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Simple Thermodynamics?
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SloppyGroove
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PostPosted: Wed Mar 05 08 8:06 am    Post subject: Simple Thermodynamics? Reply with quote

Now I’ve been catching little bits about this sand versus water business and I’m still a little undecided on the whole thing. I’ve always used hot water in my water pan. I never use cold because it has problems getting up to temp. But on more than one occasion I’ve seem suggestions on sand. Now I know the pan is to help deflect some of that heat coming in. But simple thermodynamics here,…water evaporates with heat. And in a smoker that keeps thing in the air a little humid if not moist, and for long cooks I can see this as being a benefit. But how would sand have an advantage in this case, besides retaining heat and conserving fuel? Obviously no additional moisture. No matter if you think your wrong or right or even a simple guess,I would still enjoy hearing your input. Thanks!

Last edited by SloppyGroove on Wed Mar 05 08 8:10 am; edited 1 time in total
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Harry Nutczak
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PostPosted: Wed Mar 05 08 8:09 am    Post subject: Reply with quote

Sand can be heated well above 212 degrees while water has a maximum obtainable temperature of 212 degrees, (depending on barometric pressure and altitude)

So water acts has a heat exchanger leveling out the temperatures to the low to mid 200 degree mark
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Ozz
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PostPosted: Wed Mar 05 08 8:14 am    Post subject: Reply with quote

Only time I think you'd use sand would be in the colder months. It would/should help in temp stabilization.
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SloppyGroove
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PostPosted: Wed Mar 05 08 8:18 am    Post subject: Reply with quote

Quote:
Sand can be heated well above 212 degrees while water has a maximum obtainable temperature of 212 degrees, (depending on barometric pressure and altitude)

So water acts has a heat exchanger leveling out the temperatures to the low to mid 200 degree mark


So sand would be good for anything your running above the 212 range...correct?
So that mean that temps above a certain amount (in this case water)would not be an effective heat exchanger due to its boiling point.
But would evaporation/condensation still be useful for meats? Or would it be negated at a certain temp?
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roxy
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PostPosted: Wed Mar 05 08 8:19 am    Post subject: Reply with quote

But sand will absorb heat and over a long cook that will effect the temp causing you to have to adjust air flow to regulate the cooking temp... which means defeating the beauty of the design of the cooker... Dont make much sense to me but what do I know.
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SloppyGroove
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PostPosted: Wed Mar 05 08 8:22 am    Post subject: Reply with quote

Love the modesty roxy! Laughing Thanks.

Quote:
Only time I think you'd use sand would be in the colder months. It would/should help in temp stabilization.

that's a great point Ozz...I can see how that would help in the colder months.
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burgandy-smoke
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PostPosted: Wed Mar 05 08 9:28 am    Post subject: Thermodynamics 101 Reply with quote

roxy wrote:
But sand will absorb heat and over a long cook that will effect the temp causing you to have to adjust air flow to regulate the cooking temp... which means defeating the beauty of the design of the cooker... Dont make much sense to me but what do I know.


Sand and water both serve as a thermal mass. Both absorb and retain heat. Also, the process of converting water to steam requires more energy (heat) and, as Harry N said, water is limited to 212 degrees (at sea level).

I think that both have advantages for different uses. I hope that this doesn't become FOIL/NO FOIL.


I read on the forum not too long ago that you can pre-heat the pan of sand on the grill.
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bigabyte
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PostPosted: Wed Mar 05 08 11:38 am    Post subject: Reply with quote

I control my temps by the amount of fuel that is burning in my WSM. I know how many lit coals to add, where to place them, and where to set the intakes, and I know what the cooker will run at. I don't see a need to use water at all. I'm not saying it's a bad idea to use water, I just don't see the benefit.

As for the heat issue, the only thing staying near 212 is the water. The air going around and up over the pan can be much hotter. Steam is not limited to 212 degrees, it can get much hotter. You can run your vertical with a water pan over 212 degrees very easily. So the whole idea of keeping temps down seems a little ridiculous to me. If it works for some, then that's great, they shoudl keep using it.

I like the fact that I do not have to refill my pans, that it is easy clean up because I just put foil on and take it off when done, and that it takes a long time for the sand to lose heat which helps in windy conditions. I cooked this last weekend with 40+ mph wind gusts, and the temps stayed rock soild in my WSM's the whole time (except when I took the lid off of course).

Also, the heat the pan is designed to deflect is direct heat. You could leave the pan empty to block this, and is called a baffle in offsets.
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DawgPhan
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PostPosted: Wed Mar 05 08 12:57 pm    Post subject: Reply with quote

Yeah I have moved away from using water in my WSM. I have been just wrapping the pan in foil and calling it done. I like the results that I get using a foiled pan in conjunction with a stoker. With water it is always a mess to deal with and you need to maintain the water or it boils out and messes up the temps.

Of course I do use the water pan in my BWS, but that seems to cook a little differently.
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Harry Nutczak
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PostPosted: Wed Mar 05 08 2:33 pm    Post subject: Reply with quote

WoooDoggy wrote:


Steam is not limited to 212 degrees, it can get much hotter. .


