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Can you answer this question ?

PostPosted: November 16th, 2015, 4:22 pm
by Integza
Can you correctly answer this question?

Imagine this, you put a working refrigerator with his door open and at ambient temperature, in a completely thermally insulated room also at ambient temperature, what means this room doesn’t allow heat transfer from the inside to the outside and vice-versa .

The question is the following, after 10h what will happen to the room’s temperature?

Will the room be colder? Hotter? Or at the same temperature?


Re: Can you answer this question ?

PostPosted: November 16th, 2015, 4:25 pm
by Integza
You can find the answer here:

https://www.youtube.com/watch?v=ifD8GlgFhXY

Re: Can you answer this question ?

PostPosted: November 16th, 2015, 5:02 pm
by Dave_Oblad
The room will warm up. The refrigerator is a heat exchanger and cools the inside at the cost of heating the outside. Thus the room should be a constant. However.. the active refrigerator will be in continuous operation converting electricity to heat in running the compressor (and lights) and, if the room is thermally insulated, the room will heat up due to the work the refrigerator is performing, trying to do its job.

Regards,
Dave :^)

Re: Can you answer this question ?

PostPosted: November 16th, 2015, 5:17 pm
by Marshall
Of course the room will be warmed. Let's see how much heat goes into the room.
Assume the refrigerator draws a steady 700 watts. So every second you are putting 700 joules of heat into the room.
In 10 hours there are 36000 seconds and therefore you are putting
36000*700 = 25,200,000 joules of heat into the room.

Re: Can you answer this question ?

PostPosted: December 18th, 2015, 7:37 am
by zetreque
I was asked this question during a job interview... I ended up getting hired and working there for nearly 8 years. haha

Re: Can you answer this question ?

PostPosted: December 18th, 2015, 9:38 am
by vivian maxine
Dave_Oblad » November 16th, 2015, 4:02 pm wrote:The room will warm up. The refrigerator is a heat exchanger and cools the inside at the cost of heating the outside. Thus the room should be a constant. However.. the active refrigerator will be in continuous operation converting electricity to heat in running the compressor (and lights) and, if the room is thermally insulated, the room will heat up due to the work the refrigerator is performing, trying to do its job.

Regards,
Dave :^)


And if you leave it that way long enough, I hope you have the funds to buy a new fridge. :-)

Re: Can you answer this question ?

PostPosted: January 4th, 2016, 7:35 am
by NittanyJ
good question though