EXPERIMENTAL STUDY OF HEAT TRANSFER ENHANCEMENT USING Al2O3/WATER AND TiO2/WATER NANOFLUIDS IN A SHELL-AND-TUBE HEAT EXCHANGER

Abstract

Various enhancement techniques may lead to a significant drop in energy consumption and increase the efficiency of power plants. The shell-and-tube heat exchanger is an essential part of the power plant cooling system, and it is one of the broad types of heat exchangers which is used in this region in which water or water mixed with ethylene glycol is used as conventional coolants. Finding new efficient approaches to improve the performance of the shell-and-tube heat exchanger is essential. One of the approaches is replacing water with a higher thermal conductivity fluid containing stable nanoparticles known as nanofluid. In this study, the impact of using nanofluids (TiO2/water and Al2O3/water) as well as water in the shell-and-tube heat exchanger was presented and discussed. The experimental findings of water and these nanofluids were evaluated based on the effect of varying volume concentrations of 0.1, 0.2, and 0.3% of each kind of nanofluids at volume flow rates of 5, 5.5, 6, 6.5, and 7 L/min for each concentration of the proposed nanofluids and water on the activity of the heat exchanger. Parameters comprising the rate of heat transfer, the coefficient of convective heat transfer, the overall heat transfer coefficient, the Reynolds number, and the Nusselt number were determined. Besides, the results of all experiments were analyzed to create a comparison among them. The results revealed that the mentioned parameters were enhanced with a rise in the volume concentration of the nanofluid. Moreover, they were higher in the Al2O3/water nanofluid than in the TiO2/water nanofluid and base fluid. In this analysis, the maximum obtained values of heat transfer rate, total heat transfer coefficient, convective heat transfer coefficient, and the Reynolds number were 1741.54 W, 1326.86 W/m(2) K, 4414.96 W/m K, and 4425.86 in Al2O3/water nanofluid for 0.3% concentration and 7 L/min volume flow rate, respectively. The highest value of the Nusselt number was 34.37 in the TiO2/water nanofluid for a concentration of 0.3% and a volume flow rate of 7 L/min.