AN EXPERIMENTAL STUDY ON HEAT TRANSFER ENHANCEMENT FOR DOUBLE-PIPE HEAT EXCHANGER USING Al2O3/WATER AND TiO2/WATER NANOFLUIDS

The modern heat transfer science ends in using small and more effective devices by developing heat transfer methods to get the best results. The double-pipe heat exchanger is considered to be one of the essential types of exchangers of heat that is used in various industrial fields. To increase the efficiency of such heat exchangers, many researchers have proposed different heat transfer techniques. One of these techniques is replacing the base fluid with another kind of fluid that has better heat transfer characteristics, called nanofluids. The main objective of this study is to investigate experimentally the impact of adding Al2O3 and TiO2 nanoparticles to deionized water as a base fluid on the performance of the horizontal counterflow double-pipe heat exchanger under turbulent flow conditions. Several experiments were conducted with different nanofluid volume concentrations of 0.1, 0.2, and 0.3% of each kind of nanofluids at volume flow rates of 2.5, 3.0, 3.5, 4.0, and 4.5 L/min for each concentration of the proposed nanofluids and water in the cold loop (nanofluids) and at a constant flow rate of 7 L/min in the hot loop (pure water). The experimental results of TiO2/water, Al2O3/water nanofluids and pure water, shows that the values of the heat transfer rate, convective heat transfer coefficient, overall heat transfer coefficient, Nusselt number, and the Reynolds number were increased when the volume flow rate was increased. They were also increased as the volume concentration of nanofluids increased. It was declared that all the values of the properties which were mentioned above were higher in Al2O3/water nanofluids than in TiO2/water nanofluids and water, respectively. The highest values obtained for the heat transfer rate, convective heat transfer coefficient, overall heat transfer coefficient, the Nusselt and Reynolds numbers were 1340 W, 3237 W/m(2) K, 1694 W/m(2) K, 62.5, and 10,370 at 0.3% concentration and 4.5 L/min volume flow rate in Al2O3/water nanofluid.