A solar parabolic trough collector is a solar thermal device that concentrates solar radiation onto a receiver tube to generate high temperature thermal energy. This study presents a numerical investigation to evaluate the thermal performance of a solar parabolic trough collector using inclined internal fin insertions. The standard LS-2 collector geometry is employed, with stainless steel as the absorber tube material and Syltherm-800 as the heat transfer fluid. Circular, rectangular, and conical fins are inserted at inclination angles of 45°, 60°, 75°, and 90° , and their thermo-fluid performance is evaluated under non-uniform heat flux conditions across Reynolds numbers from 4,000 to 16,000 and inlet temperatures of 400 K and 500 K. The non-uniform heat flux distribution is determined using Monte Carlo ray-tracing in Tonatiuh 2.2.4, and three-dimensional flow and conjugate heat transfer are simulated using ANSYS Fluent 2021 R1. A fin inclination angle of 600, provides the optimum thermo-fluid performance, achieving a maximum performance evaluation factor of 1.43 at a Reynolds number of 16,000 and an inlet temperature of 400 K, corresponding to improvements of 16% and 13% compared with the 90° and 45° configurations, respectively. The 60° conical fin lowered pumping power by 31.94% and 14.29% compared with 90° and rectangular fins. Among the investigated geometries, the conical fin exhibits the best overall performance, attaining a maximum Nusselt number of 235. Optimization of fin height identifies an optimum fin height to inner diameter ratio of 0.25, yielding a maximum performance evaluation factor of 1.515. The highest thermal efficiency of 68.0% is achieved with 90° fins. This optimal configuration remains consistent at both inlet temperatures, confirming its robustness and potential for improving the thermal performance of solar parabolic trough collectors.