Numerical Study of Gas-Liquid Two-Phase Flow in Ultra-High-Aspect-Ratio Microchannel With Capillary-Structured Wall

2019 ◽  
Author(s):  
Xiang Mei ◽  
Zhenyu Liu ◽  
Huiying Wu
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Two Phase Flow ◽  
Flow Behavior ◽  
Phase Flow ◽  
Two Phase ◽  
Chip Cooling ◽  
Evaporation Heat ◽  
Evaporation Heat Transfer

Abstract The understanding of the liquid-gas flow and heat transfer in the high-aspect-ratio microchannel is very important to realize the high-efficiency phase change chip cooling. In this work, a novel ultra-high-aspect-ratio microchannel with capillary-structured wall was developed to enhance the evaporation heat transfer in microchannel, in which the capillary grooves on the side walls (capillary-structured wall) were designed to avoid the dryout phenomenon. A three-dimensional VOF model was established to predict the immiscible gas-liquid flow in microchannel. The influences of wettability of capillary grooves on the gas-liquid two-phase flow behavior in microchannel were investigated based on the numerical predictions. The slug bubble can be observed for different inlet flow conditions. Variation of pressure loss between inlet and outlet of microchannel with time were studied for different flow rates and gas-liquid ratios. The results show that the existence of capillary structured wall has a significant influence on the liquid-gas two-phase flow behavior in the microchannel. The liquid flow in microgrooves is driven by the capillary force, which can supply more liquid to the side wall to promote the evaporation heat transfer process. The design of capillary-structured wall for ultra-high-aspect-ratio microchannel in this work provides a new approach to improve the performance of the chip cooling technique with microchannels.

scholarly journals Numerical Simulation of Evaporating Two-Phase Flow in a High-Aspect-Ratio Microchannel with Bends

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
Zhenhai Pan ◽  
Justin A. Weibel ◽  
Suresh V. Garimella
Keyword(s):  
Aspect Ratio ◽  
Liquid Film ◽  
High Aspect Ratio ◽  
Two Phase Flow ◽  
Flow Boiling ◽  
Fluid Velocity ◽  
Thin Liquid Film ◽  
Heated Wall ◽  
Phase Flow ◽  
Two Phase

Despite the demand for high-performance, two-phase cooling systems, high-fidelity simulations of flow boiling in complex microchannel geometries remains a challenging numerical problem. We conduct a first-principles-based simulation of an evaporating two-phase flow in a high-aspect-ratio microchannel with bends using a volume of fluid-based numerical model. For the case shown, the lower horizontal section of the microchannel has a constant flux of 20 W/cm2 applied to the wetted wall area (heat flux at the base of 133 W/cm2); HFE-7100 vapor and liquid enter the channel at 2 m/s. The three-dimensional channel geometry requires a refined near-wall numerical mesh to resolve thin liquid film flow features. The recently developed saturated-interface-volume phase change model (Int J Heat Mass Trans 93:945-956, 2016) is implemented for prediction of mass and energy exchange across the liquid-vapor interface at a low computational cost (~80 hr; 6-core parallelization on Intel Xeon E3-1245V3). The model reveals transport details including the interface shape and fluid velocity and temperature fields. The interfacial temperature remains fixed at saturation with smooth velocity contours near the interface. The highest evaporation flux is located in the thin liquid film region near the heated wall.

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