Numerical prediction of deterioration in heat transfer in vertical supercritical water channels

The present work investigates the numerical prediction capabilities of the thermal-hydraulic model, THRUST for predicting the event of deterioration in heat transfer in a vertical supercritical channel under high mass flow rates. Available experimental data is taken as the basis of the present investigation where DHTC was observed for a range of bulk enthalpies under supercritical pressure flow conditions. The simulation begins with the steady state numerical analysis of the same experiment in order to validate the results obtained against that of the experimental ones. The deterioration in heat transfer predicted used the different heat transfer coefficient correlations in order to predict the required wall temperature values and their capability in predicting the deterioration is compared. This steady state simulation is then followed by a numerical simulation of the fast transient case study following a time dependent depressurization of the channels. The transient responses following the perturbation are obtained until the new asymptotic steady state is achieved. It has been observed that the predicted values of the wall temperatures in the case of time dependent depressurization of the channel leads to a much severe DHT being observed as compared to that of the steady state result. (author)