Why vent fully open?

Started by Nizztos, October 20, 2011, 11:19:54 AM

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Caneyscud

However,  in a Bradley you are probably dealing with water vapor and not steam.  Steam is just water vapor that is above the boiling point.  Until well into the cook does the temp of the meat gets past the boiling point and even then only at the surface or near the surface.  So up until then the moisture is due to evaporation and is water vapor.   And if your CT is 200 or 220, you aren't making much if any steam.  Moist air can hold a lot more heat than dry air.  Maybe it absorbs more of the limited heat that the element puts out than dry air does. 

or maybe

Dry air can get hotter than moist air because it doesn't contain the water that must change states before it can get hotter.
"A man that won't sleep with his meat don't care about his barbecue" Caneyscud



"If we're not supposed to eat animals, how come they're made out of meat?"

Sailor

This has become a very interesting topic.  I am not a scientist and sure wish I knew the answers.  Here are some things to think about.  If it's true that water boils and creates steam at 212 degrees then would it not make since that steam is being created in a smoker if the cabinet temp is greater than 212 degrees?

It is my understanding that steam is considered a gas and water vapor is just tiny water particles suspended in the atmosphere.   So if this is true then would it be true that a smoker is producing both steam and water vapor?  If water and water vapor changes to a gas at 212 degrees then would it be true that the vent is ejecting steam and not vapor when the cabinet temp reaches 212 degrees? 

We have humidity that we are also dealing with.  As 1 cubic foot of heated air/smoke is taken out of the cabinet we are replacing that cubic foot of air with ambient air that hold the current humidity.  Is humidity considered to be water vapor?  If this is true then the cabinet does have water vapor being introduced all through the cook.  Remember the water pan has water that is heated and producing water vapor also.

It takes 1,334 BTU's are required to raise 1 gallon of water from 40 degrees to 200 degrees Fahrenheit.  So would it not be true that it will take less BTU's to heat a cabinet that has meat put in at 77 degrees?  Would it not be true that if the meat temp comes up to 100 degrees it will take less BTU's to get the meat to 200 degrees.  If this is all true then would it be true that to heat up and maintain a cabinet temp of 225 degrees it is best to eject as much water vapor and steam as quickly as possible?

If the cabinet temp is 225 and the exterior of the meat is 190 degrees with an IT of 140 degrees are we producing steam in the meat.  I would think not since the meat is not at boiling point.  Would it be true that the meat is creating water vapor at the above temps?  I would think so as the water is evaporating and becoming water vapor.  If this is true then again would the water vapor coming off the meat turn into a gas as the cabinet temp is above 212?

My head hurts and I need a beer  :o


Enough ain't enough and too much is just about right.

phild

'latent heat' may have something to do with it.
http://www.splung.com/content/sid/6/page/latentheat

In this case the additional energy required to cause the phase state transition of the moisture in the cabinet to a gas (steam).


Habanero Smoker

The definition of steam has come up before. We commonly think of steam as a product of boiling water, but as phild pointed out the term steam is used for water in it's gaseous state, so water that evaporates at any temperature produces steam, and can raise the RH level of the air.

Depending on the temperature of the air will determine how much moisture it can hold before condensation begins. If the steam cannot escape then condensation will begin, once condensation begins, it takes more energy to convert the condensation into steam, so the heat goes toward converting water into steam, instead of heating the air.



     I
         don't
                   inhale.
  ::)

GusRobin

Long story short, just keep the @#&% vent open!
Just kidding,I also enjoy the scientific explanations.
"It ain't worth missing someone from your past- there is a reason they didn't make it to your future."

"Life is tough, it is even tougher when you are stupid"

Don't curse the storm, learn to dance in the rain.

Nizztos

I really think I need to experiment a bit. I can be a bit contrary when all the pieces of a puzzle is not in front of me ....

We decided that vent has to be open to keep temperature up. But it seems to me that we came to that conclusion based on what water does to temperature. Not what the chicken does to temperature. I.e. how do I know that the chicken releases enough water to make the arguments valid? (my missing piece of the puzzle)

One of these days I will buy a couple of frozen chickens that I thaw and cook one at a time with vent fully open and less open to see if temperature is affected (by a single chicken).

It is not obvious to me that a single chicken would release more water than a cabinet filled with buts for instance.
American chickens seem to be way larger than ours though, from reading recipe posts, so that could make a difference.

muebe

Here is the honest truth behind the science...

When the vent is fully closed the Bradley Gnome(Who lives in every Bradley) will get really scared and start breathing heavy. He likes the small amount of light he gets from the vent being open when the cabinet door is closed. This heavy breathing and perspiration causes excessive moisture to build-up in the cabinet. And without the vent open he gets really scared causing more sweating and heavier breathing. By opening the vent you alleviate his fear and allow the rest of moisture to escape out the vent. 

