OPTIMIZATION OF VACUUM FLASKPablo Vazquez

Rakesh PatancheruSai Kiran Gattu

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.

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

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

CONSTRAINTSOuter 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

TemperatureFluid TH = 373 K = 100°C • Hottest temperature a fluid can be

Ambient TC = 294.261 K = 21.261°C • Standard ambient temperature

DESIGN VARIABLES

Design Variables Lower limit Symbol Value Upper limitInner Shell Thickness 0.03937 t 0.15876 0.15876Outer Shell Thickness 0.03937 To 0.07874 0.07874

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

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.

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

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.

THANK YOU