Specifics of forced-convection heat transfer in a vertical 7-element bundle cooled with upward flow of SuperCritical Water

Abstract

Current Generation II/III/III+ Nuclear Power Plants (NPPs) are no longer economically competitive partially due to low thermal efficiencies. Six Generation IV NPP concepts were proposed having increased thermal efficiency, with Canada investigating the SuperCritical Water Reactor (SCWR) concept. However, determining Heat Transfer specifics for SuperCritical Water in bundle configurations is required. Many empirical Nusselt number (Nu) correlations derived from bare tubes are available, with only one derived from a bundle. No assessments of Nu correlations are available for 7-rod bundle datasets, representing the centre of 37-element bundles currently used in Canadian NPPs. A Nu correlation derived from a 7-rod bundle dataset is proposed, and assessed against 35 common Nu correlations, using Root Mean Square error and graphical investigation. The assessment indicates the proposed Nu correlation is the most suitable for 7-rod bundles and bare tubes. One typical Canadian SCWR design is confirmed based on maximum fuel centreline and sheath temperatures.