Parabolic trough collector (PTC) is a widely used and efficient Concentrating Solar Power (CSP) technology for generating solar thermal power. Supercritical CO2 (s-CO2) is a heat transfer fluid (HTF) that shows good promise for use in solar PTC for further improvement in its efficiency and operations. A numerical thermal model is developed to understand the performance of s-CO2 as an HTF in a solar PTC. The local temperature and velocity fields were used to calculate the entropy generated within HTF due to finite temperature differences and fluid flow friction. A commercially available LS-3 parabolic trough collector is used for the analysis with a modified receiver. An optical analysis tool based on Monte Carlo Ray tracing is used to calculate non-uniform heat flux distribution around the circumference of the PTC receiver. Entropy generated at various operating pressures, inlet temperatures, and inlet Reynolds number using s-CO2 as HTF is calculated and analyzed. Results showed that entropy generated in the PTC receiver is reduced to a minimum at optimal Reynolds number for each of the operating pressures and inlet temperatures of the HTF. The Bejan number estimates the contribution of entropy generated due to heat transfer irreversibilities to the entropy generated due to heat transfer and fluid flow irreversibilities which is between 0.2-0.4 at high flow rates and close to 1 at low flow rates. Exergy efficiency analysis supported the optimized inlet boundary conditions.