Modeling of Two-Phase Flows in Horizontal Tubes

Vij, A.K.; Dunn, W.E.

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https://hdl.handle.net/2142/11309 Copy

Description

Title

Modeling of Two-Phase Flows in Horizontal Tubes

Author(s)

• Vij, A.K.
• Dunn, W.E.

Issue Date

1996-05

Keyword(s)

microchannel condenser tubes

Abstract

This work focusses on the modeling of two-phase flows in horizontal, constant-crosssection tubes by a two-fluid approach. The objectives are to develope a framework for two-fluid modeling, to highlight issues related to two-phase phenomena and to implement the model on a computer. The two-fluid equations are derived from the basic conservation laws for mass, momentum and energy by assuming a steady state and averaging the conservation laws over the cross-section plane of the tube. It is shown that the integration of the two-fluid equations along the axial direction of the tube requires models for the distribution of the liquid and vapor in the cross-section plane of the tube, as well as models for the transport of heat, mass and momentum at the boundaries of each phase. Several phenomena are identified that affect the liquid-vapor distribution by causing wetting of the tube wall. Mechanistic models are proposed for these phenomena and several dimensionless groups are derived by nondimensionalizing the governing equations for each model. Models are proposed for the calculation of shear stresses at the wall using a single-phase friction factor approach. The interfacial shear stress is considered to be significantly greater than the shear stress at the wall due to the dissipative effect of wave generation and decay. The effect of condensation on interfacial friction is also condsidered. Heat fluxes from each phase into the wall and into the interface are modeled by a singlephase heat transfer coefficient approach. Two approaches are suggested for determining the mass transfer flux at the interface. One of these assumes a temperature jump at the interface and employs the kinetic theory of gases. The other approach utilizes the difference between the liquid and vapor heat fluxes at the interface to determine the mass transfer rate. A computer program was developed to solve the two-fluid model numerically. The use of this program is illustrated by solving a condensing-flow problem.

Publisher

Air Conditioning and Refrigeration Center. College of Engineering. University of Illinois at Urbana-Champaign.

Series/Report Name or Number

Air Conditioning and Refrigeration Center TR-98

Type of Resource

text

Language

en

Permalink

http://hdl.handle.net/2142/11309

Sponsor(s)/Grant Number(s)

Air Conditioning and Refrigeration Project 48

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