Application of the Convolution Theorem to Predict Heated Wall Temperature Subject to Various Axial Power Distributions

One of the important parameters that affect the thermal-hydraulic performance of nuclear fuel assemblies is the spatial — that is the lateral and the axial — distribution of power. Since this parameter may have a significant influence on thermal margins of nuclear reactors, it is necessary to take it into account in various models and/or correlations. One practical difficulty in doing so is the fact that the spatial power distribution is a function of space variables, which makes it very inconvenient to implement into single-parameter correlations. In addition, there is still lack of a simple theoretical model that captures the effect of spatial power distributions on the thermal-hydraulic performance of nuclear fuel assemblies. In this paper, an accurate and fast running convolution method is presented to predict the influence of axial power distribution on wall temperature distributions. The method has been verified against CFD predictions of the wall temperature in a heated pipe and an excellent agreement between the two approaches is demonstrated. The method is applicable only for constant fluid properties and for a fully developed flow regime.