Abstract:
Energy is required to power the world. The demand for energy is rising rapidly. To fulfil this energy demand power plants are being engineered. Power plants are a major contributor to pollution. They emit carbon dioxide into the environment and causing global warming. To keep the environment safe, there is a need to move towards clean and renewable energy resources. There are many renewable resources available i.e. solar, wind, ocean wave, hydro and geothermal energy. All these resources have the potential for large-scale power production but their applicability depends upon the geographical location of the area and capital cost required. Among these resources, solar energy is in abundance in Pakistan. Solar energy can be harnessed using solar PV and solar thermal technology. Solar thermal technology is suitable for cogeneration and based upon conventional proven technologies. There are different methods to harness thermal energy from the sun but the solar tower has highest concentration ratio and can achieve a very high working fluid temperature. But there are complexities related to working fluid at such high operating conditions. Few of these are high operating pressure, fluid stability and corrosion and heat transfer properties. Supercritical CO2 can be used in solar tower due to its favourable properties at such operating conditions. Micro-channels can be used to enhance heat transfer which improves thermal efficiency. In this research, a 3D rectangular microchannel is considered and heat transfer in near critical region is studied using ANSYS Fluent. Inlet mass flow rate, pressure and heat flux is varied to study their effects on heat transfer. Also, experiments are performed for pressure drop in microchannel test section and compared results with available pressure drop correlations. Due to sudden property variations, a peak in heat transfer coefficient is observed at the pseudocritical point. Also, it is found that available correlations are unable to predict accurately the pressure drop in microchannels for sCO2.
