This paper presents a multiple flow-regime model for pressure drop during condensation of refrigerant R134a in horizontal microchannels. Two-phase pressure drops were measured in five circular channels ranging in hydraulic diameter from 0.5 mm to 4.91 mm. For each tube under consideration, pressure drop measurements were first taken over the entire range of qualities from 100% vapor to 100% liquid for five different refrigerant mass fluxes between 150 kg/m2-s and 750 kg/m2-s. Results from previous work by the author on condensation flow mechanisms in microchannel geometries were used to assign the applicable flow regime to the data points. Pressure drop models for intermittent (Garimella et al. 2002) and annular (Garimella et al. 2003a) flow reported earlier by the authors were modified and combined to develop a comprehensive model that addresses the entire progression of the condensation process from the vapor phase to the liquid phase. This combined model accurately predicts condensation pressure drops in the annular, disperse wave, mist, discrete wave, and intermittent flow regimes. Overlap and transition regions between the respective regimes are also addressed using an appropriate interpolation technique that results in relatively smooth transitions between the predicted pressure drops. The resulting model predicts 82% of the data within ±20%.
- Nanotechnology Institute
Condensation Pressure Drops in Circular Microchannels
Garimella, S, Agarwal, A, & Killion, JD. "Condensation Pressure Drops in Circular Microchannels." Proceedings of the ASME 2004 2nd International Conference on Microchannels and Minichannels. ASME 2nd International Conference on Microchannels and Minichannels. Rochester, New York, USA. June 17–19, 2004. pp. 649-656. ASME. https://doi.org/10.1115/ICMM2004-2393
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