Validation of the STEG Code against Experimental Data on Hydrodynamics of a Horizontal Steam Generator

Abstract

A numerical analysis of the experiments addressed to studies of hydrodynamic processes in a horizontal steam generator has been performed using the STEG (STEam Generator) code. The main components of the experimental model include a staggered tube bundle, a submerged perforated sheet (SPS) with baffles, and a downcomer. An air–water mixture was used as a two-phase fluid. The working fluid flow in the model was driven by natural circulation induced by air supply to the lower, middle, and upper sections of the tube bundle. The gas void fraction was measured by the γ-radiography method. In addition, pressure drops along the height of the tube bundle and water levels in the model and above SPS were also measured. Each experiment was performed at a prescribed air load on the evaporation surface and water level in the model. The STEG code was developed at the Department of Nuclear Power Plants of NRU MPEI to model thermohydraulic processes in a horizontal steam generator. The mathematical model is based on a two-fluid approach to the description of a two-phase flow using balance mass, momentum, and energy conservation equations and semiempirical closing correlations for interfacial interactions and interactions with various surrounding structures (tube bundle, walls, etc.). The STEG code was used to perform calculations for nine experimental regimes differing in the perforation ratio of the submerged perforated sheet and the supplied air flowrate. The qualitative regularities of the two-phase air–water mixture circulation in the model of a horizontal steam generator and the effect of experimental values of the main parameters on the circulation have been established. Quantitative results of comparison of the predictions with the experiment demonstrate their good agreement since the relative errors in the predicted air void fractions and pressure drops do not exceed 10%.