Temperature experiment

[car54]

Since switching over to a PID I have noticed that it takes longer to cook something to a desired temperature, which I contributed to the PID's consistency with no temperature over runs.

Last week I smoked a 6 pound pork roast and it took over 16 hours to reach 195 degrees and then only when I increased the box temperature from 205 to 230 degrees. That is when I questioned the accuracy of the thermocouple.

I initially checked it in boiling water and it read 213 degrees, so the accuracy was not the problem. Then I decided to test it in the smoker with boiling water. The smoker was pre warmed to 250 degrees and I added a pot of boiling water to the box.  Because of the heat loss the water was not boiling and after 30 minutes at 250 degrees it was still not boiling so I raised the box temperature to 300 degrees. After 2 hours it was still not boiling I was running out of time and decided to continue this experiment in the stove at a later date.

During the week I bought a temperature crayon that would melt at 200 degrees which has a 1 percent accuracy. At 200 degrees reading from the PID, the crayon would not melt. I had to the raise the temperature up to 215 degrees before the crayon would melt. I also checked the temperature with a Maverick remote temperature reader and it too read 215 degrees so I believe that the PID is reading correctly. There must be some offset in the temperature transfer between air and a solid.

This weekend I continued the boiling water experiment in the stove and after 3 hours at 550 degrees it was still not boiling. It measured 205 degrees.

I have always smoked under the boiling point of 212 degrees believing that at or above that temperature the water would boil out of the meat and dry out. There seems to be a difference between air temperature and a solid mass temperature. My thinking now is the PID takes longer to cook because there are no temperature spikes and I don't think that there will be any harm in raising the box temperature between 5 and 10 degrees.

Your feedback would be appreciated.

Thanks, Brad

[BigSmoker]

I don't have a clue bout none of that but I smoke my products between 225-250 all the time with only 1 bad brisket and it was a select flat. 

[Oldman]

This weekend I continued the boiling water experiment in the stove and after 3 hours at 550 degrees it was still not boiling.....There seems to be a difference between air temperature and a solid mass temperature. 

My take on this is a simple minded one. Air can only hold so many calories of energy. An example of this is in this question: Why does wet steam burn a person greater than dry steam given the same time / contact period. The answer is mass. The wet steam is capable of contain more calories of energy than dry steam as it has more mass. The more calories of energy the greater amount that is transfered, thus the greater the burn.

In your box as these calories are transfer to the item being cooked the next factor to be considered  is the speed of calorie balance. This balance happens via an equilibrium of all calories in the box. In more simple terms these calories move on from one area of the box to the next filling the box to its maximum and findley on to the exit point which is the meat's mass.

The next factor to look at is calorie replacement. This is done via the heat source or in our case the heating element.  Depending upon how much power we give the element will determine how fast or slow these expended calories are replaced.

If we step back and look at this then what you found out is true in the context that you stated: "There seems to be a difference between air temperature and a solid mass temperature."

Now let's look at how the calories are transfered from the "air" to the "mass." Is it through adsorption or absorption? A possible argument might be made for both. Perhaps even both are applicable  First the mass (meat) is porous; thus it will absorb the calories.  Next, given that once the mass (meat)  reaches a certain temperature pores close and then it can only adsorb the calories.

A good example of this is why we sear beef steak (close the pores) in the beginning of the cook. To seal in the juices as we are cooking the meat under higher temperatures. If we did not do this then the juices would boil out via the pores. Thus beef will accept the calories of energy via both adsorptions and absorptions. The variable, the determining factor here is the amount of calories that are available and the speed of the equilibrium within the carrier (air.)

It is for this very reason I feel that on most items it is so important to keep the meat's surface temperature in a smoker under the point of boiling water. If not and due to the lack of a searing the juices at the surface will boil out through the pores. Just like the calories when transfered an equilibrium of juices within the meat will happen.

I know that the above  is a little off of topic but I feel it is important to look at the whole picture and not just calories of energy.

