Numerical Analysis of Deterioration in Heat Transfer to Supercritical Water

Deterioration in heat transfer to supercritical water is numerically studied using a k-ε model. Physical properties are treated as variables and calculatd from the steam table library. The numerical result agrees with the experimental data of Yamagata et al. [Trans. JSME, 38–2 (1972)] It is found that heat-transfer deterioration is caused by two mechanisms depending on the flow rate. In the case of large flow rate, heat transfer is reduced near the wall where the fluid properties are locally changed due to the heat flux. In the case of small flow rate, buoyancy force flattens the flow velocity distribution and the turbulent heat transfer is decreased. The present analysis shows that supercritical thermal hydraulics can be explained by the single-phase turbulent fluid dynamics.