How does a pressure cooker work? How does it cook the food faster and why the whistle?
In: Engineering
Put a pot of water on a flame. The heat energy from the flame will go into the water and start raising the temperature of the water. Higher and higher, until the water hits the boiling temperature of 100 Celsius 212 Fahrenheit.
At this point, the heat energy from the flame goes into “breaking apart” the molecules of water, from the tightly packed “liquid” phase to the very spaced out “steam / gas” phase. The temperature of the water remains constant at 100 / 212 until the last drop of water has boiled off.
So basically the reason why your food doesn’t char like a steak left too long on the barbecue, is because water limits the temperature (of the soup or meal or what have you) to 100 / 212. Without water, your food would char to a burned crisp because that flame can reach much higher temperatures than the water.
In any case, that temperature of 100 / 212 *depends on pressure*. It’s 100 / 212 only in 1 atmosphere of pressure like we have on Earth (outdoors). If you get a pressure cooker and allow steam pressure to build up inside, the pressure can build up to 2 atmospheres of pressure, so, water will start boiling at 121 Celsius / 250 Fahrenheit, and that “chars” (cooks) the food faster.
You’re cooking at 121 / 250 instead of at 100 / 212. It’s cooking “hotter”.
Again, in both cases, water will limit the temperature of the food so it can’t go past the boiling temperature, which prevents the food from charring (as long as it has water).
The whistle is a pressure indicator, to notify when the 2 atmospheres have been reached. Basically you have pressure in there, so if there’s a defect and the pressure gets too high, things could explode.
Latest Answers