Characteristics of pressure drop for single-phase and two-phase flow across sudden contraction in microtubes |
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Authors: | Li Zhuo Yu Jian Ma ChongFang |
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Affiliation: | (1) Key Laboratory of Enhanced Heat Transfer and Energy Conservation, Ministry of Education of China, Key Laboratory of Heat Transfer and Energy Conversion, Beijing Education Commission, Beijing University of Technology, Beijing, 100022, China |
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Abstract: | Single-phase and gas-liquid two-phase pressure drops caused by a sudden contraction in microtubes were experimentally investigated
at room temperature and atmospheric pressure, using nitrogen and water. The experimental results on pressure drop with a novel
measurement method, the tiny gaps on the tubes, were used to characterize the sudden contraction pressure drop for tube diameters
from 850 to 330 μm. The ranges of the gas and liquid superficial velocity were 2.55–322.08 and 0.98–9.78 m/s in the smaller
tube respectively. In single-phase flow experiments, the contraction loss coefficients were larger than the experimental results
from conventional tubes in the laminar flow. While in the turbulent flow, the contraction loss coefficients were slightly
smaller than those from conventional tubes and predicted well by K
c=0.5×(1−σ2)0.75. In two-phase flow experiments, the slip flow model with a velocity slip ratio S=(ρL/ρG)1/3 showed a good prediction that reveals the occurrence of velocity slip. An empirical correlation for two-phase flow pressure
drops caused by the sudden contraction was developed based on the proposed contraction loss coefficients correlation for single-phase
flow and Martinelli factor.
Supported by the National Key Basic Research Program (Grant No. G2000026300) and Beijing Open Fund |
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Keywords: | microtube sudden contraction pressure measurement loss coefficients single- and two-phase flow |
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