University of Maryland, College Park Acknowledgements: Luvata, Modine Manufacturing Company

1. Multi-Objective Optimization of Microscale Heat Exchange TechnologyOmar AbdelAziz, Vikrant Aute, Reinhard Radermacher, Shapour Azarm University of Maryland, College Park Acknowledgements: Luvata, Modine Manufacturing Company and Office of Naval Research

2. Contents Objectives Problem Definition Approach Integrated Approach Header Challenges Parameterized CFD and Coupled Solver Approximation Assisted Optimization DOE and Metamodeling New DOE w/Verification and Comparison Optimization Model and Results Work Accomplished and Remaining

3. Objectives Develop an approximation assisted multi-objective multi-disciplinary optimization tool Use the tool to design microscale heat exchanger (HX) technology for naval applications

4. Problem Definition: HX Optimization • Integrated optimization: From HX segment to assembly

5. Approach The fig in this slide is too close to the boundary…please revise to have 0.5 margin from the boundary!

6. Header Challenges Smaller flow channels leads to increased ΔP More headers  lower ΔP but diminished compactness Trade-off between ΔP and HX volume Headers performance affects the overall HX performance: Additional ΔP Additional material/volume Refrigerant maldistribution

7. Selected Header • New header design for reducing volume and maldistribution

8. Parallel Parameterized CFD: PPCFD

9. Coupled Solver PPCFD for NGHX-13 is used to estimate the overall heat transfer coefficient and airside pressure drop CoilDesigner (a segmented ε-NTU solver) is used to evaluate the overall HX performance Water flow propagation from tube inlet to outlet Calculate outlet conditions and evaluate objective functions and constraints PPCFD HTCOverall, ΔPair New Designs CoilDesigner Overall HX performance: Volume, Material volume, cost, air and water pressure drop, heat capacity, ..etc

10. Approximation Assisted Optimization (AAO)

11. Overview of AAO Analysis & Optimization Heat Exchanger Design of Experiments (DOE) Meta-modeling Approximation: Steps 1 - 3 Step 2 Step 1 Validation Step 3 DOE (new approach) and metamodeling (offline) are important steps in AAO!

12. Why Offline Metamodeling? • HX solver evaluates all performance parameters, e.g. heat transfer rate, volume, material, pressure drop, etc • Segment performance (airside HTC and ΔP) should be estimated for the entire design space • CFD simulations are computationally expensive • Use Approximation to find segment performance • Use segment performance to obtained different HX performance objectives/constraints depending upon the application

13. DOE Related:Leave-One-Out (LOO) Error • Leave-one-out (LOO) cross-validation (e.g., Cressie, 1993) • Leave 1 point out from current design, and build metamodel with remaining points, use metamodel to predict response for left-out point and calculate error LOO error evaluates sensitivity of metamodel to ‘missing’ information  likely “sensitive” regions

14. DOE Objective • DOE is a tradeoff between filling the entire region vs. “sensitive” (CAMM) regions non-CAMM region CAMM region Objective:Develop a multi-input, single response adaptive DOE method based on Space-Filling and Cross-Validation Tradeoff (SFCVT)

15. New DOE Approach: SFCVT Find new sample point: max. estimated LOO error s.t. space-filling condition

16. SFCVT Verification/Comparison • SFCVT compared with 2 previous methods: • Max Entropy Design or MED (e.g., Shewry and Wynn, 1987) • MED is non-adaptive • Maximin Scaled Distance or MSD (Jin et al., 2002) • MSD is adaptive • “Kriging” (e.g., Cressie, 1993) was used for metamodeling • Verification of metamodel by a random test set of points

17. Error Eqs Used in Comarison • RMSE, MAE, RRMSE, RMAE: • MAS (Metamodel Acceptability Score: Hamad, 2006) • Factor of Improvement (FoI) for comparing metamodels

18. Test Problems for Comparison Test Problems 1 to 6 Test Problems 7 to 12 Test Problems 13 to 16

19. MED Vs. SFCVT Comparison Changing correlation parameters gave “better” performance for 6 more!

20. MSD Vs. SFCVT Comparison

21. HX Pareto Optimum Solutions Approximation involved 300 CFD runs for metamodeling plus 250 randomly generated designs for verification!

22. HX Pareto Optimum Verification

23. Project Status • FY09 Work Accomplished • Developed new approach for rapid evaluation of HX designs • Automated CFD; 3D CFD replaced with 2D CFD + CoilDesigner • Preliminary header analysis • Approximation assisted optimization: SFCVT • 2X reduction in heat exchanger volume • 3X reduction in heat exchanger material • 90% reduction in computational effort • Additional Studies: Material thermal conductivity effect; Tube thickness effects, single phase water flow in microtubes, and A-coil optimization using multi-scale approach • Work Remaining • Integrate header design w/ the rest of HX • Improvements in AAO, e.g., reduce # of function calls significantly for single- vs. multi-output simulation • Possibly use NURBS to define the HX surface (additional degrees of freedom in the HX element design) • Others??

24. FY08 Publications • ???“Cross-validation Based Single Response Adaptive Design of Experiments for Deterministic Computer Simulations,” Proceedings of the 12th AIAA/ISSMO Multidisciplinary Analysis and Optimization Conference, Victoria, British Columbia, Canada, Sep 2008 • ???“A-Type Heat Exchanger Simulation Using 2-D CFD for Airside Heat Transfer and Pressure Drop,” International Refrigeration and Air Conditioning Conference at Purdue, July 2008 • Li, G., V. Aute, and S. Azarm, 2008, “An Accumulative Error Based Adaptive Design of Experiments for Offline Metamodeling,” Structural and Multidisciplinary Optimization (under revision) • Rademacher, R., O. Abdelaziz, V. Aute, and S. Azarm, 2008, “Compact Mini-Channel Heat Exchangers,” Invention Disclosure No. PS-2008-033, Office of Technology Commercialization, University of Maryland, College Park PLEASE GIVE COMPLETE DETAILS: NAMES FOR ALL CO-AUTHORS for the first two, following the format for the last publication!? Any other journal paper??? Weak wrt journal publication output!!!

25. Thank You! Questions?