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EXPERIMENTAL STUDY OF HYDROCARBON CONVECTIVE BOILING IN COMPLEX GEOMETRIES: CORRELATIONS FOR HEAT TRANSFER BASED ON A LOCAL ANALYSIS OF FLOW PATTERNS AND VOID FRACTION

DOI: 10.1615/IHTC13.p28.110
12 pages

Lounes Tadrist
Laboratoire IUSTI CNRS UMR 6595, Aix-Marseille Universite, Technopole de Chateau-Gombert, 5, rue Enrico Fermi, 13453 Marseille Cedex 13, France

C. Desrats
Laboratoire GREThE, Commissariat à l'Energie Atomique de Grenoble, France

Laurent Aprin
Laboratoire LGEI, Génie de l'Environnement Industriel, Ecole des Mines d'Alès, France

P. Mercier
Laboratoire GREThE, Commissariat à l'Energie Atomique de Grenoble, France

Abstract

This paper deals with vertical two-phase flow of hydrocarbons in staggered tube bundle. Experiments were performed on a test rig typical of bundle boilers commonly used in process industries. Propane, n-pentane and iso-butane are successively investigated and the influence of the fluid nature thus examined. An optical probe allows to measure the local void fraction which was found to have a significantly different trend for each hydrocarbon tested. The drift-flux model is used with the experimental results about void fraction to build a model of prediction. A statistical analysis using Probability Density Functions was performed to characterise the flow regimes. Two flow patterns have been identified in the bundle: bubbly and dispersed flow. In between, an intermittent two-phase flow regime is evidenced. The transitions between the flow patterns do not correspond to those found for adiabatic air / water flows. They appear at lower superficial gas velocity and do not depend on the superficial liquid velocity. The analysis of the friction factor and the heat transfer coefficient at different saturation pressures shows exactly the same tendencies. As a consequence, a correlation based on our knowledge of the phenomenology of boiling flow in shell and tube bundle boilers was proposed for the heat transfer coefficient.

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Measurement of fluid temperature with an arrangement of three thermocouples