In this paper, a numerical simulation of fluid flow and conjugate heat transfer in a solar thermal parabolic trough collector (PTC) system is presented. The simulation is being carried out on a prototype designed in the Mechanical Laboratory in order to analyze the performance of this system. The main objective is to compare the system performance with and without a secondary reflector (SR). PVSYST software is used to provide numerical temporal values of the solar heat flux in Laghouat city (ALGERIA). Solar flux density values for four days in different seasons have been taken. SolTrace code is used to determine the heat flux distribution on the absorber tube. The conjugate heat transfer and fluid flow equations in the tube absorber are solved by using ANSYS-CFX CFD software. A comparison between two cases (traditional PTC and PTC with parabolic secondary reflector) with the same working fluid (Therminol VP-1) is carried out. The obtained results show that the system performance are practically the same for the four seasons. Moreover, the performance of the system with a second collector is better than that without a second reflector with a ratio of about 1.65.