Performance of microchannel condensers with metal foams on the air-side: Application in small-scale refrigeration systems

The thermal-hydraulic performance of microchannel condensers with open-cell metal foams to enhance the air-side heat transfer is investigated in this paper. Three different copper metal foam structures with distinct pore densities (10 and 20 PPI) and porosities (0.893 and 0.947) were tested. A conventional condenser surface, with copper plain fins, was also tested for performance comparison purposes. The experimental apparatus consisted of a closed-loop wind tunnel calorimeter and a refrigerant loop, which allowed the specification of the mass flow rate and thermodynamic state of R-600a at the condenser inlet. The experiments were performed at a condensing temperature of 45 °C. The air-side flow rate ranged from 1.4 × 10−3 to 3.3 × 10−3 m3/s (giving face velocities in the range of 2.1–4.9 m/s). The heat transfer rate, the overall thermal conductance, the Colburn j-factor, the friction factor and the pumping power were calculated as part of the analysis.