LAUSR

With the aim to improve overall thermal-hydraulic and thermodynamic performance of parabolic trough solar receiver (PTR), a new configuration with partial insertion of gradient metal foam (GMF) is proposed. The effects of GMF with pore density gradient or porosity gradient on turbulent forced convection heat transfer, flow resistance, entropy generation rate and exergetic efficiency of PTR tube are numerically analyzed. The distribution of non-uniform heat flux on receiver tube wall is calculated by Monte Carlo Ray-Trace Method, and the local thermal non-equilibrium model is used, which considers the temperature difference between metal skeleton and fluid. The numerical method is validated by experimental data. The results show that GMF enhances the heat transfer of PTR tube, with Nusselt number being increased by 43.7%–812.6%; brings the increase of flow resistance, with friction factor being 4.2 to 16.7 times of empty tube; improves the overall thermal-hydraulic performance with performance evaluation criteria ranging from 1.5–3.6. The GMF causes maximum reduction of total entropy generation rate and maximum enhancement of exergetic efficiency to be 92.6% and 24.4%, respectively. The PTR tube partially filled with GMF can obtain higher thermal-hydraulic and thermodynamic performance than that with uniform metal foam.