Double Boiler/Pressure Cooker Combo

This is a thermal question...

I was making some gravy tonight and, as I was stirring and not having much else I could do, got to thinking about boiling water (sort of like why there are so many "toilet oriented inventions", leading one to suspect where most inventors do their pondering). Anyway.

If one puts the bottom part of a double boiler on the stove, filled with water and then sets a sealed pressure cooker, with water in it, on top of it, can the temperature of the water in the pressure cooker exceed the temperature of the water in the lower pan?

Of course, all the usual standard ambient conditions apply and extraneous heat sources are ignored.

crashsite said:

This is a thermal question...

If one puts the bottom part of a double boiler on the stove, filled with water and then sets a sealed pressure cooker, with water in it, on top of it, can the temperature of the water in the pressure cooker exceed the temperature of the water in the lower pan?

Of course, all the usual standard ambient conditions apply and extraneous heat sources are ignored.

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Had a little think about this one. Obviously, this is speculation on my part, since I'm not about to carry out an experiment.

How "filled with water" the bottom pan is, as well as how much it is heated would be important.

If the bottom pan is partially filled and heated to boiling point, creating steam, the latent heat stored within the steam will be transferred to the pressure cooker upon condensing, and thus the water within.

Since the pressure cooker is pressurised, this raises the boiling point of the water above 100 degrees, before evaporation occurs.

An example of how this raised boiling point is regularly utilised, is within the automobile cooling system. Typically pressurised to around a figure of 1 Bar, coolant temperature can reach figures of 105 - 110 degrees before overheating and bypass of the pressure cap occurs.

Normally though, the cooling fan is activated well below this point.

Or perhaps I'm way off. I'm sure someone else will confirm/correct this S.W.A.G.

Seems pretty simple, the only transfer is via steam at 100 degrees, so the top part can't get any hotter than that. It's basically a 'ban marie' a standard cooking pot, designed specifically to keep the top part from getting too hot.

The pressure's on...

Nigel Goodwin said:

Seems pretty simple, the only transfer is via steam at 100 degrees, so the top part can't get any hotter than that. It's basically a 'ban marie' a standard cooking pot, designed specifically to keep the top part from getting too hot.

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That's kind of what my thought was but, I wasn't sure about the pressure aspect of it and the ability of the water to continue absorbing energy. "Ban marie" must be a foreign term as we Yanks call it a "double boiler".

crashsite said:

That's kind of what my thought was but, I wasn't sure about the pressure aspect of it and the ability of the water to continue absorbing energy. "Ban marie" must be a foreign term as we Yanks call it a "double boiler".

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Presumably it's a French term?, certainly sounds French.

Nigel Goodwin said:

Presumably it's a French term?, certainly sounds French.

Click to expand...

bain marie

David James said:

bain marie

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I was always crap at French