Comments on: Is That Really Condensation?

By: Colby

Colby — Wed, 06 Mar 2024 18:06:29 +0000

In reply to RoyC. Allison, I am also curious about this. The table implies that the rate of adsorption is dependent on both RH and temperature, not just RH. Am I missing something?

By: Dale Pickard

Dale Pickard — Thu, 21 Sep 2023 20:29:11 +0000

In reply to Gene DeJoannis. Van der Waals forces give water a number of unique qualities including the phenomenon of siphons. It's kinda sticky to itself.

By: RoyC

RoyC — Thu, 21 Sep 2023 18:39:18 +0000

In reply to Allison Bailes. Allison, that's what I thought, but then why do you say that the moisture content is a function of RH and not dewpoint? Since it is also a function of temperature, I could easily generate a table of moisture content as a function of temperature and dewpoint or any other humidity measurement and temperature.

By: Dale

Dale — Thu, 21 Sep 2023 14:29:49 +0000

Great article! Thanks for sharing this. I’ve learned that vapor pressure is Pressure – capital P!

By: Allison Bailes

Allison Bailes — Thu, 21 Sep 2023 11:43:38 +0000

In reply to RoyC. Roy: In the case of the graphs, the answer is yes. The sample sits in the middle of the chamber, and everything inside is at thermal equilibrium when they make measurements. I haven't done those measurements myself, but that has to be the case if they're measuring equilibrium moisture content. The table comes from a paper on wood being stored outdoors, but they're still talking about equilibrium moisture content.

By: RoyC

RoyC — Wed, 20 Sep 2023 19:17:21 +0000

In the graphs and tables above, is there an assumption that the wood and adjacent air are at the same temperature?

By: Allison Bailes

Allison Bailes — Wed, 20 Sep 2023 11:23:18 +0000

In reply to JayW. JayW: Thanks for sharing that link here. I've just added a table from that paper to the article.

By: Allison Bailes

Allison Bailes — Tue, 19 Sep 2023 19:35:47 +0000

In reply to Gene DeJoannis. Gene: Yes, the microwave oven is a great example of how we take advantage of the water molecule's polarity. Thanks for mentioning that here.

By: JayW

JayW — Tue, 19 Sep 2023 16:17:40 +0000

Have you seen this:

https://www.fpl.fs.usda.gov/documnts/fplrn/fplrn268.pdf

This gives what the moisture content is of wood exposed to the outdoors by location and month. It appears to be for building materials but thought it might apply to seasoning firewood as in the lowest possible drying content for firewood.

Any thoughts?

By: Gene DeJoannis

Gene DeJoannis — Tue, 19 Sep 2023 16:11:21 +0000

Allison, There’s one effect of the polarity of water vapor that turns out to be very handy in daily life. If you apply a high frequency electromagnetic field to a batch of water molecules they will start to oscillate at the frequency of the E-M field. All that molecular jiggling causes a lot of internal friction and the molecule’s temperature will rise. Since virtually all foods contain water you can heat them in an E-M field because of the polarity of the water molecule with two hydrogens off to one side. And that’s what happens when you put food in a microwave oven! Thanks to that peculiar water molecule that is electrically neutral, but polarized by it’s molecular shape, illustrated in your sketch, it jiggles when excited by that E-M field. It would be interesting to read about many other effects of the polarity of water molecules that we are experiencing constantly and not aware of.