Why does the cold air fall out of the freezer when it's opened?

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    Thermodynamics
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Discussion Overview

The discussion revolves around the phenomenon of cold air escaping from a freezer when it is opened, exploring the thermodynamic principles involved, including heat transfer and the behavior of gases. Participants examine the implications of this process on both the freezer's operation and the surrounding environment.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant suggests that opening the freezer allows heat to enter rather than cold air to escape, referencing the first law of thermodynamics.
  • Another participant agrees that cold air falls out of the freezer and is replaced by warm air, leading to increased energy expenditure by the freezer to remove heat from the newly entered warm air.
  • A different viewpoint questions the distinction between "letting in heat" and "letting out cold," noting that the net effect is an increase in the freezer's internal temperature, which ultimately raises the room temperature more than the cooling effect of the escaping cold air.
  • One participant emphasizes the need to specify the type of heat transfer involved, mentioning convection as the primary mechanism for cool air escaping and warm air entering.
  • Another participant points out that the cold air's heat capacity is negligible compared to the freezer's contents, highlighting that the real issue is the heating of the contents by warm air and the energy cost of cooling them down.
  • A participant raises a common question about using a freezer to cool a kitchen, stating that it is not a viable solution.
  • One participant reiterates the earlier point about cold air rolling out and being replaced by warm air, while also advising against pointing this out to parents in a humorous manner.

Areas of Agreement / Disagreement

Participants generally agree on the basic principles of heat transfer involved when opening a freezer, but there are differing opinions on the implications of this process and the terminology used to describe it. The discussion remains somewhat unresolved regarding the best way to articulate the effects of opening the freezer.

Contextual Notes

Participants express varying assumptions about the mechanisms of heat transfer and the roles of different types of energy exchange, which may influence their interpretations of the situation.

bjon-07
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This may be a stupid, but here it goes,

When ever i stand in front of the freezer i always get yelled at for letting the cold air of of the freezer.

But according to thermodynamics (the 1st law a beileve) heat moves from hot to cold. So when i leave the freezer open am i letting IN HEAT, reather than letting out the colder air that is inside the freezer.

I also relazie that the deinsity of a gas is proprational to it temperature, so mabye the cold air falls out of the freezer.

Can someone please tell me what is happening when i open the freezer, i have taken G-Chem in college so i know the basics of thermo,

i
 
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You've got it right. The cold air rolls out of the freezer and falls toward the floor. It is replaced by warm air already present in the room.

The freezer then has to expend energy removing the heat from the warm air now present in the freezer cavity.

- Warren
 
I am not sure that there is any difference between "letting in heat" or "letting out cold". The net effect is that the temperature inside the freezer increases, this must be accompanied by running the compressor to cool it back down, this work done increases the room temperature MORE then the decrease due to the "escaping cold" of the freezer. In the long run by keeping the freezer door open you heat up the room.
 
Just to avoid confusion, maybe we should specify what type of transfer we are talking about: Convective, radiative, or conductive. Convection carries the cool air out of the fridge. Convection also allows the cool, escaped air to warm. Conduction allows heat to leak in through the walls into the fridge, Radiation wouldn't apply much here.
 
It's not the cold air per se that is the problem since its heat capacity is usually negligible compared with that of the contents of the freezer and its walls. The problem is when the contents are heated by the warm air entering the freezer and it costs energy ($$$) to remove the heat.
 
Thats a very common question: Can we use the freezer to cool the kitchen? And the answer is obviously NO...
 
chroot said:
You've got it right. The cold air rolls out of the freezer and falls toward the floor. It is replaced by warm air already present in the room.
- Warren


HOWEVER! It would be really, really dumb to point this out to your parents the next time they tell you not to let the "cold" out!
 

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