Heat transfer and thermal stress of a parabolic trough solar collector with secondary reflector using microencapsulated phase change material slurries

•Optical-thermal-mechanical coupling problem of the absorber tube is settled.•Secondary reflector effectively uniforms solar flux distribution on absorber tube.•Secondary reflector enhance local heat transfer of slurry at phase change section.•Mean Nusselt number increases 29.3% for 15vol% slurry compared with water.•Equivalent thermal stress at the absorber outlet presents petal-like distribution.