Study the performance improvement of shell and tube heat exchanger with graphene nanofluids
摘要
This study investigates the formulation, stability and thermophysical properties of graphene-water nanofluids and its impact on heat transfer efficiency in a shell-and-tube counterflow heat exchanger. Nanofluids were prepared using concentrations of 0.1%, 0.2%, 0.3% and 0.5%. As the volume fraction increased, density and viscosity rose, while both parameters decreased with rise in temperature. Initially, when tested with water, the overall convection heat transfer coefficient (Ui) on the tube side increased with the flow rate. At a temperature of 70 °C and a flow rate of 2.37 L min-1, the maximum Ui of 633 W m-2 K-1 was measured, signifying a 65.2% increase in performance over 40 °C. The total heat transfer coefficient was improved by 37.4% and the heat transfer coefficient in comparison to water was increased by 45.7% when 0.5 mass percent graphene nanofluids were used as the cooling medium. The Nusselt number increased by 43.2% at this concentration. However, the friction factor increased by 16%, while pressure dropped by 8.3%. There was a maximum gain of 6% in the thermal performance factor. Not with standing these compromises, the results indicates that the graphene nanofluids have energy-saving potential in heat exchanger applications and significantly increase heat transfer efficiency.