In this study, an investigation is conducted on a parabolic trough collector (PTC) equipped with a tubular receiver to explore the impact of different parameters on convective heat losses within the collector. The parameters taken into consideration are the focal ratio, aperture ratio, and Rayleigh number. The convective heat transfer is modeled using a laminar model exclusively. The computed heat losses are further utilized to determine the Nusselt number, employing the receiver diameter as a characteristic dimension. The findings demonstrate that the Nusselt number rises as the Rayleigh number increases. The fluid flow within the enclosure shows an increase with an elevation in the focal ratio, whereas it decreases with a higher aperture ratio. A correlation for Nusselt number is proposed incorporating Rayleigh number. By conducting this simulation, a better understanding of convective heat transfer in enclosures can be gained, aiding in the design and optimization of systems such as boilers and parabolic solar water heaters.