Effect of Plate Numbers on Optimal Condition of Gasket Heat Exchanger with Graphene-Carbon Nanotube Hybrid

In this study, the nanofluid hybrid (the graphene-Carbon nanotube) was stabilized in a water-based fluid by sodium dodecyl sulfate as a surfactant. The prepared nanofluid was in contact with hot water in a plate heat exchanger with 11, 13, 15, and 17 plates. The flow rate and the number of plate effects on heat transfer coefficient and pressure drop were analyzed experimentally. Results in laminar flow regime showed that any increase in plate numbers causes a decrease in the overall heat transfer coefficient (26.1%) and pressure drop (52.5%). The efficiency, and pumping power, and thermal effectiveness of nanofluid were also examined. It indicated that any increase in plate numbers increases the effectiveness and efficiency, and decreases the pumping power. Experiments were also designed to find the optimal conditions by the Taguchi method. The results showed that reduction in nanofluid volume flow rate is more effective than increase in the number of plates for exchanger efficiency. The optimal condition relates to the maximum number of plates and minimum hybrid volume flow rate (overall heat transfer coefficient 978.5 W/ m2.K, pressure drop 0.070 kPa, hybrid thermal effectiveness 93%, pumping power 0.0023 kW and exchanger efficiency of 1.2098). The accuracy of the results was confirmed by comparing Taguchi results to the experiments.