In this study, the efficiency of a double pipe heat exchanger with the plain tube as well as coil insert tube is investigated by using water and various nanofluids mixed with water. Silicon Oxide and silver nanofluid are the nanofluids mixed with water at volume fractions of 0.35 percent. The properties of nanofluids are determined by theoretical calculations, which are then used as inputs for analysis. CATIA parametric software is used to build a 3D model of the double pipe heat exchanger (plain and coil insert tube). At different mass flow rates of 0.32, 0.52, and 0.72 kg/sec, CFD analysis is performed on the double pipe heat exchanger with water, silicon oxide, and silver nanoparticle. Furthermore, theoretical calculations on the double pipe heat exchanger were performed.