On 3/03/2012 11:42 PM, Ed Pawlowski wrote:
> On Sat, 03 Mar 2012 19:27:48 +1100, >
> wrote:
>
>
>
>>
>> Let's try this again...
>>
>> What is condensate if not steam that has been condensed? If you have
>> condensate on the walls of your bathroom after having a shower, how did
>> the condensate get there? Was it a "miracle"?
>
>
> It sure was not from steam. To make steam, water has to be heated to
> a minimum of 212F at sea level. Steam is invisible, a vapor. When we
> "see" steam, it is really vapor mixed with the condensate.

So pray tell how evaporative cooling works? They sure as hell don't boil
the water in those systems yet they cool through latent heat of
evaporation. Something's evaporating in them and it's my guess it is the
water.
>>
>> Now, let's look at fog. Fog is technically water vapour which has
>> condensed. Been down to the river lately. Go down there on a cool
>> morning sometime just as the sun is rising. You will see "fog" rising
>>from the water. This fog is just condensate. It was given off from the
>> surface of the water as steam or water vapour if you prefer.
>
> Half right. No steam in the river. Have you ever seen a river boil?
>
Latent heat of evaporation again.
>
> Water vapor is formed by evaporation or boiling. Water vapor though,
> is not steam. Water vapor can condense on the walls when you shower,
> it can condense over a river, make clouds in the sky.
>
> Sublimation can also form water vapor. Much of the snow in Alaska is
> sublimated rather than melted.

Have you ever poured a little methylated spirits onto the skin of your
hand? Noticed that your hand suddenly begins to feel cold? Do you know
why that is?

The boiling point of methylated spirits (denatured alcohol) is very
close to that ethanol which is 78 °C (172 °F). It has a lower boiling
point than water but not by all that much in the general scheme of
things. The methylated spirits you put on your hind will soon disappear.
If you prevent runoff, it will still disappear. Where does it go? Easy,
it evaporates. It changes state and will turn into a gas. Has it reached
boiling point in order to do this? No! At least I cannot see it boiling.
The body temperature of a healthy human being is 37.5C (99.5F). So it
would seem that the heat of the human body into which this methylated
spririts is in contact is insufficient to bring it to the boil. So why
does the methylated spirits evaporate at only 37.5C? The methylated
spirits does not need to be raised to boiling point in order to
evaporate, it just needs the application of considerable amounts of heat
energy and it gets it from your body heat. That's why your hand feels
cold, its heat is being removed from the area of contact more quickly
than your blood flow can replace it.
QED, it is the amount of heat energy applied to the methylated spirits
that determines the rate of evaporation, not the absolute temperature of
the methylated spirits itself.
The same principle applies to water. Methylated spirits demonstrates the
principle better than water as you can definitely feel the heat being
removed from your skin.

Have a look at this Wikipedia entry;

http://en.wikipedia.org/wiki/Latent_heat

If you're feeling brave, look at this one;

http://en.wikipedia.org/wiki/Enthalpy_of_vaporization


--

Krypsis