Pressure Drop in Rectangular Microchannels as Compared With Theory Based on Arbitrary Cross Section

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Mohsen Akbari ◽  
David Sinton ◽  
Majid Bahrami
Keyword(s):  
Pressure Drop ◽  
Cross Section ◽  
Soft Lithography ◽  
Rectangular Cross Section ◽  
Streaming Potential ◽  
Arbitrary Cross Section ◽  
Working Fluid ◽  
Aspect Ratios ◽  
Flow Through ◽  
Developed Pressure

Pressure driven liquid flow through rectangular cross-section microchannels is investigated experimentally. Polydimethylsiloxane microchannels are fabricated using soft lithography. Pressure drop data are used to characterize the friction factor over a range of aspect ratios from 0.13 to 0.76 and Reynolds number from 1 to 35 with distilled water as working fluid. Results are compared with the general model developed to predict the fully developed pressure drop in arbitrary cross-section microchannels. Using available theories, effects of different losses, such as developing region, minor flow contraction and expansion, and streaming potential on the measured pressure drop, are investigated. Experimental results compare well with the theory based on the presure drop in channels of arbitrary cross section.

Numerical Design of a High-Flux Microchannel Solar Receiver

2013 ◽  
Author(s):  
Charles J. Rymal ◽  
Sourabh V. Apte ◽  
Vinod Narayanan ◽  
Kevin Drost
Keyword(s):  
Pressure Drop ◽  
Cross Section ◽  
Thermal Stresses ◽  
Computational Study ◽  
Rectangular Cross Section ◽  
Working Fluid ◽  
Operating Pressure ◽  
Pin Fin ◽  
Fin Design ◽  
Solar Receiver

This computational study investigates design of microchannel based solar receiver for use in concentrated solar power. A design consisting of a planar array of channels with solar flux incident on one side and using supercritical carbon dioxide as the working fluid is sought. Use of microchannels is investigated as they offer enhanced heat transfer in solar receivers and have the potential to dramatically reduce the size and increase the performance. Designs are investigated for an incident heat flux of 1 MW/m2, up to 3.3 times that of current solar receivers [1], resulting in significant reduction of size and cost. The goal is to design a microchannel receiver with inlet and outlet temperatures of the working fluid of 500°C and 650°C, operating pressure of 100 bar, pressure drop less than 0.35 bar and surface efficiency greater than 90% defined by radiation and convection losses to the environment. Three micro-channel designs are considered: rectangular cross section with high and low aspect ratio (designs A and B) and rectangular cross section with an array of micro pin-fins of various shape spanning the height of the channel (design C). Numerical simulations are performed on individual channels and on a unit cell of the pin-fin design. Structural analysis is performed to ensure that the design can withstand the operating pressure and thermal stresses. The effects of flow maldistribution and header system in an array of channels are also investigated. Preliminary results show that all three designs are capable of meeting the requirements, with the pin-fin design having the lowest pressure drop and highest efficiency.

Analytical and Experimental Characterization of Flow in Slowly-Varying Cross-Section Microchannels

2010 ◽  
Author(s):  
M. Akbari ◽  
M. Bahrami ◽  
D. Sinton
Keyword(s):  
Pressure Drop ◽  
Cross Section ◽  
Cross Sections ◽  
Rectangular Cross Section ◽  
Arbitrary Cross Section ◽  
Geometrical Parameters ◽  
Elliptical Cross ◽  
Proposed Model ◽  
Hyperbolic Contraction ◽  
Asymmetric Microchannel

This paper outlines a novel approximate solution for determining the pressure drop of laminar, single-phase flow in slowly-varying microchannels of arbitrary cross-section. The proposed analysis is general and applicable to symmetric and asymmetric microchannel cross-sections, as examples compact relationships are reported for elliptical and rectangular shapes for three common wall profiles of linear, sinusoidal and hyperbolic. An experimental setup is designed and pressure drop measurements are conducted to validate the proposed model for streamwised periodic microchannels with rectangular cross-section and linear wall with a range of channel geometrical parameters such as aspect ratio and channel slope. The model is also compared against the numerical and experimental data of hyperbolic contraction with rectangular cross-section collected by others. It is observed that although the proposed model is based on the solution of the elliptical cross-section, it can accurately predict the pressure drop in microchannels of rectangular cross-section.

