Thermal hydraulic behavior in the deteriorated turbulent heat transfer regime for a gas-cooled reactor

One of the key issues in a gas-cooled system with a passive heat removal measure is the correct prediction of thermal hydraulic behavior in the deteriorated turbulent heat transfer (DTHT) regime. Here, a simple one-dimensional analysis of a gas-cooled reactor system was performed to show its strong potential for operation in the DTHT regime. A numerical calculation using computational fluid dynamics (CFD) was done to verify the capability of the Launder–Sharma (LS) turbulence model to predict wall and bulk temperatures while a gas system is operating in the DTHT regime. The results by the LS model are compared to those by the high Reynolds turbulent model, a newly proposed correlation, and recently obtained experimental data. The comparison shows that the LS turbulence model can provide a reasonable prediction in the buoyancy-induced DTHT regime. Additionally, it was found that the LS model predicted strong laminarization near the entrance which deteriorated turbulent heat transfer further compared to the measurements, but re-turbulization took place much earlier than in the experiment which recovered the heat transfer to a normal turbulent heat transfer.