Multi-Objective Optimization Study of LED
Light using SC/Tetra and HyperStudy
2014 European ATC
©2014 Cradle North America Inc.
Overview
• The goal is to minimize the LED temperature and the heat sink volume
for the ty...
©2014 Cradle North America Inc.
• The following computational domain is set since heatsink, housing, and
LED is installed ...
©2014 Cradle North America Inc.
• Detail geometry of LED downlight is shown below.
Analysis Model
Heatsink
Housing
LED
Lat...
©2014 Cradle North America Inc.
• Design Parameters
Analysis Model
Design Parameter Min Max Type
Number of fins 24 48 Inte...
©2014 Cradle North America Inc.
• Diagram to show the relationship of HyperStudy and SC/Tetra
Analysis Procedure
HyperStud...
©2014 Cradle North America Inc.
• Brief Procedure
1. Build VBScript to run CFD simulation in SC/Tetra
2. Prepare template ...
©2014 Cradle North America Inc.
• Analysis Type
• Steady State
• Flow(laminar flow), temperature and radiation are conside...
©2014 Cradle North America Inc.
• Material Property
Analysis Condition for CFD Simulation
Material Density
[kg/m3]
Viscosi...
©2014 Cradle North America Inc.
• DOE
• Full factorial with 48 samplings
• Fit
• Least Squares Regression method
• Optimiz...
©2014 Cradle North America Inc.
• Response Surface
• Kriging-based interpolation method
DOE Result
Number of Fins [-]
Fin ...
©2014 Cradle North America Inc.
• Contributing Percentage
• Based on the contributing percentage, almost 50% of contributi...
©2014 Cradle North America Inc.
• Variable Distribution (Part 1)
Optimization Result
BoreThickness[mm]
OuterRadius[mm]
©2014 Cradle North America Inc.
• Optimal Pareto Graph
Optimization ResultRisingLEDTemperature[C]
Heatsink Volume [m^3]
©2014 Cradle North America Inc.
• Priority on light weight
Optimum Design Result
case1 case2 case3
Heatsink Volume [m^3] 0...
©2014 Cradle North America Inc.
• Preparation time is shown below.
• Note that once the VBS is created, this can be reused...
©2014 Cradle North America Inc.
• Min, max and average value are shown blow.
• Computation time and memory consumption is ...
©2014 Cradle North America Inc.
• Machine used for this simulation is below.
• Cluster1 is used to generate the meshes.
• ...
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Optimization of a heat sink for a LED device using SC/Tetra and HyperStudy

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The purpose of the multi-objective optimization of the heat sink for a LED device using SC/Tetra and HyperStudy is minimizing the heat sink material while minimizing the LED temperature.

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Optimization of a heat sink for a LED device using SC/Tetra and HyperStudy

