ADAPTATION OF TEMPERATURE WALL FUNCTION FOR CALCULATION THE HEAT TRANSFER AT SUPERCRITICAL COOLANT PARAMETERS

Abstract

To date, the engineering community pays special attention to the study, research and development of methods for predicting the behavior of the coolants at supercritical parameters. This paper discusses the problem of adaptation of the existing universal or specialized tools of thermohydraulic analysis for nonlinear heat transfer problems at supercritical coolant parameters with deterioration of heat transfer. Complexities of prediction the nonlinear heat transfer at supercritical parameters of the coolant by engineering methods of computational fluid dynamics are considered. A simple way to adapt the dual-zone Kader's temperature wall function on the basis of existing probe measurements for carbon dioxide is proposed. The problem of implementation into universal packages of computational fluid dynamics (CFD), which is based on the method of choosing the reference coordinate of the near-wall zone to determine the dynamic speed and dimensionless temperature, is discussed. The example on the ANSYS CFX using shows one of the ways to create a special user procedure, which has an improved tendency to predict the axial temperature profile with deteriorated heat transfer. Calibration and validation of the obtained results on the basis of experimental investigations for vertical pipes and rod assemblies of fuel simulators is carried out in the work. The paper also discusses the features of the proposed implementation, and formed recommendations for the application and further improvement of engineering approaches to predict the heat transfer deterioration at supercritical parameters of the coolant.