experimental and numerical study of the effect of geometric parameters on liquid single-phase...
TRANSCRIPT
Experimental and Numerical Study of the Effect of Geometric
Parameters on Liquid Single-Phase Pressure Drop in Micro-Scale Pin-
Fin Arrays
Valerie Pezzullo, Florida State UniversitySteven Voinier, The College of New Jersey
Jonathan Mita and Dr. Weilin Qu
High Performance Computing Applications Research Experiences for Undergraduates Program: Computational Fluid Dynamics (HARP)
University of Hawai’i at ManoaDept. of Mechanical Engineering
Honolulu, HI, USA
Overview● Objectives● Background● Experimental Methods● Experimental Results● Numerical Methods● Numerical Results● Conclusions● Acknowledgements & References
Objectives● Experimentally determine water single-phase
pressure drop across a staggered circular micro pin-fin array
● Use OpenFOAM to calculate pressure drop and friction factor for a range of Reynolds numbers and various pin geometries
● Compare numerical results with experimental data to validate computational models
Background● Micro-scale pin-fin heat sinks are in the
process of being implemented in electronics as cooling devices
● Current air-cooled heat sinks are becoming less effective as more transistors are put on a single chip, increasing the heat flux
● Liquid-cooled micro-scale heat sinks are being studied for compared efficiency and effectiveness
Background
● Experimental study can be time consuming and expensive when different geometries are desired
● Numerical analysis and simulations are performed to estimate pressure drop when it is not feasible to manufacture and experiment on many different heat sink geometries
Experimental Methods
Flow Loop
Test Module
Heat Sink Geometry
Original Geometry:
● 180 x 683 µm
● 1840 staggered pin-fins
● 1 x 3.38 cm projected area
● 81 rows in flow direction
Experimental Results
0 200 400 600 800 1000 1200 1400 1600 18000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Pressure vs Gmax
235080
Gmax [kg/m²s]
ΔP [b
ar]
Temperature
(°C)
Previous Experimental Results
Experimental ResultsFriction Factor vs Reynolds Number
235080
Re_sp
f_fin
,sp
Temperature
(°C)
Previous Experimental Results
Numerical Methods
Geometry and Computational Domain
● Using a simplified geometry of 20 staggered-pin rows in flow direction
Assumptions● Steady flow
● Incompressible fluid
● Laminar flow
● Adiabatic flow
● Constant Fluid Properties
● Used upwind differencing scheme with simpleFoam
– Steady State
– Incompressible
– Turbulent flow (turned off)● No-slip wall conditions at top, bottom, and pin surfaces
Solution Method● Continuity Equation:
∇∘U = 0
● Momentum Equation:
ρf(U∘∇U) = -∇P + ∇∘(μf∇U)
● Three-dimensional finite volume simulation
ConvectiveAcceleration
Pressure Gradient
Viscosity
Incompressible fluid
Boundary Conditions
● No-slip wall● Inlet
– Flow field is uniform and only has velocity in flow direction
● Outlet– Ambient Pressure
● Symmetry
Mesh
● Mesh for original geometry
Changes in Geometry
● Alter existing mesh
● Scale all parameters, keep ratio constant
º Multipliers: 0.5; 1.5; 2
● Scale ST, all other parameters constant
º Multipliers: 1; 1.5; 2; 2.5; 3
Equations Used in Post-Processing
Equations Used in Post-Processing
Numerical Results
1 10 100 10000.3
3
Friction Factor vs Reynolds Number for Scaling All Parameters
x0.5x1.5x2 EXP
Re_sp
f_fin
, sp
Numerical Results
10 100 10000.1
1
10
Friction Factor vs Reynolds Number for Scaling ST
Exp x1X1X1.5x2X2.5x3
Re_sp
f_fin
, sp
Conclusions
● Scaling all parameters does not significantly affect the pressure drop and friction factor vs. Reynolds number correlation
● Scaling ST does affect the pressure drop and friction factor vs Reynolds number correlation
– As scaling multiplier increases, f vs Re curves are shifted some factor below the previous curve
– Curves begin to converge as Re increases
Recommendations for Future Work
● Revise mesh to yield more accurate results● Repeat numerical study, changing SL and
height H● Compare changes in ST, SL, and H
independently to study effect on friction factor● Formulate f vs Re correlation equation based
on power regression from numerical analysis● Heat Transfer applications using our generated
mesh
Mesh Revision● New Mesh:
● Old Mesh:
Heat Transfer Mesh
● Top: cover plate● Bottom: baseplate● Mesh is reverse of fluid flow mesh
Acknowledgements● We would like to thank the following people and
organizations for their guidance and support:
– Jonathan Mita
– Dr. Weilin Qu
– Dr. Susan Brown
– University of Hawaii at Manoa
– UH Manoa College of Engineering
– National Science Foundation
– OpenFOAM
● This material is based upon work supported by the National Science Foundation under Grant No. 0852082. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
References
J. Mita, W. Qu, M. Kobayashi “Experimental and Numerical Analysis of Water Single-Phase Pressure Drop Across an Array of Circular Micro-Pin-Fins.” University of Hawaii at Manoa Dept of Mechanical Engineering. PowerPoint. 2011.
J. Mita "Experimental and Numerical Study of Water Single-Phase Pressure Drop Across An Array of Circular Micro-Pin-Fins.” MS thesis. University of Hawaii at Manoa, 2011. Print.