COMPARATIVE ANALYSIS OF TWO SUPERCRITICAL CARBON DIOXIDE(S) BRAYTON CYCLES FOR POWER PRODUCTION

The Supercritical carbon dioxide (s2) cycle is a promising alternative to both conventional steam and gas turbine cycles. It gained a lot of attention, as witnessed by the large volume of publications on its performance due to the various advantages ascribed to it; such as high thermal efficiency, small physical footprint with simple layouts. Several layouts of this increasingly popular cycle have been devised and studied. This project work made contributions in this direction by comparing the performances of two of these layouts in a more thorough study. The two cycles, reheating and split expansion supercritical carbon dioxide (2) Brayton cycles were analytically compared, to determine their exergy and thermal efficiencies at different working conditions. Simulations were done using Engineering Equation Solver (EES) software. Parametric analyses using pressure ratio, turbine inlet temperature, compressor inlet temperature, isentropic compressor efficiency, and isentropic turbine efficiency were carried out to determine the effect of these parameters on the thermal and exergy efficiencies of both cycles. This work considered; compressor inlet temperature of 305K, the compressor inlet pressure of 7.43 bar, the operating pressure ratio of 3.33, a mass flow rate of 32Kg/s, compressor efficiency of 89%, turbine efficiency of 93%, and turbine inlet temperature of 773K. The results showed that with comparable working conditions, the reheating cycle has the highest thermal efficiency of 52.17% compared to the split expansion cycle that has the highest efficiency of 44.67% at rp of 2.06 and 3.33 respectively. The exergy efficiencies of the two cycles are however 95.44% and 90.91% respectively.