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My question is an odd one that I haven't been able to prove or disprove...

If a pot is on top of an oven and the flame is on, say the flame/pot reaches 400 degrees F.

Say we turn the oven on and the heat inside the oven is 500 degrees F.

Can the pot become hotter than the supposed 400 degrees?

I can only assume the pot doesn't actually reach 400 and that the heat wouldn't just bump up to 500 just because there is another source under it that is that heat. But I'm making an assumption that there's gotta be some equilibrium that is reached between the 400 and 500 degrees.

This theory may not be right with a new oven, but potentially with an old oven/stove?

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  • $\begingroup$ you are correct $\endgroup$
    – user126422
    Commented Feb 12, 2017 at 23:19

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In most situations I'd say the oven is insulated enough that it's effects are minimal or have no effect.

Unless your oven had really bad insulation (and costs a fortune to run), I doubt that anything near the surface reaches 500 or even 400 degrees from the heat inside the oven.

At best it will keep the air warm so that it is easier to keep the pot heated to 400 degrees. But since the stove will only ever make the outside of the stove warm, not above 400 degrees, the pot will also never be able to go above that.

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You're thinking about it wrong.

For this scenario, think of heat as a process, not a state. You are not "setting" the temperature to 400; you are setting the rate at which heat goes into the pot, and observing that when it reaches equilibrium, [heat in] = [heat out], the pot is at 400.

"The pot" is probably not all the same temperature. If you have water inside (including water that is part of other food), that water is going to cap out around its boiling point, so there will be some gradient from the 400-degree pot bottom to whatever water is in the pot. Other substances will have a different gradient.

Those gradients meant that heat at the measurement point might stay approximately constant at 400, but adding more heat could change those gradients, and e.g. make the water boil faster.

There are also many ways that heat leaves the pot. Some of it goes to state changes with the pot's contents. Some of it is radiated away. That radiation is a function of environment, and it will radiate more as you put more heat in, or less as the ambient temperature rises.

All of which is just to point out that this is heat moving around, not a single state.

But what is setting the heat input? This turns out to be quite important. Let's consider two control schemes.

The first is simply a power setting. You turn a gas stove to gas mark 7, it burns gas at a constant rate and shoves a constant flow of heat out. If gas mark 7 makes an iron skillet hit 400 on the bottom while you're frying eggs, that's just a neat coincidence. The same setting might give a much lower pot temperature for a big pot of spaghetti. If you add another heat source (e.g. take a blowtorch to the bottom of the pot at the same time), the stove output is unchanged but the heat input is increased and the pot gets hotter. (Same thing with most older electric stoves; it's just easier to picture with gas.)

The second control has a feedback mechanism. You have an inductive stove, you set it for 400. There is some sort of sensor pointed at the bottom of the pot. The inductor fires until the sensor reads 400, then turns off until it drops. Eventually, it will hit some equilibrium where it's firing (say) 10 times per minute. If you add an extra heat source (the blowtorch again), it will fire less often to maintain the same temperature. With a temperature setting, the amount of heat coming in will dynamically change based on the heat flows.

So what does that tell us about your specific question? It depends what you mean by "the flame/pot reaches 400 degrees."

Probably, you're talking about the first situation. In that case, yes: the pot will get marginally hotter from the increased ambient temperature. That effect is likely minimal (an oven that raises the ambient temperature more than a few degrees is called a "kitchen fire").

If you're talking about the second situation, you will not raise the pot temperature. You will instead use a negligible amount less energy to maintain the temperature.

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If the pot is exposed to a net energy gain its temperature will rise above 400.

If the amount of energy/heat lost exceeds the heat/energy gained, it will drop below 400.

There are three main ways for heat to be lost or gained: Radiation, convection, and conduction. There's also evaporation, but I'm assuming that in a cooking-type situation most of that already happened a long time ago. Unfortunately your description is insufficient to quantify the effects of these.

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  • $\begingroup$ Thank you for your thorough response. In an attempt to explain a little more clear, I'll say look at it this way. The pot is on a burner which is set to 400 degrees on a direct flame. Then the oven underneath is turned on to 500 degrees. Will the pot reach 500 degrees? Or will there be too much heat lost from the oven when it is going from inside the oven to the pot above, meaning by the time it reaches the pot, the heat from inside the oven would be lower heat than the direct flame? $\endgroup$ Commented Feb 13, 2017 at 9:27
  • $\begingroup$ How good is the insulation of the oven - or, how long are you willing to wait for the outside temperature of the oven to rise above 400? Is the pot in direct contact with the oven? As it's sitting above a flame I assume it's not. $\endgroup$
    – hdhondt
    Commented Feb 13, 2017 at 9:46

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