Experimental study on pool boiling heat transfer in gradient metal foams.

Pool boiling heat transfer of metal foams with gradient pore densities has been investigated at atmospheric pressure in saturated deionized water. The gradient foams are made of two foam layers. The foam materials are copper and nickel. Pore densities of foam layers are from 5 PPI to 100 PPI, while the porosity remains the fixed value of 0.98. A parametric study is performed by varying the foam pore size and thickness. The effects of alumina nanoparticles and surfactant (SDS) on pool boiling heat transfer of gradient metal foams are also investigated in the present study. Images of foam fiber deposited by nanoparticles are captured by SEM. Compared to single-layer foams, gradient metal foams significantly enhance pool boiling heat transfer and the enhancement is heavily dependent on foam thickness and pore density gradient. The effects of SDS and nanoparticles on pool boiling heat transfer of gradient foams are dependent on concentrations. [ABSTRACT FROM AUTHOR]