In this study, heat transfer in a horizontal double pipe heat exchanger, with air and water as the working fluid have been increased by means of louvered turbulator. In the experimental set up, a galvanized steel iron pipe of (ID = 47mm, OD= 52mm with 1200mm length for outer pipe) and (ID = 21.4mm and OD = 25.4mm with 1800mm length for inner pipe) was used. And a leaf shape louvered turbulator with louver size (major diameter = 15mm, minor diameter = 10mm and thickness = 2mm) was inserted in the inner pipe as a turbulator. Cold air in ambient condition was passed through the inner pipe while hot water was flowing through outer tube by means of water pump in counter flow heat exchanger. The Reynolds number of air varied from 2300 to 25000. During test time volume flow rate is varied for each run to get the required Reynold numbers. The results were validated with Blasius equation for friction factor and with Dittus bolter correlation for Nusselt number and all Experimental results were compared with CFD values. In louvered turbulator, it was observed that the heat transfer coefficient varied from 1.30 to 1.88 times that of the smooth pipe value at Re = 15,812 for backward and forward arrangements respectively, and the corresponding friction factor increased from 1.66 to 2.04 times that of the smooth pipe value at Re = 3167 for backward and forward arrangement, respectively. For louvered turbulator, the increase in hydraulic efficiency comes out to be laying between 148% and 176%. The heat transfer enhancement ratio Qturbulator / Qsmooth indicates that the louvered turbulator for backward arrangement has 175% and for forward arrangement has 223% increments compared to plain pipe. For CFD simulation, the Nusselt number varied from 58% to 65% compared with plain pipe, while heat transfer rate was 1.39 and 1.82 times that of plain pipe for backward and forward arrangements, respectively. Key word; Enhancement, louvered strip inserts, arrangement, mass flow rate, pressure drop.