Numerical Analysis of Flow and Heat transfer in Sub-channel of Supercritical Water Reactor

Investigation on the thermal-hydraulic behaviour in the High performance Light Water Reactor (HPLWR) fuel assembly has obtained a significant attention in GENERATION-IV. In this paper, CFD analysis is carried out to study the heat transfer behaviour of supercritical water in sub-channels of squared annular assembly. Effect of various parameters, e.g. thermal boundary conditions and pitch-to-diameter ratio on the thermal–hydraulic behaviour is investigated. Boundary conditions, i.e., constant heat flux at the outer surface of cladding are applied. The effect of pitch-to-diameter ratio (P/D) on the distributions of surface temperature and heat transfer coefficient (HTC) was analyzed .For typical (gap between two rod) channel analysis, it is found that HTC increases with p/d first and then decreases significantly when p/d is <1.2. If P/D is larger than 1.2 heat transfer deterioration (HTD) occurs as main stream enthalpy is quite small. One/eight channel of 40 pin fuel assembly show that the structure of the secondary flow mainly depends on the rod bundle configuration as well as the pitch-to-diameter ratio, whereas, the amplitude of the secondary flow is affected by the thermal boundary conditions, as well. Furthermore, the HTD under wire-wrapped spacer were evaluated.