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Nokia Mechanical Engineer Intern Interview Question

I interviewed in San Diego, CA and was asked:
"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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Answer

Part of a Mechanical Engineer Intern Interview Review - one of 195 Nokia Interview Reviews

Answers & Comments

1
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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
0
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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
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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
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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

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