Heat Transfer for Laminar Flow in Spiral Ducts of Rectangular Cross Section

2005 ◽  
Vol 127 (3) ◽  
pp. 352-356 ◽  
Author(s):  
Michael W. Egner ◽  
Louis C. Burmeister
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Laminar Flow ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Three Dimensional ◽  
Radius Of Curvature ◽  
Dean Number ◽  
Aspect Ratios ◽  
Small Pitch

Laminar flow and heat transfer in three-dimensional spiral ducts of rectangular cross section with aspect ratios of 1, 4, and 8 were determined by making use of the FLUENT computational fluid dynamics program. The peripherally averaged Nusselt number is presented as a function of distance from the inlet and of the Dean number. Fully developed values of the Nusselt number for a constant-radius-of-curvature duct, either toroidal or helical with small pitch, can be used to predict those quantities for the spiral duct in postentry regions. These results are applicable to spiral-plate heat exchangers.

scholarly journals Flow through a helical pipe with rectangular cross-section

1970 ◽  
Vol 4 (2) ◽  
pp. 99-110
Author(s):  
Md Mahmud Alam ◽  
Delowara Begum ◽  
K Yamamoto
Keyword(s):  
Aspect Ratio ◽  
Iterative Method ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Main Tool ◽  
Numerical Approach ◽  
Dean Number ◽  
Helical Pipe ◽  
Flow Through ◽  
Marine Engineering

The effects of torsion, aspect ratio and curvature on the flow in a helical pipe of rectangular cross- section are studied by introducing a non-orthogonal helical coordinate system. Spectral method is applied as main tool for numerical approach where Chebyshev polynomial is used. The numerical calculations are obtained by the iterative method. The calculations are carried out for 0≤ δ ≤0.02, 1≤ λ ≤ 2.85, 1≤ γ ≤2.4, at Dn = 50 & 100 respectively, where d is the non-dimensional curvature, l the torsion parameter, g the aspect ratio and  Dn the pressure driven parameter (Dean number).DOI: http://dx.doi.org/10.3329/jname.v4i2.991 Journal of Naval Architecture and Marine Engineering Vol.4(2) 2007 p.99-110

Evaluation of Nusselt number and pressure drop in hexagonal and rectangular micro-channels in the presence of nano-fluids

2020 ◽  
Vol 234 (6) ◽  
pp. 665-672
Author(s):  
S Emami ◽  
MH Dibaei Bonab ◽  
M Mohammadiun ◽  
H Mohammadiun ◽  
M Sadi
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Pressure Drop ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Heat Sinks ◽  
Nano Particles ◽  
Geometrical Parameters ◽  
Micro Channels ◽  
Nano Fluids

Few papers investigated the effect of different nano-fluids and geometrical parameters of the micro channels on the performance of heat sinks. In this study, Nusselt number and pressure drop are investigated in differential geometry and Reynolds numbers. Then the effect of the micro-channel is studied for different heat flux. The results show that hexagonal micro-channels represents a better performance than the rectangular and the heat transfer of without using nano-particles in the hexagonal cross-section is about 9% higher than the rectangular cross-section and with the presence of nanoparticles (Al2O3 - CUO- TiO2, φ  =  4%), heat transfer is about 30 to 40% higher than the base liquid.

Secondary Flow and Hydraulic Losses Within Sinuous Conduits of Rectangular Cross Section

1992 ◽  
Vol 114 (4) ◽  
pp. 593-600 ◽  
Author(s):  
Yukimaru Shimizu ◽  
Yoshiki Futaki ◽  
C. Samuel Martin
Keyword(s):  
Aspect Ratio ◽  
Secondary Flow ◽  
Cross Section ◽  
Rectangular Cross Section ◽  
Flow Patterns ◽  
Geometric Configuration ◽  
Hydraulic Losses ◽  
Aspect Ratios ◽  
Wide Range ◽  
The Relationship

This paper describes the relationship between hydraulic losses and secondary flow within sinuous conduits with complicated bends. It has been found that the nature of secondary flow present in the bends is quite sensitive to the geometric configuration of the bend and the actual aspect ratio of the conduit section. Indeed, many different secondary flow patterns have been found to exist as the bend geometry is altered. A wide range of experiments has been conducted for various aspect ratios of a rectangular conduit with different curvatures.

scholarly journals INFLUENCE OF SKIN EFFECT ON THE CALCULATION OF BUSBAR SYSTEMS HAVING RECTANGULAR CROSS SECTION

2021 ◽  
Vol 20 (1) ◽  
pp. 057
Author(s):  
Nebojša Raičević ◽  
Ana Vučković ◽  
Mirjana Perić ◽  
Slavoljub Aleksić
Keyword(s):  
Electromagnetic Field ◽  
Cross Section ◽  
Current Density ◽  
Proximity Effect ◽  
Skin Effect ◽  
Rectangular Cross Section ◽  
Error Function ◽  
Current Density Distribution ◽  
Accurate Solution ◽  
Flow Through

One method for the calculation of current density distribution in a finite number of long parallel conductors, having rectangular cross section, is proposed in this paper. Numerical results aim to highlight the importance of the skin effect, which can be combined with the proximity effect. The method of superposition of these two effects was applied to the calculation of the electromagnetic field in electric power busbars systems. It has been shown that the skin effect has a much greater impact, especially when the conductors are thin and strong electric currents flow through them, so special attention is paid to its calculation. For numerical solution the integral equations are used. The function of current density is approximated by the finite functional series. This way leads to a very accurate solution with only two terms. Differential evolution method is applied for minimization of error function. To demonstrate the application of the proposed approach, numerical values for busbars are presented and compared with values obtained by using the finite elements method.

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