期刊
EXPERIMENTAL THERMAL AND FLUID SCIENCE
卷 57, 期 -, 页码 344-352出版社
ELSEVIER SCIENCE INC
DOI: 10.1016/j.expthermflusci.2014.05.020
关键词
Flow boiling; R134a; R407C; Smooth horizontal tube; Heat transfer coefficient; Pressure drops; Flow regimes
Experiments to measure flow boiling heat transfer coefficients and pressure drops of R134a and R407C inside a smooth horizontal tube (9.52 mm outside diameter, 1.2 m length) were performed at a refrigerant mass flux range of about 100-400 kg/m(2) s varying the inlet temperature of the evaporator within the range of 5-9 degrees C, with heat fluxes within the range 3-10 kW/m(2). The experimental data are described in terms of the heat transfer coefficients and pressure drop gradient as a function of the vapor quality. The experimental results clearly show that the heat transfer coefficients of R134a are always higher than those of R407C (for a minimum of +55% to a maximum of +87%) for same operating conditions. Furthermore, an assessment of predictive methods is provided for heat transfer coefficients and pressure drop gradients; also a comparison of flow regimes visualizations for R134a with a flow pattern map available in the literature has been presented. (C) 2014 Elsevier Inc. All rights reserved.
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