Heat Transfer Characteristics of a Heat Exchanger in a Solar-Assisted, Supercritical Brayton Cycle for Power Generation

Abstract

Supercritical carbon dioxide (sCO2) has become a popular subject in sustainable energy research due to its low critical properties and enhanced operating conditions compared to previous heat transfer fluids. sCO2 power cycles integrated with solar and thermal energy storage have shown significant potential to generate energy alongside an off-grid, zero-waste desalination system. In this thesis, sCO2 is observed as a heat transfer fluid both numerically and experimentally. Numerically, a simulation of the Brayton cycle is run with sCO2, integrated with solar collectors and a cooling tower. A sCO2 heat exchanger was also observed with varying parameters to determine the effects of sCO2 as a working fluid in regenerative cycles. Numerical results indicate that there is a relationship between the addition of the regenerative components and an increase in thermal efficiency of the system. In addition, a double-pipe, counter-flow (DP-CF) heat exchanger is indicated as the best performing configuration. Experimentally, the sCO2 had a maximum heat transfer rate of 0.27 kW, as well as performed at the highest effectiveness with water inlet temperatures around 390[degrees]C. Additionally, an empirical correlation between the calculated Nusselt number and the Reynolds and Prandtl numbers was examined with the experimental work.