Effect of aspect ratio on saturated boiling flow in microchannels with nonuniform heat flux

2019 ◽  
Vol 48 (7) ◽  
pp. 3312-3327 ◽  
Author(s):  
Wen-Tao Yan ◽  
Wei-Biao Ye ◽  
Cong Li
Keyword(s):  
Heat Flux ◽  
Aspect Ratio ◽  
Boiling Flow ◽  
Saturated Boiling

scholarly journals Numerical investigation on saturated boiling flow and heat transfer of mixture refrigerant in a vertical rectangular mini-channel

2018 ◽  
Vol 22 (Suppl. 2) ◽  
pp. 617-627
Author(s):  
Jie Chen ◽  
Weihua Cai ◽  
Shulei Li ◽  
Yan Ren ◽  
Hongqiang Ma ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Liquefied Natural Gas ◽  
Gas Field ◽  
Flow And Heat Transfer ◽  
Boiling Flow ◽  
Saturated Boiling

Plate-fin heat exchanger with rectangular minichannels, as a type of high-perfor- mance compact heat exchangers, has been widely used in liquefied natural gas field. However, the studies on saturated boiling flow and heat transfer for mixture refrigerant in plate-fin heat exchanger have been scarcely explored, which are helpful for designing more effective plate-fin heat exchanger using in liquefied natural gas field. Therefore, in this paper, the characteristics of saturated boiling flow and heat transfer for mixture refrigerant in rectangular minichannels of plate-fin heat exchanger were studied numerally based on validated model. Then, the effect of different parameters (vapor quality, mass flux, and heat flux) on heat transfer coefficient and frictional pressure drop were discussed. The results indicated that the boiling heat transfer coefficient and pressure drop are mainly influenced by quality and mass flux while heat flux has little influence on them. This is due to the fact that the main boiling mechanisms were forced convective boiling and the evaporation of dispersed liquid phase while nucleate boiling is slight.

Confinement Effects on FKE-774 Critical Heat Flux in Buoyancy-Driven Microgap Channels

2015 ◽  
Vol 8 (2) ◽  
Author(s):  
Karl J. L. Geisler ◽  
Shweta Natarajan
Keyword(s):  
Heat Flux ◽  
Aspect Ratio ◽  
Critical Heat Flux ◽  
Atmospheric Pressure ◽  
Aluminum Surface ◽  
Confinement Effects ◽  
Channel Spacing ◽  
Aspect Ratios ◽  
Channel Aspect Ratio ◽  
Saturated Boiling

Critical heat flux (CHF) of the fluoroketone fluid FKE-774 in vertical microgap channels is explored, with a focus on submillimeter spacings. Experiments were conducted using a 20 mm × 20 mm heated aluminum surface. Microgap channel spacings were decreased down to 0.3 mm, providing channel aspect ratios (height/spacing) as high as 67. In the limit where channel spacing is large, CHF was found to be 140 kW/m2 for saturated boiling at atmospheric pressure. A reduction in CHF of 55% was observed for the largest channel aspect ratio investigated. Results for degradation of the CHF limit with decreasing microgap spacing are compared to a correlation available in the literature and show a roughly hyperbolic dependence on channel aspect ratio (height/spacing) for aspect ratios larger than 10.

Numerical Simulation Of A Microchannel For Microelectronic Cooling

2012 ◽  
Author(s):  
Wai Hing Wong ◽  
Normah Mohd. Ghazali
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Flux ◽  
Aspect Ratio ◽  
Three Dimensional ◽  
Large Temperature ◽  
Rectangular Microchannel ◽  
Numerical Work ◽  
Solid Region ◽  
Wall Interaction