Now as to your testing of water in "...the stove and after 3 hours at 550 degrees it was still not boiling." I believe we need to look at the earlier explanation here. We need to look at not only the mass, but how many calories are needed in order to break the covalent bonding of oxygen and hydrogen that makes up water, so that it turns into steam.  Next we need to look at the available amount of calories in the air, and consider the speed of the equilibrium, and the type of heat transfer which is adsorb (to accumulate on the surface.)

At this point we could get into a long dry discussion of kilo calorie (kcal) and the amount of kcal that is needed to raise the temperature of a pound of water (about one pint) one degree. However, we won't or I'd have to go dig an old school book out--Yuck!  But something in the back of my mind says it takes in BTU measurements 1 calorie.  Now contrast that with the amount of energy needed  to raise  1 cubic foot of air one degree F which is 0.02 BTU. Thus it would take all of the energy in 50 cubic feet to raise one pint of water one degree F. If I'm wrong please someone correct me as I'm digging this out of my ole memory. If we take a pint of water at 0 degrees (and keep it liquid) and wanted to break the covalent bonding so it boils it would take all of the energy that can be stored in 10,600 cubic feet of heated air.

While the speed of recovery is important (equilibrium) the real factor in this heat transfer in the way water accepts the energy. That is adsorb to accumulate on or from the surface. With this understanding I could very well see how after 3 hours your water was only 205 degrees F.

Now as I said if I'm wrong about this or my math is off please someone correct me.

Nevertheless, I do believe we can all agree that the mass (water or meat) will hold a thousand fold the amount of energy that dry air is capable of before it reaches the same temperture as the air around it.

My thinking now is the PID takes longer to cook because there are no temperature spikes

I can agree with this to some degree. However, this statement does not take into account the downward swing.  Once I have my box balanced (takes about an hour after I place the meat into it) my box does not swing unless the ambient temperature changes. It might vary one or two degrees, but for the most part that is all.

So lets do this. It takes close to 12 hours for me to take a 6.5 pound brisket to 185F. My box is a constant 205 F. Why not you take a 6.5 pound brisket, set your controller to 205 F and see how long it takes you.  Do note that I preheat my box to 300 F before I place in the brisket. Reduce my slider, check it in 15 minutes. If still too hot I will open the door and allow the air to change out. Check again in 15 minutes or so and if needed reduce the slider a little more and change out the air again.  Once the box is balanced to 205 F I stop.

Well I don't know if I've help answer your questions or just muddy up the waters.  I do know that you ask tough ones to answer.
Olds

[car54]

Olds,

I really appreciate your reply. I like science and learning, you gave me an  Alton Brown  answer.

Thank you, Brad

[Arcs_n_Sparks]

Okay all you budding thermodynamic types...... :D :D :D :D

It takes a lot of energy to take water at 212 degrees and turn it into vapor at 212 degrees. This is the latent heat of vaporization. The reason steam burns is that, as it condenses into liquid, it dumps a lot of energy in converting to liquid.

Same principle as air conditioning systems.

The "Steam Tables" are etched into many engineers brains.

Arcs_n_Sparks

[MallardWacker]

.....Last week I smoked a 6 pound pork roast and it took over 16 hours to reach 195 degrees and then only when I increased the box temperature from 205 to 230 degrees.....

Brad,

Couple things may come into play that might have nothing to do with the PID.  First I might wonder about the beginning internal temp of the butt and second that might play a bigger roll than anything...that it is the piece of meat itself.  I have nothing in writing on this but it is my experience that some pieces of meat just take longer and I mean way longer.  "I THINK" (and I know that is dangerous) it is do to the rending properties of each piece..fat content and where it is.  I have had some butts get done quick and others take the slow boat to done-ness.  Just my thoughts and humbly submitted.

[whitetailfan]

My take on this is a simple minded one.

LMOA
I never heard such an indepth "simple minded" response in my life. :D

[Biggun]

LOL, WTF, I thought it was just me! My suggestion was gonna be touch the grill and see if it burns you. You guys are way too smart for me! :o

[threerivers]

Is there a homework assignment that goes with this lesson ??? :D