Re: What the hell am I doing wrong? water, Cobbled together WSM imitation

nailshooter41@xxxxxxx wrote:
On Nov 29, 3:35 pm, Dave <d...@xxxxxxxxxxxxxxxxxxxxxx> wrote:

Not really, the water is there to help avoid temperature >spikes. When it evaporates, it cools the pit.

The water is in the cooker as a heat sink to help keep the temperature
up. Personal experience with a water bowl will tell you the lower the
water gets, the more susceptible to temp spikes the cooker is while in
use. We know since the same surface area is exposed for evaporation
whether the water bowl is completely full, or 1/8 full yields
completely different (opposite) results, you can see that the actual
evaporation has little to do with function of the water in the bowl as
a coolant.

Incorrect. The rate of evaporation has everything to do with the temperature in the cooker. To understand this, forget about the surface area of the water, and forget about the measured temperature of the water. Instead, think about the water as a mass and think about units of thermal energy. 1 cubic foot of water requires a lot more thermal energy to change states than 1/2 cubic foot of water, and once the state is changed how much thermal energy is required to maintain the gaseous state. Hence, when the water pan is low, the amount of energy required to make steam is less. The excess energy remains in the cooker. OTOH, when the pan is full and the water has been brought to a boil it contains a GREAT deal of thermal energy and that energy exits the cooker through the vents as steam.

In fact, using your model, the lower the bowl is in water the more
aggresively it would boil or convert to vapor since the btu intake
would be significantly reduced as the mass of the water reduces.
Again in this model, increased vaporization would lead to a _colder_
smoker, not a hotter one prone to termperature spikes. Field
experience tell us the opposite of this to be true.

Water only boils at one degree. there is no "more aggressively". You are correct that a smaller amount of water would induce a reduced amount of BTU intake.

Therefore when the temperature starts to spike, more >water evaporates and more cooling happens. If you want
to understand the science part,

Once the water is boiling (now here's the good part) **It does not have the ability to absorb energy over and above the amount of energy it is losing in evaporation**. That is why a low pan does not work as well as a full pan.

While the science of the webpage is completely sound, I think the
model is applied incorrectly in this instance. If the water in the
bowl turns to vapor (steam) in a closed environment under constant
temp and pressure, it cannot cool since it will remain a gas. If it
cannot return to a liquid state, (say for instance inside a hot
cooker) there will be no cooling effect as the two key variables
(again, look at your model) heat and pressure are unchanged.

See my first paragraph above.

Soo.... unless you have seen your cooker sweat inside, no cooling is
taking place.

Given the constant temp of a pit, a closed vessel maintaining a
constant pressure in which the water was heated, I see no cooling
benefit whatsoever. The water simply converts to vapor (steam) and
goes out the vents.

Now you've got it! The steam going out the vent is loaded with thermal energy. Try holding your hand over the vent. That steam will give you a boo-boo.



--
Dave T.

Never put both feet in your mouth at the same time,
Because then you won't have a leg to stand on.
.

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