The Great Bottle Opener Giveaway

Home Brew Forums > Home Brewing Beer > General Techniques > Evaporation sensitivity to ambient temp?

Reply
 
LinkBack Thread Tools
Old 01-18-2008, 08:43 PM   #1
skifast1
Feedback Score: 0 reviews
 
skifast1's Avatar
Recipes 
 
Join Date: Mar 2006
Location: Lake Zurich, IL
Posts: 311
Liked 3 Times on 3 Posts

Default Evaporation sensitivity to ambient temp?

I'm many years removed from my engineering classes - will the evaporation rate in a full boil be higher or lower at cold ambient temps (assuming equal humidity)? I'm celebrating MLK day by brewing a British Bitter - close enough

__________________
"Those are my principles, and if you don't like them...well, I have others" --Groucho Marx


Primary: echos
Secondary: Nukey Brown
Keg 1: echos
Keg 2: echos
Bottled: Wind 'er Up Winter Ale

skifast1 is offline
 
Reply With Quote Quick reply to this message
Old 01-18-2008, 09:05 PM   #2
Scimmia
Feedback Score: 0 reviews
Recipes 
 
Join Date: Oct 2007
Location: QCA, Iowa
Posts: 959
Liked 5 Times on 5 Posts

Default

Hmm, that's a good question. First off, though, when you say equal humidity, are you talking about relative humidity or absolute humidity? Assuming relative humidity, I think the partial pressure of water vapor would be lower at the lower temperature, so I think that boil off rates would be higher.

__________________
Scimmia is offline
 
Reply With Quote Quick reply to this message
Old 01-18-2008, 09:09 PM   #3
skifast1
Feedback Score: 0 reviews
 
skifast1's Avatar
Recipes 
 
Join Date: Mar 2006
Location: Lake Zurich, IL
Posts: 311
Liked 3 Times on 3 Posts

Default

Ha - I meant relative. There's another subject that made a quick exit out of my brain after the final exam.

__________________
"Those are my principles, and if you don't like them...well, I have others" --Groucho Marx


Primary: echos
Secondary: Nukey Brown
Keg 1: echos
Keg 2: echos
Bottled: Wind 'er Up Winter Ale

skifast1 is offline
 
Reply With Quote Quick reply to this message
Old 01-20-2008, 05:11 PM   #4
modenacart
Feedback Score: 0 reviews
Recipes 
 
Join Date: Nov 2007
Location: New Bern, NC
Posts: 625
Liked 7 Times on 7 Posts
Likes Given: 3

Default

Warm air can hold more mosture so a high ambient temperature should have more boiled off vapor. That is why you see condisation on you window when you have ac blowing on you winshield.

__________________
modenacart is offline
 
Reply With Quote Quick reply to this message
Old 01-20-2008, 05:34 PM   #5
david_42
Feedback Score: 0 reviews
 
david_42's Avatar
Recipes 
 
Join Date: Oct 2005
Location: Willamina & Oak Grove, Oregon, USA
Posts: 25,648
Liked 131 Times on 124 Posts

Default

There will be a slightly greater wort loss when it is cold, but wind is far more important. Wind carries off heat from the flame, the kettle and the blowing over the wort surface accelerates evaporation and heat loss.

__________________

Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"

"I would like to die on Mars, just not on impact." Elon Musk

david_42 is offline
 
Reply With Quote Quick reply to this message
Old 01-20-2008, 05:39 PM   #6
modenacart
Feedback Score: 0 reviews
Recipes 
 
Join Date: Nov 2007
Location: New Bern, NC
Posts: 625
Liked 7 Times on 7 Posts
Likes Given: 3

Default

The wind blowing makes sense because of the moisture gradient, but cold air does not hold more moisture then hot air. It does not make sense that the air being cold will lead to more evaporation.

__________________
modenacart is offline
 
Reply With Quote Quick reply to this message
Old 01-21-2008, 01:49 PM   #7
Scimmia
Feedback Score: 0 reviews
Recipes 
 
Join Date: Oct 2007
Location: QCA, Iowa
Posts: 959
Liked 5 Times on 5 Posts

Default

modenacart, air doesn't "hold" moisture at all. Water vapor can exist, regardless of the presence of air. But yes, more water can exist as vapor in higher temperatures. Don't forget, though, that we're talking about boiling water (HOT), not water at ambient temperatures, and evaporation depends SOLELY on the temperature of the liquid, not the temperature of the air; and with the lower partial pressure of water vapor at lower temperatures, there would be less recondensing on the surface, making me think that boil off would be higher. Now when that water vapor cools to ambient temperatures, a lot of it will recondense, but who knows where that will be. Very little of it in the pot, I'm sure.

__________________
Scimmia is offline
 
Reply With Quote Quick reply to this message
Old 01-21-2008, 01:59 PM   #8
skifast1
Feedback Score: 0 reviews
 
skifast1's Avatar
Recipes 
 
Join Date: Mar 2006
Location: Lake Zurich, IL
Posts: 311
Liked 3 Times on 3 Posts

Default

Woohoo - thermodynamics cage fight!!

__________________
"Those are my principles, and if you don't like them...well, I have others" --Groucho Marx


Primary: echos
Secondary: Nukey Brown
Keg 1: echos
Keg 2: echos
Bottled: Wind 'er Up Winter Ale

skifast1 is offline
 
Reply With Quote Quick reply to this message
Old 01-21-2008, 02:13 PM   #9
Scimmia
Feedback Score: 0 reviews
Recipes 
 
Join Date: Oct 2007
Location: QCA, Iowa
Posts: 959
Liked 5 Times on 5 Posts

Default

The more I think about it, though, I'm not sure that enough of the ambient humidity will be reaching the surface of the liquid to make any difference at all. hmm, doesn't seem like we have any experts in the house, how about personal experiences?

Like david_42 said, though, wind would be absolutely critical. It would carry away the boiled vapor quickly, not giving it a chance to recondense into the kettle.

__________________
Scimmia is offline
 
Reply With Quote Quick reply to this message
Old 01-21-2008, 03:10 PM   #10
modenacart
Feedback Score: 0 reviews
Recipes 
 
Join Date: Nov 2007
Location: New Bern, NC
Posts: 625
Liked 7 Times on 7 Posts
Likes Given: 3

Default

Quote:
Originally Posted by Scimmia
modenacart, air doesn't "hold" moisture at all. Water vapor can exist, regardless of the presence of air. .
When water becomes a vapor its in the gas form and becomes part of the "air".
__________________
modenacart is offline
 
Reply With Quote Quick reply to this message
Reply


Quick Reply
Message:
Options
Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
Fermenting in fridge/freezer - when ambient/room temp colder than desired? RoaringBrewer Fermentation & Yeast 15 10-29-2009 01:40 AM
at what point would it help to increase the ambient temp? MisterGreen Beginners Beer Brewing Forum 4 10-15-2009 07:54 PM
Starters and ambient temp. bad coffee Fermentation & Yeast 6 08-17-2009 12:16 AM
Ideal Ambient Temp for Ales in Temp Controlled Environment? xinunix Beginners Beer Brewing Forum 4 05-12-2009 03:58 AM
Ideal ambient temp for lager fermentation temp? tinydancer Beginners Beer Brewing Forum 2 06-30-2008 03:54 PM