A numerical study on the performance of Exhaust Gas Recirculation (EGR) cooler for diesel engines is carried out on a 3-Dimensional shell and tube heat exchanger to study the flow field and heat transfer characteristics using CFD codes. A parametric analysis is carried out numerically using a multi tube EGR cooler by varying the number of tubes, inner diameter of tubes and mass flow rate of coolant. The numerical study is validated by carrying out experiments using a shell and tube heat exchanger in the Thermal laboratory of VIT University, Vellore. Temperature, velocity and pressure contours with streamlines are plotted along the length of the EGR cooler and an optimized EGR cooler is obtained based on minimal pressure drop and better heat transfer characteristics. © Research India Publications.