Journal Article10.1016/J.IJREFRIG.2008.06.013
Flow boiling characteristics and flow pattern visualization of refrigerant/lubricant oil mixtures
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TL;DR: A comprehensive review of flow boiling characteristics and flow pattern visualization of refrigerant/lubricant oil mixtures is presented in this article, where the effects of the unavoidable introduction of the lubricant oil on the thermodynamics properties of a refrigerant are described.
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Abstract: A comprehensive review of flow boiling characteristics and flow pattern visualization of refrigerant/lubricant oil mixtures is presented in this paper. First, various parameters influenced by the lubricant oil in convective boiling of refrigerants, such as mass velocity, vapor quality, oil concentration and geometric characteristics of the heat transfer tube are discussed. The effects of the unavoidable introduction of the lubricant oil on the thermodynamics properties of a refrigerant are described. Then, a review of the main experimental studies of flow boiling of refrigerant/lubricant oil mixtures is presented and also describes research with halocarbons, carbon dioxide, hydrocarbons and ammonia. There is no agreement among these studies regarding the effect of the oil in the evaporator, with studies showing an increase or decrease in the heat transfer coefficient. However, in relation to pressure drop, all the results presented the same trend, increasing the pressure drop with increasing oil concentration. Next, the flow patterns of refrigerant/oil mixtures are illustrated together with a selection of video images. It is possible to notice the difference in frothing formation with respect to the particular refrigerant and tube geometry. Some predictions of oil effects on the heat transfer coefficient and pressure drops based on the mixture physical properties are then presented and the trends compared to data. Finally, some suggestions for future work are given.
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References
A model for predicting flow regime transitions in horizontal and near horizontal gas-liquid flow
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Condensation in horizontal tubes, part 2: new heat transfer model based on flow regimes
TL;DR: In this paper, a flow pattern/flow structure based heat transfer model for condensation inside horizontal, plain tubes is proposed based on simplified flow structures of the flow regimes, and also includes the effect of liquid-vapor interfacial roughness on heat transfer.
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Investigation of flow boiling in horizontal tubes: Part I—A new diabatic two-phase flow pattern map
TL;DR: In this paper, a new version of the Kattan-thome-favrat flow pattern map is presented, which is based on the dynamic void fraction measurements described in [Int. J. Multiphase Flow 30 (2004) 125,137], the stratified-wavy region has been subdivided into three subzones: slug, slug/stratifiedwavy and stratified wavy.
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Flow Boiling in Horizontal Tubes. Part 1; Development of a Diabatic Two–Phase Flow Pattern Map
TL;DR: In this paper, an improved two-phase flow pattern map is proposed for evaporation in horizontal tubes based on flow pattern data for five different refrigerants covering a wide range of mass velocities and vapor qualities.
515
Condensation in Horizontal Tubes, Part 1: Two-Phase Flow Pattern Map
TL;DR: In this paper, a new flow pattern map and flow pattern based heat transfer model for condensation inside horizontal plain tubes are proposed, which incorporates a newly defined logarithmic mean void fraction (LM e ) method for calculation of vapor void fractions spanning from low pressures up to pressures near the critical point.
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