When the COP of refrigerator is greater or less than 1?

  • #1
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I still confuse about COP of refrigerator. When i read some journal, it is said that COP of VCRS can be greater than 1 (usually 2 - 4). But, why the COP other than VCRS usally lower than 1? like vortex tube, vapour absorption refrigeration system, etc.

Actually, now i am doing a research about vortex tube as air conditioner, but i stuck in COP because it has very small COP just 0,2
 

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  • #2
russ_watters
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[this is going to hurt...]
What is a VCR?

Anyway, the basic answer is that the goal of heat pumps and air conditioners is not to convert energy from one form to another like heat engines. Instead, they move heat energy from one place to another.
 
  • #3
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[this is going to hurt...]
What is a VCR?

Anyway, the basic answer is that the goal of heat pumps and air conditioners is not to convert energy from one form to another like heat engines. Instead, they move heat energy from one place to another.
VCRS is Vapour Compression Refrigeration Systems. So, if i have COP below 1, it means that the ability to remove heat is very bad?
 
  • #4
russ_watters
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VCRS is Vapour Compression Refrigeration Systems.
Ahh. I've never heard it used as an acronym before!
So, if i have COP below 1, it means that the ability to remove heat is very bad?
It would depend on the type of system, but for normal refrigerators and air conditioners, yes. For example, in the USA, normal residential split systems are required to have a seasonal average efficiency (SEER) of 3.8:1 or better (13 SEER).
 
  • #5
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Ahh. I've never heard it used as an acronym before!
It would depend on the type of system, but for normal refrigerators and air conditioners, yes. For example, in the USA, normal residential split systems are required to have a seasonal average efficiency (SEER) of 3.8:1 or better (13 SEER).
so the different type of system have different standard of COP? is it mean if i have the COP of 0,2 of a vortex tube system is equivalent to COP of 2 Vapour Compression Refrigeration Systems?
 
  • #6
256bits
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so the different type of system have different standard of COP? is it mean if i have the COP of 0,2 of a vortex tube system is equivalent to COP of 2 Vapour Compression Refrigeration Systems?
Here is the COP for a vapour system heat pump.
https://en.wikipedia.org/wiki/Coefficient_of_performance.
See the two different equation for cooling and heating.
What does that tell you about the utility of comparing COP's of two different systems, if the COP's are calculated differently.

Look up how the COP of an absorption system and compare that to the vapour COP. Completely different.
 
  • #7
russ_watters
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so the different type of system have different standard of COP?
Yes.
is it mean if i have the COP of 0,2 of a vortex tube system is equivalent to COP of 2 Vapour Compression Refrigeration Systems?
Those numbers are not equal, so I don't know what you mean.
 
  • #8
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Those numbers are not equal, so I don't know what you mean.
I found this when searching in other forum about COP. the forum discussed about COP of Vapour absorption refrigeration system. and somenone post a photo from this book "C.P. Arora “Refrigeration and air conditioning”" and the book says that "COP of 0,34 of vapour absorption system is equivalent to COP of 3,69 of vapour compression system".

So, that why i asked, if i have the COP of 0,2 of a vortex tube system (this my case), can it be equivalent to COP of 2 Vapour Compression Refrigeration Systems?
 

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  • #9
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Here is the COP for a vapour system heat pump.
https://en.wikipedia.org/wiki/Coefficient_of_performance.
See the two different equation for cooling and heating.
What does that tell you about the utility of comparing COP's of two different systems, if the COP's are calculated differently.

Look up how the COP of an absorption system and compare that to the vapour COP. Completely different.
thanks for the explanation. So, it is mean that we can't compare COP of a system with the other system?
 
  • #10
russ_watters
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I found this when searching in other forum about COP. the forum discussed about COP of Vapour absorption refrigeration system. and somenone post a photo from this book "C.P. Arora “Refrigeration and air conditioning”" and the book says that "COP of 0,34 of vapour absorption system is equivalent to COP of 3,69 of vapour compression system".
This presentation, starting on slide 11, may help:
https://www.slideshare.net/IanLouiseCelestino/simple-vapor-absorption-refrigeration-system

It looks like in the example problem conclusion you highlighted, they are considering the input heat to be free (which is often reasonable), so they are omitting it from the COP calculation after the fact, which leaves just the normal Carnot refrigeration equation: electrical work in divided by cooling out.
So, that why i asked, if i have the COP of 0,2 of a vortex tube system (this my case), can it be equivalent to COP of 2 Vapour Compression Refrigeration Systems?
No, I would not say this aplies to vortex tubes at all. Vortex tubes do not use waste heat that you can ignore. They use a compressor (input power) and generate cold air (output cooling).

What is the purpose of this line of questioning? What are you trying to do or use this information for?
 

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