Experimental investigation on the thermal-hydraulic performance of channel with gradient metal foam baffles

Abstract

Metal foam is a novel material recently utilized in baffles as an alternative to solid baffles for reducing flow resistance. However, the metal foam baffles are accompanied by low heat transfer efficiency. To overcome this issue, a new design of copper foam baffles has been suggested in this research, called baffles having a gradient pore density of the copper foam. The pore density either increases or decreases towards the wall. So, the experimental tests were carried out in a square channel and heated uniformly at the bottom wall of the test section. Its walls are mounted copper foam baffles at a fixed porosity of 95%. Baffles were alternately fixed upon the walls' bottom and top in staggered mode. The results were determined for various kinds of copper foam (10 and 20) pores per inch (PPI), and the gradient pore density was either with the order decreasing (DPPI) 10/20 PPI or increasing (IPPI) 20/10 PPI with a window cut ratio of 25% and a constant heat flux of 4.4 kW/m2 . The Reynolds number was changed from 3.8x104 to 5.4x104 . The data for conventional copper solid baffles were used to compare the influence of foam metal type. The obtained results revealed an enhancement in thermohydraulic performance for baffles with a gradient pore density of the order decreasing DPPI (10/20 PPI) higher than all the models of copper foam baffles.