Let's say that I held a hot object with a warm cloth. It instantly feels less hot and only warm to the touch. This is because the cloth is an insulator and doesn't allow as large a heat transfer as if I held the object with my bare hands.
However, I presume that eventually the cloth will reach the same temperature as the object in question when it reaches steady state. In that scenario, the same amount of heat must be transferred from the object to my hand as before. So why can I perpetually hold, say, a hot pan with oven mitts without burning my hand?
Best Answer
Your body’s circulatory system is removing heat from your hand inside the oven mitt. This makes your whole body act as a radiator to dissipate the slight temperature increase in your hand and keep the temperature from rising too much inside the mitt. The mitt acts as an insulator and slows the heat transfer into your hand to a rate that can be radiated by the body.
So the heat goes from “hot object” to “mitt” to “hand” to “the rest of the human body” to “ambient air.” You need an insulator so the transfer from “hot object” to “mitt” is much slower than from “mitt” to “ambient air” (through your hand and body).
If the system were closed, then it would eventually heat up inside the mitt, as you suggested. An example of this is firefighters. They wear insulation all over their body and go into burning buildings. But they are super quick because unless the insulator is perfect, which it isn’t, they will eventually cook to death as the inside of the suit warms up. Despite using really good insulators! If there’s nowhere for the heat to escape, it will eventually heat up.
So your mitt isn’t even close to what firefighters use, but you can hold a hot pot forever because your body is given enough time to remove the heat without getting burned.