Evaporative cooling of beverage problem involving thermodynamics and heat concepts


by laksate
Tags: evaporation
laksate
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#1
Oct31-08, 08:21 PM
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A cold beverage can be kep cold even on a warm day if it is slipped into a porous ceramic container that has been soaked in water. Assume that energy lost to evaporation matches the net energy gained via the radiation exchange through the top and side surfaces. The container and beverage have temperatures of 15 degrees C, the environment has temperature of 32 degrees C and the container is a cylinder with radius of 2.2cm and height of 10cm. Approximate the emissivity as 1 and neglect other energy exchanges. At what rate dm/dt is the container losing water mass.

Now I have attached the solution from the solutions manual. However my problem with the solution is shouldn't it be considered that heat must be transferred to bring the temperature of the water up to 100 degrees C?
Attached Thumbnails
66_sol.jpg  
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laksate
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#2
Oct31-08, 08:50 PM
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can you guys access the attachment or is it still pending approval
LowlyPion
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Oct31-08, 09:48 PM
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Quote Quote by laksate View Post
can you guys access the attachment or is it still pending approval
Generally it's better to put in a link to the picture if you can.

laksate
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#4
Oct31-08, 10:58 PM
P: 3

Evaporative cooling of beverage problem involving thermodynamics and heat concepts


Well I only have the file, it is not available anywhere on the internet. The picture has been approved and now you guys can view the picture.

Can anyone help me with this problem?
tiny-tim
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#5
Nov1-08, 04:44 AM
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Thanks
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Hi laksate ! Welcome to PF!
Quote Quote by laksate View Post
Now I have attached the solution from the solutions manual. However my problem with the solution is shouldn't it be considered that heat must be transferred to bring the temperature of the water up to 100 degrees C?
No evaporation happens without any change in temperature

even at "room temperature", some of the molecules are going fast enough to get away!

For some more detail, se http://en.wikipedia.org/wiki/Thermal_radiation


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