Transient analysis of subcritical/supercritical carbon dioxide based natural circulation loops with end heat exchangers: Numerical studies

Transient analysis of carbon dioxide based natural circulation loop (NCL) with end heat exchangers has been carried out. Subcritical and supercritical phases of CO2 are considered with operating pressures in the range of 50–100 bar for an operating temperature range of 323 K to 363 K. Studies are carried out for various loop tilt angles, different initial conditions, and different water mass flow rates.Results are obtained for various inlet temperatures of water in the hot heat exchanger while keeping the inlet temperature of cooling water in the cold heat exchanger fixed. Effect of tilting the loop in XY and YZ planes on transient as well as steady state behaviour of loop are also studied. Validation of simulation results against experimental and numerical results reported in the literature in terms of modified Grashof number (Grm) and Reynolds number (Re) show good agreement.