scholarly journals Numerical Study on the Fluid Flow and Heat Transfer Characteristics of Al2O3-Water Nanofluids in Microchannels of Different Aspect Ratio

Micromachines ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 868
Author(s):  
Huajie Wu ◽  
Shanwen Zhang
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Volume Fraction ◽  
High Heat ◽  
High Heat Flux ◽  
Nanoparticle Volume Fraction ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Heat Transfer Capacity

The study of the influence of the nanoparticle volume fraction and aspect ratio of microchannels on the fluid flow and heat transfer characteristics of nanofluids in microchannels is important in the optimal design of heat dissipation systems with high heat flux. In this work, the computational fluid dynamics method was adopted to simulate the flow and heat transfer characteristics of two types of water-Al2O3 nanofluids with two different volume fractions and five types of microchannel heat sinks with different aspect ratios. Results showed that increasing the nanoparticle volume fraction reduced the average temperature of the heat transfer interface and thereby improved the heat transfer capacity of the nanofluids. Meanwhile, the increase of the nanoparticle volume fraction led to a considerable increase in the pumping power of the system. Increasing the aspect ratio of the microchannel effectively improved the heat transfer capacity of the heat sink. Moreover, increasing the aspect ratio effectively reduced the average temperature of the heating surface of the heat sink without significantly increasing the flow resistance loss. When the aspect ratio exceeded 30, the heat transfer coefficient did not increase with the increase of the aspect ratio. The results of this work may offer guiding significance for the optimal design of high heat flux microchannel heat sinks.

scholarly journals Numerical Study on the Fluid Flow and Heat Transfer Characteristics of Al2O3-water Nanofluids in Microchannels of Different Aspect Ratio

2021 ◽  
Author(s):  
Huajie Wu ◽  
Shanwen Zhang
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Volume Fraction ◽  
High Heat ◽  
High Heat Flux ◽  
Nanoparticle Volume Fraction ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Heat Transfer Capacity

The study of the influence of the nanoparticle volume fraction and aspect ratio of microchannels on the fluid flow and heat transfer characteristics of nanofluids in microchannels is important in the optimal design of heat dissipation systems with high heat flux. In this work, the computational fluid dynamics method was adopted to simulate the flow and heat transfer characteristics of two types of water–Al2O3 nanofluids with two different volume fractions and five types of microchannel heat sinks with different aspect ratios. Results showed that increasing the nanoparticle volume fraction reduced the average temperature of the liquid–solid heat transfer surface and thereby improved the heat transfer capacity of the nanofluids. Meanwhile, the increase of the nanoparticle volume fraction led to a considerable increase in the pumping power of the system. Changing the aspect ratio of the microchannel effectively improved the heat transfer capacity of the heat sink. Moreover, increasing the aspect ratio effectively reduced the average temperature of the heating surface of the heat sink without significantly increasing the flow resistance loss. When the aspect ratio exceeded 30, the heat transfer coefficient did not increase with the increase of the aspect ratio. The results of this work may offer guiding significance for the optimal design of high heat flux microchannel heat sinks.

High heat flux flow boiling in silicon multi-microchannels – Part I: Heat transfer characteristics of refrigerant R236fa

2008 ◽  
Vol 51 (21-22) ◽  
pp. 5400-5414 ◽  
Author(s):  
Bruno Agostini ◽  
John Richard Thome ◽  
Matteo Fabbri ◽  
Bruno Michel ◽  
Daniele Calmi ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flow Boiling ◽  
High Heat ◽  
High Heat Flux ◽  
Heat Transfer Characteristics ◽  
Flux Flow ◽  
Transfer Characteristics

scholarly journals Flow and Heat Transfer of Cu-Water Nanofluid between a Stretching Sheet and a Porous Surface in a Rotating System

2012 ◽  
Vol 2012 ◽  
pp. 1-18 ◽  
Author(s):  
M. Sheikholeslami ◽  
H. R. Ashorynejad ◽  
G. Domairry ◽  
I. Hashim
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Base Fluid ◽  
Stretching Sheet ◽  
Volume Fraction ◽  
Rotation Parameter ◽  
Nanoparticle Volume Fraction ◽  
Heat Transfer Characteristics ◽  
Rotating System ◽  
Flow And Heat Transfer

