UTSR Summer Internship: Siemens Energy

Transcription

1 UTSR Summer Internship: Siemens Energy David Billups / September 13, 2015 Answers for energy.

2 Table of Contents Validation of StarCCM+ V CFD* Study of IDC** Cavities 16 V-Shaped Dimples 21 IDC S1 Model 29 Case 1 32 Case 2 36 Case 3 40 Case 4 44 Experimental Impingement Work 51 Conclusions 58 * Computational Fluid Dynamics ** Internal Duct Cooling Page

3 Validation of StarCCM+ Version David Billups / August 2015 Page

4 StarCCM+ Validation Content This Validation required the analysis a case study. The results obtained with the new version of StarCCM+ would be compared to those from the previous version. The two case study was: Han 84 Periodic CFD models for fast simulation Purpose By comparing new results to previously calculated and understood solutions, we are able to assess the performance of the new StarCCM+ code. Page

5 StarCCM+ Validation Han 84 Page

6 StarCCM+ Validation Han 84 Case Study Version Version The convergence history shows much less variation in the new solution, however both codes converge to similar magnitudes. Page

7 Han 84 Case Study Velocity Scalar Version Version The velocity scalar results are nearly identical. Version Version Percent Difference Friction Factor % Page

8 Han 84 Case Study Temperature Scalar Version Version The temperature distribution is nearly identical. Version Version Percent Difference Smooth Wall Temp (K) % Ribbed Wall Temp (K) % Page

9 Han 84 Case Study Nusselt Number Version Version The Nusselt number results are nearly identical, showing only an 0.137% difference in average Nu. Version Version Percent Difference Average Nu % Page

10 StarCCM+ Validation Conclusions Based on the results obtained for the Han 84 case, it was observed that there is very little difference in the solutions produced by StarCCM+ Version and past versions. Slightly better convergence results obtained for the Han 84 case. Indiscernible differences in Nusselt number. StarCCM+ Version is deemed suitable for production use. Page

11 CFD Study of IDC Cavities David Billups / September 2015 Page

12 CFD Study of IDC Cavities Purpose In experimental literature, dimples have been found to produce 2-3 times the heat transfer capability of a smooth channel 1-4 times the friction factor of a smooth channel Ribs have been shown to produce 2-5 times the heat transfer of a smooth channel times the friction factor of a smooth [1] Brown, C. P., Wright, L. M., & McClain, S. T. (2015). Comparison of Staggered and In-Line V-Shaped Dimple Array Using S-PIV. Proceedings of ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. Validate experimental studies of cavities with StarCCM+ Page

13 V-Shaped Dimples GT Summary of Experimental Study - Flow Researchers at Baylor University used SPIV to analyze the secondary flow characteristics at each of the x/d h locations specified. For presentation of flow characteristics, the authors non-dimensionalized velocity by average core velocity this ambiguous value made it impossible to exactly replicate the PIV results. Page

14 V-Shaped Dimples GT Summary of Experimental Results Heat Transfer The researchers performed a steady state heat transfer study using thermocouples placed at the blue diamonds. The data shows that the In-Line geometry outperformed the Staggered geometry, but both produced times larger Nusselt number than that produced in a smooth channel. Heat Transfer measurements were not included, thus it is impossible to replicate the study Model using same conditions as previous rib geometry [1] Brown, C. P., Wright, L. M., & McClain, S. T. (2015). Comparison of Staggered and In-Line V-Shaped Dimple Array Using S-PIV. Proceedings of ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. Page

15 V-Shaped Dimples (GT ) September 2015 Page

16 V-Shaped Dimples In-Line Case In-Line Geometry Consecutive rows of 3 dimples Equally spaced in X and Z on centers Mesh Parameter Acceptable Limit Mesh Quality Model Limit (Worst Case) # of Cells outside Acceptable Limit Percentage outside Acceptable Limit Face Validity > Cell Quality > Volume Change > 1E E Skewness Angle [deg] < Total Number of Cells 7,662,078 Page

17 V-Shaped Dimples In-Line Average Nusselt number is low relative to ribbed features. Avg Nu= Velocity Streamlines show exactly what is found in the experimental study, which is that the V-Shaped dimples direct flow outwardly from the center of the dimple. The velocity profile shows low flow into the dimples. Page

18 In-Line Dimple Array Secondary Flow Experimental Results (Re=37k) CFD Results (Re=70k) Page

19 V-Shaped Dimples Staggered Case Staggered Geometry Alternating rows of 2 and 3 dimples. Each dimple is centered between the two in front. Same dimensions as In-Line case Mesh Parameter Acceptable Limit Mesh Quality Model Limit (Worst Case) # of Cells outside Acceptable Limit Percentage outside Acceptable Limit Face Validity > Cell Quality > Volume Change > 1E E Skewness Angle [deg] < Total Number of Cells 7,662,078 Page

