Flow characteristics of water in microtubes
TL;DR: In this paper, a roughness-viscosity model was proposed to interpret the experimental data and the results indicated significant departure of flow characteristics from the predictions of the conventional theory for microtubes with smaller diameters.
About: This article is published in International Journal of Heat and Fluid Flow.The article was published on 1999-04-01. It has received 711 citations till now. The article focuses on the topics: Water flow & Pressure drop.
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TL;DR: A review of experimental studies regarding the phenomenon of slip of Newtonian liquids at solid interfaces is provided in this article, with particular attention to the effects that factors such as surface roughness, wettability and the presence of gaseous layers might have on the measured interfacial slip.
Abstract: For several centuries fluid dynamics studies have relied upon the assumption that when a liquid flows over a solid surface, the liquid molecules adjacent to the solid are stationary relative to the solid. This no-slip boundary condition (BC) has been applied successfully to model many macroscopic experiments, but has no microscopic justification. In recent years there has been an increased interest in determining the appropriate BCs for the flow of Newtonian liquids in confined geometries, partly due to exciting developments in the fields of microfluidic and microelectromechanical devices and partly because new and more sophisticated measurement techniques are now available. An increasing number of research groups now dedicate great attention to the study of the flow of liquids at solid interfaces, and as a result a large number of experimental, computational and theoretical studies have appeared in the literature. We provide here a review of experimental studies regarding the phenomenon of slip of Newtonian liquids at solid interfaces. We dedicate particular attention to the effects that factors such as surface roughness, wettability and the presence of gaseous layers might have on the measured interfacial slip. We also discuss how future studies might improve our understanding of hydrodynamic BCs and enable us to actively control liquid slip.
985 citations
TL;DR: In this article, an experimental investigation was conducted to explore the validity of classical correlations based on conventionalsized channels for predicting the thermal behavior in single-phase flow through rectangular microchannels.
752 citations
Cites background from "Flow characteristics of water in mi..."
...the deviation from classical theory have included surface roughness [4], electrical double layer [5] and aspect ratio [6] effects....
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TL;DR: In this article, a bibliographical review on the convective heat transfer through microchannels is presented, highlighting the main results obtained on the friction factor, on the laminar-to-turbulent transition and on the Nusselt number in channels having a hydraulic diameter less than 1 mm.
647 citations
TL;DR: In this article, the authors investigated heat transfer characteristics of water flowing through trapezoidal silicon microchannels with a hydraulic diameter ranging from 62 to 169 μm and found that the measured lower Nusselt numbers may be due to the effects of surface roughness of the microchannel walls.
384 citations
Cites methods from "Flow characteristics of water in mi..."
...Based on Merkle et al.’s modified-viscosity model [6], Mala and Li [ 4 ] suggested a roughness-viscosity model which accounts for this additional momentum transfer by introducing a roughness-viscosity mR in a manner similar to the eddy-viscosity concept in the turbulent flow model....
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TL;DR: In this paper, a roughness-viscosity model was proposed to interpret the experimental data and showed that pressure gradient and flow friction in microchannels are higher than those given by the conventional laminar flow theory.
384 citations
Cites background or methods from "Flow characteristics of water in mi..."
...The detailed information about how to determine the empirical relation for A can be found elsewhere, [7]....
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...Based on Merkle's modi®ed viscosity model, Mala and Li [7] suggested a roughness viscosity model and applied it to explain the eects of the surface roughness on laminar ̄ow in microtubes....
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...Mala and Li [7] measured pressure gradients of water ̄ow in microtubes with inner diameter ranging from 50....
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References
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Book•
01 Jan 1955
TL;DR: The flow laws of the actual flows at high Reynolds numbers differ considerably from those of the laminar flows treated in the preceding part, denoted as turbulence as discussed by the authors, and the actual flow is very different from that of the Poiseuille flow.
Abstract: The flow laws of the actual flows at high Reynolds numbers differ considerably from those of the laminar flows treated in the preceding part. These actual flows show a special characteristic, denoted as turbulence. The character of a turbulent flow is most easily understood the case of the pipe flow. Consider the flow through a straight pipe of circular cross section and with a smooth wall. For laminar flow each fluid particle moves with uniform velocity along a rectilinear path. Because of viscosity, the velocity of the particles near the wall is smaller than that of the particles at the center. i% order to maintain the motion, a pressure decrease is required which, for laminar flow, is proportional to the first power of the mean flow velocity. Actually, however, one ob~erves that, for larger Reynolds numbers, the pressure drop increases almost with the square of the velocity and is very much larger then that given by the Hagen Poiseuille law. One may conclude that the actual flow is very different from that of the Poiseuille flow.
17,321 citations
TL;DR: In this article, the friction factors for the flow of gases in the fine channels used for microminiature Joule-Thomson refrigerators have been measured using a photolithographic technique.
524 citations
TL;DR: In this paper, the authors investigated the single-phase forced-flow convection of water or methanol flowing through microchannels with rectangular cross-section and found that the fully developed turbulent convection regime was initiated at about Re = 1000-1500.
418 citations
TL;DR: In this paper, the authors investigated the flow characteristics of water flowing through rectangular microchannels having hydraulic diameters of 0.133-0.367 mm and H/W ratios between 0.333-1.72i.
Abstract: Experiments were conducted to investigate the flow characteristics of water flowing through rectangular microchannels having hydraulic diameters of 0.133-0.367 mm and H/W ratios of 0.333-1. Experimental results indicated that the laminar flow transition occurred at Reynolds numbers of 200-700. This critical Re for the laminar transition was strongly affected by the hydraulic diameter, decreasing with corresponding decreases in the microchannel. In addition, the size of the transition range was diminished and fully developed turbulent flow also occurred at much lower Re. The friction behavior of both the laminar and turbulent flow was found to depart from the classical thermqfluid correlations. lite friction factor, f, was found to be proportional to Re−1.98 rather than Re for the laminar condition, and proportional to Re−1.72i for turbulent flow. The geometric parameters, hydraulic diameter, and H/W were found to be the most important parameters and had a critical effect on the flow. Generally, increasing...
366 citations
TL;DR: In this article, heat transfer characteristics have been measured for the flow of gas in the fine channels of the heat exchangers used for microminiature J-T refrigerators.
315 citations