Simulating Microwave Heating of Rotating Object in Domestic Ovens

Transcription

1 Simulating Microwave Heating of Rotating Object in Domestic Ovens K. Pitchai 1, J. Raj 1, S. Birla 1, J. Chen 1, R. Gonzalez 2, D. Wiemann 2, J. Subbiah 1, D. Jones 1 46 th Annual Microwave Power Symposium Las Vegas, NV 22 June 2012 Session: Computer Simulation 1 University of Nebraska Lincoln 2 ConAgra Foods, Inc.

2 Microwave Heating Modeling Softwares 2

3 Wasn t that microwave heat transfer model developed for rotating food in turntable? Yes, models were developed 3

4 Rotation Model - Datta s Group ANSYS and FIDAP software Discrete positions Single component food potato Rotation improved heating uniformity One-way coupling Geedipalli, S.S.R, Rakesh, V. and Datta, A. K. Modeling the heating uniformity contributed by a rotating turntable in microwave ovens, J of Food Engg, 82, (2007). 4

5 Rotation Model QWED Group QWED software Determine power dissipation at discrete positions Average all powers The optimal angle is 30 degrees P.Kopyt, M.Celuch-Marcysiak, "FDTD modelling of electromagnetic power dissipated in rotated objects", 14th International Conference on Microwaves, Radar and Wireless Communications MIKON-2002, Gdansk, Poland, May 2002, pp

6 Limitations of the QWED s model Quickwave software does not simulate microwave heating of multi-component rotating objects Single component food Multi compartment food Multi component food 6

7 Rotation Model in COMSOL Our research group presented feasibility of simulating microwave heating of rotating cylinder at the center of turntable using COMSOL Radio Frequency and ALE modules S.Birla, K. Pitchai, J. Raj, D. Jones, J. Subbiah, and V. Komarov, A critical comparison of COMSOL and QuickWave 3D softwares for modeling of microwave heating in domestic oven", 45 th Annual Microwave Power Symposium. New Orleans, LA. 7

8 Limitations of the Rotation Model in COMSOL Multiphysics ALE modules does not work for any other shapes and offset position of food in turntable J. Raj, S.Birla, K. Pitchai, J. Subbiah, and D. Jones, Modeling of Microwave Heating of a Rotating Object in Domestic Oven", 2011 Comsol conference, Boston, MA. 8

9 Not sufficient to rely with just COMSOL Multiphysics to rotate the food!!! Raising the importance of integrating COMSOL Multiphysics with some other tool 9

10 Objectives Develop a microwave electromagnetic -heat transfer model of rotating 10-oz food tray using COMSOL MATLAB software 10

11 How does the electromagneticheat transfer model works? 11

12 Coupled electromagnetic heat transfer microwave model Power dissipation Heat equation c p T t.( k T ) Q Maxwell s equation Temperature field EM properties

13 Materials and Methods 13

14 Implementing Rotation Model using Comsol-Matlab Simulate microwave heating for time Δt Save temperature field in data file Matlab rotates the object to next position Initialize temperature from previous position 14

15 Different Approaches for Solving Electromagnetic- Heat Transfer Equations Fully coupled Partially coupled One way coupling 15

16 Comparison of Different Approaches Fully coupled Partially coupled EM field T field Remarks Sub-time step (solver time step) Time step Sub-time step Sub-time step Most accurate Memory intensive Takes too long Properties are updated every angular steps One-way coupling Average EM field stays constant over cooking time Sub-time step Properties do not change with temperature Heat diffusion is considered 16

17 Effect of Rotation Angle Effect of rotation angle (15, 30, and 45 degrees) on accuracy computation time 17

18 Mashed Potato Preparation Fill 500 g of mashed potatoes in the tray Cover with shrink wrap film until used 18

19 Measuring Dielectric and Thermal Properties Dielectric properties setup Differential Scanning Calorimetry KD-2 Pro 19

20 Dielectric properties 55 Dielectric Properties of Mashed Potato Dielectric Constant Loss Factor Temperature, C 20

21 Specific heat capacity, J/Kg C Specific Heat Capacity of Mashed Potato Temperature, C 21

22 Preliminary Results Effect of coupling method on computation time on a cylindrical gel 22

23 Rotating Food in MW Oven 23

24 Comparison of Different Approaches Temperature after 30 s of MW heating using 8 discrete positions on turntable C C C C C C Fully coupled Partially coupled One-way coupling 48 h 12 h 4 h 24

25 Results 10-oz tray filled with mashed potato Partial Coupling 25

26 Temperature Profile Animation 15 degree 26

27 Top Middle Bottom 88.2 C C C 80 Experiment C C C 15 degree 30 degree 45 degree 27

28 Top Middle Bottom Validation: After 3 minutes of cooking 45 degrees Rep1 Rep2 Rep3 28

29 Future Work Partial coupling took more than 48 hours for 3 minutes of cooking Iterations for EM field prediction starts from scratch and takes over 10 minutes for convergence for each discrete position If we can initialize previous EM field, the convergence would be faster, which should result in faster computation 29

30 Conclusion Simulation of microwave heating of rotating objects can be performed using MATLAB- COMSOL interface Angular step of 45 degrees seems to be sufficient Partial coupling is the best approach There is a need for improvement in algorithm for initialize E-field from previous angular position 30

31 Acknowledgement ConAgra Foods, Inc. USDA CSREES NIFSI grant (Project number: ) 31

32 Questions? 32