Effect of aspect ratio on the flow and heat transfer characteristics of mist/steam in rectangular ribbed channels

2017 ◽  
Vol 72 (3) ◽  
pp. 255-273 ◽  
Author(s):  
Tieyu Gao ◽  
Junxiong Zeng ◽  
Jun Li ◽  
Jianying Gong
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer

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.

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.

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.

Numerical Investigation of Fully Developed Fluid Flow and Heat Transfer in Double-Trapezoidal Microchannels

2013 ◽  
Author(s):  
Mostafa Shojaeian ◽  
Ali Koşar
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Fluid Flow ◽  
Aspect Ratio ◽  
Heat Transfer Characteristics ◽  
Constant Wall Temperature ◽  
Base Angle ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Poiseuille Number

Fully developed fluid flow and heat transfer characteristics of double-trapezoidal microchannels with constant wall temperature are numerically investigated in the slip flow regime. The governing equations are solved together with the appropriate boundary conditions using finite volume method. The effect of rarefaction on Poiseuille number, Po, and Nusselt number, Nu, is studied for Knudsen numbers, Kn, varying from 0 to 0.1. The effects of base angle, B, and aspect ratio, A, on the fluid flow and the heat transfer characteristics are also examined. The results reveal that the rarefaction and the cross-section shapes have prominent effects on these characteristics of double-trapezoidal microchannels. According to the results, the Poiseuille number decreases with increasing Kn, while the values of the Nusselt number completely depend on the impacts of the rarefaction and the fluid-surface interaction. Po and Nu decrease with aspect ratio for A<1, while the effect of aspect ratio on Po and Nu becomes unclear for A>1. Moreover, an increase in the base angle has a positive effect on Po and Nu, however this increasing trend is less pronounced for B > 60 ° and A < 1.67.

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