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Title: Mechanistic modeling of CHF in forced-convection subcooled boiling

Abstract

Because of the complexity of phenomena governing boiling heat transfer, the approach to solve practical problems has traditionally been based on experimental correlations rather than mechanistic models. The recent progress in computational fluid dynamics (CFD), combined with improved experimental techniques in two-phase flow and heat transfer, makes the use of rigorous physically-based models a realistic alternative to the current simplistic phenomenological approach. The objective of this paper is to present a new CFD model for critical heat flux (CHF) in low quality (in particular, in subcooled boiling) forced-convection flows in heated channels.

Authors:
; ; ; ;  [1]
  1. Rensselaer Polytechnic Inst., Troy, NY (United States). Center for Multiphase Research
Publication Date:
Research Org.:
Knolls Atomic Power Lab., Schenectady, NY (United States)
Sponsoring Org.:
USDOE Assistant Secretary for Nuclear Energy, Washington, DC (United States)
OSTI Identifier:
319776
Report Number(s):
KAPL-P-000162; K-97043; CONF-9705305-
ON: DE99001886; TRN: 99:003949
DOE Contract Number:
AC12-76SN00052
Resource Type:
Conference
Resource Relation:
Conference: International conference on convective flow, Munich (Germany), 18-23 May 1997; Other Information: PBD: May 1997
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING NOT INCLUDED IN OTHER CATEGORIES; CRITICAL HEAT FLUX; MATHEMATICAL MODELS; FORCED CONVECTION; SUBCOOLED BOILING; TWO-PHASE FLOW; BUBBLE GROWTH; DRYOUT

Citation Formats

Podowski, M.Z., Alajbegovic, A., Kurul, N., Drew, D.A., and Lahey, R.T. Jr.. Mechanistic modeling of CHF in forced-convection subcooled boiling. United States: N. p., 1997. Web.
Podowski, M.Z., Alajbegovic, A., Kurul, N., Drew, D.A., & Lahey, R.T. Jr.. Mechanistic modeling of CHF in forced-convection subcooled boiling. United States.
Podowski, M.Z., Alajbegovic, A., Kurul, N., Drew, D.A., and Lahey, R.T. Jr.. 1997. "Mechanistic modeling of CHF in forced-convection subcooled boiling". United States. doi:. https://www.osti.gov/servlets/purl/319776.
@article{osti_319776,
title = {Mechanistic modeling of CHF in forced-convection subcooled boiling},
author = {Podowski, M.Z. and Alajbegovic, A. and Kurul, N. and Drew, D.A. and Lahey, R.T. Jr.},
abstractNote = {Because of the complexity of phenomena governing boiling heat transfer, the approach to solve practical problems has traditionally been based on experimental correlations rather than mechanistic models. The recent progress in computational fluid dynamics (CFD), combined with improved experimental techniques in two-phase flow and heat transfer, makes the use of rigorous physically-based models a realistic alternative to the current simplistic phenomenological approach. The objective of this paper is to present a new CFD model for critical heat flux (CHF) in low quality (in particular, in subcooled boiling) forced-convection flows in heated channels.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 1997,
month = 5
}

Conference:
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  • Because of its practical importance and various industrial applications, the process of subcooled flow boiling has attracted a lot of attention in the research community in the past. However, the existing models are primarily phenomenological and are based on correlating experimental data rather than on a first-principle analysis of the governing physical phenomena. Even though the mechanisms leading to critical heat flux (CHF) are very complex, the recent progress in the understanding of local phenomena of multiphase flow and heat transfer, combined with the development of mathematical models and advanced Computational Fluid Dynamics (CFD) methods, makes analytical predictions of CHFmore » quite feasible. Various mechanisms leading to CHF in subcooled boiling have been investigated. A new model for the predictions of the onset of CHF has been developed. This new model has been coupled with the overall boiling channel model, numerically implemented in the CFX 4 computer code, tested and validated against the experimental data of Hino and Ueda. The predicted critical heat flux for various channel operating conditions shows good agreement with the measurements using the aforementioned closure laws for the various local phenomena governing nucleation and bubble departure from the wall. The observed differences are consistent with typical uncertainties associated with CHF data.« less
  • A study has been performed to predict CHF in pool boiling and subcooled forced convection boiling using the dry-spot model presented by the authors and existing correlations for heat transfer coefficient, active site density and bubble departure diameter in nucleate boiling. Comparisons of the model predictions with experimental data for pool boiling of water and subcooled upward forced convection boiling of water in vertical, uniformly-heated round tubes have been performed and the parametric trends of CHF have been investigated. The results of the present study strongly support the validity of physical feature of the present model on the CHF mechanismmore » in pool boiling and subcooled forced convection boiling. To improve the prediction capability of the present model, further works on active site density, bubble departure diameter and suppression factor in subcooled boiling are needed.« less
  • Extensive testing has been conducted in the Simulant Boiling Flow Visualization (SBFV) loop in which water is boiled in a vertical transparent tube by circulating hot glycerine in an annulus surrounding the tube. Tests ranged from nonboiling forced convection to oscillatory boiling natural convection. The program LOOP-W has been developed to analyze these tests. This program is a multi-leg, one-dimensional, two-phase equilibrium model with slip between the phases. In this study, a specific test, performed at low power where non-boiling forced convection was changed to boiling natural convection and then to non-boiling again, has been modeled with the program LOOP-W.