Two-Phase Flow Regimes and Heat Transfer Coefficients with R245fa in Manifolded-Microgap Channels

As an excellent cryogenic cooling medium, Nitrogen (N2) has been used in a variety of engineering fields, where the determination of N2 two-phase flow boiling heat transfer is required. There were some studies evaluating the correlations of flow boiling heat transfer coefficient for N2. However, either the number of correlations covered or the number of data used was limited. This work presents a comparative review of existing correlations of flow boiling heat transfer coefficients for N2 applications. A database of N2 flow boiling heat transfer containing 1043 experimental data points is compiled to evaluate 45 correlations of two-phase flow boiling heat transfer. The experimental parameters cover the ranges of mass flux from 28.0 to 1684.8 kg/m2s, heat flux from 0.2 to 135.6 kW/m2, vapor quality from 0.002 to 0.994, saturation pressure from 0.1 to 3.16 MPa, and channel inner diameter from 0.351 to 14 mm. The results show that the best correlation has a mean absolute deviation of 31.8% against the whole database, suggesting that more efforts should be made to study N2 flow boiling heat transfer to develop a more accurate correlation.

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Modeling and Prediction of Two-Phase Refrigerant Flow Regimes and Heat Transfer Characteristics in Microgap Channels

ASME 5th International Conference on Nanochannels, Microchannels, and Minichannels ◽

10.1115/icnmm2007-30216 ◽

2007 ◽

Cited By ~ 13

Author(s):

Avram Bar-Cohen ◽

Emil Rahim

Keyword(s):

Heat Transfer ◽

Annular Flow ◽

Two Phase Flow ◽

Flow Regimes ◽

Phase Flow ◽

Transfer Coefficients ◽

Two Phase ◽

Channel Diameter ◽

Dielectric Liquids ◽

Transition Criteria

This keynote lecture will open with a brief review of the primary two-phase flow regimes and their impact on thermal transport phenomena in tubes and channels. The Taitel and Dukler flow regime mapping methodology will then be described and applied to the two-phase flow of refrigerants and dielectric liquids in microgap channels. The effects of channel diameter, as well as alternative transition criteria, on the prevailing flow regimes in microgaps will be explored along with available criteria for microchannel behavior. Available microgap data will then be shown to reflect the dominance of annular flow and to display a characteristic heat transfer coefficient curve in such configurations. It is found that the heat transfer coefficients in the low-quality annular flow segment of this locus can be predicted by available, microtube correlations, but that the moderate-quality transition to the axially-decreasing segment occurs at substantially.

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Correlation for Predicting Two-Phase Flow Boiling Heat Transfer Coefficients for Refrigerant HFO-1234yf

10.4271/2018-01-0055 ◽

2018 ◽

Cited By ~ 1

Author(s):

Gursaran D. Mathur

Keyword(s):

Heat Transfer ◽

Boiling Heat Transfer ◽

Two Phase Flow ◽

Flow Boiling ◽

Phase Flow ◽

Transfer Coefficients ◽

Two Phase ◽

Heat Transfer Coefficients ◽

Flow Boiling Heat Transfer

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Visualization of Two-Phase Flow in Serpentine Heat Exchanger Passages With Microscale Pin Fins

Volume 2: Micro/Nano-Thermal Manufacturing and Materials Processing; Boiling, Quenching and Condensation Heat Transfer on Engineered Surfaces; Computational Methods in Micro/Nanoscale Transport; Heat and Mass Transfer in Small Scale; Micro/Miniature Multi-Phase Devices; Biomedical Applications of Micro/Nanoscale Transport; Measurement Techniques and Thermophysical Properties in Micro/Nanoscale; Posters ◽

10.1115/mnhmt2016-6576 ◽

2016 ◽

Author(s):

Dhruv C. Hoysall ◽

Khoudor Keniar ◽

Srinivas Garimella

Keyword(s):

Two Phase Flow ◽

Flow Regimes ◽

High Heat ◽

Phase Flow ◽

Transfer Coefficients ◽

Two Phase ◽

Pressure Drops ◽

Heat Transfer Coefficients ◽

High Heat Transfer ◽

Pin Fins

Multiphase flow phenomena in single micro- and minichannels have been widely studied. Microchannel heat exchangers offer the potential for high heat transfer coefficients; however, implementation challenges must be addressed to realize this potential. Maldistribution of phases among the microchannels in the array and the changing phase velocities associated phase change present design challenges. Flow maldistribution and oscillatory instabilities can severely affect heat and mass transfer rates as well as pressure drops. In components such as condensers, evaporators, absorbers and desorbers, changing phase velocities can change prevailing flow regimes from favorable to unfavorable. Geometries with serpentine passages containing pin fins can be configured to maintain favorable flow regimes throughout the length of the component for diabatic phase-change heat and mass transfer applications. Due to the possibility of continuous redistribution of the flow across the pin fins along the flow direction, maldistribution can also be reduced. These features enable the potential of high heat transfer coefficients in microscale passages to be fully realized, thereby reducing the required transfer area, and achieving considerable compactness. The characteristics of two-phase flow through a serpentine passage with micro-pin fin arrays with diameters 350 μm and height 406 μm are investigated here. An air-water mixture is used to represent two-phase flow through the serpentine test section, and a variety of flow features are visually investigated using high-speed photography. Improved flow distribution is observed in the serpentine geometry. Distinct flow regimes, different from those observed in microchannels are also established. These observations are used to obtain void fraction and interfacial area along the length of the serpentine passages and compared with the corresponding values for straight microchannels. Models for the two-phase frictional pressure drops across this geometry are also developed.

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