Numerical study of heat transfer enhancement in the receiver tube of direct steam generation with parabolic trough by inserting metal foams

► Optimum thermo-hydraulic performance is obtained when H = 0.25 (bottom). ► Optimum thermal performance is obtained when H = 0.75 (top). ► Maximum circumferential temperature difference decreases about 45%. ► Layout, H effects on the thermal performance greatly, but φ effects on it slightly. ► Main methods and results can be extended to all solar concentrated receiver tube.