Investigation on thermal hydraulic parameters and instability under two different heating conditions based on RELAP5 code

The subject of heat transfer behaviors of steam generator is of great interest for better heat transfer efficiency and safety in industry. On most previous study, the models of SG based on RELAP5 used heat structures as the power generation, which is different from heating by primary side. This paper investigates the distinctions of different heat transfer methods on the thermal-hydraulic parameters by RELAP5. Two different heat transfers are selected, case 1 is uniformly heated by heat structure and case 2 is heated by the primary side of SG. The results show that the onset position of critical heat flux for case 2 is ahead of that for case 1. Besides, the temperature of tube wall corresponding to position of critical heat flux increases abruptly in case 1, and the wall temperature in superheated region in case 1 increases faster than that in case 2 when the water becomes fully superheated vapor. Then instability distinctions for two heat transfer cases are studied in this investigation. It is detected the fluid flow heated by second method is more stable than the first one, and the system has a higher ultimate thermal power when density wave oscillation occurs for case 2.