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Journal of Enhanced Heat Transfer
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ISSN Imprimir: 1065-5131
ISSN En Línea: 1026-5511

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Journal of Enhanced Heat Transfer

DOI: 10.1615/JEnhHeatTransf.v15.i3.30
pages 211-226

Horizontal Convective Boiling of Pure and Mixed Refrigerants within a Micro-Fin Tube

L. J. Hamilton
U.S. Naval Academy, Annapolis, MD 21402
Mark Kedzierski
NIST
M. P. Kaul
Bristol Compressors, Bristol, VA 24202

SINOPSIS

This paper presents local convective boiling measurements in a micro-fin tube** for four pure refrigerants: R22, R32, R125, and R134a; and four refrigerant mixtures: R410B (R32/125, 45/55% mass), R32/R134a (27/73% and 30/70% mass), and R407C (R32/125/134a, 25/23/52% mass). All testing was conducted using a counterflow water-heated horizontal 9.5 mm (Do) U-tube with helical micro-fins. Saturation temperatures ranged from 274.5 K to 293.6 K. Flow boiling heat transfer coefficients for the mixtures' pure components and R22 were measured to establish a baseline for the heat transfer degradation calculations. The measured convective boiling Nusselt numbers for all of the test refrigerants were correlated to a single expression consisting of a product of dimensionless properties valid for mass velocities ranging from 70 kg/m2·s to 370 kg/m2·s and for vapor qualities between 0 and 0.7. These measurements were within ±20% of the new correlation predictions for 94.6% and 87.3% of the pure refrigerant and mixed refrigerant measurements, respectively. The correlation was shown to predict some existing data from the literature to within 20%. The degradation in heat transfer performance of the mixtures was found to range from 1% to 50% for all refrigerants tested.