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Author
Domanski, P. A. | Hermes, C. J. L.
Title
Improved Correlation for Two-Phase Pressure Drop of R-22 and R-410A in 180° Return Bends.
Coporate
National Institute of Standards and Technology, Gaithersburg, MD Federal University of Santa Catarina, Florianópolis, SC, BRAZIL
Book or Conf
Thermal Sciences and Engineering, 11th Brazilian Congress. ENCIT 2006--ABCM. Proceedings. December 5-8, 2006, Curitiba, Brazil, 2006
Keywords
pressure drop | short return bends | two-phase pressure drop | curvature multiplier | Buckinhan-PI theorem | databases | equations
Identifiers
Geary's (1975) database and correlation; Chen's et al. (2004b) database and correlation; Chisholm / Idelshik Method; bend geometries tested by Chen et al. (2004b); fitted coefficients; statistical evaluation of predictions for the 241-point database for four studied correlations
Abstract
A new correlation for two-phase flow pressure drop in 180° return bends is proposed based on a total of 241 experimental data points for R-22 and R-410A from two independent studies. The data span smooth tubes with inner diameters (D) from 3.3 mm to 11.6 mm, bend radiuses (R) from 6.4 mm to 37.3 mm, and curvature ratios (2R/D) from 2.3 to 8.2. The correlation consists of a two-phase pressure drop for straight tubes and a multiplier that accounts for the bend curvature. The Buckinham-PI Theorem was used to formulate the curvature multiplier in terms of refrigerant properties, flow characteristics, and bend geometry. The correlation predicts all data with a mean deviation of 15.7%, and 75% of the data fall within ± 25% error bands.