Experimental Investigation on Heat Transfer Characteristics of Supercritical Water in 2×2 Tight Rod Bundle

Within the experimental parameters of pressure of 23.28 MPa, mass flux of 350-1000 kg/(m²•s) and heat flux of 200-1000 kW/m², heat transfer characteristics of supercritical water in a 2×2 rod bundle were experimentally investigated. The variations of circumferential wall temperature distribution were obtained, and the reasons for this phenomenon were discussed. The effects of pressure, mass flux and heat flux on heat transfer characteristics were investigated and the heat transfer deterioration which occurred at low mass flux-condition was analyzed. The experimental results indicate that the circumferential wall temperature is non-uniform, the wall temperature in the corner sub-channel is the highest, whereas the central sub-channel is the lowest. The wall temperature difference is closely related to the non-uniform cross-sectional flow area. The heat transfer of supercritical water is weakened with the increase of heat flux or the decrease of mass flux. Deteriorated heat transfer occurs in the rod bundle when the heat flux to mass flux ratio increases to a certain level.