Heat transfer correlation for boiling flows in small rectangular horizontal channels with low aspect ratios

• Published in: International journal of multiphase flow Vol. 27; no. 12; pp. 2043 - 2062
• Main Authors: Lee, Han Ju, Lee, Sang Yong
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.12.2001; Elsevier
• Subjects: Applied sciences; Aspect ratio; Boiling heat transfer; Boiling liquids; Devices using thermal energy; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Flow patterns; Frictional pressure drop; Heat exchangers (included heat transformers, condensers, cooling towers); Heat flux; Heat transfer coefficients; Horizontal rectangular channel; Refrigerants; Two-phase flow; Two-phase frictional multiplier; Boiling heat transfer; Two-phase flow; Two-phase frictional multiplier; Horizontal rectangular channel; Frictional pressure drop; Horizontal pipe; Two phase flow; Friction; Pressure drop; Heat exchanger; Compact heat exchanger; Aspect ratio; Rectangular channel; Boiling; Heat transfer
• ISSN: 0301-9322; 1879-3533
• DOI: 10.1016/S0301-9322(01)00054-4

In the present experimental study, a correlation is proposed to represent the heat transfer coefficients of the boiling flows through horizontal rectangular channels with low aspect ratios. The gap between the upper and the lower plates of each channel ranges from 0.4 to 2 mm while the channel width being fixed to 20 mm. Refrigerant 113 was used as the test fluid. The mass flux ranges from 50 to 200 kg/m 2 s and the channel walls were uniformly heated up to 15 kW/m 2 . The quality range covers from 0.15 to 0.75 and the flow pattern appeared to be annular. The modified Lockhart–Martinelli correlation for the frictional pressure drop was confirmed to be within an accuracy of ±20%. The heat transfer coefficients increase with the mass flux and the local quality; however the effect of the heat flux appears to be minor. At the low mass flux condition, which is more likely to be with the smaller gap size, the heat transfer rate is primarily controlled by the liquid film thickness. A modified form of the enhancement factor F for the heat transfer coefficient in the range of Re LF⩽200 well correlates the experimental data within the deviation of ±20%. The Kandlikar's flow boiling correlation covers the higher mass flux range ( Re LF>200) with 10.7% mean deviation.