Heat Transfer Enhancement in a Shell-and-Tube Type of Heat Exchanger Using Al2O3/Water Nanofluid

Abstract

Shell-and-tube heat exchangers are widely used in industrial processes, but improving the shell-side heat transfer without causing excessive pressure losses remains a major engineering challenge. Numerical simulations provide an efficient approach for evaluating thermohydraulic enhancement techniques while reducing experimental costs. The present study evaluates the heat transfer in a shell-and-tube heat exchanger using computational fluid dynamics by means of ANSYS Fluent software. Unlike previous numerical studies that mainly focused on thermal enhancement, this work provides a comprehensive thermohydraulic assessment by simultaneously evaluating heat-transfer improvement together with the associated pressure-drop and pumping-power penalties over different nanoparticle concentrations and mass flow rates. Therefore, a simplified heat-exchanger model was developed with six baffles operating under turbulent flow conditions. The working fluid in the shell is initially water, which is subsequently replaced by nanofluid composed of water and 15 nm Al2O3 nanoparticles, while the inner tube walls are kept at a constant temperature. The results show that the Al2O3/water nanofluid significantly enhances the heat transfer. Thermal conductivity and nanoparticle concentrations play a crucial role in this enhancement. The largest increase in heat transfer, 37.83%, occurs at a nanoparticle concentration of 1.25% at mass flow rates of 0.5 kg/s, 0.6 kg/s, and 0.7 kg/s. Lower concentrations result in 30.76% (concentration of 1.00%), 23.32% (concentration of 0.75%), 15.47% (concentration of 0.50%), and 7.16% (concentration of 0.25%) improvements compared to water. Similarly, the heat transfer coefficient increases by 47.84%, 38.32%, 28.62%, 18.70%, and 8.51%, for concentrations of 1.25%, 1.00%, 0.75%, 0.50%, and 0.25%, respectively. However, the use of nanofluids leads to an increase in the pressure drop, with maximum values reaching 5.30%. The results demonstrate that dilute Al2O3/water nanofluids can significantly enhance shell-side thermal performance while maintaining relatively low pressure drop and pumping power penalties, highlighting their potential as a practical thermo-hydraulic enhancement strategy for shell-and-tube heat exchangers and providing useful guidance for the design and optimization of industrial heat exchangers.