Only if it is under pressure, otherwise water and it's vapors are limited to maximum temperature of 212 degrees.
From my nderstanding of bullet/water smokers is the water absorbs the heat, evaporates the water in the pan to both keep the meat from drying out, and to keep the temperature in that 200-220 degree sweet-spot for low & slow!
The evaporation of water has a cooling effect, That is the whole basis of why we sweat!
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Satch
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PostPosted: Wed Mar 05 08 4:58 pm    Post subject: Reply with quote

Being a physicist (got my Bachelors' from Bucknell University in Physics) I figured I could add some to this conversation:

The main principle of Thermodynamics is this: The entropy of a given thermodynamic system will tend toward a maximum value. This occurs when the thermal energy of the system is distributed equally throughout the entire system. You do this all the time when placing Ice into a glass of warm liquid. The warm liquid has far more thermal energy then ice, so heat is transferred from the liquid to the ice. The heat from your liquid does work on the ice by changing the state of the ice into water. (This is a result of the first law of thermodynamics). Lets apply this principle to our Q:

Heat enters your system from your charcoal, heating element, propane burner, or wood. Due to the Second Law mentioned earlier, all entities in the thermodynamic system will take the same temperature as to maximize the amount of entropy in the system. The water regulates temperature because it cannot exist in its liquid state above 212*F. The only way to get it above this temperature is to vaporize (boil) it all to its gas form. The water acts as a temperature regulator because the amount of energy needed to vaporize water is extremely high. With adequate ventilation this vapor then flows out of the system. As long as you provide a source of continuing heat capable of pumping heat into the water, your temperature inside the cooking chamber will never rise above 212*F. (I am assuming a completely homogenous system here, which does ignore the fluid physics of the air movement in the chamber, but is a close enough approximation for this discussion.) Bottom Line: Water = heat sink for hot fires.

Sand on the other hand, does not vaporize at any temperature close to what is achieved in a smoker. Your sand instead acts as, basically, a storage unit for excess heat. An example: You wish to smoke your tasty meat at 235*F, but you have trouble maintaining a consistent fire. So instead of cooking your meat anywhere between 180* and 275* (or what ever your cooker's variation may be, you decide to add a sand pan near your meat. After bringing your cooking chamber up to heat, you add your sand and meat. The meat absorbs heat from the heated air and smoke, which does work on the liquids in the meat (warms them), the proteins of the meat (warms and denaturates them, a fancy word for the changes of peptide bonds in a protein) as well as the fats in the meat (warms and renders them). The sand also absorbs heat from the hot air, warming to the air's temperature. Now, all of a sudden, your fire peters out! Without sand in the chamber, the temperature of the air inside the chamber nosedives (because the specific heat of Nitrogen gas is very low). However, the temperature of sand does not fall as quickly as temperature of air. The sand's temperature slowly falls as it radiates its heat back into the air in the chamber, which in-turn keeps your meat cooking at a temperature close to your desired temp. The opposite happens when you kick that fire up to 11, and blast super hot air into the cooking chamber. The sand helps collect that extra heat, keeping that hot air blast from damaging the Q as much as it would have w/o the sand. Bottom line: Sand = insulation for your meat.

That being said, from a temperature control aspect: Water is most useful for managing fires that can be too hot, while sand is more useful for managing fires that are inconsistent. While it's true that water can basically be used to do the same job as the sand, I'm not sure how many people want a lot of excess water soggying up their ribs, and de-crusting their bark. Thats a physicist's objective take on the situation, least ways.
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Satch
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PostPosted: Wed Mar 05 08 5:03 pm    Post subject: Reply with quote

WoooDoggy wrote:
Steam is not limited to 212 degrees, it can get much hotter.


That is true, if you have a system with a pressure over 1ATM. Since smokers require airflow, the pressure inside is not going to be noticably different inside the smoker. Running a smoker w/ water pan above 212 is a result of air coming off the ehating element that has not yet lost it's excess heat to the water.
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xxfubarxx
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PostPosted: Wed Mar 05 08 8:48 pm    Post subject: Reply with quote

I just got home from work and that hurt my brain. After reading it 4 or 5 times I think it made sense, sorta. I need an adult beverage now. I should have just read the last paragraph. Confused
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gotwood
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PostPosted: Wed Mar 05 08 11:48 pm    Post subject: Reply with quote

water takes 1 calorie to raise its temperature 1 degree.
BUT... 212 degree water takes 540 calories to be converted into 212 degree steam...per gram that is
steam contains much more energy...that is why you need to be very careful and why burns can be so bad from steam

this huge amount of energy that is needed absorbs tons of energy that would otherwise be running wild in your smoker.
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bigabyte
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PostPosted: Thu Mar 06 08 12:48 am    Post subject: Reply with quote

