Experimental investigation on heat transfer and flow resistance of drag-reducing alumina nanofluid in a fin-and-tube heat exchanger

One of the main drawbacks of using nanofluids as a heat transfer media which limited its application in industries is higher pressure drop in comparison with the conventional fluids. In this research, it is the aim to decrease the nanofluid pressure drop using drag reducing agent (DRA). Water based γ-alumina nanofluids at different concentrations were mixed with different concentrations of cetyltrimethylammonium chloride (CTAC) surfactant to reduce the nanofluid pressure drop. On the other hand, it is very important to know that the addition of DRA could decrease the heat transfer performance of the system. So, it is a complicated problem since we have two objective functions (pressure drop and heat transfer) which are varied inversely. The addition of nanoparticles increases both objective functions while the addition of DRA decreases both of them. Results showed that the use of 0.2 %wt nanofluid (without the addition of DRA) causes %20 heat transfer enhancement with the penalty of %5 increase in pressure drop. It was also obtained that at the optimum condition, which was the highest concentration of CTAC (100 ppm) and the highest concentration of nanoparticle (0.2 %wt), the overall heat transfer coefficient enhancement of %17.2, and the friction factor reduction of %4.8 could be obtained in comparison with pure water.