Single-Phase Capillary Effects in Rectangular Microchannels Heat Sinks

2007 ◽  
Author(s):  
Carlos A. Rubio-Jime´nez ◽  
Jesu´s Garci´a-Gonza´lez ◽  
Abel Herna´ndez-Guerrero ◽  
Daniela Popescu
Keyword(s):  
Fluid Flow ◽  
Rectangular Cross Section ◽  
Reynolds Numbers ◽  
Constant Heat Flux ◽  
Heat Sinks ◽  
High Tech ◽  
Cooling Fluid ◽  
Capillary Effects ◽  
Channel Water ◽  
Necessary And Sufficient

In this work a steady state numerical analysis of the capillary effects in channels of a microscopic scale with rectangular cross section is presented. The diameter range under analysis falls on the microchannels classification. The velocities of the fluid flow satisfy the condition We<<Re, necessary and sufficient condition to guarantee that the capillary effects are present in the fluid flow in the channel. Water is used as the cooling fluid. A constant heat flux is applied at the heat sink bottom wall with a rating typical of the generated heat flow in current electronics high-tech devices. The results of thermal resistance are compared with the experimental results of Tuckerman, and the friction coefficient is compared with Peng and Peterson experiments, showing a good approximation when the capillary effects are considered in the numerical solution at lower Reynolds numbers.

Hydrodynamic Characteristics of Micro Heat Sinks With In-Line and Staggered Arrangements of Cylindrical Micro Pin Fins

2017 ◽  
Author(s):  
Ali Mohammadi ◽  
Ali Koşar
Keyword(s):  
Reynolds Numbers ◽  
Constant Heat Flux ◽  
Heat Sinks ◽  
Hydrodynamic Characteristics ◽  
Bottom Surface ◽  
Ansys Fluent ◽  
Phase Study ◽  
Pin Fins ◽  
Interacting Surfaces ◽  
Micro Pin Fins

This study compares the hydraulic performance of rectangular micro heat sinks (MHS) with different in-line and staggered arrangements of micro pin fins (MPF). With fixed MHS dimensions of 50 × 1.5 × 0.1 mm3 (1 × w × h), the height (H) and diameter (D) of MPFs are both set to be 0.1 mm which corresponds to a fixed H/D ratio of 1 in all cases. Four in-line and four staggered arrangements of MPFs with alternative horizontal and vertical pitch ratios (SL/D and ST/D) of 1.5 and 3 are considered. Streamline profiles are used to illustrate the flow patterns and wake regions. Using ANSYS FLUENT v.14.5 for this single phase study, the simulations are done at five Reynolds numbers of 20, 40, 80, 120 and 150, ensuring the flow remains in the laminar flow regime. Considering water as the coolant, a constant heat flux of 30 W/cm2 is applied through the bottom surface of the MHS and the MPFs liquid interacting surfaces. The results show a great dependency of the evaluating parameters on the arrangement type, geometrical specification and Reynolds numbers. For pressure drop, clear comparison could be made regarding each of the geometrical specifications. However, the trends with friction factor depend on geometrical specification and Reynolds number at the same time.

Experimental and Analytical Investigation of Compact Liquid Cooled Heat Sinks

2004 ◽  
Author(s):  
M. Zugic ◽  
J. R. Culham ◽  
P. Teertstra ◽  
Y. Muzychka ◽  
K. Horne ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Experimental Tests ◽  
Reynolds Numbers ◽  
High Heat ◽  
Analytical Investigation ◽  
Boundary Resistance ◽  
Heat Fluxes ◽  
Heat Sinks ◽  
Air Cooling ◽  
Design Tools

Compact, liquid cooled heat sinks are used in applications where high heat fluxes and boundary resistance preclude the use of more traditional air cooling techniques. Four different liquid cooled heat sink designs, whose core geometry is formed by overlapped ribbed plates, are examined. The objective of this analysis is to develop models that can be used as design tools for the prediction of overall heat transfer and pressure drop of heat sinks. Models are validated for Reynolds numbers between 300 and 5000 using experimental tests. The agreement between the experiments and the models ranges from 2.35% to 15.3% RMS.

Meshless local Petrov–Galerkin method-higher Reynolds numbers fluid flow applications

2012 ◽  
Vol 36 (11) ◽  
pp. 1671-1685 ◽  
Author(s):  
Mohammad Najafi ◽  
Ali Arefmanesh ◽  
Vali Enjilela
Keyword(s):  
Fluid Flow ◽  
Galerkin Method ◽  
Reynolds Numbers

Compact Modeling of Fluid Flow and Heat Transfer in Straight Fin Heat Sinks

2004 ◽  
Vol 126 (2) ◽  
pp. 247-255 ◽  
Author(s):  
Duckjong Kim ◽  
Sung Jin Kim
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Fluid Flow ◽  
Pressure Drop ◽  
Heat Sink ◽  
Volume Averaging ◽  
Thermal Design ◽  
Heat Sinks ◽  
Compact Modeling ◽  
Flow And Heat Transfer

