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.