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So this is a question based on a debate I was having with a friend of mine. We were discussing how heat escapes from an oven and how it heats up the room in which it is located.

The debate started when after cooking something, I suggested we open the oven to let the heat escape and warm up the apartment (we live in a cold city). He replied saying that keeping the oven closed would do the same job.

We argued about this for a while, with the following views:

My side - opening the oven allows all the heat to pour out at once, heating the apartment quickly and then eventually, slowly dissipating. In my mind, leaving the oven closed wouldn't really heat the apartment, because at the rate heat slowly leaks out of the stove, the cold from the outside of the apartment will leak in and counter it- leaving the apartment at a relatively constant temp.

Friends side - keeping the oven closed or leaving it open will result in the same amount of heat being transferred from the oven into the apartment, therefore resulting in an equivalent exchange of heat. His view suggested that opening the oven door would result in a similar temp change as keeping it closed.

So here I ask, what do you physics folks make of this?

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    $\begingroup$ I agree with your argument $\endgroup$ – Wolphram jonny Nov 27 '19 at 4:05
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They would have two different effects on the temperature of the room.

In theory, it should have the same net amount of available heat to put in the room; but the way the heat is transferred to the room will effect the temperature over time.

If you open the oven, it will transfer the heat quickly. This will raise the temperature of the room to a greater max temperature; but the heat in the oven and the room will be dissipated quicker, so the heating will not last as long.

If you leave the oven closed, it will release that heat over time. This means the temperature of the room wont get as high, but it will maintain the heating for longer.

The higher the temperature of the room, the quicker it cools too, so typically, I would think leaving the oven closed would be beneficial in the long term. You're keeping the heat around for longer.

One (potentially) good thing about opening the oven door is that it directs more of the heat towards the inside of the room. Some of the heat is going to go into the walls, and may be heating your neighbors rooms instead (depending on the layout, wall insulation, etc). I'm not sure how insulated the back of the oven typically is though. If it's not well insulated, opening the door may be beneficial to make sure you aren't losing a lot of heat through the walls over time, but I expect that's fairly negligible in most cases.

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Though I realize you are talking about turning the oven off before opening the door, we don't want folks to come away from this discussion thinking it may be a good idea to use an oven to heat their home. For one thing, if it is a gas oven there is the risk of carbon monoxide poisoning. For another, if is electric it would in most areas be economically inefficient. And finally, regardless of what kind of oven it is, it is not designed to be a room heater. For example, opening the door and leaving the appliance unattended could put small children at risk of incurring thermal burns from contact with surfaces they would not normally be exposed to during intended use.

The above being said, let's first consider the objective. If it is to feel warmer on a cold day, and any potential safety risks are adequately addressed, then opening the door would better meet the objective then leaving it closed. Although either way heat will eventually transfer through the oven enclosure and into the environment of the oven, the advantages of leaving the door open are:

  1. The rate of heat transfer out of the oven and into the desired environment will be faster so as to potentially have a noticeable effect on the room air temperature, compared to leaving the door closed which slows down the heat transfer rate.

  2. As @JMac pointed out, some areas of the oven enclosure through which heat transfers may not be adjacent to the space where heating is desired. For example, in my apartment the back of the oven faces an exterior wall. This means some heat may transfer to an exterior wall and then to the outdoor environment. Opening the door assures that more of the heat will transfer to the desired space and less to other parts of the environment that do not contribute to your comfort level.

Bottom line: Given the above stated caveats, I agree with your side of the argument.

Hope this helps.

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