Multi-Objective Optimization of Laminar Heat Transfer and Friction Factor in Rectangular Microchannel With Rectangular Vortex Generators: An Application of NSGA-II With Gene Expression Programing Metamodel

2017 ◽  
Vol 139 (7) ◽  
Author(s):  
Aparesh Datta ◽  
Ajoy Kumar Das ◽  
Prasenjit Dey ◽  
Dipankar Sanyal
Keyword(s):  
Gene Expression ◽  
Heat Transfer ◽  
Friction Factor ◽  
Numerical Study ◽  
Vortex Generator ◽  
Algorithm Optimization ◽  
Nsga Ii ◽  
Rectangular Microchannel ◽  
Numerical Predictions ◽  
The Cost

Improvement of the effectiveness of heat exchanger is the demand of compact and efficient cooling devices. In that respect, a numerical study of fluid flow and heat transfer has been conducted with different arrangements of simple vortex generator (VG) in a rectangular microchannel Reynolds number (Re) in the range between 200 and 1100. The combined effect of spanwise and pitchwise distance of VG on heat transfer is investigated rigorously to observe the dependence of heat transfer on both. By processing the numerical predictions through gene expression programing and genetic algorithm optimization, the output variations in heat transfer, or Nusselt number, and friction factor with Re and locations of VGs in the channel are predicted in the form of explicit equations. The predicted monotonic increase of the outputs with Re shows heat transfer enhancement of 40–135% at the cost of increased pressure drop by 62–186.7% with respect to channels without VGs.

Numerical Study on Effect of Secondary Surface on Rectangular Vortex Generator

2020 ◽  
Vol 13 (1) ◽  
Author(s):  
Uddip Kashyap ◽  
Koushik Das ◽  
Biplab Kumar Debnath ◽  
Upasana Kashyap ◽  
Sandip K. Saha
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Heated Surface ◽  
Linear Regression Analysis ◽  
Vortex Generator ◽  
Heat Extraction ◽  
Heated Plate ◽  
Primary Vortex ◽  
Reference Case ◽  
Numerical Predictions

Abstract One way of achieving higher efficiency in electro-mechanical is by inducing vortices over the heated surface with the help of a vortex generator (VG). The strength of these vortices is proportionate to the amount of heat transported. In this paper, the evolution and propagation of the produced primary vortex behind a VG with the attached secondary surface (SS) are studied experimentally and numerically. The addition of SS is found to augment heat transfer significantly with an additional drag. The obtained experimental results complement the numerical predictions for the modified VG. Linear regression analysis is performed to optimize the geometry of SS for a higher heat extraction rate and lower drag. The SS placed at an optimum location increases the Nusselt number on the heated plate by 8.9%, with a decrement in the drag by 3.2%, compared to the reference case. The addition of SS produces a vortex of higher strength and propagates downstream at a slower rate. Moreover, it exposes the vortex to higher shear in the flow, which in turn enhances the heat transfer rate.

Experimental and Numerical Study of Methanol-Water Mixture Single-Phase Heat Transfer in a Micro-Channel Heat Sink

2012 ◽  
Author(s):  
Chun K. Kwok ◽  
Matthew M. Asada ◽  
Jonathan R. Mita ◽  
Weilin Qu
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Sink ◽  
Single Phase ◽  
Numerical Study ◽  
Pure Water ◽  
Molar Fraction ◽  
Water Mixture ◽  
Micro Channel ◽  
Numerical Predictions

This paper presents an experimental study of single-phase heat transfer characteristics of binary methanol-water mixtures in a micro-channel heat sink containing an array of 22 microchannels with 240μm × 630μm cross-section. Pure water, pure methanol, and five methanol-water mixtures with methanol molar fraction of 16%, 36%, 50%, 63% and 82% were tested. Key parametric trends were identified and discussed. The experimental study was complemented by a three-dimensional numerical simulation. Numerical predictions and experimental data are in good agreement with a mean absolute error (MAE) of 0.87%.

