1. Reheating and Sterilization Technology for Food, Waste and Water: Design and Development Considerations for Package and Enclosure Soojin Jun, Brian Heskitt and Sudhir Sastry The Ohio State University Ritesh Mahna and Joseph Marcy Virginia Tech Michele Perchonok NASA/JSC

2. Introduction Long-duration space missions –Food systems to provide the crew with a palatable, nutritious, and safe food system and minimize volume, mass, and waste –A thermal process in need of food reheating to serving temperature, or sterilization during in-transit and on evolved planetary base –Food package to pose a disposal problem after use

3. Introduction Ohmic heating –Electrical energy to thermal energy with higher energy efficiency (close to 100%) Reusable pouch –Sterilized to yield food quality with long shelf life –Enabled ohmic treatment in transit –Used to contain and sterilize waste post-food consumption

4. Objectives Develop and optimize a pulsed ohmic heating system and reusable pouch –Minimize ESM –Eliminate gas generation –Eliminate electrode corrosion Numerical Approach –Optimize electrode configuration Most uniform, yet rapid heating thermal profiles –Predict and prevent worst-scenario during food heating

5. Pulsed ohmic heater Circuit diagram IGBT module Input TTL signal Output Isolation IGBT output waveform Ideal for minimizing electrochemical reaction Frequency: 10 kHz Pulse duty ratio: 0.2 Compact design

6. Ohmic heater enclosure and frame

7. Reusable pouch Foil electrodes Flexible package First realized version Newly designed version

8. Electrode materials Degassing and ohmic treatment of NaCl solution to observe likely gas generation at the interface between solution and electrodes Aluminum –Generate lots of gas –Serious self-corrosion Stainless steel –Food grade 300 series –Little gas generation with ideal wave conditions

9. Secure bond in electrode-package construction Hot press to seal stainless steel electrode pouches –However, electrodes unlikely to adhere to inner PE layer of pouches Stainless steel foil PE Aluminum foil PE Nylon Multi-layered laminate Sealant

10. Secure bond in electrode-package construction PE extruded on stainless steel foil –Contact select vendors Use of food grade adhesive –Long curing time Etching one side of foil to enhance the surface energy

11. Electrical conductivities and locations of temperature sensors 12345 3 2 1 X Y 1/2 L Chicken noodle soup Black beans

12. 2D Electrode configuration and field distribution Electrode Pouch A V/m Pouch B Pouch C

13. Comparison of temperature profiles of chicken noodle soup between simulation and measurement data Temperature ( o C) Pouch A Pouch B X Y X Y Temperature ( o C) Pouch C X Y  : Experimental data : Simulation data

14. 2D temperature distribution and cold zones 8012 oCoC 40 Pouch A Pouch B Pouch C

15. Predicted temperature distributions and cold zone in Pouch B with different electrode widths Dimensionless electrode width Temperature distributionPotential cold zone 0.063 0.127 0.147 0.202 0.268 : Electrode

16. Optimization of electrode width with respect to cold zone ratio, power consumption, average temperature, and temperature variation

17. ESM estimation based on potential final product with optimized power consumption Mass 1 (kg) Volume 2 (m3) Power (kWe) Cooling (KWth) ESM (kg) Allocated ESM 3 (kg) Percentage (%) System values3.980.0120.15 Equivalencies 4 Volume (kg/m3) Power (kg/kWe) Cooling (kg/kWth) Mission Type Mars Transit Vehicle9.162374045.636141.3 Mars Descent / Ascent Lander66.722814560.77058.6 Surface Habitat Lander9.168714538.957710.7

18. Initiated sterilization experiment Pressured environment –Counterbalance internal pressures developed due to heating –Installed air pressure regulator Employed cooling system

19. Preliminary data Symmetry

20. Deliverables Shelf life study of food package –Gassing, corrosion, and leakage Minimize cold zones to ensure the sterility of treated product –System optimization with numerical approach Study wastes related to human activities –Microbiological analysis, sterility testing