Flow boiling visualization and heat transfer in metal-foam-filled mini tubes – Part II: Developing predictive methods for heat transfer coefficient and pressure drop

Abstract

High-porosity metal foams are proposed for insertion into heat exchanger channels to enhance the heat transfer mechanism in evaporators that are mainly used in organic Rankine cycle applications. This two-part experimental study investigates the two-phase flow inside a circular copper mini tube. Part I visualized the flow pattern and presented flow pattern maps, heat transfer coefficient data, and pressure drop data. Part II compares experimental data to recent correlations developed for metal-foam-filled mini tubes. The experimental conditions of the present study fall outside the valid range of the correlations, so none of them can predict the heat transfer coefficient or pressure drop accurately. Therefore, both the heat transfer coefficient and pressure drop are correlated using new approaches based on previous works and the present experimental data. Good agreement is observed between the experimental data and the new correlations in these experimental conditions.