Fluid Flow and Heat Transfer Behavior for Turbulent Flows in a Tube With Vortex Generator Pairs for an Efficient Heat Exchanger

2018 ◽  
Author(s):  
Md. Islam ◽  
Z. Chong ◽  
S. Bojanampati
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Factor ◽  
Turbulent Flows ◽  
Flow Behavior ◽  
Vortex Generator ◽  
Tube Diameter ◽  
Vortex Generators ◽  
Blockage Ratio ◽  
Delta Winglet

Various technologies have been developed to enhance flow mixing and heat transfer in order to develop an efficient compact heat exchanging devices. Vortex generators/turbulent promoters generate the vortices which reduce the boundary layer thickness and introduce the better mixing of the fluid to enhance the heat transfer. In this research experimental investigations have been carried out to study the effect of delta winglet vortex generator pairs on heat transfer and flow behavior. To generate longitudinal vortex flow, two pairs of the delta winglet vortex generators (DWVG) with the length of 10mm and winglet-pitch to tube-diameter ratio (PR = 4.8) are mounted on the inner wall of a circular tube. The DWVG pairs with two different winglet-height to tube-diameter ratios (Blockage ratio, BR = 0.1 and 0.2), three attack angles (α = 10°, 20°, 30°) and three spacings between leading edges (S = 10, 15 and 20mm) are studied. The experiments were conducted with DWVGs pairs for the air flow range of Reynolds numbers 5000–25000. The influence of the DWVGs on heat transfer and pressure drop was investigated in terms of the Nusselt number and friction factor. The experimental results indicate that DWVG pair in a tube results in a considerable enhancement in Nusselt number (Nu) with some pressure penalty. It is found that DWVG increases Nu up to 85% over the smooth tube. It is also observed that Nusselt number increases with Re, blockage ratio and attack angle. Friction factor decreases with Re but increases with blockage ratio, spacing and attack angle. And 30° DWVG pair with S = 20mm, BR = 0.2 gets the highest friction factor. The Highest thermal performance enhancement (TPE) was noticed for α = 10°, S = 20mm, BR = 0.2 for turbulent flows. To obtain qualitative information on the flow behavior and vortex structures, flow was visualized by laser sheet using smoke as a tracer supplied at the entrance of the test section. The generation and development of longitudinal vortices influenced by DWVG pairs were clearly observed.

Numerical Investigation of a Crossflow Jet in a Rectangular Microchannel

2013 ◽  
Vol 284-287 ◽  
pp. 849-853
Author(s):  
Kok Cheong Wong
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Numerical Study ◽  
Three Dimensional ◽  
Horizontal Flow ◽  
Transfer Performance ◽  
Rectangular Microchannel ◽  
Transverse Jet ◽  
Nozzle Position ◽  
Jet Nozzle

The present numerical study is conducted in three dimensional to investigate the crossflow of an external round jet and a horizontal stream of microchannel flow. The results of heat transfer performance for the cases with and without transverse jet are compared. The patterns of different crossflow jet were analyzed to understand the flow and heat transfer characteristics. The effect of jet nozzle position on the heat transfer is investigated. Generally, the heat transfer performance increases with the jet Reynolds number. However, some cases of weak jet are found to cause lower heat transfer rate relative to the case without external jet. When vertical weak jet encounter strong horizontal flow, the horizontal flow is dominant that the jet cannot reach the microchannel bottom wall but imposes resistance to the horizontal flow. The investigation on the jet nozzle location shows that the jet nozzle location closer to the channel inlet gives better heat transfer performance.

Nonlinear Study of Convective Heat Transfer in Tightly Curved Rectangular Microchannels

2016 ◽  
Author(s):  
Fang Liu
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Steady State ◽  
Friction Factor ◽  
Flow Instability ◽  
Numerical Study ◽  
Chaotic Oscillation ◽  
Periodic Oscillation ◽  
Stable Steady State ◽  
Rectangular Microchannels

To address the effects of curvature, initial conditions and disturbances, a numerical study is made on the fully-developed bifurcation structure and stability of the forced convection in tightly curved rectangular microchannels of aspect ratio 10 and curvature ratio 0.5 at Prandtl number 7.0. Eleven solution branches (seven symmetric and four asymmetric) are found with 10 bifurcation points and 27 limit points. The flows on these branches are with 2, 4, 6, 7, 8, 9 or 10-cell structures. The flow structures change along the branch because of the flow instability. The average friction factor and Nusselt Number are different on different solution branches. It is found that more than 22.33% increase in Nu can be achieved with less than 9.34% increase in fRe at Dk of 2000. As Dean number increases, finite random disturbances lead the flows from a stable steady state to another stable steady state, a periodic oscillation, an intermittent oscillation, another periodic oscillation and a chaotic oscillation. The mean friction factor and mean Nusselt Number are obtained for all physically realizable flows. A significant enhancement of heat transfer can be obtained at the expense of a slightly increase of flow friction in tightly coiled rectangular ducts.

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