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Re: [Phys-l] The Rain it Raineth.



2B should be correct.

At 20 degC the saturation vapor pressure is around 22 kPa, so at 50 percent
RH the actual vapor pressure in the room is 11 kPa.

Water at 2 degC has a saturation vapor pressure of about 3 kPa, so the vapor
in the room would condense on the cool droplets.

Bob at PC

-----Original Message-----
From: phys-l-bounces@carnot.physics.buffalo.edu
[mailto:phys-l-bounces@carnot.physics.buffalo.edu] On Behalf Of Brian
Whatcott
Sent: Saturday, May 27, 2006 3:15 PM
To: phys-l@carnot.physics.buffalo.edu
Subject: [Phys-l] The Rain it Raineth.


I ran across an interesting debate on a newsgroup recently.
I will put it in the form of a pop quiz for your entertainment.

[Warning: information relayed from newsgroups, like excerpts
from provincial newspapers, is not guaranteed to be correct]

In an experimental setting an ordinary room of 4000 cubic feet
was provided with a fan and a shower head over a drain in
one corner. This air mixed quickly with the room air.
Air leakage into the room was minimized.

Q1: The room air temperature was 20 degC, humidity 50% RH
What was the effect on the room's humidity of opening a faucet
to the shower head and blowing room air through the water fall
at a rate of 400 cu ft/min?
1A: The room's humidity increased
1B: The room's humidity decreased.
1C: the room's humidity was unchanged.
1D: Unsure.

Q2: If you answered 1D to Q1, then here is further information -
the temperature of the water falling from the shower could be switched
to 2 degC, or 20 deg C or 80degC.

If the fan was started with the water temperature set to 2 degC,
other conditions as above, which of the following was observed:
2A: RH increased in the room
2B: RH decreased
2C: RH unchanged.

I will relay the received answer in a day or two, if it is not
generally recognized by that time.


Brian Whatcott Altus OK Eureka!


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