Nokia Interview Question: If you have a refrigerator in... | Glassdoor

Interview Question

Mechanical Engineer Intern Interview San Diego, CA

If you have a refrigerator in an isolated room (no heat in

  or out) and left the door to the refrigerator open, what would happen to the temperature to the room? Would it go up, down or say the same?
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technical
Answer

Interview Answer

11 Answers

7

If the door to the refrigerator is left open, the frige has to work harder because now it has to try to cool the entire room rather than just the inside of the frige. The coils and condenser in the back of the frige would create more heat thus heating the room up.

Interview Candidate on Mar 9, 2012
4

The temperature of the room would stay the same - the key is the fact that it is in an isolated room. There is no heat exchange between the room and it's external surroundings.

Anonymous on Jan 12, 2013
18

The refrigerator will warm up the room. If you look on the back of the refrigerator, you will see metal grating. Touch it. Its warm! A refrigerator is transporting heat from the inside cavity to the outside. However, the power cord running from the wall is pumping energy into the refrigerator/room.

Energy is powering the refrigerator. It is also running an irreversible process, the energy dissipates out as heat and work (mostly heat), making the net temperature of the room increase.

Someone who knows thermodynamics on Jun 13, 2013
2

I propose the room remains constant - but for the following reason. The room is reported to be isolated. I denote that to be a cube with no walls, windows, doors, plumbing, OR conduit or an electrical box that would allow cable or air to move within or without the isolated cube.

Logically, in that the fridge is not powered, it is not generating heat through the use of the motor, condenser or heat - exchange coils.

Really, it doesn't matter what the answer is... you've just got to defend it logically.

If the fridge were powered - but was an excessively large model (as you might find in a grocery store walk in) the room might cool. If it were a smaller unit - the motor would have to work overtime to try and keep it cool - thus heating the room.

Just be creative! That's what they're looking for. Can you think on your feet.

Just another smarta$$ on Oct 18, 2013
1

Aa

Anonymous on Apr 16, 2015
0

The room's temperature will be exactly as the refrigerator's temperature. Heat will be absorbed by the grating metal on the back of the refrigerator, so no need to worry about where the heat that refrigerator produces go.

Anonymous on Jun 6, 2015
0

Majority of the answers here are wrong. A refrigerator is a heat pump that move thermal energy opposite to the direction of spontaneous heat flow by absorbing heat from a cold space and releasing it to a warmer one. There is some work required to move this thermal energy from Cold to Hot. If we assume that the amount of work used to move this energy is negligible, if you leave a refrigerator door open in an isolated room, the room temperature will stay the same.

https://en.wikipedia.org/wiki/Heat_pump
https://en.wikipedia.org/wiki/Refrigerator

Anonymous on Sep 9, 2015

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0

The room temperature will remain the same. The reason for this lies in its basic principle of vapor compression cycle. Its true that refrigerator transfers the heat from one place to another. But one has to remember that the door is open. So, As heat is extracted by refrigerant and thrown in room using condenser and since the room is isolated and refrigerator door is open.. the same heat will be added inside refrigerator and same refrigeration cycle continues after that. In a way refrigerator is not able to cool anything. it is just continuously maintaining energy equivalence.

rbawa on Oct 21, 2015
3

In this case, there is a net gain of energy from the refrigerator outlet into the room and no loss of energy out of the room. Thus, the room will warm up since there is a gain of energy.

Damian on Nov 17, 2015
0

Part of the room's temperature would decrease slightly. The other part of the room's temperature will stay the same. Since the refrigerator's energy is not large enough to cool the whole room it will cool a small portion of the room.

Anonymous on Dec 13, 2015

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