CFD Studies on Pressure Drop for Low Reynolds Fluid Flows Across Orifice in Similarly Shaped Microchannel
Microfluidic devices have great potential in the fields of automation and miniaturization for handling and analysis of fluids. In the present work, study on single-phase flow across orifice in similar shaped microchannel (circular) was carried out under i
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1 Introduction Microfluidic devices have great potential in the fields of automation and miniaturization for handling and analysis of fluids resulting in faster and economical diagnostic procedures. These include enhancement in mass and heat transfer rates, improved energy efficiency, low by-product formation and inherent safety (Zhao et al. 2006; Dessimoz et al. 2008). It has a wide range of applications in the areas of biotechnology, diagnostics, medicine and biosecurity (Jensen 2001; Abgrall and Gue 2007; Haeberle and Zengerle 2007; Melin and Quake 2007). Power requirement of a microfluidic device, which depends on the pressure drop across the device, is an important factor to be considered. This study deals with analysis of pressure drop across an orifice placed in a similarly shaped microchannel.
2 Problem Statement In the present work, the orifice was positioned mid-way along the microchannel length to give equal upstream and downstream lengths. This arrangement was to ensure that the velocity profiles at the inlet and outlet of the microchannel were fully developed. The studies were carried out to determine pressure drop across an G. Bhuvaneswari H.M. Reddy V.V. Ananthula (&) Department of Chemical Engineering, National Institute of Technology, Warangal 506004, Telangana, India e-mail: [email protected] G. Bhuvaneswari e-mail: [email protected] H.M. Reddy e-mail: [email protected] © Springer Science+Business Media Singapore 2016 I. Regupathi et al. (eds.), Recent Advances in Chemical Engineering, DOI 10.1007/978-981-10-1633-2_39
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Fig. 1 Circular microchannel with similar shaped orifice Table 1 Reynolds number at different mean velocities (at 28 °C) Feed solution
Re(Um = 50 µm/s)
Re(Um = 60 µm/s)
Re(Um = 70 µm/s)
Re(Um = 80 µm/s)
1.5 % CMC aqueous solution
0.000265
0.000318
0.000371
0.000424
Water
0.024
0.028
0.033
0.038
orifice in a microchannel, varying the fluid velocity (Um ), orifice contraction ratio (cdo ¼ d=D) and orifice length to diameter ratio (kdo ¼ l=d). Figure 1 shows the arrangement of micro channel and orifice (Table 1).
3 Numerical Solution The following assumptions were made in solving the problem of steady laminar flow in microchannel: (i) The flow is axial (One dimensional), (ii) the flow is laminar, (iii) there is no slip at the wall, (iv) no heat transfer to/from surroundings, (v) the energy dissipation is negligible, (vi) fluid/wall interaction is purely viscous, (vii) straight channel walls, (viii) the smooth walls. The governing partial differential equations were numerically solved by finite volume method with multi-grid solver with high resolution in the commercial CFD code CFX 14.0. A refined mesh with tetrahedral elements was used in simulation. The RMS convergence criterion used was about 1 10−5 for all variables calculated.
4 Results and Discussion 4.1
Mesh Independency Test
Mesh independency test was carried out for circular microchannel of 400 µm diameter and 4000 µm length using water as the fluid. The refined mesh
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