Thermal Performance Analysis of a Twisted-Tube Absorber in a Parabolic Trough Solar Collector under Variable Flow Conditions

This paper presents a comprehensive CFD-based thermal performance analysis of a parabolic trough solar collector equipped with a twisted-tube absorber under variable flow conditions. The investigation focuses on four different tube materials - stainless steel, iron, copper, and aluminium -evaluated across a range of inlet velocities (0.2 to 0.32 m/s) using COMSOL Multiphysics. The simulation results showed that both the mbe material and flow velocity significantly influenced the temperature distribution, heat transfer, and fluid outlet temperature. Materials with lower thermal conductivity, such as stainless steel and iron, yielded higher outlet temperatures owing to reduced wall heat conduction, while copper and aluminum promoted more uniform temperature profiles and enhanced thermal dispersion. Increasing the inlet velocity improved the convective heat transfer, but decreased the outlet temperatures owing to the reduced residence time. The findings provide practical guidance for optimizing material selection and flow control strategies in the design of high-efficiency solar thermal systems.