Experimental study on hydraulic and thermal characteristics of composite porous wick with spherical-dendritic powders

A composite porous wick with spherical-dendritic powders is proposed, in which the dendritic powders fill the gap between the spherical powders. A unique biporous structure can be realized in this composite porous wick, including small pores between dendritic powders, small pores between spherical and dendritic powders and large pores between spherical powders. Two metal powders (copper and nickel) with two structures (spherical and dendritic) are chosen as the prepared materials, and four composite porous wicks are fabricated. The hydraulic and thermal characteristics of the composite porous wick are studied experimentally. Two capillary pumping stages have been observed in the composite porous wick. And the combination of powders with different metal materials or different structures reduces the effective thermal conductivity of porous wick. Two evaporation heat transfer modes have been observed in evaporation heat transfer experiment, including the evaporation in the vapor grooves and the meniscus evaporation in porous wick. The composite porous wick with dendritic copper powders shows good evaporation heat transfer performance, in which the effective thermal conductivity is not the lowest. Both higher local thermal conductivity and larger equivalent pore diameter exist in this composite porous wick, which is advantage to the meniscus evaporation.