Understanding Motor Controls
4th Edition
ISBN: 9781337798686
Author: Stephen L. Herman
Publisher: Delmar Cengage Learning
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Transcribed Image Text:PROBLEM 2 (20 POINTS)
A number of studies have been conducted on the diffusion of
substances such as water and oxygen in plastics with
particular relevance to the food packaging industry. It turns
out that at 30°C, the diffusivity of water in polyvinylidene
chloride (PVDC) (a.k.a. Saran™) is 9.1×108 cm²/s.1
Imagine you cover a glass with 100 mL (5.55 mol) of water
with a 10 μm thick PVDC film as depicted to the right.
Assuming that the water concentration on the lower surface
(inside the glass) of the PVDC is 1.7 mol/m³ (based on the
equilibrium vapor pressure of 4.25 kPa for water at 30°C)
and "dry air" conditions (no water, a.k.a. 0% humidity) are
maintained outside the glass, determine how long (in years!!!)
it will take for the water to completely evaporate from the
glass assuming it can only escape the glass by diffusion through the PVDC film and that the
temperature is constant at 30°C. The diameter at the top of the glass is 10 cm.
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Recommended textbooks for you
- Understanding Motor ControlsMechanical EngineeringISBN:9781337798686Author:Stephen L. HermanPublisher:Delmar Cengage Learning
Understanding Motor Controls
Mechanical Engineering
ISBN:9781337798686
Author:Stephen L. Herman
Publisher:Delmar Cengage Learning