Measurement of Refrigeration Capacity

[mad fridgie]

I didn't see any plant with ammonia flow meters.
Compressor problem. Discharge temperature will jump if discharge valves leak. Suction valves leak will reduce energy use. Compare current energy use at certain operating conditions with compressor engineering data from manufacturer.

You can get a flow meter for just about any material.
To calculate COP of a system you need to know your load (the bit you are cooling) In rooms this is quite difficult (practically hugh variables) By knowing the actual mass flow of the refrigerant and the conditions it is at, you can calculate refrigeration effect, if you then remove system losses either by detail measurement or theoretical calcs you will end u with nett refrigeration effect. (how detailed to determins accuracy)
Damage to compressor parts valves, rings etc, effect volumetric efficiency, which inturn effects actual mass flow, thus makes changes to power draw (COP)

[Segei]

You can get a flow meter for just about any material.
To calculate COP of a system you need to know your load (the bit you are cooling) In rooms this is quite difficult (practically hugh variables) By knowing the actual mass flow of the refrigerant and the conditions it is at, you can calculate refrigeration effect, if you then remove system losses either by detail measurement or theoretical calcs you will end u with nett refrigeration effect. (how detailed to determine accuracy)
Damage to compressor parts valves, rings etc, effect volumetric efficiency, which inturn effects actual mass flow, thus makes changes to power draw (COP)

Did you see any ammonia refrigeration plant with flow meters?
Theoretically we can do everything but practically.... Typically ammonia refrigeration has a few evaporative temperatures. You need flow meter for every temperature. To compare apple and apple suction pressures and discharge pressure should be kept constant. Efficiency of the compressors should not be changed(no unloading for screw compressors). I didn't get about system losses. What do you mean?

[mad fridgie]

Did you see any ammonia refrigeration plant with flow meters?
Theoretically we can do everything but practically.... Typically ammonia refrigeration has a few evaporative temperatures. You need flow meter for every temperature. To compare apple and apple suction pressures and discharge pressure should be kept constant. Efficiency of the compressors should not be changed(no unloading for screw compressors). I didn't get about system losses. What do you mean?

Yes seen mass flow devices on ammonia!
These flow meters are normally coupled to computers and give real time readings, they also totalise (add up the total flow, like a water meter)
If a single plant (common refrigeration system)
then liquid flow is common, compressor suction pressure and temperature are common. You can calculate your nett refrigeration effect.
How you record the data can determine if instantaneous performance is calculated or long term averages.
If you have a LT pot and a HT pot, then you need 2 flow meters and 2 sets of temp/pressure equipment.
Let the compressor unload. we are measuring all, not a problem.
System losses, total change in enthalpy gives refrigeration effect, but not all the change is related to chiling the product/area.
Such as pressure drop down suction line and heat ingress to the suction line, to what level you go to is determided by the mighty Dollar, Euro, Pound, Yen etc. ( I sorted stated this already)
On a practical note the bigger the plant, the more worth while.
The original writer did not give size or application, only wanted to know how to do it.
He state that the comps were recips, so will have some for of wear and thus reduced performance.
The more actual correct info you have the more accurate your result.
I am certainaly not detracting the skill of a good engineer, I would rather have one of these than a computer. The combination complements each other.

[Segei]

Yes seen mass flow devices on ammonia!
These flow meters are normally coupled to computers and give real time readings, they also totalise (add up the total flow, like a water meter)
If a single plant (common refrigeration system)
then liquid flow is common, compressor suction pressure and temperature are common. You can calculate your nett refrigeration effect.
How you record the data can determine if instantaneous performance is calculated or long term averages.
If you have a LT pot and a HT pot, then you need 2 flow meters and 2 sets of temp/pressure equipment.
Let the compressor unload. we are measuring all, not a problem.
System losses, total change in enthalpy gives refrigeration effect, but not all the change is related to chiling the product/area.
Such as pressure drop down suction line and heat ingress to the suction line, to what level you go to is determined by the mighty Dollar, Euro, Pound, Yen etc. ( I sorted stated this already)
On a practical note the bigger the plant, the more worth while.
The original writer did not give size or application, only wanted to know how to do it.
He state that the comps were recips, so will have some for of wear and thus reduced performance.
The more actual correct info you have the more accurate your result.
I am certainly not detracting the skill of a good engineer, I would rather have one of these than a computer. The combination complements each other.

It looks like laboratory but not real life plant. Probably, this is one or two plants in the world that have flow meters. I are lucky that you saw one. It is costs money. Assume that we install flow meters and measured the power use. What is the next? To determine COP. OK we have it. What can we do about this COP? That is the goal of all this investments and measurements. To determine these compressors are good or bad. I'm sorry. I didn't get about the money.

[mad fridgie]

It looks like laboratory but not real life plant. Probably, this is one or two plants in the world that have flow meters. I are lucky that you saw one. It is costs money. Assume that we install flow meters and measured the power use. What is the next? To determine COP. OK we have it. What can we do about this COP? That is the goal of all this investments and measurements. To determine these compressors are good or bad. I'm sorry. I didn't get about the money.

Not that expensive, but yes your are right it is a measuring device. This have generally been used to prove a systems performance, (penalty clauses on new installations, where the contractor designs a system and guarantess efficiency).
Once in along with all other devices that measure you can see other failings such insulation, compressor, fouling. It is just a tool.

[Segei]

Not that expensive, but yes your are right it is a measuring device. This have generally been used to prove a systems performance, (penalty clauses on new installations, where the contractor designs a system and guarantess efficiency).
Once in along with all other devices that measure you can see other failings such insulation, compressor, fouling. It is just a tool.

I think that it is expensive toy(meters, installation, computers software and etc). How you can guaranty efficiency? Is this efficiency at design conditions? What about efficiency at operating conditions? There are cost effective ways to check insulation, compressors, fouling and etc.

[mad fridgie]

I think that it is expensive toy(meters, installation, computers software and etc). How you can guaranty efficiency? Is this efficiency at design conditions? What about efficiency at operating conditions? There are cost effective ways to check insulation, compressors, fouling and etc.

When you quote a 15Mw job, clients want to know the running costs, you have design figures and you have installed figures. Of course it is near on impossible to run plant under steady state at design conditions. I think all understand that, so methods have to be undertaken to prove actual performance, other wise you state what ever you wanted in your tender, and when it came to performance testing you could say not perfect design condtions, so we will not guarantee our figures.
Lets look at this job 15Mw for ease say stated COP 3
this make 5000Kw power draw, lets say calcls are out by 1% and you use 5050Kw or 50Kw more than stated. over 20 years full time running that would be.
9,125,000Kwhrs at $0.15 Kwhr comes to $1,368,750
Is it now an expensive toy?
Does it fix any thing "NO"
You need to put the thread in context!
How would you measure COP on older equipment?
As far as your other comments there are lots of ways to check.
Knowledge is gained by gathering information.