Numerical Investigation of Microchannel Geometry Effects on Thermal Performance of Parabolic Trough Solar Collectors

This study numerically investigates the effect of different microchannel geometries integrated into the absorber tube on the thermal performance of a parabolic trough solar collector. Four configurations were analyzed: empty (straight pipe), circular, square, and triangular microchannels. Computational Fluid Dynamics simulations were conducted using ANSYS Fluent 19.0, adopting a Finite Volume Method with a pressure‐based solver, the SIMPLE algorithm for pressure–velocity coupling, and second‐order upwind discretization for momentum and energy equations. Simulations were performed across mass flow rates ranging from 0.25 to 1.0 kg/h, with an inlet fluid temperature of 25°C and a constant solar irradiance of 884 W/m 2 . The corresponding Reynolds numbers ranged approximately from 110 to 420, indicating laminar flow across all cases. Among the configurations, the triangular microchannel exhibited the best performance. At 0.25 kg/h, it achieved an outlet temperature of 101.73°C and a thermal efficiency of 85%, compared with 92°C and 37.15% in the nonchanneled base case. At 1.0 kg/h, the triangular design reached a Nusselt number of 30.48, more than double that of the baseline (14.45), indicating superior convective heat transfer. Validation against published results showed a maximum deviation of only 2.6%, confirming the accuracy of the simulation model. The findings highlight that triangular and square microchannels significantly enhance heat transfer and thermal efficiency, particularly at low flow rates, making them promising designs for advancing solar thermal energy systems.