Kertas kerja ini membincangkan simulasi berangka ke atas sinki haba saluran mikro dalam penyejukan alatan mikroelektronik. Model Dinamik Bendalir Berkomputer (CFD) tiga dimensi dibina menggunakan pakej komersil, FLUENT, untuk mengkaji fenomenon aliran bendalir dan pemindahan haba konjugat di dalam suatu sinki haba segi empat yang diperbuat daripada silikon. Model ditentusahkan dengan keputusan daripada uji kaji dan pengkajian berangka yang lepas untuk lingkungan nombor Reynolds kurang daripada 400 berdasarkan diameter hidraulik 86 mm. Kajian ini mengambil kira kesan kelikatan bendalir yang bersandaran dengan suhu dan keadaan aliran pra–membangun dari segi hidrodinamik dan haba. Model memberi maklumat tentang taburan suhu dan fluks haba yang terperinci di dalam sinki haba saluran mikro. Kecerunan suhu yang tinggi dicatat pada kawasan pepejal berdekatan dengan sumber. Fluks haba paling tinggi didapati pada dinding tepi saluran mikro diikuti oleh dinding atas dan bawah. Purata pekali pemindahan haba yang lebih tinggi bagi silikon menjadikan ia bahan binaan sinki haba saluran mikro yang lebih baik berbanding dengan kuprum dan aluminium. Peningkatan nisbah aspek saluran mikro yang bersegi empat memberi kecekapan penyejukan yang lebih tinggi kerana kelebaran saluran yang berkurangan memberi kecerunan halaju yang lebih tinggi dalam saluran. Nisbah aspek yang optimum yang diperoleh adalah dalam lingkungan 3.7 – 4.1. Kata kunci: Saluran mikro, CFD, FLUENT, simulasi berangka, penyejukan mikroelektron The paper discusses the numerical simulation of a micro–channel heat sink in microelectronics cooling. A three–dimensional Computational Fluid Dynamics (CFD) model was built using the commercial package, FLUENT, to investigate the conjugate fluid flow and heat transfer phenomena in a silicon–based rectangular microchannel heatsink. The model was validated with past experimental and numerical work for Reynolds numbers less than 400 based on a hydraulic diameter of 86 mm. The investigation was conducted with consideration of temperaturedependent viscosity and developing flow, both hydrodynamically and thermally. The model provided detailed temperature and heat flux distributions in the microchannel heatsink. The results indicate a large temperature gradient in the solid region near the heat source. The highest heat flux is found at the side walls of the microchannel, followed by top wall and bottom wall due to the wall interaction effects. Silicon is proven to be a better microchannel heatsink material compared to copper and aluminum, indicated by a higher average heat transfer. A higher aspect ratio in a rectangular microchannel gives higher cooling capability due to high velocity gradient around the channel when channel width decreases. Optimum aspect ratio obtained is in the range of 3.7 – 4.1. Key words: Microchannel, CFD, FLUENT, numerical simulation, microeletronics cooling

scholarly journals The effect of different aspect ratio and bottom heat flux towards contaminant removal using numerical analysis

2013 ◽  
Vol 50 ◽  
pp. 012015
Author(s):  
M N A Saadun ◽  
C S Nor Azwadi ◽  
Z A A Malek ◽  
M Z A Manaf ◽  
M S Zakaria ◽  
...  
Keyword(s):  
Heat Flux ◽  
Numerical Analysis ◽  
Aspect Ratio ◽  
Contaminant Removal ◽  
Bottom Heat

Simulation of boiling flow in evaporator of separate type heat pipe with low heat flux

2015 ◽  
Vol 75 ◽  
pp. 158-167 ◽  
Author(s):  
Y.W. Kuang ◽  
Wen Wang ◽  
Rui Zhuan ◽  
C.C. Yi
Keyword(s):  
Heat Flux ◽  
Heat Pipe ◽  
Separate Type ◽  
Boiling Flow

Stability and Enhancement of Boiling in Microchannels

2011 ◽  
Author(s):  
A. E. Bergles
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
High Heat ◽  
Heat Fluxes ◽  
Transfer Enhancement ◽  
The Past ◽  
The Stability ◽  
Saturated Boiling ◽  
Microelectronic Components

During the past 20 years, there has been intense worldwide interest in microchannel heat exchangers, particularly for cooling of microelectronic components. Saturated boiling of the coolant is usually indicated in order to accommodate high heat fluxes and to have uniformity of temperature. However, boiling is accompanied by several instabilities, the most severe of which can sharply limit the maximum, or critical, heat flux. These stability phenomena are reviewed, and recent studies will be discussed. Elevation of the critical heat flux will be discussed within the context of heat transfer enhancement. Means to improve the stability of boiling and the enhancement of boiling heat transfer, in general, are discussed.

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