Numerical Investigation of Heat Transfer in Rough Microchannels Using a Kinetic Continuum Solver

2015 ◽  
Author(s):  
Olga Rovenskaya ◽  
Giulio Croce
Keyword(s):  
Heat Transfer ◽  
Slip Boundary Condition ◽  
Navier Stokes ◽  
Channel Height ◽  
First Order ◽  
Slip Boundary ◽  
Relative Roughness ◽  
Flow And Heat Transfer ◽  
Hybrid Solutions ◽  
Hybrid Solver

A numerical analysis of flow and heat transfer fields in a rough microchannel is carried out using a hybrid solver dynamically coupling kinetic and Navier–Stokes solutions computed in local rarefied and continuum areas of the flow, respectively. The roughness geometry is modeled as a series of triangular obstructions and a relative roughness up to 5% of the channel height is considered. Keeping Mach number low (incompressible flow) while varying Knudsen number allow us to investigate different rarefaction levels of the flow. The competition between roughness, rarefaction and heat transfer effects is discussed in terms of averaged Nusselt and Poiseuille numbers and mass flow rate. Discrepancy between the full Navier–Stokes and hybrid solutions is investigated, assessing the range of applicability of the first order slip boundary condition for rough geometries with and without heat transfer presence.

Effect of slip boundary condition on flow and heat transfer of a double fractional Maxwell fluid

2020 ◽  
Vol 68 ◽  
pp. 214-223 ◽  
Author(s):  
Weidong Yang ◽  
Xuehui Chen ◽  
Zeyi Jiang ◽  
Xinru Zhang ◽  
Liancun Zheng
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Maxwell Fluid ◽  
Slip Boundary Condition ◽  
Slip Boundary ◽  
Flow And Heat Transfer

Numerical Analysis of Rarefaction and Compressibility Effects in Bent Microchannels

2010 ◽  
Author(s):  
O. Rovenskaya ◽  
G. Croce
Keyword(s):  
Gas Flow ◽  
Flow Characteristics ◽  
Wall Slip ◽  
Outer Wall ◽  
Slip Boundary Condition ◽  
Central Line ◽  
Navier Stokes ◽  
Strong Impact ◽  
First Order ◽  
Slip Boundary

Numerical investigation of a gas flow through microchannels with a sharp, 90 degrees bend is carried out using Navier-Stokes (N-S) equations with the classical Maxwell first-order slip boundary condition, including the tangential gradient effect due to the wall curvature, and Smoluchowski first order temperature jump definition. The details of the flow structure near the corner are analyzed, investigating the competing effects of rarefaction and compressibility on the channel performances. The flow characteristics in terms of velocity profiles, slip velocity distribution along inner and outer wall, pressure, average Mach number along central line of the channel have been presented. The results showed that impact of the bend on the channel performances is smaller at high rarefaction levels. The behaviour of pressure and velocity away from the bend is similar to that of a straight microchannel; however, the asymmetry in the flow at the bend, with high velocities and high velocity gradients on its inner side, has a strong impact on wall slip velocities. The presence of a recirculation is detected on both the inner and outer walls of the corner for larger Reynolds. However, rarefaction may delay the onset of recirculation. It is also observed that the mass flux through a bend microchannel can even be slightly larger than that through a straight microchannel of the same length and subjected to the same pressure difference.

Numerical Investigation of Slip Flow and Heat Transfer in Rotating Rectangular Microchannels

2012 ◽  
Author(s):  
Pratanu Roy ◽  
N. K. Anand ◽  
Debjyoti Banerjee
Keyword(s):  
Heat Transfer ◽  
Boundary Condition ◽  
Convective Heat Transfer ◽  
Secondary Flow ◽  
Convective Heat ◽  
Slip Flow ◽  
Slip Boundary Condition ◽  
Fluid Temperature ◽  
Slip Boundary ◽  
Flow And Heat Transfer

Investigation of fluid flow and heat transfer in rotating microchannels is important for centrifugal microfluidics, which has emerged as an advanced technique in biomedical applications and chemical separations. The pseudo forces namely the centrifugal force and the Coriolis force arising as a consequence of the rotating reference frame change the flow pattern significantly from the parabolic profile in a non-rotating channel. The convective heat transfer process is also influenced by the secondary flow introduced by the rotational effect. Moreover, if the microchannel wall is hydrophobic, slip flow can occur inside the channel when the conventional no slip boundary condition is no longer valid. In this work, we have numerically investigated the flow and heat transfer inside a straight rotating rectangular microchannel in the slip flow regime. A pressure based finite volume technique in a staggered grid was applied to solve the steady incompressible Navier-Stokes and energy equations. It has been observed that, depending on the rotational velocity, different slip velocities are induced at the channel walls. The average fluid temperature increases with the increase of rotation as convective heat transfer mechanism is increased due to the secondary flow. However, the slip boundary condition has a negligible effect on the temperature profiles.

Investigation of Heat Transfer in Microchannels With Asymmetric and Periodic Slip at the Walls

2010 ◽  
Author(s):  
Akshay C. Gunde ◽  
Suman Chakraborty ◽  
Sushanta K. Mitra
Keyword(s):  
Heat Transfer ◽  
Slip Length ◽  
Slip Boundary Condition ◽  
Fluid Interfaces ◽  
Theoretical Studies ◽  
X Ray ◽  
Silicon Chips ◽  
Slip Boundary ◽  
Flow And Heat Transfer ◽  
Transport Fluid

Recent development of microfluidic applications in various areas like cooling of silicon chips, VLSI, aircraft avionics, X-Ray and laser equipments has led to an increased study of coupled fluid flow and heat transfer in microchannels. A major issue in the mathematical modeling of these phenomena is the applicability of the no-slip boundary condition at solid-fluid interfaces. Most of such micro-scale investigations consider a slip velocity at solid boundaries, which has been observed in a number of experiemntal studies [1], [2]. In cases involving the heating of substrate and/or transport fluid, definite formation of nanobubbles from the fluid has been established [3]. These bubbles migrate to the channel walls and deposit on them in the form of random clusters. As a result, due to the minimized shear resistance offered by the surfaces of such bubbles to the fluid, variation in slip length is observed along the channel walls. Hence, in order that theoretical studies lead to physically acceptable results required for the fabrication of microfluidic devices, such variation of slip length encountered by a fluid in a microchannel must be included in these analysis.

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