With over 50% of the world’s population dwelling in urban areas, responsible for 75% of global energy consumption and 70% of greenhouse gas emissions, there is a need to ensure that urban energy systems are sustainable. One way to achieve this is to develop efficient energy systems that utilize captured and stored CO2 as the working fluid. Also, the awareness of climate change and the environmental impact of human activities has necessitated research into using natural refrigerants and environmentally friendly nanoparticles in the heating, ventilation, and air conditioning (HVAC), process, chemical, nuclear, and energy sectors. Metallic and non-metallic nanoparticles have been studied extensively in the past few decades. Though they have improved the rate of heat energy transfer, the environmental impact assessment is questionable. The environmental impact of the common nanofluids necessitates the investigation of renewable bio-nanoparticles such as mango bark. The present study investigates the thermal and hydraulic characteristics of CO2-mango bark nanofluids for application in gas cooling. The Reynolds number of the nanofluid is varied between 100 and 1000; nanoparticle volume concentration is between 0.5 and 2.0%, and the inclination angle is -90o to +90o. The heat transfer coefficient and pressure difference show a significant relationship with the inclination angle, Reynolds number and nanoparticle volume concentration. However, the heat transfer enhancement due to the nanofluid is about 10%, and the inclination angle is up to 40%. The inclination angle of ±30o, ±45o, and ±60o consistently possess higher thermal and hydraulic characteristics.
Keywords Heat transfer enhancement, CO2-mango bark nanofluid, gas cooling, convective heat transfer, inclined heat exchanger