Tjose of you who believe that putting a water pan in a WSM will limit you cooker to 212 degrees are really fooling yourselves. Even without the pressure, just because there is steam in the cooker does not keep the temp in the cooker from going over 212. Everyone has their preferred way of doing things, but trying to convince a newbie that the pit temp won't go over 212 if they use a water pan are really doing a disservice to that new person. I cooked a WSM just last weekend with a water pan as part of my experiment and the temp held steady at 275, well over 212. The WSM right next to it with the sand pan also held 275 temps, and I used the same amount of charcoal/wood, and started both cookers with the same number of lit briquettes. No difference was noted in temps in the cookers.
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roxy
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PostPosted: Thu Mar 06 08 1:07 am    Post subject: Reply with quote

I second that one Wooodoggy
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SloppyGroove
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PostPosted: Thu Mar 06 08 1:08 am    Post subject: Reply with quote

Sand it is! Shocked Very Happy
Or maybe water.... Smile
Thanks guys! I appreciate all your feedback, each and everyone one of you! Wink
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Harry Nutczak
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PostPosted: Thu Mar 06 08 1:42 am    Post subject: Reply with quote

Nobody ever stated that using a water pan will keep a cooker from exceeding 212 degrees. We stated that water and it's vapors cannot exceed 212 degrees if not under pressure.
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Teleking
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PostPosted: Thu Mar 06 08 1:52 am    Post subject: Reply with quote

Let me throw a wrench in the mix. What happens if you use both a water pan and a pan with sand in it???
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PostPosted: Thu Mar 06 08 2:38 am    Post subject: Reply with quote

Alien BBQ Heat and Water Experiment

There are a few controversies that spark a heated discussion among the BBQ brethren. Discussions such as fat side up or fat side down, foil or no foil, and water or no water. In this experiment we will look at the effects of water in the pan of a ECB. The belief is that by putting water in the pan above the fire in an ECB, you can control the temperature of the pit to around 212 degrees (the point at which water boils.)By doing so, you can properly smoke your meat for long periods of time at that temperature.
We start this experiment on a normal non-windy day. The outside air temperature is 54 degrees and I will be using an ECB loaded with Kingsford charcoal.




Once the charcoal is going, I took my first temperature reading without water in the pan. Within the past few years there has been interest in putting sand instead of water in the pan. The idea is that sand would create a heat mass and would not reduce the temperature like water. The pan itself acts like a shield already so the sand inside would just be adding thermal mass. I have tried this on many occasions and it does work. You do get higher temperatures with sand instead of water. However, while it does even out the temperatures to a more constant range, once you exceed your target temperature, it is hard to get the temperature down quickly. If you have only water in the pan, you can simply add cold water to drop the pit temperature. Sand in the pan should only be considered when you want temperatures in the 325 – 400 degree range and or during winter conditions.



With just the pan (no water) in the ECB, the temperatures rise quickly to 411 degrees.



I am using three temperature gauges to verify my findings. Two digital probes and the gauge spring gauge on the smoker (not OME.) The digital probes read the same throughout the experiment. The spring gauge is pegged out reading 450 degrees (a 39 degree difference.) This shows the importance in not using this type of gauge and why they should be replaced out of the box.



After the temperature evened out, I added one gallon to the water pan. I used hot tap water @150 degrees to speed the time the smoker would take to recover.
It is important to note that the more food (mass) you put in a smoker, the more heat it pulls out of the surrounding internal air. In a small smoker such as this, where you do not have a lot of thermal mass to offset adding cold meat, the temperature swings can be dramatic.

After about 15 minutes, the smoker has settled down to 267 degrees. This is well above the believed 212 degree ceiling. The reason for this difference is thermal plumes. Anyone who has cooked on an ECB type smoker knows that the hottest part of the cooker is on the sides. While the fire is heating the water to 212 degrees, there is hot air that escapes around the edges of the pan that can still be as high as 400 degrees or more. It is the mixed air (caused by air flow) at the top of the ECB that your temperature gauge is reading.



You can see that the spring gauge is still off by about 40 degrees.



Now if you were just going to cook with only charcoal, this experiment would be over. However, this is a smoker and we like smoke, so in goes a large chunk of mesquite to add flavor. This is where many BBQ enthusiasts make a mistake. The mistake involves throwing in too many chunks. When you throw in too many chunks, they all catch on fire at the same time. Fire is generally hotter than coals so the temp spikes, and they freak out over what to do. The solution to this problem is to only put in one chunk or two smaller ones to begin with. Do not mix them in the charcoal at the beginning, or soak them with water for later use. One chunk per hour is more than enough to give you a great smoky flavor.
As you can see after throwing in a chunk of mesquite, the temperature has risen to 303 degrees. Don’t worry; it will go down in about 20 minutes. When it comes to smoking in an ECB you have to work on averages.



The final reading on the spring gauge is 375 degrees (a 72 degree difference.) Is there any better reason to get yourself a nice probe. It is no wonder that so many new individuals to BBQ have such a big problem with producing consistent BBQ. You have got to know what is going on inside the pit to correctly cook you meat. When Pit Master University students ask me what to do with the OEM gauge, I normally tell them to leave it in to plug the hole!


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Last edited by Alien BBQ on Thu Mar 06 08 2:55 am; edited 1 time in total
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