In the present work, a compact modeling method based on a volume-averaging technique is presented. Its application to an analysis of fluid flow and heat transfer in straight fin heat sinks is then analyzed. In this study, the straight fin heat sink is modeled as a porous medium through which fluid flows. The volume-averaged momentum and energy equations for developing flow in these heat sinks are obtained using the local volume-averaging method. The permeability and the interstitial heat transfer coefficient required to solve these equations are determined analytically from forced convective flow between infinite parallel plates. To validate the compact model proposed in this paper, three aluminum straight fin heat sinks having a base size of 101.43mm×101.43mm are tested with an inlet velocity ranging from 0.5 m/s to 2 m/s. In the experimental investigation, the heat sink is heated uniformly at the bottom. The resulting pressure drop across the heat sink and the temperature distribution at its bottom are then measured and are compared with those obtained through the porous medium approach. Upon comparison, the porous medium approach is shown to accurately predict the pressure drop and heat transfer characteristics of straight fin heat sinks. In addition, evidence indicates that the entrance effect should be considered in the thermal design of heat sinks when Re Dh/L>∼O10.

scholarly journals The transient swimming of a waving sheet

2009 ◽  
Vol 466 (2113) ◽  
pp. 107-126 ◽  
Author(s):  
On Shun Pak ◽  
Eric Lauga
Keyword(s):  
Fluid Flow ◽  
Reynolds Numbers ◽  
Geometrical Model ◽  
Small Scale ◽  
Transient Effects ◽  
Initial Value ◽  
Low Reynolds Numbers ◽  
The Past ◽  
Low Reynolds Number Swimming ◽  
Low Reynolds

Small-scale locomotion plays an important role in biology. Different modelling approaches have been proposed in the past. The simplest model is an infinite inextensible two-dimensional waving sheet, originally introduced by Taylor, which serves as an idealized geometrical model for both spermatozoa locomotion and ciliary transport in Stokes flow. Here, we complement classic steady-state calculations by deriving the transient low-Reynolds number swimming speed of such a waving sheet when starting from rest (small-amplitude initial-value problem). We also determine the transient fluid flow in the ‘pumping’ setup where the sheet is not free to move but instead generates a net fluid flow around it. The time scales for these two problems, which in general govern transient effects in transport and locomotion at low Reynolds numbers, are also derived using physical arguments.

scholarly journals Simulation of Nanofluid Flow in a Micro-Heat Sink With Corrugated Walls Considering the Effect of Nanoparticle Diameter on Heat Sink Efficiency

2021 ◽  
Vol 9 ◽  
Author(s):  
Yacine Khetib ◽  
Hala M. Abo-Dief ◽  
Abdullah K. Alanazi ◽  
Goshtasp Cheraghian ◽  
S. Mohammad Sajadi ◽  
...  
Keyword(s):  
Heat Sink ◽  
Figure Of Merit ◽  
Reynolds Numbers ◽  
Constant Heat Flux ◽  
Maximum Temperature ◽  
Nanofluid Flow ◽  
Numerical Work ◽  
Volume Percentage ◽  
Flow And Heat Transfer ◽  
20 Nm

In this numerical work, the cooling performance of water–Al2O3 nanofluid (NF) in a novel microchannel heat sink with wavy walls (WMH-S) is investigated. The focus of this article is on the effect of NP diameter on the cooling efficiency of the heat sink. The heat sink has four inlets and four outlets, and it receives a constant heat flux from the bottom. CATIA and CAMSOL software were used to design the model and simulate the NF flow and heat transfer, respectively. The effects of the Reynolds number (Re) and volume percentage of nanoparticles (Fi) on the outcomes are investigated. One of the most significant results of this work was the reduction in the maximum and average temperatures of the H-S by increasing both the Re and Fi. In addition, the lowest Tmax and pumping power belong to the state of low NP diameter and higher Fi. The addition of nanoparticles reduces the heat sink maximum temperature by 3.8 and 2.5% at the Reynolds numbers of 300 and 1800, respectively. Furthermore, the highest figure of merit (FOM) was approximately 1.25, which occurred at Re=1800 and Fi = 5%. Eventually, it was revealed that the best performance of the WMH-S was observed in the case of Re=807.87, volume percentage of 0.0437%, and NP diameter of 20 nm.

Micropolar Fluid Flow Between Two Inclined Parallel Plates

2017 ◽  
Author(s):  
Abbas Hazbavi ◽  
Sajad Sharhani
Keyword(s):  
Fluid Flow ◽  
Pressure Gradient ◽  
Micropolar Fluid ◽  
Constant Heat Flux ◽  
Hydrodynamic Characteristics ◽  
Parallel Plates ◽  
Governing Equations ◽  
Micropolar Fluid Flow ◽  
Flow Through ◽  
The Magnetic Field

In this study, the hydrodynamic characteristics are investigated for magneto-micropolar fluid flow through an inclined channel of parallel plates with constant pressure gradient. The lower plate is maintained at constant temperature and upper plate at a constant heat flux. The governing equations which are continuity, momentum and energy are are solved numerically by Explicit Runge-Kutta. The effect of characteristic parameters is discussed on velocity and microrotation in different diagrams. The nonlinear parameter affected the velocity microrotation diagrams. An increase in the value of Hartmann number slows down the movement of the fluid in the channel. The application of the magnetic field induces resistive force acting in the opposite direction of the flow, thus causing its deceleration. Also the effect of pressure gradient is investigated on velocity and microrotation in different diagrams.

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