This paper reports the development of an experimentally validated model for pressure drop during intermittent flow of condensing refrigerant R134a in horizontal, noncircular microchannels. Two-phase pressure drops were measured in six noncircular channels ranging in hydraulic diameter from 0.42 mm to 0.84 mm. The tube shapes included square, rectangular, triangular, barrel-shaped, and others. For each tube under consideration, pressure drop measurements were taken over the entire range of qualities from vapor to liquid at five different refrigerant mass fluxes between 150 kg/m2s and 750 kg/m2s. Results from previous work by the authors were used to select the data that correspond to the intermittent flow regime; generally, these points had qualities less than 25%. The pressure drop model previously developed by the authors for circular microchannels was used as the basis for the model presented in this paper. Using the observed slug/bubble flow pattern for these conditions, the model includes the contributions of the liquid slug, the vapor bubble, and the transitions between the bubble and slugs. A simple correlation for nondimensional unit-cell length was used to estimate the slug frequency. The model successfully predicts the experimentally measured pressure drops for the noncircular tube shapes under consideration with 90% of the predictions within ±28% of the measurements (average error 16.5%), which is shown to be much better than the predictions of other models in the literature. The effects of tube shape on condensation pressure drop are also illustrated in the paper.
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e-mail: srinivas.garimella@me.gatech.edu
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September 2003
Technical Papers
An Expermentally Validated Model for Two-Phase Pressure Drop in the Intermittent Flow Regime for Noncircular Microchannels
Srinivas Garimella,
e-mail: srinivas.garimella@me.gatech.edu
Srinivas Garimella
George W. Woodruff School of Mechanical Engineering, Georgia Institue of Technology, Atlanta, GA 30332-0405
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Jesse D. Killion,
Jesse D. Killion
George W. Woodruff School of Mechanical Engineering, Georgia Institue of Technology, Atlanta, GA 30332-0405
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John W. Coleman
John W. Coleman
George W. Woodruff School of Mechanical Engineering, Georgia Institue of Technology, Atlanta, GA 30332-0405
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Srinivas Garimella
George W. Woodruff School of Mechanical Engineering, Georgia Institue of Technology, Atlanta, GA 30332-0405
e-mail: srinivas.garimella@me.gatech.edu
Jesse D. Killion
George W. Woodruff School of Mechanical Engineering, Georgia Institue of Technology, Atlanta, GA 30332-0405
John W. Coleman
George W. Woodruff School of Mechanical Engineering, Georgia Institue of Technology, Atlanta, GA 30332-0405
Contributed by the Fluids Engineering Division for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received by the Fluids Engineering Division April 2, 2002; revised manuscript received April 30, 2003. Associate Editor: M. W. Plesniak.
J. Fluids Eng. Sep 2003, 125(5): 887-894 (8 pages)
Published Online: October 7, 2003
Article history
Received:
April 2, 2002
Revised:
April 30, 2003
Online:
October 7, 2003
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Citation
Garimella, S., Killion , J. D., and Coleman, J. W. (October 7, 2003). "An Expermentally Validated Model for Two-Phase Pressure Drop in the Intermittent Flow Regime for Noncircular Microchannels ." ASME. J. Fluids Eng. September 2003; 125(5): 887–894. https://doi.org/10.1115/1.1601258
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