Using a Thermalhydraulics System Code to Estimate Heat Transfer Coefficients for a Critical Heat Flux Experiment

Abstract

RELAP5/SCDAPSIM MOD 3.4 is used to predict wall temperature before and after critical heat flux (CHF) is reached in a vertical, uniformly heated tube using light water as the working fluid. The heated test section is modeled as a 1 m long Inconel 600 tube having an OD of 6.35 mm and ID of 4.57 mm with a 0.5 m long unheated development length at the inlet. Simulations are performed at pressures of 0.5 to 2.0 MPa with mass fluxes from 500 to 2000 kg m-2 s-1 and inlet qualities ranging from -0.2 to 0. Loss of flow simulations are performed with flow reduction rates of 10, 20, 50, and 100 kg m-2 s-2. Inlet mass flux at CHF was nominally independent of rate in the model; this may or may not be realistic.