Specifics of Heat Transfer to Supercritical Water Flowing Upward over a Three Rod Bundle

Abstract

Water-cooled Nuclear Power Plants (NPPs) have thermal efficiencies ranging between 26-38%, lagging behind modern Thermal Power Plants (ThPPs). One Generation-IV nuclear-reactor concept will use SuperCritical Water (SCW) as a reactor coolant and working fluid in the SC- pressure Rankine cycle to increase the plant thermal efficiency. Knowledge of heat-transfer regimes possible in a fuel bundle cooled with SCW is a very important task. Experimental data have been obtained on heat-transfer characteristics of SCW flowing upward in a 3-rod bundle in which each rod is equipped with four helical ribs. This dataset was obtained by Dr. V. Razumovskiy at the National Technical University of Ukraine within the range of pressures 22.6-27.5 MPa, mass fluxes of 1500-2700 kg/m²s, and heat fluxes within 1738-3289 kW/m². Normal, Improved, and Deteriorated Heat-Transfer (NHT, IHT, and DHT) regimes have been identified and recorded, which provides insight on the behaviour of SCW coolant.