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Abstract

This paper presents a numerical analysis of the thermal-flow characteristics for a laminar flow inside a rectangular microchannel. The flow of water through channels with thin obstacles mounted on opposite walls was analyzed. The studies were conducted with a low Reynolds number (from 20 to 200). Different heights of rectangular obstacles were analyzed to see if geometrical factors influence fluid flow and heat exchange in the microchannel. Despite of the fact that the use of thin obstacles in the microchannels leads to an increase in the pressure drop, the increase in the height of the obstacles favors a significant intensification of heat exchange with the maximum thermal gain factor of 1.9 for the obstacle height coefficient h/H=0.5, which could be acceptable for practical application.
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Bibliography

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[9] G. Wang, T. Chen, M. Tian, and G. Ding. Fluid and heat transfer characteristics of microchannel heat sink with truncated rib on sidewall. International Journal of Heat and Mass Transfer, 148:119142, 2020. doi: 10.1016/j.ijheatmasstransfer.2019.119142.
[10] S. Mahjoob and S. Kashkuli. Thermal transport analysis of injected flow through combined rib and metal foam in converging channels with application in electronics hotspot removal. International Journal of Heat and Mass Transfer, 177:121223, 2021. doi: 10.1016/j.ijheatmasstransfer.2021.121223.
[11] L. Chai, G.D. Xia, and H.S. Wang. Numerical study of laminar flow and heat transfer in microchannel heat sink with offset ribs on sidewalls. Applied Thermal Engineering, 92:32–41, 2016. doi: 10.1016/j.applthermaleng.2015.09.071.
[12] Y. Yin, R. Guo, C. Zhu, T. Fu, and Y. Ma. Enhancement of gas-liquid mass transfer in microchannels by rectangular baffles. Separation and Purification Technology, 236:116306, 2020. doi: 10.1016/j.seppur.2019.116306.
[13] A. Behnampour O.A. Akbari, M.R. Safaei, M. Ghavami, A. Marzban, G.A.S. Shabani, M. Zarringhalam, and R. Mashayekhi. Analysis of heat transfer and nanofluid fluid flow in microchannels with trapezoidal, rectangular and triangular shaped ribs. Physica E: Low-Dimensional Systems and Nanostructures, 91:15–31, 2017. doi: 10.1016/j.physe.2017.04.006.
[14] M.R. Gholami, O.A. Akbari, A. Marzban, D. Toghraie, G.A.S. Shabani, and M. Zarringhalam. The effect of rib shape on the behavior of laminar flow of {oil/MWCNT} nanofluid in a rectangular microchannel. Journal of Thermal Analysis and Calorimetry, 134(3):1611–1628, 2018. doi: 10.1007/s10973-017-6902-3.
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Authors and Affiliations

Małgorzata Kmiotek
1
ORCID: ORCID
Robert Smusz
1
ORCID: ORCID

  1. Rzeszow University of Technology, The Faculty of Mechanical Engineering and Aeronautics, Rzeszow, Poland
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Abstract

The paper presents the results of a numerical study devoted to the hydraulic properties of a network of parallel triangular microchannels (hydraulic diameter Dh = 110 um). Previous experimental investigations had revealed that pressure drop through the microchannels system dramatically increases for the Reynolds number exceeding value of 10. The disagreement of the experimental findings with the estimations of flow resistance based on the assumption of fully developed flow were suspected to result from the so-called scale effect. Numerical simulations were performed by using the classical system of flow equations (continuity and Navier-Stokes equations) in order to explain the observed discrepancies. The calculations showed a very good agreement with the experimental results proving that there is no scale effect for the microchannels considered, i.e. the relevance of the constitutive flow model applied was confirmed. It was also clearly indicated that the excessive pressure losses in the high Reynolds number range are due to the secondary flows and separations appearing in several regions of the microchannel system.

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Authors and Affiliations

M. Niklas
M. Favre-Marinet
D. Asendrych
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Abstract

The aim of this paper is to study the applicability of the theory of micropolar fluids to modelling and calculating flows in microchannels depending on the geometrical dimension of the flow field. First, it will be shown that if the characteristic linear dimension of the flow becomes appropriately large, the equations describing the micropolar fluid flow can be transformed into Navier-Stokes equations. Next, Poiseuille flows in a microchannel is studied in detail. In particular, the maximal cross-sectional size of the channel for which the micropolar effects of the fluid flow become important will be established. The experimentally determined values of rheological constants of the fluid have been used in calculations.

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Authors and Affiliations

A. Kucaba-Piętal
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Abstract

Dissipative Particle Dynamics (DPD) is a simulation method at mesoscopic scales that bridges the gap between molecular dynamics and continuum hydrodynamics. It can simulate efficiently complex liquids and dense suspensions using only a few thousands of virtual particles and at speed-up factors of more than one hundred thousands compared to Molecular Dynamics. Lowe’s approach provides a powerful alternative to the usual DPD integrating schemes. Here, we demonstrate the details and potential of Lowe’s scheme. We compute viscosity, diffusivity and Schmidt number values and we present comparison of wormlike chain models under shear with experimental and Brownian Dynamics results for ll-phage DNA.

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Authors and Affiliations

V. Symeonidis
G.E. Karniadakis
B. Caswell
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Abstract

A principle diagram of a high-voltage low-power power supply for devices comprising a microchannel plate (MCP) has been developed. A mathematical model was built according to the developed scheme for a detailed study of the operation of the power supply and the selection of the optimal parameters of its components and obtaining the best output voltages. The power supply circuit comprises a control circuit, a pulse transformer, a voltage multiplier circuit, a feedback circuit, and an input stabilizer. The input stabilizer provides the maintenance of the voltage switched in the primary winding of the transformer at a given level regardless of the voltage drop of the power supply primary source. Moreover the stabilizer provides constant voltage maintenance when the load resistance changes. (with Rload changing from 100 to 200 MΩ, Uout did not exceed 3 V).
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Bibliography

[1]. Rosanna Rispoli, Elisabetta De Angelis, Luca Colasanti, Nello Vertolli, Stefano Orsini «ELENA microchannel plate detector: absolute detection efficiency for low energy neutral atoms», Optical Engineering, 2013.
[2]. O. Chassela A. Grigoreiv A. Fedorov N. André, «Resistance and gain of the microchannel plate (MCP) detector as a function of temperature», International Conference on Space Optics—ICSO, 2018.
[3]. J Upadhyay, H. R. Bundel, R. Chandra, J. A. Chakera, C.P. Navathe and P.D. Gupta, «A simple power supply and control unit for pulsed operation of a microchannel plate imaging detector», 1998.
[4]. Zhi Qiang, Yang Ye, Yan Bo, Li Jun-guo, Ni Xiao-bing, Wang Yu, Yao Ze, «The Cathode Control Circuit Design of Auto-Gating Power Supply for Low-Light-Level Image Intensifier», Science and Technology on Low-Light-Level Night Vision Laboratory, Xi’an, China, 2015.
[5]. Chengquan Peia, Jinshou Tianb, Zhen Liua, Hong Qinc, Shengli Wua, «A novel ZVS high voltage power supply for micro-channel plate photomultiplier tubes», 2017.
[6]. Cristian H. Belussi, Mariano Gómez Berisso, Yanina Fasano, «Low-noise High-voltage DC Power Supply for Nanopositioning Applications», 2014.
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Authors and Affiliations

Boris Martemianov
1
Alexander Ryzhkov
1
Grigoriy Vdovin
1

  1. Limited Liability Company Vladikavkaz Technological Center "BASPIK", North Osetia

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