Heat transfer characteristics of high heat flux vapor chamber

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.

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Flow Boiling Heat Transfer of Liquid Nitrogen in Heated U-Tubes

Journal of Heat Transfer ◽

10.1115/1.4025542 ◽

2013 ◽

Vol 136 (2) ◽

Cited By ~ 1

Author(s):

D. Deng ◽

S. W. Xie ◽

X. D. Li ◽

R. S. Wang

Keyword(s):

Heat Transfer ◽

Heat Flux ◽

Heat Transfer Coefficient ◽

Boiling Heat Transfer ◽

Flow Boiling ◽

High Heat ◽

High Heat Flux ◽

Heat Transfer Characteristics ◽

Curvature Ratio ◽

Flow Boiling Heat Transfer

The flow boiling heat transfer characteristics of liquid nitrogen in three U-tubes with different curvature ratios were investigated experimentally. The effects of inlet pressure, heat flux, and curvature ratio on heat transfer characteristic are analyzed. The results indicate that the local heat transfer characteristics change obviously as fluid flows through the return bend, especially in the case of high heat flux. The drying out occurs near the inner wall of the return bend under high heat flux. A parameter Rh (down/up), which is defined as the ratio of heat transfer coefficient between the downstream and upstream section of U-bend, is proposed to evaluate the contributions of the curvature ratio to the heat transfer. It is found that the Rh (down/up) increases with the decrease of the curvature ratios. Furthermore, the experiments results of the average heat transfer coefficient are compared with the calculated results of the empirical correlations.

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

Micromachines ◽

10.3390/mi12080868 ◽

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.

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