Absorber tubes 1 Artery porous structure Collector efficiency 1 Heat Transfer enhancement 1 Heat flux 1 Heat transfer performance 1 Liquids 1 Microporous 1 Porosity 1 Porous structures 1 Sintering 1 Solar absorbers 1 Thermal enhancement 1 Trough solar collectors 1 Tubes (components) 1 Vapor-liquid 1 Water absorption 1 Working fluid 1 artery porous structure 1 heat transfer 1 thermal enhancement 1 trough solar collector 1