Cooking For Engineers

smellthatsmoke · Joined: 17 Jul 2007 Posts: 3 Location: St. Louis, Mo

I posted this question on another forum (Barbeque news forum) And was sent here to get a better explanation of what was happening inside my smoker on my last cook.

To add further info...I am using a small Brinkmann Smoke-N-Pit offest smoker with all the usual modifications. A baffle between firebox and smoke chamber, smokestack extension to bring it level to the cooking grate, charcoal basket...(an improvised basket)...it's really a vegetable basket for a grill.

My question was posted as follows-

I know there is always a debate on the use of water pans, and I'm not one to favor their use, but I tried using one on my last cook and have some questions about the effects.

I am in the process of trying to even out temps in my offset, so I figured I would give the water pan a shot...as well as some strategic placement of 2 drip pans.

I placed two aluminum drip pans side by side with one edge resting right on my baffle, and about an inch space between this pan and the next drip pan in effect creating a channel for the heat to travel under them to the far side of the chamber. (poor man's tuning plates)

I placed a loaf pan about 3/4 full of water right on top of my baffle right next to the chamber wall.

These things did even out my temp differences greatly, but it also had an effect I wasn't anticipating. I couldn't get my temps over 235 no matter how big my fire was. I kept adding and adding fuel with exhaust and intake full open but the temp held amazingly steady around 235.

Once the water got to about 1/4 full then the temp started to slowly rise, and once the water was gone it rose to around 290...at that point I finally had to shut my intake down to about 1/4 open to get back to low and slow range.

I had no idea that a water pan did this. How is this possible? I didn't even have the pan in the direct flow coming from the firebox.

I'm a little confused about the science behind this. I know water turns to steam at 212 degrees, and I figure the water was absorbing a great deal of the heat, but I am looking for more insight into this.

Can anyone explain this to me?

Thanks

Michael

I've been told that you guys are a smart group, and I hope you can help me understand what was happening inside my smoke chamber. I'm just trying to get the most even temps I can in my smoker, and understanding this will help me to reach that goal.

Howard · Joined: 21 Nov 2005 Posts: 64

Same reason why a pot of water cannot exceed 100C until all (well, most) of the water is gone.

GaryProtein · Joined: 26 Oct 2005 Posts: 535

smellthatsmoke · Joined: 17 Jul 2007 Posts: 3 Location: St. Louis, Mo

Ok I understand that, but if I put a pan of water in my oven it won't stall at 235 degrees...will it?

Thats where I'm confused.

GaryProtein · Joined: 26 Oct 2005 Posts: 535

The conversion of liquid water to vapor consumes a significant amount of energy-much more than heating air. If you had much more fuel (wood, gas, etc.) you could get the temperature higher more easily but the presence of the water buffers or tempers the temperature variations inside the smoker. The relatively limited air supply and space for burning wood (not necessarily gas, except that the gas burner has low BTU's) inside a smoker is a limiting factor in preventing large temperature rises in a smoker. They are designed to cook at low temperatures so the smoke can have a long exposure to the food as it slowly cooks. If the smoker had a large gas burner or allowed you to burn a roaring wood fire inside, you would just have a wood or gas fired oven.

Thor · Joined: 24 Jul 2006 Posts: 112 Location: Camp Hill, PA

GaryProtein · Joined: 26 Oct 2005 Posts: 535

smellthatsmoke · Joined: 17 Jul 2007 Posts: 3 Location: St. Louis, Mo

Ok that makes sense. I'm starting to get it now.

Here's a what if........what if I put salt into the water? Raising the boiling point. Whats your best guess as to the temp could I reach inside the smoke chamber?

Who's this dude who cycles his fridge on and off?

I don't even know what your talking about on that one and it made me laugh.

GaryProtein · Joined: 26 Oct 2005 Posts: 535

Where's a chemical engineer when you need one? Isn't the molal bp elevation of water something like .5 deg C per mole of ion? A 1 molal solution will only raise the bp of water by one degree C. I'm thinking back a LONG LONG time here so my number may not be exact. I don't think I'd bother with the salt. It won't make a difference in your cooking time.

Adding salt to water when boiling foods to raise the bp, to me anyway, is of no value. You need about 58 g (two ounces by weight for you non-metricized people) of salt per liter (quart) to raise the bp only one degree C (or less than 2 degrees F). That change in bp doesn't even qualitfy for a high altitude recipe adjustment. To me, that is way too much salt for flavoring anything. If you want to add salt to water, do it for the flavor, not bp elevation.

There was someone who wanted to defrost a turkey, I believe, by cycling his fridge on and off every few hours.

Michael Chu · Joined: 10 May 2005 Posts: 1654 Location: Austin, TX (USA)

If you're interested in the refrigerator power cycling turkey thaw, read this thread:
http://www.cookingforengineers.com/forums/viewtopic.php?t=923

I too had a good chuckle when Thor mentioned it. I even stopped and told my coworkers about it, but they didn't find it as amusing as I did.

Thor · Joined: 24 Jul 2006 Posts: 112 Location: Camp Hill, PA

Yeah. The fridge turkey thawer dude. I think his name was "Guest". He seemed to have a better developed working knowledge of thermodynamic principles than I, and he gave the impression he could support his theories with calculations, tables, and maybe even charts and diagrams. This would be a good problem for him. I remember enjoying thermo a LONG LONG time ago. Then I passed my EIT exam and drove across country. By the time I returned, PV=nRT was no longer part of my repertoire.

I agree that chemically changing the water will not likely improve the current smoker problem. I'm leaning towards smaller amounts of water, or intermittent insertion of smaller amounts of water.

GaryProtein · Joined: 26 Oct 2005 Posts: 535

I'm still curious to know why the smoker has a problem. If it gets to 235F, that's hot enough to break down the collagen fibers, and cook what you want to smoke. Just leave your food in there, and walk away. Check it every couple of hours, but basically leave it alone. You don't want your smoker to get too hot because if you smoke it long enough to get the smokey goodness into it, you'll end up with 4 pound DRY smokey pork shoulder resembling jerky, instead of the delicious succulent roast that it can be.