Electroosmotic flow and heat transfer in a heterogeneous circular microchannel

Surface roughness is one of the most important factors to determine the flow and heat transfer characteristics of the microchannel. This paper experimentally and theoretically investigated the effects of surface roughness for the flow and heat transfer behavior within the circular microchannel. The stainless steel circular microchannels were fabricated by electrical spark-erosion perforating and drilling separately to control the relative roughness of the surface which is 1% for drilling method and 1.5% for electrical spark-erosion perforating method. Each test piece includes 44 identical circular microchannels in parallel with diameter of 0.4 mm. In the experiments, the air flowed through the circular microchannels with Reynolds number changing from 200 to 2600. The results showed that the surface roughness in microchannels has a remarkable effect on the performance of flow behavior and heat transfer within the circular microchannel. The values of Poiseuille number and Nusselt number are higher when the surface relative roughness is larger. At the same time, the flow behavior is inconsistent with the behavior within the macrochannel. For the flow behavior, Poiseuille number increases monotonously with the increase of Reynolds number, and is higher than the constant theoretical value. The Reynolds number for the transition from laminar to turbulent flow is between 1400 and 1600. For the heat transfer property, Nusselt number also increases as the increase of the Reynolds number.

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Numerical Study of Fluid Flow and Heat Transfer Characteristics in a Cone-Column Combined Heat Sink

Energies ◽

10.3390/en14061605 ◽

2021 ◽

Vol 14 (6) ◽

pp. 1605

Author(s):

Wei Zheng ◽

Jianjun Sun ◽

Chenbo Ma ◽

Qiuping Yu ◽

Yuyan Zhang ◽

...

Keyword(s):

Heat Transfer ◽

Heat Sink ◽

Heat Transfer Performance ◽

Base Temperature ◽

Transfer Performance ◽

Heat Transfer Characteristics ◽

Enhanced Heat Transfer ◽

Flow And Heat Transfer ◽

Heat Transfer Factor ◽

Circular Microchannel

Temperature has a great influence on the normal operation and service life of high-power electronic components. To cope with the increasingly severe heat problems in integrated circuits, an enhanced heat transfer factor E is introduced to evaluate the comprehensive heat transfer performance of microchannel heat sinks (MCHS). The computational fluid dynamics (CFD) software was used to numerically study the fluid flow and heat transfer characteristics in the cone-column combined heat sink. The research results obtained the velocity field and pressure field distribution of the heat sink structure in the range of 100 ≤ Re ≤ 700. When Re changes, the change law of pressure drop ΔP, friction factor f, average Nussel number Nuave, average substrate temperature T, and enhanced heat transfer factor E, are compared with the circular MCHS. The results show that the uniform arrangement of the cones inside the cone-column combined heat sink can change the flow state of the cooling medium in the microchannel and enhance the heat transfer. In the range of 100 ≤ Re ≤ 700, the base temperature of the cone-column combined heat sink is always lower than the base temperature of the circular MCHS, and the average Nusselt number Nuave is as high as 2.13 times that of the circular microchannel. The enhanced heat factor E is 1.75 times that of the circular MCHS, indicating that the comprehensive heat transfer performance of the cone-column combined heat sink is significantly better than that of the circular microchannel.

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Single-phase fluid flow and heat transfer characteristics of nanofluid in a circular microchannel: Development of flow and heat transfer correlations

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406220916537 ◽

2020 ◽

Vol 234 (18) ◽

pp. 3689-3708 ◽

Cited By ~ 1

Author(s):

Mangal Singh Lodhi ◽

Tanuja Sheorey ◽

Goutam Dutta

Keyword(s):

Heat Transfer ◽

Experimental Study ◽

Reynolds Number ◽

Fluid Flow ◽

Friction Factor ◽

Nanoparticle Concentration ◽

Heat Transfer Characteristics ◽

Transfer Characteristics ◽

Flow And Heat Transfer ◽

Circular Microchannel

The convective heat transfer in microchannels with the use of nanofluids has proved to be a potential candidate for cooling of micro-electromechanical system devices. The current research article presents the experimental study on fluid flow and heat transfer characteristics of [Formula: see text]/water nanofluid in a microchannel under thermally developing laminar flow at Reynolds number ranging from 300 to 1000. The experimental set-up of a circular microchannel test section with an inner diameter of [Formula: see text] and length of [Formula: see text] is fabricated to conduct the experimental study. The effect of nanoparticle concentration ([Formula: see text]), Reynolds number ([Formula: see text]) on fluid flow and heat transfer characteristics of [Formula: see text]/water nanofluid have been measured and compared with that of distilled water (DW). The results indicate that the maximum enhancement in local heat transfer coefficient is achieved up to [Formula: see text], while friction factor is achieved up to [Formula: see text] for [Formula: see text]/water nanofluid with nanoparticle concentration of [Formula: see text] as compared to DW. The results showed that the performance evaluation criterion of [Formula: see text]/water nanofluid is greater than unity ([Formula: see text]), implying the benefits of nanofluids as compared to DW. Moreover, the predicted data obtained by the present proposed correlations for friction factor and local Nusselt number using [Formula: see text]/water nanofluid show reasonably good agreement with the deviations of [Formula: see text] and [Formula: see text], respectively, with the numerical data as compared to the predicted data obtained by the existing correlations available in the literature.

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