The paper is concerned the use of ferrofluids in solar parabolic trough collectors enhances thermal efficiency of solar collectors. Ferromagnetic nanoparticles dispersed in common heat transfer fluids (ferrofluids) exhibit better thermos-physical properties compared to the base fluids. By applying the right magnetic intensity and magnetic field direction, the thermal conductivity of the fluid enhanced more than conventional nanofluids. Therefore, ferrofluids based concentrating solar collector design is slightly different from conventional solar collectors. External magnetic source is installed to alter the thermos-physical properties of the fluid. In this paper, a heat transfer model based on energy balance of the solar collector is presented. The balance includes the direct thermal solar irradiation on the collector, optical losses, thermal losses, and heat gain of solar absorber. Various nanoparticle concentrations (<0.05 %) at the operational temperatures between 300 K and 500 K were used in the current study. The model was compared to experimental data that used conventional heat transfer fluid. The results of the model were in a good agreement with the experimental data. Using ferrofluids as a heat transfer fluid increases the efficiency of solar collectors. Increasing the concentration of particles increase the efficiency of the collector. In the presence of external magnetic field, the solar collector efficiency increase to the maximum. At higher temperatures, the ferrofluids shows much better efficiency than convectional heat transfer fluid. The ferrofluids shows better heat transfer coefficient and decrease the surface temperature of the absorber. Ferromagnetic particles build a chain like structure in the presence of external magnetic field allowing faster heat transfer throw conduction.