Absorber tube performance enhancement by using passive techniques is one of the major topics of research in the field of solar thermal power engineering. Earlier studies on ducts revealed that passive augmentation techniques have shown considerable enhancement in heat transfer. Experiments were conducted earlier on Parabolic Trough Collector (PTC) with plain absorber tube without inserts for different flow rate conditions. It was observed that fluid flow rate with 85 kg/hr has shown higher temperature difference for solar flux condition of 850 W/m2. In the present study, numerical analysis using CFD is performed by using inserts of different cross-section inside the fluid flow path of an absorber tube to study the flow characteristics. The fluid flow and heat transfer phenomena through a 3-dimensional absorber tube with varying heat source are obtained by solving the fundamental governing equations namely: conservation of mass, momentum and energy. Turbulence is modeled using SST k-ωmodel of closure. The heat transfer and pressure drop is calculated from the studies conducted for a mass flow rate of 85 kg/hr using the ANSYS CFX 12.1 software. The result of the numerical analysis is validated with the experiments carried out with the parabolic trough collector. The numerical study is carried out with triangle, inverted triangle and semi-circular inserts and compared with that of plain absorber tube. It has been found that triangle insertion gives optimized results with respect to uniform heat transfer which reduces the thermal fatigue even the pressure drop is relatively high compared to the plain absorber tube without insertion. © 2006-2014 Asian Research Publishing Network (ARPN).