Actual cop

[richardmatira]

hi,
How to determine ACTUAL COP?

[Rob White]

.

COP is the equation of input power divided by Refrigeration Effect.

The only accurate way to calculate this is by plotting your system
on a Ph chart and using the data it supplies.

You need to know how much work your evaporator is doing at any one time.
This will be in kJ per kg or written as kJ/kg. When you have that value you
divide it by the work done over the compression process (also written as kJ/kg)

This will give you a value, a factor or what ever you call it and it will represent
the efficiency of the system.

So

Evaporator or Refrigeration effect (RE) as it is written is divided by Compressor
work done (WD) as written.

RE
WD

If RE = 2500 kJ/kg
If WD= 400 kJ/kg

(RE) 2500
(WD) 400

= 6.25. COP = 6.25. The higher the value the more efficient the system.

Regards

Rob

.

[FreezerGeezer]

COP = RE/Input kW as Rob says.

Be careful though. True COP includes fans etc. & not every chiller manufacturer (in my personal experience) includes that in their figures, thus giving a falsely high COP.
Curiously the French factory test bed of a certain well known chiller company does (did? It's been a while since I was last there) this, but thankfully the literature has the correct figure. Just about every consultant taken on a witness test looks at the COP meter & raises an eyebrow. Then borrows a calculator, adds the fan kW meter reading & proves the literature. Dunno why the factory never fixed that.

[Rob White]

COP = RE/Input kW as Rob says.

Be careful though. True COP includes fans etc. & not every chiller manufacturer (in my personal experience) includes that in their figures, thus giving a falsely high COP.
Curiously the French factory test bed of a certain well known chiller company does (did? It's been a while since I was last there) this, but thankfully the literature has the correct figure. Just about every consultant taken on a witness test looks at the COP meter & raises an eyebrow. Then borrows a calculator, adds the fan kW meter reading & proves the literature. Dunno why the factory never fixed that.

What you say is correct but don't confuse Coefficient of performance (COP) with Energy Eficiency Ratio (EER).
COP is only the relationship between Compressor and evaporator, EER is the whole relationship and does
include fans, heaters, relays and can even be used as a annual - seasonal calculation, seasonal energy efiency ratio (SEER).

Regards

Rob

.

[FreezerGeezer]

Damn! Yes of course Rob. Clearly I've been back on the tools for too long! Lol

[moideen]

Thermal KW divided by total electrical power input is the COP and EER. But both are calculating different way. In this calculation you can include condenser fan electrical input, in chilled water system the pump input, in water cooled cooling tower the fan electrical input. So the manufactures will have mentioned the TOTAL COP or MACHINE COP. I have seen some trane catalogue mention total EER.

COP=EER/3.412,EER=COP*3.412.
THERMAL KW/UNIT POWER INPUT in kw=COP
TOTAL BTUperHR/unit power input in watts=EER.