Naked Science Forum
General Science => Question of the Week => Topic started by: Lewis Thomson on 27/06/2022 14:24:31
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Listener Josie submitted this question with the hope we can figuring out this function of fridges.
"Why can't I immediately open my fridge door after closing it? It feels like air pressure is keeping it closed. Is this the case?"
Why do you think this is the case? Discuss in the comments below...
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You can open it immediately if you use enough force. There is a flexible seal around the door to keep external heat out. When you pull the door there is a momentary negative pressure differential(inside versus outside) before the seal breaks contact with the door, allowing air in.
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We now have the answer up on The Naked Scientists site and you can listen to through the following link:
https://www.thenakedscientists.com/podcasts/question-week/why-are-fridges-difficult-quickly-reopen
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Normally when you open the door, all the cold air inside the fridge flows out, and then is replaced by warm air. Then when you close the door the warm air now has to radiate heat to the cold interior, and in doing so cools down and becomes slightly smaller in volume, needing to be equalised in pressure by outside air that slowly bleeds in via the vent tube for the condensate water. Thus the inside pressure is lower, and the force on the door from the difference makes it harder to open till the pressure inside equalises. For chest freezers the same, just there is a small vent instead in the seal, lots of small holes punched in the seal at places.
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Listener Josie submitted this question with the hope we can figuring out this function of fridges.
"Why can't I immediately open my fridge door after closing it? It feels like air pressure is keeping it closed. Is this the case?"
Why do you think this is the case? Discuss in the comments below...
After closing the door, the door seal will be subject to inertia extrusion, so that the space inside the refrigerator becomes smaller, the air from each seal inside the extrusion to the outside, the pressure inside becomes smaller. The pressure outside is normal, at this time the refrigerator door body is pressed by the air, can not open the door. With the air through the seal into the freezer inside, the internal air pressure balance, so it can open!
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It is likely due to a built-in mechanism in your refrigerator designed to create an airtight seal when the door is closed. This helps to maintain the temperature inside the fridge and conserve energy.