The heat losses within exhaust gases are an unavoidable part of operating any fuel-fired system. The flue gases still hold considerable thermal energy, which is exhausted to the atmosphere as waste heat and contributes to global warming. This paper presents a developed technique to enhance the performance of low temperature solar thermal systems by utilization of thermal energy recovery of flue gases. A CFD model was established based on the energy, momentum and mass conservation and the state equation in 2-D, steady assumption with kepsilon for the turbulence modelling using FLUENT - version 6.2.16 software. The model simulates the thermal and fluids flow processes in an inclined modified solar chimney. The flue inlet temperature was varied as, Tf g= 603K, 843K, and 983K. The simulation results were validated by comparison with experimental results obtained from a lab scale model, and acceptable agreement was gained. When the flue temperature is increased from 605K to 843K, the performance is enhanced by 75. The interesting find is that the efficiency of heat collection tends to increase as the absorber length increases up to a certain length, and then starts to decrease. In this study, the suitable dimension for solarflue gas collector is about 2.5 m. © 2012 WIT Press.