Visualization of R134a flow boiling in micro-channels to establish a novel bubbly-slug flow transition criterion

In this paper, flow patterns transition criteria from bubble growth to confined bubbly flow, from isolated/confined bubbly flow to slug flow, and from slug flow to annular flow are numerical analyzed. The prediction of the theoretical model agrees well with experimental data. By carrying out comparative study, it is indicated that there is an apparent postponement of flow patterns transition of flow boiling in mini/micro-channel than that under adiabatic conditions.

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INVESTIGATION OF BUBBLE FREQUENCY IN SLUG FLOW REGIME FOR FLOW BOILING IN A SINGLE ROUND UNIFORMLY HEATED MICRO-CHANNEL

Proceeding of First Thermal and Fluids Engineering Summer Conference ◽

10.1615/tfesc1.mph.012657 ◽

2016 ◽

Author(s):

Amen Younes ◽

Ibrahim Hassan ◽

Lyes Kadem

Keyword(s):

Flow Regime ◽

Slug Flow ◽

Flow Boiling ◽

Micro Channel ◽

Bubble Frequency

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Experimental Studies of Adiabatic Flow Boiling in Fractal-Like Branching Micro-Channels

Volume 10: Heat Transfer, Fluid Flows, and Thermal Systems, Parts A, B, and C ◽

10.1115/imece2008-69240 ◽

2008 ◽

Cited By ~ 2

Author(s):

Brian J. Daniels ◽

James A. Liburdy ◽

Deborah V. Pence

Keyword(s):

Pressure Drop ◽

Void Fraction ◽

Flow Boiling ◽

Experimental Studies ◽

Channel Length ◽

Channel Height ◽

Channel Network ◽

Adiabatic Flow ◽

Numerical Predictions ◽

Micro Channels

Experimental results of adiabatic boiling of water flowing through a fractal-like branching microchannel network are presented and compared to numerical simulations for identical flow conditions. The fractal-like branching channel network had channel length and width ratios between adjacent branching levels of 0.7071, a total flow length of 18 mm, a channel height of 150 μm and a terminal channel width of 100 μm. The channels were DRIE etched into a silicon disk and pyrex was anodically bonded to the silicon to form the channel top and allowed visualization of the flow within the channels. The water flowed from the center of the disk where the inlet was laser cut through the silicon to the periphery of the disc. The flow rates ranged from 100 to 225 g/min and the inlet subcooling levels varied from 0.5 to 6 °C. Pressure drop across the channel as well as void fraction in each branching level were measured for each of the test conditions. The measured pressure drop ranged from 20 to 90 kPa, and the measured void fraction ranged from 0.3 to 0.9. The pressure drop results agree well with the numerical predictions. The measured void fraction results followed the same trends as the numerical results.

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Comparison of 30 Boiling and Condensation Correlations for Two-Phase Flows in Compact Plate-Fin Heat Exchangers

Volume 2: Heat Transfer Equipment; Heat Transfer in Multiphase Systems; Heat Transfer Under Extreme Conditions; Nanoscale Transport Phenomena; Theory and Fundamental Research in Heat Transfer; Thermophysical Properties; Transport Phenomena in Materials Processing and Manufacturing ◽

10.1115/ht2017-4907 ◽

2017 ◽

Cited By ~ 4

Author(s):

Wenhai Li ◽

Ken Alabi ◽

Foluso Ladeinde

Keyword(s):

Heat Transfer ◽

Heat Exchangers ◽

Flow Boiling ◽

Transfer Coefficients ◽

Two Phase Flows ◽

Two Phase ◽

Heat Transfer Coefficients ◽

Heat Exchanger Design ◽

Micro Channels ◽

Vertical Tubes

Over the years, empirical correlations have been developed for predicting saturated flow boiling [1–15] and condensation [16–30] heat transfer coefficients inside horizontal/vertical tubes or micro-channels. In the present work, we have examined 30 of these models, and modified many of them for use in compact plate-fin heat exchangers. However, the various correlations, which have been developed for pipes and ducts, have been modified in our work to make them applicable to extended fin surfaces. The various correlations have been used in a low-order, one-dimensional, finite-volume type numerical integration of the flow and heat transfer equations in heat exchangers. The NIST’s REFPROP database [31] is used to account for the large variations in the fluid thermo-physical properties during phase change. The numerical results are compared with Yara’s experimental data [32]. The validity of the various boiling and condensation models for a real plate-fin heat exchanger design is discussed. The results show that some of the modified boiling and condensation correlations can provide acceptable prediction of heat transfer coefficient for two-phase flows in compact plate-fin heat exchangers.

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