  1. 1. Multi-Objective Optimization Study of LED Light using SC/Tetra and HyperStudy 2014 European ATC
  2. 2. ©2014 Cradle North America Inc. Overview • The goal is to minimize the LED temperature and the heat sink volume for the typical LED downlight. • 2 objective functions (responses) are defined. • Optimization will be performed using HyperStudy. • For the CFD simulation, SC/Tetra will be used. • Heatsink dimensions can be changed. • 5 design parameters are defined. Design Parameters The number of fins Fin height Bore thickness Inner radius Outer radius Objective Function LED temperature Heatsink volume
  3. 3. ©2014 Cradle North America Inc. • The following computational domain is set since heatsink, housing, and LED is installed in the closed double ceiling. • The following assumption is made to run the simulation. • Upper side is exposed to outside air with 30[C]. • Lower side is exposed to inside air with air conditioned(24[C]). • Quarter (1/4) model is used to reduce the CFD computation time. Analysis Model 0.245[m] 1.0[m] 1.0[m]
  4. 4. ©2014 Cradle North America Inc. • Detail geometry of LED downlight is shown below. Analysis Model Heatsink Housing LED Lateral View from upper side Lateral View from lower side View for Separated Parts
  5. 5. ©2014 Cradle North America Inc. • Design Parameters Analysis Model Design Parameter Min Max Type Number of fins 24 48 Integer(Discrete) Fin height 80 120 Real(Continuous) Bore thickness 2 5 Real(Continuous) Inner radius 25 35 Real(Continuous) Outer radius 65 75 Real(Continuous) Fin height Inner radius Outer radius Bore thickness Close View in Red Square
  6. 6. ©2014 Cradle North America Inc. • Diagram to show the relationship of HyperStudy and SC/Tetra Analysis Procedure HyperStudy Setup HyperStudy DOE HyperStudy Optimization Suitable Design HyperStudy Fit (Approximation) Response Curve Updated Response Curve Pareto Graph SCT/Tetra Base Run SCT/Tetra Sampling Run SCT/Tetra Check Run VBScript VBScript VBScript
  7. 7. ©2014 Cradle North America Inc. • Brief Procedure 1. Build VBScript to run CFD simulation in SC/Tetra 2. Prepare template to set design variables using VBScript from 1 3. Setup “New Study” with parameterized file in HyperStudy 4. Execute the base run using the initial value to test the VBScript 5. Set up Objective Functions (responses) 6. Execute Design of experiment (DOE) to obtain response surface 7. Execute Fit to obtain meta model and update the response surface 8. Execute Optimization to obtain pareto graph. Analysis Procedure
  8. 8. ©2014 Cradle North America Inc. • Analysis Type • Steady State • Flow(laminar flow), temperature and radiation are considered • Boundary Condition • Xmin, Xmax, Ymin and Ymax: Symmetry • Zmax: Heat transfer coefficient (22.4 [W/(m2.K)]*), outside temperature (30 [C]) • Zmin: Heat transfer coefficient (6.13 [W/(m2.K)]*), inside temperature (24 [C]) • Other Conditions • Gravity: 9.80665 [m/s2] to the negative Z direction • Heat Generation: 12.5 [W] for LED Analysis Condition for CFD Simulation *Ashrae Handbook 2013 p26.20
  9. 9. ©2014 Cradle North America Inc. • Material Property Analysis Condition for CFD Simulation Material Density [kg/m3] Viscosity [Pa.s] Specific Heat [J/(kg.K)] Thermal Conductivity [W/(m.K)] Emissivity [-] Thermal Expansion rate [1/K] Air (1) 1.1763 1.862-e5 1007 0.02614 n/a 0.00333 Heat Sink (2) 2690 n/a 900 209 0.8 n/a LED (3) 8880 n/a 386 398 0.8 n/a Housing (5) 1200 n/a 1050 0.2 0.8 n/a TopCeil (4) 2400 n/a 900 0.2 0.8 n/a
  10. 10. ©2014 Cradle North America Inc. • DOE • Full factorial with 48 samplings • Fit • Least Squares Regression method • Optimization • MOGA Analysis Condition for HyperStudy
  11. 11. ©2014 Cradle North America Inc. • Response Surface • Kriging-based interpolation method DOE Result Number of Fins [-] Fin Height [mm] Bore Thickness [mm] Inner Radius [mm] HeatsinkVolume[m^3] Outer Radius [mm] HeatsinkVolume[m^3] HeatsinkVolume[m^3] HeatsinkVolume[m^3] HeatsinkVolume[m^3]
  12. 12. ©2014 Cradle North America Inc. • Contributing Percentage • Based on the contributing percentage, almost 50% of contribution to rising LED temperature is outer radius. This makes sense because the outer radius directly affects the surface area of the heatsink. • The contribution of Fin Height, Bore thickness and Inner radius to the thermal effect is very small, so these design parameters can be changed freely without affecting the LED temperature. Fit Result 0 10 20 30 40 50 % Contributing Percentage Rising LED Temperature Heatsink Volume Outerradiusincrease 65[mm] 70[mm] 75[mm]
  13. 13. ©2014 Cradle North America Inc. • Variable Distribution (Part 1) Optimization Result BoreThickness[mm] OuterRadius[mm]
  14. 14. ©2014 Cradle North America Inc. • Optimal Pareto Graph Optimization ResultRisingLEDTemperature[C] Heatsink Volume [m^3]
  15. 15. ©2014 Cradle North America Inc. • Priority on light weight Optimum Design Result case1 case2 case3 Heatsink Volume [m^3] 0.00015 0.00028 0.00041 Rising LED Temperature [C] 48.09 38.26 32.73 Number of Fins 24 36 48 Heatsink Height [mm] 82.76 92.48 119.09 Bore Thickness [mm] 2.01 2.06 3.76 Outer Radius [mm] 28.97 25.00 25.00 Inner Radius [mm] 65.02 75.00 74.94 Simulation result [C] 48.92 36.71 33.86 Case1 Case2 Case3 Case1 Case2 Case3 RisingLEDTemperature[C] Heatsink Volume [m^3]
  16. 16. ©2014 Cradle North America Inc. • Preparation time is shown below. • Note that once the VBS is created, this can be reused for similar project. Total Time to Obtain Result Software Process Machine Time [hr] Human Time [hr] SC/Tetra Build VBS to create geometry, create mesh, run simulation and extract values in SC/Tetra 0 10 HyperStudy (SC/Tetra) Setup DOE Study and execute VBS automatically 73 0.5 HyperStudy Setup Fit and execute 0.1 0.1 HyperStudy Setup Optimization 0.5 0.1
  17. 17. ©2014 Cradle North America Inc. • Min, max and average value are shown blow. • Computation time and memory consumption is for solver only. Mesh and Computation Time Case No. of Node No. of Elements Computation time [hr:min] Memory Consumption [GB] Min 2,359,133 8,434,121 0:30 13.5 Max 7,267,109 24,351,288 2:02 37.2 Average 4,300,727 14,857,177 1:16 23.0 Total (48 cases) - - 60:44 -
  18. 18. ©2014 Cradle North America Inc. • Machine used for this simulation is below. • Cluster1 is used to generate the meshes. • Cluster2 is used to run the simulation. • Software used for this simulation is below. • SC/Tetra V11 • HyperStudy v12.0.0 Environmental Information Cluter1 Cluster2 OS Windows 7 Professional Windows Server 2012 CPU Intel Core i7 3.20GHz (6 cores) * 2 / node Intel Xeon E5-2687W 3.10GHz (8 cores) * 2 RAM 24GB 64GB

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