This may sound very far fetched but the fact is you cannot argue with science! ;D
Natural Gas 4 burner stainless RED with auto-clean
2 TBEs(1 natural gas & 1 LP gas)
OBS(Auberins dual probe PID, 900w finned element & convection fan mods)
2011 Memphis Select Pellet Smoker
BBQ Grillware vertical smoker(oven thermostat installed & converted to natural gas)

Nizztos

Quote from: muebe on October 21, 2011, 09:42:21 PM
Here is the honest truth behind the science...

When the vent is fully closed the Bradley Gnome(Who lives in every Bradley) will get really scared and start breathing heavy. He likes the small amount of light he gets from the vent being open when the cabinet door is closed. This heavy breathing and perspiration causes excessive moisture to build-up in the cabinet. And without the vent open he gets really scared causing more sweating and heavier breathing. By opening the vent you alleviate his fear and allow the rest of moisture to escape out the vent. 

This may sound very far fetched but the fact is you cannot argue with science! ;D

LOL

Does that make other food than poultry comfort food then :)

PS It is true that the full open thing applies to poultry only? Or did I miss something?

GusRobin

my vent has been wide open from the first day.
"It ain't worth missing someone from your past- there is a reason they didn't make it to your future."

"Life is tough, it is even tougher when you are stupid"

Don't curse the storm, learn to dance in the rain.

Habanero Smoker

Nizztos;

You are right. One chicken with skin, may not make that big of a difference. I always adjust my vent according to what I am cooking and how large the load, but with any amount of chicken with skin I always start with 3/4 open and adjust from there. During the cooking occasionally I will hold my hand over the vent to check the moisture. Checking the moisture this way takes a little practice, but after a few tries, you will see that you can hold your hand over the vent longer when air is dryer, then when it is saturated with moisture; even though the cabinet temperature is the same during both tests. As the air feels dryer I will slightly close the vent.

I do know that cooking chicken with skin absolutely will bring your cabinet temperature done more the whole muscle meats. Skin has a lot of moisture. My thought is that moisture from the skin will release easier and faster than the moisture that is trapped in the cells of a 8 pound butt, or a 10 brisket.

Large loads generally will produce a lot of moisture, picnic shoulders or hams with skin on will also produce a lot of moisture in the cabinet.

Quote from: GusRobin on October 21, 2011, 01:43:55 PM
Long story short, just keep the @#&% vent open!
Just kidding,I also enjoy the scientific explanations.

;D   ;D   ;D   ;D   ;D



     I
         don't
                   inhale.
  ::)

viper125

Hmmm now you got this old country boy confused. I was always taught to raise the humidity in a house in the winter. This is because moist air heats quicker and holds more heat. If so it causes you to be warmer. This is what I thought all these years.
First problem I had with the Bradley was it wouldn't heat enough while doing a load of ribs. Found out I had to open vent all the way. Then it proceeded to warm up.
Ok in a simple basic language could some body tell me whats wrong and why with my theory. I'm not calling anyone wrong or me right. Just a little thick skulled some times. And I want to understand.
A few pics from smokes....
http://photobucket.com/smokinpics
Inside setup.

Wildcat

Generally, one wants to not let the air in the home get too dry in the winter. Heat (gas, wood, coal, oil, etc. in particular) tends to get the air so dry that many (including myself) have sinus problems and nose bleeds. In high heat and humid environments we tend to feel the heat more. Likewise in a cold humid environment we tend to feel the cold more. At the same time, the moisture in reality actually helps to moderate the heat and cold. The desert is very hot, but the Gulf Coast feels hotter and and more stuffy at the same temp due to the higher humidity. In the desert communities many people have swamp coolers vice air conditioners which is basically air being forced through water vapor. The water absorbs the heat in a dry environment and cools the air which is forced into the home.
Life is short. Smile while you still have teeth.



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Habanero Smoker

Quote from: viper125 on November 02, 2011, 01:00:49 PM
Hmmm now you got this old country boy confused. I was always taught to raise the humidity in a house in the winter. This is because moist air heats quicker and holds more heat. If so it causes you to be warmer. This is what I thought all these years.
First problem I had with the Bradley was it wouldn't heat enough while doing a load of ribs. Found out I had to open vent all the way. Then it proceeded to warm up.
Ok in a simple basic language could some body tell me whats wrong and why with my theory. I'm not calling anyone wrong or me right. Just a little thick skulled some times. And I want to understand.

Raising the RH in your house will have very little to do with your house temperature rising faster. Though warmer air can hold more moisture, the amount of moisture does not increase the heat.

In addition to what Wildcat pointed out, 70°F with 70% RH, will feel warmer then 70°F at 25% RH. It has to do with the rate the body will perspire. The drier air makes it easier for moisture to evaporate from  the skin, the faster the evaporation rate the cooler we feel. When you watch the weather you will frequently hear the weather person state it is 70°F, but will feel like 72°F. To find out more on how RH effects human comfort do a google on "heat index", that should explain it more clearly.




     I
         don't
                   inhale.
  ::)