An experimental study of heat transfer and flow regimes during condensation of refrigerants in horizontal tubes was conducted. Measurements were made in smooth, round tubes with diameters ranging from 3.14 mm to 7.04 mm. The refrigerants tested were R-12, R-22, R-134a, and near-azeotropic blends of R-32/R-125 in 50 percent/50 percent and 60 percent/40 percent compositions. The study focused primarily on measurement and prediction of condensing heat transfer coefficients and the relationship between heat transfer coefficients and two-phase flow regimes. Flow regimes were observed visually at the inlet and outlet of the test condenser as the heat transfer data were collected. Stratified, wavy, wavy annular, annular, annular mist, and slug flows were observed. True mist flow without a stable wall film was not observed during condensation tests. The experimental results were compared with existing flow regime maps and some corrections are suggested. The heat transfer behavior was controlled by the prevailing flow regime. For the purpose of analyzing condensing heat transfer behavior, the various flow regimes were divided into two broad categories of gravity-dominated and shear-dominated flows. In the gravity dominated flow regime, the dominant heat transfer mode was laminar film condensation in the top of the tube. This regime was characterized by heat transfer coefficients that depended on the wall-to-refrigerant temperature difference but were nearly independent of mass flux. In the shear-dominated flow regime, forced-convective condensation was the dominant heat transfer mechanism. This regime was characterized by heat transfer coefficients that were independent of temperature difference but very dependent on mass flux and quality. Heat transfer correlations that were developed for each of these flow regimes successfully predicted data from the present study and from several other sources.

Condensation in Smooth Horizontal Tubes

A unified model for predicting flow-pattern transitions for the whole range of pipe inclinations

Characterization of two-phase flow patterns in small diameter round and rectangular tubes

Comparison of void fraction correlations for different flow patterns in horizontal and upward inclined pipes

A comprehensive review of solid particle erosion modeling for oil and gas wells and pipelines applications

A comprehensive model is formulated to predict the flow behavior for upward two-phase flow. This model is composed of a model for flow-pattern prediction and a set of independent mechanistic models for predicting such flow characteristics as holdup and pressure drop in bubble, slug, and annular flow. The comprehensive model is evaluated by using a well data bank made up of 1,712 well cases covering a wide variety of field data. Model performance is also compared with six commonly used empirical correlations and the Hasan-Kabir mechanistic model. Overall model performance is in good agreement with the data. In comparison with other methods, the comprehensive model performed the best.

A Comprehensive Mechanistic Model for Upward Two-Phase Flow in Wellbores

Flow pattern transition for gas-liquid flow in horizontal and inclined pipes. Comparison of experimental data with theory

This paper presents a general and unified equation for flowing temperature prediction that is applicable for the entire range of inclination angles. The equation degenerates into Ramey's equations for ideal gas or incompressible liquid and into the Coulter and Bardon equation, with the appropriate assumptions. This work also proposes an approximate method for calculating the Joule- Thomson coefficient for black-oil models

Ovadia Shoham

Papers

A Comprehensive Mechanistic Model for Upward Two-Phase Flow in Wellbores

Flow pattern transition for gas-liquid flow in horizontal and inclined pipes. Comparison of experimental data with theory

A Unified Model for Predicting Flowing Temperature Distribution in Wellbores and Pipelines

Flow pattern transition for vertical downward two phase flow

An Analysis of Oil/Water Flow Phenomena in Horizontal Pipes