Void fractions for condensing refrigerant flow in small channels. Part II: Void fraction measurement and modeling

• Published in: International journal of refrigeration Vol. 35; no. 2; pp. 246 - 262
• Main Authors: Winkler, Julian, Killion, Jesse, Garimella, Srinivas
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.03.2012; Elsevier
• Subjects: Applied sciences; Chute de pression; Condensation; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Heat transfer; Microcanal; Microchannel; Pressure drop; Refrigerants; Refrigerating engineering; Refrigerating engineering. Cryogenics. Food conservation; Theoretical studies. Data and constants. Metering; Transfert de chaleur; Two-phase flow; Écoulement diphasique; Two-phase flow; Pressure drop; Microchannel; Transfert de chaleur; Écoulement diphasique; Microcanal; Chute de pression; Condensation; Heat transfer; Refrigeration installation; Correlation; Two phase flow; Flow regime; Image processing; Void fraction; Modeling; Pressure; Refrigerant fluid
• ISSN: 0140-7007; 1879-2081
• DOI: 10.1016/j.ijrefrig.2011.08.012

In this paper, (Part II of a two-part study), an investigation of void fractions for condensing flows of refrigerant R-134a in minichannels is presented. Custom digital image processing techniques were used to quantitatively analyze these flows in transparent minchannel geometries (square, rectangular and circular) with 2 < Dh < 4.91mm. A total of 140 void fraction values in the intermittent flow regime (slug and plug flow), the wavy flow regime, and an intermittent-wavy overlap region were measured. A new model was developed based on these measured values and predicts void fraction better than correlations from the literature. ► Void fractions for condensation of refrigerant R-134a in minichannels investigated. ► Image processing is used to analyze condensation for 2 ≤Dh ≤ 4.91 mm. ► Void fractions for intermittent and wavy flows, and an overlap region are obtained. ► A new model for void fractions for condensing flows in minichannels is developed.