Next Article in Journal
Charged Satellite Drop Avoidance in Electrohydrodynamic Dripping
Next Article in Special Issue
Gas Mixing and Final Mixture Composition Control in Simple Geometry Micro-mixers via DSMC Analysis
Previous Article in Journal
Three-Dimensional Printed Piezoelectric Array for Improving Acoustic Field and Spatial Resolution in Medical Ultrasonic Imaging
Previous Article in Special Issue
Interactive Effects of Rarefaction and Surface Roughness on Aerodynamic Lubrication of Microbearings
Open AccessArticle

A Comparison of Data Reduction Methods for Average Friction Factor Calculation of Adiabatic Gas Flows in Microchannels

Microfluidics Laboratory, Department of Industrial Engineering (DIN), University of Bologna, Via del Lazzaretto 15/5, 40131 Bologna BO, Italy
Microscale Heat Transfer Laboratory, Department of Mechanical Engineering, Kagoshima University, Kagoshima Prefecture 890-8580, Japan
Author to whom correspondence should be addressed.
Micromachines 2019, 10(3), 171;
Received: 9 February 2019 / Revised: 9 February 2019 / Accepted: 23 February 2019 / Published: 28 February 2019
(This article belongs to the Special Issue Gas Flows in Microsystems)
In this paper, a combined numerical and experimental approach for the estimation of the average friction factor along adiabatic microchannels with compressible gas flows is presented. Pressure-drop experiments are performed for a rectangular microchannel with a hydraulic diameter of 295 μ m by varying Reynolds number up to 17,000. In parallel, the calculation of friction factor has been repeated numerically and results are compared with the experimental work. The validated numerical model was also used to gain an insight of flow physics by varying the aspect ratio and hydraulic diameter of rectangular microchannels with respect to the channel tested experimentally. This was done with an aim of verifying the role of minor loss coefficients for the estimation of the average friction factor. To have laminar, transitional, and turbulent regimes captured, numerical analysis has been performed by varying Reynolds number from 200 to 20,000. Comparison of numerically and experimentally calculated gas flow characteristics has shown that adiabatic wall treatment (Fanno flow) results in better agreement of average friction factor values with conventional theory than the isothermal treatment of gas along the microchannel. The use of a constant value for minor loss coefficients available in the literature is not recommended for microflows as they change from one assembly to the other and their accurate estimation for compressible flows requires a coupling of numerical analysis with experimental data reduction. Results presented in this work demonstrate how an adiabatic wall treatment along the length of the channel coupled with the assumption of an isentropic flow from manifold to microchannel inlet results in a self-sustained experimental data reduction method for the accurate estimation of friction factor values even in presence of significant compressibility effects. Results also demonstrate that both the assumption of perfect expansion and consequently wrong estimation of average temperature between inlet and outlet of a microchannel can be responsible for an apparent increase in experimental average friction factor in choked flow regime. View Full-Text
Keywords: underexpansion; Fanno flow; flow choking; compressibility underexpansion; Fanno flow; flow choking; compressibility
Show Figures

Figure 1

MDPI and ACS Style

Rehman, D.; Morini, G.L.; Hong, C. A Comparison of Data Reduction Methods for Average Friction Factor Calculation of Adiabatic Gas Flows in Microchannels. Micromachines 2019, 10, 171.

Show more citation formats Show less citations formats
Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Article Access Map by Country/Region

Search more from Scilit
Back to TopTop