Heat transfer measurements and correlation of refrigerant flow boiling in tube filled with copper foam

Flow boiling heat transfer characteristics of refrigerant in tubes filled with metal foams were experimentally investigated at a saturation temperature of 7 °C, mass flux from 10 to 90 kg m−2 s−1, vapor quality from 0.1 to 0.8 and heat flux from 3.1 to 18.3 kW m−2. The refrigerant is R410A. The test sections are tubes with inner diameter of 23.4 or 13.8 mm, filled with 5 or 10 PPI copper foam. The experimental results reveal that, metal foam enhances the flow boiling heat transfer by a maximum of 220% and promotes the flow pattern transition from stratified flow to stratified-wavy flow and from stratified-wavy flow to annular flow. The heat transfer coefficient decreases with vapor quality under low mass flux, while it increases with vapor quality under high mass flux. A correlation for predicting the flow boiling heat transfer was developed and it agrees well with the experimental data.