Influence of metal foam on heat transfer characteristics of refrigerant-oil mixture flow boiling inside circular tubes

The influence of metal foam on heat transfer characteristics of refrigerant and oil mixture flow boiling inside circular tubes was experimentally investigated on two horizontal circular tubes filled with 5 PPI and 10 PPI copper foams, respectively. The experimental conditions include saturation pressure of 995 kPa, mass flux from 10 to 30 kg m(-2) s(-1), heat flux from 3.1 to 9.3 kW m(-2), inlet vapor quality from 0.175 to 0.775 and oil concentration from 0% to 5%. The experimental results reveal that metal foam enhances the flow boiling heat transfer coefficient of refrigerant by a maximum of 185%, while the enhancement effect of metal foam is weakened at oil presence conditions. A new correlation is developed, which can agree with 98% of the experimental data within a deviation of +/- 30%. (C) 2012 Elsevier Ltd. All rights reserved.