ow rate, kg/m 2 s Q = heat power, W Tl = temperature of the subcooled liquid water, ± C Ts = saturation temperature, ± C Tv = temperature of the exhaust vapor, ± C TW = temperature of the heating block, ± C 1H = adverse hydrostatic head, mm = porosity Subscripts l = liquid s = saturation v = vapor w = wall