Solar Air Heaters (SAH's) which are being widely used for the purposes of drying and space heating, because of their simplicity and low cost. Numerous SAH devices are designed, developed and used experimentally. Different factors affect the SAH's thermal efficiency .e.g. surface area of the collector, absorbent material, wind speed, glass cover etc. Increasing the absorber plate area will increase the heat transfer rate to the air, but on the other hand it results in the increase of the pressure drop in the collector. This increases the required power consumption which is required to pump the air flow crossing the collector. This project is all about the optimized results of an Analytical and Experimental investigation performance for flat plate SAH with obstacles (Semi annular fins) and without obstacles arrangements. The outlet temperature and pressure drop of SAH which are to be determined by changing the fin densities with the help of CFD software tool FLUENT.The analysis result states that the outlet temperature was maximum and pressure drop was minimum in the case of SAH with obstacles when compared to the SAH without obstacles