Entropy of a sealed room with an open-door refrigerator

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SUMMARY

The entropy of a sealed room with an open-door refrigerator increases, contrary to the initial assumption that it remains unchanged. The refrigerator's compressor compresses refrigerant, releasing latent heat of condensation into the room, while the open door allows for heat exchange. The adiabatic processes involved do not negate the overall energy dynamics at play, as work is done on the system, leading to an increase in internal energy and, consequently, entropy. The mark scheme correctly identifies that the entropy increases due to these factors.

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  • Knowledge of adiabatic processes and their implications in thermodynamics.
  • Basic grasp of latent heat concepts, including condensation and fusion.
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  • Investigate the implications of heat transfer in open systems and its effect on entropy.
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Homework Statement
A working refrigerator with the door open is placed in a sealed room.

What change occurs to the entropy of the room?
Relevant Equations
Q= ΔU + W
dS = dQ / T
A working refrigerator with the door open is placed in a sealed room.
The entropy of the room
A. is zero.
B. decreases.
C. remains unchanged.
D. increases.

I chose C.
Here's my thought process:
In a working refrigerator, a compressor compresses a refrigerant (at a gas state) in the coil, and the refrigerant turns into liquid. The latent heat of condensation is rejected into the room, making room hotter. When the refrigerant travels into the refrigerator, an expansion valve expands the refrigerant and converts it into gas. The latent heat of fusion comes from the interior of the refrigerator, which causes the inside to become cooler. However, in this case, the door is open. This means that the net heat exchange is 0 as latent heat of condensation = latent heat of fusion.

In my knoweldge, the compression and expansion processes are adiabatic, so there is no heat transferred to or from the system.

But the mark scheme says the entropy increases. Can you explain which part of my solution is wrong and why?
 
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Is it plugged in?
 
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it says 'working'
 
techsingularity2042 said:
it says 'working'
Right, so think about the energy.
 
techsingularity2042 said:
it says 'working'
What @haruspex is saying is that you've gotten lost in the details. Take as your system the combination of room (assumed insulated) and refrigerator. Is work being done on that system? Is the internal energy of that system increasing?
 
techsingularity2042 said:
In my knowledge, the compression and expansion processes are adiabatic, so there is no heat transferred to or from the system.

But the mark scheme says the entropy increases. Can you explain which part of my solution is wrong and why?
What energizes the compression process, which must overcome the friction resistance of the tubes-condenser-evaporator to circulate through the system and to go through the expansion orifice or valve?
It seems to me that the "sealed room" is still being penetrated by some kind of external energy.

Fig.-6-6_revised-768x630.png
 

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