Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: [Phys-l] Water vapor condensation



Antti,
Since condensation is a nucleation process, the roughness of the surface may play a significant role since rough spots are good nucleation sites. Consider a different situation, boiling. When the surface of the container is smooth, you can easily superheat water above the normal boiling point because there are few sites for the vapor to nucleate and form. If there is a rough surface in the water, that bubbles form easily and boiling occurs normally.
I recall seeing a presentation from a chap from King's in London, as I recall, in which he showed that the boiling point of water could be changed simply by adjusting the number of nucleation sites and the rate of heating. You could think of it as heating being the energy input mode and boiling the energy loss mode, and the temperature at boiling being a measure of the balance of these two kinetic processes.

So the roughness may affect the rate of water condensation. As I think about it, the resulting drop size will affect the rate of reevaporation ie small water drop size means more surface area and smaller radius of curvature, probably leading to a larger evaporation rate. Since the amount of condensed water depends on the balance between condensation and evaporation, it could have an effect, not sure how large.

Perhaps another factor is the cleanliness of the surface. If there are oil or grease on the surface the nucleation will be different than on a cleaner surface.

just some thoughts, hope it helps.

joe
Joseph J. Bellina, Jr. Ph.D.
Professor of Physics
Saint Mary's College
Notre Dame, IN 46556

On Jul 2, 2010, at 4:58 AM, Savinainen Antti wrote:

Hi,

a student of mine is doing a HS project in which she is seeking for a correlation between relative humidity and temperature difference of a surface and air. Her idea is to use a plate that is taken from a freezer and measure the mass of water condensed onto the plate within a certain time frame. Obviously, among other things, the mass depends on the area of the plate.

I was wondering whether of not any other properties of the *surface* besides the area, temperature difference might affect the condensing. Could you suggest a useful reference related to the project topic? AJP and TPT has already been
looked for.

Regards,

Antti



Antti Savinainen, Ph.D., B.Ed.
Adjunct Professor (University of Jyväskylä)
Senior Lecturer in Physics and Mathematics
Kuopion Lyseo High School
Finland
E-mail: <antti.savinainen@kuopio.fi>
Website: <http://kotisivu.dnainternet.net/savant/>


--

********************************************************************** **********************
Viesti on tarkastettu roskapostisuodatus- ja virustorjuntaohjelmistolla.
Tarkastuksesta huolimatta noudata asianmukaista varovaisuutta liitteitä avatessasi.

Istekki Oy
********************************************************************** ***********************

_______________________________________________
Forum for Physics Educators
Phys-l@carnot.physics.buffalo.edu
https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l