High Heat-Flux Transfer and Pressure Drop Correlations for Reactor Thermalhydraulic Simulations

Abstract

The accuracy of heat transfer and pressure drop predictions in nuclear thermalhydraulic simulations directly effects both safety and operational analysis. Under high heat flux situations correlations established based on low heat flux experiments may not be extrapolated. In order to validate and extend existing correlations an experimental investigation has been conducted for high heat flux subcooled boiling heat transfer and pressure drop in a tubular channel. The data base (Novog et al. 1995) used to verify the existing correlations covered a mass flux range from 5 to 10 Mg/m2s, inlet temperature from 100 to 175 degrees C, system pressure from 2.0 to 5.0 MPa and heat flux from 0.5 to 12 MW/m2. The inside wall temperatures are calculated using outside wall temperature measurements and the one dimensional radial conduction equation with internal heat generation. In the past, heat transfer analysis of high heat flux wall temperature measurements was based on a constant thermal conductivity solution. This paper presents the analytic and numerical simulation for inside wall temperatures based on variable thermal conductivity and compares these results to previous analysis. Comparisons were made between the present data and several existing correlations. The single-phase correlation from Pethukov et al. (1970) predicted the present results to within 25%. Satisfactory agreement was found with a modification of the Yin et al.(1993) high heat flux subcooled boiling correlation.