Effect of Pressure on Steady State and Heat Transfer Characteristics in Supercritical CO2 Natural Circulation Loop

A 2D axi-symmetric CFD code (NAFA-LOOP) has been developed for studying the heat transfer and steady state characteristics of supercritical CO2 natural circulation loop (SPNCL). NAFA-Loop is derived from the pipe flow solver (NAFA) which was developed earlier to study the heat transfer characteristics of supercritical fluid pipe flow. The code is validated at supercritical condition with experimental results. Effect of pressure on heat transfer and steady state characteristics has been studied by keeping all the operating parameters such as secondary side coolant flow rate and secondary side coolant inlet temperature constant except the pressure. And the heater power is varied from 200 W to 3000 W for each pressure. As increasing the pressure, the steady state mass flow rate increases because of increase in the density difference in loop (driving force). But the maximum value of heat transfer coefficient decreases as increasing the pressure.