20 V-Shaped Dimples Staggered Average Nusselt number is slightly less than the V-Shaped In-Line case. Avg Nu= Velocity streamlines show what is found in the experimental results which is that the staggered pattern redirects flow toward the center of downstream dimples. The velocity profile again shows that there is little flow within the dimples. Page

21 Staggered Dimple Array Secondary Flow Experimental Results (Re=37k) CFD Results (Re=70k) Page

22 V-Shaped Dimples Conclusions A discrepancy exists between the heat transfer capabilities seen in the CFD results and the experimental results. Comparisons to experimental study are abstract (Experimental Re=37k, CFD Re=70k) It would be worthwhile to run some cases at varying Re just to be sure that the CFD flow results match the experimental PIV results. Page

23 Error V-Shaped Dimples The models geometrically represent that of the experimental setup, however, without the correct information, the models could not be run in the same conditions that were present experimentally, thus it was impossible to numerically validate the experiment. At this junction, the models were run under the same conditions as a previously studied ribbed channel. This ribbed geometry is protected as Siemens Energy proprietary information. The dimensions of this channel are larger than the V-Shaped dimple channels. Due to this difference in dimension, the characteristic length in Reynolds number, which is defined as half the width of the channel, was much smaller for the V-shaped cases, thus they were subject to much higher velocities. It is the result of this that you see much higher velocity magnitudes in the V- shaped velocity scalar plots. For these reasons, drawing any conclusions from the V-shaped models presented in this study is incorrect. Page

24 Experimental Impingement Work September 2015 Page

25 Entrainment Investigation Issues There were some inconsistencies in the data which were thought to be a result of entrainment. Plan of Action Insert TC s near the jet exit to get a better measurement of jet exit temperature Build a vertical rake at the edge of the skirt to capture the temperature profile along the height of the rig. Build a horizontal TC rake radially outward from the center such that a radial temperature distribution can be obtained. Page

26 Entrainment Investigation Jet Exit Temperature Experimental Setup Placed multiple TC s around and in the jet exit Jet Exit temp previously was assumed to be same as plenum temp Results Difference in Nu from test matrix vs. jet temp characterization tests Re=20k Difference [%] z/d= z/d=6 1 Re=40k z/d= z/d= Re=60k z/d= z/d= Re=80k z/d= z/d= Page

27 Entrainment Investigation Vertical TC Rake Experimental Setup SKIRT Rebuilt vertical TC rake to get better data for CFD entrainment prediction Spaced 10 TCs evenly across z/d=3 PLENUM TC RAKE TC DIRECTION TOP VIEW SIDE VIEW SKIRT Z/D = 3 10 TC S IN TOTAL ALL EQUALLY SPACED BY 0.33D COPPER 13D Page

28 z/d Vertical Locataion z/d Vertical Locataion Entrainment Investigation Vertical TC Rake Conclusions Variation in Temp along the height of the TC rake is within TC variation (±0.4 C), but we are seeing consistently higher results from jet temp by ~2.25% (7 C) Temp Profile at r/d=13 (Run 1) Temp Profile at r/d=13 (Run 2) Re=20k 2 Re=20k Re=40k Re=60k Re=70k Re=40k Re=60k Re=70k % 1.50% 2.00% 2.50% 3.00% Percent Difference in Rake TC and Jet Exit TC Measurements % 1.50% 2.00% 2.50% 3.00% Percent Difference in Rake TC and Jet Exit TC Measurements Page

29 Entrainment Investigation Horizontal TC Rake Experimental Setup 10 equally spaced TC s Located 20mm above surface Shielded from radiation from the copper plate by wooden dowel SKIRT Z/D = 3 TC TIPS ARE 20MM FROM SURFACE 3D 10 TC S IN TOTAL COPPER 5D Page

30 Temperature ( C) Entrainment Investigation Horizontal TC Rake Conclusions At higher z/d, the core temperature of the jet is more effected by entrainment Re=20k data was taken after Re=80k, so the rig was hot which probably explains the variation in Re. At smaller z/d, recirculation temperature is higher Temp Profile at z/d= z/d=3 Re=20k z/d=6 Re=20k z/d=3 Re=80k z/d=6 Re=80k r/d Radial Distance From Center Page

31 Moving Forward Succeeding Work IDC The second alternating rib/cavity case could be run and analyzed The V-Shaped dimple cases should be run disregarding heat transfer at the same flow conditions as the experimental study. The V-Shaped dimple cases should be rebuilt to better match the geometry of the ribbed model that they will be compared to. Impingement The team at the Siemens Energy Center (SEC) is working to finish troubleshooting this rig and move on to new investigations. Thank you to those who helped guide me along the way! Page

32 Thank You! David Billups UTSR Intern PG GT LGT EN / Orlando / MT N. Alafaya Trail Orlando, FL Mobile: (804) davidbillups@siemens.com davidtbillups@gmail.com siemens.com/energy Page