1. OPTIMIZATION OF
VACUUM FLASK
Pablo Vazquez
Rakesh Patancheru
Sai Kiran Gattu

2. INTRODUCTION
• Vacuum flask minimizes heat loss for keeping drinks hot or cold.
• A vacuum flask is a bottle placed inside a bottle separated by a vacuum.
• Vacuum gap minimizes the heat loss.
• Conduction and Radiation is reduced.

3. HEAT TRANSFER
• Conduction: Flow of heat by
physical contact.
• Convection: Heat transfer
through a fluid caused by
molecular motion.
• Radiation: Heat transfer due
to electromagnetic waves.
• Neglecting the heat transfer due
to conduction and convection.
• Neglecting silver coating

4. OBJECTIVE FUNCTIONS
• Minimize
• Weight (5)
• Cost (Raw Material) (6)
• Maximize
• Vacuum Thickness (4)
• Cooling Time (1)
• Inner Shell FOS for Buckling (2)
• Outer Shell FOS for Buckling (3)
Multi-objective Design

5. CONSTRAINTS
Outer Shell
Diameter Dout = 2.85 in. • conforms to the consumer’s standard cup holders and comfort when hand-held
Height Hout = 6 in. • conforms to standard height for 12 fl. Ounce flasks
Inner Shell
Diameter din = 2.375 in.
• conforms to embody a fluid volume of 12 fl. Ounces
Height hin = 4.95 in.
Material
304
Stainless
Steel
• Food grade
• High compression strength
• Low cost
• Common
• Reflective properties to promote radiative heat transfer
Temperature
Fluid TH = 373 K = 100°C • Hottest temperature a fluid can be
Ambient TC = 294.261 K = 21.261°C • Standard ambient temperature

6. DESIGN VARIABLES
Design Variables Lower limit Symbol Value Upper limit
Inner Shell Thickness 0.03937 t 0.15876 0.15876
Outer Shell Thickness 0.03937 To 0.07874 0.07874

7. PROCESS/METHOD/SOLVER ENGINE
Find Utopia
Points
Use Max
Utopia Point to
Calculate New
Minimums
Take the
Difference
between Old
Minimums and
New Minimums
Scale O.F.s
based on
rankings
Sum O.F.s and
Minimize
• Multi Objective Optimization
• Excel GNG Nonlinear Solver
• Weighted Min-Max Method
Minimized Function with
Optimized Vacuum Flask
Thicknesses

8. RESULTS
•Cost for 12oz flask is determined,
which is $0.70
•Final values for Inner thickness is
0.158” and outer shell thickness is
0.078”, weight determined is 1lb
•The maximum cooling time
determined is 75745 hours since
only radiation is considered.

9. CONCLUSION
•We successfully optimized 12oz
vacuum flask using Weighted min
max multi objective method.
•The values adhered to the standard
vacuum flask of 12 oz

10. LIMITATIONS/DESIGN REFLECTIONS
•Heat loss due to Conduction and
Convection is neglected.
•Factor of safety assumed for outer
shell is more than inner shell.
•The maximum thickness for inner
shell is 1mm and maximum
thickness for outer flask assumed is
2mm.

11. THANK YOU