Flow boiling characteristics and flow pattern visualization of refrigerant/lubricant oil mixtures |
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| Authors: | Enio P. Bandarra Filho Lixin Cheng John R. Thome |
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| Affiliation: | 1. Air Conditioning and Refrigeration Center, Department of Mechanical Engineering, University of Illinois at Urbana Champaign, 1206 West Green Street, Urbana, IL 61801, USA;2. CTS, 2209 Willow Rd., Urbana, IL, USA;1. Key Laboratory of New Energy and Energy-saving in Building, Fujian Province University, and College of Ecological Environment and Urban Construction, Fujian University of Technology, Fuzhou, Fujian 350108, China;2. School of Energy and Power Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China;1. Air Conditioning and Refrigeration Center, Department of Mechanical Engineering and Science, University of Illinois at Urbana-Champaign, 1206 W Green St, Urbana, IL, USA;2. Oak Ridge National Laboratory, Building Equipment Group, 1 Bethel Valley Rd, Oak Ridge, TN, USA;3. CTS - Creative Thermal Solutions, 2209 Willow Rd, Urbana, IL, USA |
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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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