Cooling system design and performance analysis for a supercritical CO2 recompression cycle

In the present article, a natural draft dry cooling tower (NDDCT) is designed for a 25 MW recompression sCO Brayton cycle. The thermodynamic property variation with bulk temperature is well predicted by adapting an iterative nodal approach in the heat exchanger. The local property variations of sCO with bulk temperature are taken into consideration since the traditional method of heat exchanger fails to address the heat transfer mechanism, especially for supercritical fluids. The number of finned tube heat exchanger bundles and the tower dimensions (tower height, tower diameter and a number of tower supports) is evaluated to meet the duty requirements. The thermal efficiency of the recompression cycle is validated against various dataset available from the literature. Initially, the thermal assessment of the recompression cycle is carried out in order to obtain the optimum operating conditions (cycle pressure ratio and pre-cooler inlet temperature) for which the cooling tower is designed. Finally, the performance of the cooling tower is investigated for a range of pre-cooler inlet condition (70ºC to 110ºC) and ambient temperature (15ºC to 50ºC). Both the sCO inlet temperature and air temperature significantly influence the cooling performance. During high ambient temperature period, both the cycle efficiency and the heat rejection from the NDDCT decreases