Experimental heat transfer and pressure drop in a metal-foam-filled tube heat exchanger

Heat transfer in small tubes is of particular interest in the heat exchanger industry for manufacturing shell-and-tube or concentric-tube heat exchangers. Metal-foam-filled tubes enhance the heat transfer mechanism by providing a high surface-area-to-volume ratio. This experimental study investigates the heat transfer and pressure drop in such tubes. Single-phase experiments were performed using copper tubes with an inner diameter of 4 mm and filled with copper metal foam. R245fa refrigerant was used as the working fluid with mass flux ranging from 200 to 1000 kg/m2 s. The heat transfer coefficient and pressure drop data are reported and compared to a tube without metal foam. The experimental data are also compared to well-known correlations from the literature. Most of the correlations are unable to capture any data point since they were developed for much bigger channels. New correlations are proposed to predict the heat transfer coefficient and pressure drop in such small tubes with metal foam inside.