The aim of the present paper is to study the flow of nanofluid and heat transfer characteristics between two horizontal plates in a rotating system. The lower plate is a stretching sheet and the upper one is a solid porous plate. Copper (Cu) as nanoparticle and water as its base fluid have been considered. The governing partial differential equations with the corresponding boundary conditions are reduced to a set of ordinary differential equations with the appropriate boundary conditions using similarity transformation, which is then solved analytically using the homotopy analysis method (HAM). Comparison between HAM and numerical solutions results showed an excellent agreement. The results for the flow and heat transfer characteristics are obtained for various values of the nanoparticle volume fraction, suction/injection parameter, rotation parameter, and Reynolds number. It is shown that the inclusion of a nanoparticle into the base fluid of this problem is capable of causing change in the flow pattern. It is found that for both suction and injection, the heat transfer rate at the surface increases with increasing the nanoparticle volume fraction, Reynolds number, and injection/suction parameter and it decreases with power of rotation parameter.

Laminar Flow and Heat Transfer Characteristics of Colloid Suspensions in Water: A Numerical Study

2009 ◽  
Author(s):  
Khalid N. Alammar ◽  
Lin-wen Hu
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Heat Transfer Enhancement ◽  
Volume Fraction ◽  
Numerical Study ◽  
Volume Flow Rate ◽  
Transfer Enhancement ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer

Numerical analysis is performed to examine axisymmetric laminar flow and heat transfer characteristics of colloidal dispersions of nanoparticles in water (nanofluids). Effect of volume fraction on flow and heat transfer characteristics is investigated. Four different materials, Alumina, Copper, Copper Oxide, and Graphite are considered. Heat transfer and property measurements were conducted previously for Alumina nanofluid. The measurements have shown that nanofluids can behave as homogeneous mixtures. It is found that oxide-based nanofluids offer the least heat transfer enhancement compared to elements-based nanofluids. When normalized by friction pressure drop, it is shown that graphite can have the highest effective heat transfer enhancement. For a given volume flow rate, all nanofluids exhibited linear increase in heat transfer enhancement with increasing colloids volume fraction, up to 0.05.

Study on Thermal-Hydraulic Characteristics of Vertical Narrow Rectangular Channel With Large Aspect Ratio Under Transverse Uneven Heating

2018 ◽  
Author(s):  
Rulei Sun ◽  
Yichen Yang ◽  
Dalin Zhang ◽  
Jiawei Bian ◽  
Suizheng Qiu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Rectangular Channel ◽  
Large Aspect Ratio ◽  
Hydraulic Characteristics ◽  
Uniform Heating ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Uneven Heating

The plate type fuel element is widely used in advanced research reactors due to its excellent heat transfer performance, low fuel core temperature and large core power-to-volume ratio, etc. The fuel plate gap is generally 1 to 3 mm, and the aspect ratio is generally greater than 20, thus forming a typical large aspect ratio rectangular channel between adjacent fuel plates. In addition, in the actual research reactor, the distribution of power is uneven along the width of the channel due to the influence of the radiation target and fuel arrangement, which inevitably causes lateral migration and cross-mixing of the fluid. As a result, the flow and heat transfer characteristics may be significantly different from those in conventional narrow channels. At present, the experimental and theoretical research on the flow heat transfer characteristics in the rectangular channel are basically carried out under the condition of uniform heating. It is rarely reported that the flow and heat transfer characteristics in narrow rectangular channel with large aspect ratio under transverse non-uniform heating. Therefore, the numerical study of thermal-hydraulic characteristics in vertical narrow rectangular channel with large aspect ratio under transverse uneven heating is carried out in this study. The numerical calculation shows that the lateral power distribution has a significant effect on the temperature field distribution of the core coolant and the fuel plate, which suggests that the distribution of the lateral power of the plate fuel should be considered in the design and safety analysis of reactor cores.

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