A Numerical Study on Flow Boiling in Parallel Microchannels

2008 ◽  
Author(s):  
Jinho Jeon ◽  
Woorim Lee ◽  
Youngho Suh ◽  
Gihun Son
Keyword(s):  
Heat Transfer ◽  
Contact Angle ◽  
Bubble Dynamics ◽  
Numerical Study ◽  
Reverse Flow ◽  
Flow Boiling ◽  
Experimental Studies ◽  
Two Phase ◽  
Flow And Heat Transfer ◽  
Parallel Microchannels

Flow boiling in parallel microchannels has received attention as an effective cooling method for high-power-density microprocessor. Despite a number of experimental studies, the bubble dynamics coupled with boiling heat transfer in microchannels is still not well understood due to the technological difficulties in obtaining detailed measurements of microscale two-phase flows. In this study, complete numerical simulation is performed to further clarify the physics of flow boiling in microchannels. The level set method for tracking the liquid-vapor interface is modified to include the effects of phase change and contact angle. The method is further extended to treat the no-slip and contact angle conditions on the immersed solid. Also, the reverse flow observed during flow boiling in parallel microchannels has been investigated. Based on the numerical results, the effects of channel shape and inlet area restriction on the bubble growth, reverse flow and heat transfer are quantified.

Numerical Study of Bubble Growth on a Micro-Finned Surface

2011 ◽  
Author(s):  
Woorim Lee ◽  
Gihun Son
Keyword(s):  
Heat Transfer ◽  
Bubble Growth ◽  
Bubble Dynamics ◽  
Numerical Study ◽  
Removal Rate ◽  
Bubble Formation ◽  
Experimental Studies ◽  
Nucleate Boiling ◽  
Finned Surface ◽  
Fin Spacing

Bubble growth on a micro-finned surface, which can be used in enhancing boiling heat transfer, is numerically investigated by solving the conservation equations of mass, momentum, and energy. The bubble deformation or the liquid-vapor interface is determined by the sharp-interface level-set method, which is modified to include the effect of phase change and to treat the contact angle and the evaporative heat flux from the liquid microlayer on an immersed solid surface of a microfin. The numerical method is applied to clarify bubble growth and heat transfer characteristics on a surface including fin and cavity during nucleate boiling which have not been provided from the previous experimental studies. The effects of single fin, fin-cavity distance, and fin-fin spacing on the bubble dynamics are investigated. The micro-fin is found to affect the activation of cavity. The fin-cavity configuration is found to determine the bubble formation in a cavity. The vapor removal rate is also observed to significantly depend on the fin-fin spacing.

A Comparative Numerical Study on Two-Phase Boiling Fluid Flow and Heat Transfer in the Microchannel Heat Sink With Different Manifold Arrangements

2020 ◽  
Author(s):  
Yang Luo ◽  
Jingzhi Zhang ◽  
Wei Li
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Sink ◽  
Numerical Study ◽  
Flow Boiling ◽  
High Surface ◽  
Volume Ratio ◽  
High Heat Flux ◽  
Two Phase ◽  
Flow Maldistribution

Abstract The manifold microchannel (MMC) heat sink system has been widely used in high-heat-flux chip thermal management due to its high surface-to-volume ratio. Two-phase, three-dimensional numerical methods for subcooled flow boiling have been developed using a self-programming solver based on OpenFOAM. Four different types of manifold arrangements (Z-type, C-type, H-type and U-type) have been investigated at a fixed operational condition. The numerical results evaluate the effects of flow maldistribution caused by different manifold configurations. Before simulating the two-phase boiling flow in MIMC metamodels, single-phase liquid flow fields are performed at first to compare the flow maldistribution in microchannels. It can be concluded from the flow patterns that H-type and U-type manifolds provide a more even and a lower microchannel void fraction, which is conducive to improving the temperature uniformity and decreasing the effective thermal resistance. The simulation results also show that the wall temperature difference of H-type (0.471 K) is only about 10% of the Z-type (4.683 K). In addition, the U-type manifold configuration show the lowest average pressure drop at the inlet and outlet of the MIMC metamodel domain. However, H-type manifold also shows an impressive 59.9% decrease in pressure loss. Results indicate that both the H-type and the U-type manifolds for flow boiling in microchannels are recommended due to their better heat transfer performance and lower pressure drop when compared with Z-type and C-type.

scholarly journals A thermal-fluid coupling numerical study on the characteristics of air–oil two phase flow and heat transfer in a micro UAV bearing chamber

RSC Advances ◽  
2017 ◽  
Vol 7 (70) ◽  
pp. 44598-44604 ◽  
Author(s):  
Peng Lu ◽  
Xingwen Zheng ◽  
Wei Li ◽  
Peijie Yang ◽  
Hulin Huang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Two Phase Flow ◽  
Numerical Study ◽  
Phase Flow ◽  
Two Phase ◽  
Flow And Heat Transfer ◽  
Fluid Coupling ◽  
Coupling Characteristics

Thermal-fluid coupling characteristics of the air–oil two phase flow in a micro UAV bearing chamber are investigated.

Numerical Study of Flow and Heat Transfer in Confined and Unconfined Round Mist Impinging Jet

2010 ◽  
Author(s):  
Viktor I. Terekhov ◽  
Maksim A. Pakhomov
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Two Phase ◽  
Euler Approximation ◽  
Flow And Heat Transfer ◽  
Target Wall ◽  
Low Mass ◽  
Model Equations ◽  
The One ◽  
Circular Target

The work presents results of numerical investigation of flow structure and heat transfer of unconfined and confined impact mist jets with low mass fraction of droplets (ML1≤1%). The downward gas-droplets jet is issued from a pipe and strikes into the center of the circular target wall. Mathematical model is based on the solution to RANS equations for the two-phase flow in Euler approximation. For the calculation of the fluctuation characteristics of the dispersed phase model equations of Derevich and Zaichik [1] and Zaichik et al. [2] were applied. Predictions were performed for the distances between the nozzle and the target plate x/(2R) = 0.5–10 and the initial droplets size (d1 = 5–100 μm) at the fixed Reynolds number based on the nozzle diameter, Re = 26600. Addition of droplets causes significant increase of heat transfer intensity in the vicinity of the jet stagnation point compared with the one-phase air impact jet.

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