Why do instant pot/pressure cookers take longer to come to pressure with frozen meat vs. non frozen?
In: Engineering
Pressure cookers create pressure by boiling water into steam in an enclosed container.
The colder the stuff in the pot, the longer it takes for the water to come to a boil and create the pressure.
Phase transitions (melting, boiling) require heat energy, but the energy goes into breaking up the molecules so they go from tightly packed as a solid (frozen) to more loose as a liquid, to very loose as a gas / vapor. Heat is taken in from the fire, but the temperature does NOT increase.
So basically you have to keep the pot on the fire for a longer time to melt the ice THEN bring it up to the temperature where boiling happens and the steam forms to pressurize the cooker.
Lower temperature = lower pressure = longer time for the pressure to increase. Or that’s what my physics classes tell me.
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