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Renata
25-07-2017, 09:14 PM
Hello,

Is there any saving removing the an economizer from a medium temperature compressor -6/35ºC?

How should this service be performed? Just close the valves or is there any internal intervention on the compressor housing?

Tks,
Renata

Josip
25-07-2017, 11:09 PM
Hi, Renata


Hello,

Is there any saving removing the an economizer from a medium temperature compressor -6/35ºC?

How should this service be performed? Just close the valves or is there any internal intervention on the compressor housing?

Tks,
Renata


Maybe I misunderstood your question ...

economizer was installed to save some energy i.e. using it probably as an intercooler to sub-cool the liquid coming from condenser/receiver to feed evaporator/s ... the best is if using it at two stage systems for liquid sub-cooling ...

Anyhow:
... with economizer you increase refrigeration capacity for a given swept volume ...

... increase in specific capacity i.e. increase in refrigeration capacity as a function of input power, compared with conventional application of compressor


using an economizer/plant you can get around 18-20% more work, but you need to use about 10-12% more power .... of course compressor must work at capacity over 75-80% to have compressor eco-port at higher pressure and economizer vessel under proper condition to achieve what is written above ...

... so if you disconnect it you can calculate your savings or your loss ....

This will be much easier with plant refrigeration scheme ... to stop it simply close both economizer inlet liquid stop valves .... no liquid no heat exchange ... eco is off :-(


Best regards, Josip

RANGER1
26-07-2017, 09:47 AM
Renata,
Could you indicate compressor make & size, as if Mycom or Frick can give you exact theoretical figure.

Renata
26-07-2017, 04:09 PM
Mycom 250 VLD

Renata
26-07-2017, 05:27 PM
Hi, Renata




Maybe I misunderstood your question ...

economizer was installed to save some energy i.e. using it probably as an intercooler to sub-cool the liquid coming from condenser/receiver to feed evaporator/s ... the best is if using it at two stage systems for liquid sub-cooling ...

Anyhow:
... with economizer you increase refrigeration capacity for a given swept volume ...

... increase in specific capacity i.e. increase in refrigeration capacity as a function of input power, compared with conventional application of compressor


using an economizer/plant you can get around 18-20% more work, but you need to use about 10-12% more power .... of course compressor must work at capacity over 75-80% to have compressor eco-port at higher pressure and economizer vessel under proper condition to achieve what is written above ...

... so if you disconnect it you can calculate your savings or your loss ....

This will be much easier with plant refrigeration scheme ... to stop it simply close both economizer inlet liquid stop valves .... no liquid no heat exchange ... eco is off :-(


Best regards, Josip

Josip,

I believe that you understood correctly, the point is that the suction pressure of this system is high (-6ºC / 2.4 bar) and with this pressure the economizer has not been efficient, in addition this is an old equipment and make it operational isn't cheap. Therefore, it is already with the valves closed, but a consultant recommended "add an obstruction flange = gain in compressor performance (3% at COP)", my question is how this flange can help improve the COP?

RANGER1
26-07-2017, 09:40 PM
Mycom 250 VLD

-6 sst
35sct
100% load 50hz
without economizer 1896.6 kw absorbed power 404.9 kw
with 2014.4 kw 405.9 kw
You would need a modulating valve on liquid line make up valve to evaporator to get constant flow & subcooling.
Unusual to have on higher suction unless you really require that extra capacity.
Works best mainly at 100% load.

What type of economizer is it, open flash or closed.

As josip say's lower discharge pressure.
I wonder if consultant means orifice plate in flange in liquid line to simulate modulating valve by resticting flow.
Why not just use regulating valve to get longer constant liquid feed to evaporator.

Renata
27-07-2017, 01:09 PM
-6 sst
35sct
100% load 50hz
without economizer 1896.6 kw absorbed power 404.9 kw
with 2014.4 kw 405.9 kw
You would need a modulating valve on liquid line make up valve to evaporator to get constant flow & subcooling.
Unusual to have on higher suction unless you really require that extra capacity.
Works best mainly at 100% load.

What type of economizer is it, open flash or closed.

As josip say's lower discharge pressure.
I wonder if consultant means orifice plate in flange in liquid line to simulate modulating valve by resticting flow.
Why not just use regulating valve to get longer constant liquid feed to evaporator.

Hi,
I missed placing the first sentence of the consultant, really stuck with double interpretation as I wrote, but he wrote: "Remove ECO; Add a flange obstruction = gain ..."

Would the regulating valve work as a function of which parameter?

I have done some simulations that point out that the gain is negligible and that it is not worth investing any money in this economizer.

If I understood correctly, what Josip said is that the economizer will only be effective if the discharge pressure is high enough that the intermediate suction pressure is adequate in the economizer.

RANGER1
27-07-2017, 09:57 PM
Renata,
You would not waste money on it unless you really need the extra capacity.
-6sst
25sct
without 2020kw absorbed power 323kw
with 2076kw " " 319kw

you get extra 56kw of refrigeration & draws less absorbed power.

Set compressor to "L" port for most efficient compression ratio if not already.

As far as what consultant say's, still don't understand what they are referring to.

If you keep condensing pressure down as low as practical, you also get more capacity out of compressor with lower power input as well.

Renata
31-07-2017, 02:07 PM
Renata,
You would not waste money on it unless you really need the extra capacity.
-6sst
25sct
without 2020kw absorbed power 323kw
with 2076kw " " 319kw

you get extra 56kw of refrigeration & draws less absorbed power.

Set compressor to "L" port for most efficient compression ratio if not already.

As far as what consultant say's, still don't understand what they are referring to.

If you keep condensing pressure down as low as practical, you also get more capacity out of compressor with lower power input as well.

I agree, I am trying to have some answer from the consultant, if I have any I let you know.

Tycho
01-08-2017, 08:02 PM
Hi,
I missed placing the first sentence of the consultant, really stuck with double interpretation as I wrote, but he wrote: "Remove ECO; Add a flange obstruction = gain ..."

Would the regulating valve work as a function of which parameter?

I have done some simulations that point out that the gain is negligible and that it is not worth investing any money in this economizer.

If I understood correctly, what Josip said is that the economizer will only be effective if the discharge pressure is high enough that the intermediate suction pressure is adequate in the economizer.

I might be reading wrong here, but when the consultant says "remove ECO, add flange obstruction=gain" I read that as remove the ECO and put a blank flange on the compressor ECO port.


for a -6/35 system, the gain for an eco is minuscule, I have to side with your consultant, remove the ECO, because it doesn't really do much on this system...

Had it been a -30/35 system it would have made sense

Renata
08-08-2017, 03:31 PM
I might be reading wrong here, but when the consultant says "remove ECO, add flange obstruction=gain" I read that as remove the ECO and put a blank flange on the compressor ECO port.


for a -6/35 system, the gain for an eco is minuscule, I have to side with your consultant, remove the ECO, because it doesn't really do much on this system...

Had it been a -30/35 system it would have made sense

Tycho,
Thanks and I agree with you... for a -6/35 system, the gain for an eco is minuscule. But I am still in doubt about how I will achieve energy savings by installing a blank flange. The second question is about how to orient the compressor manufacturer to perform the service, because they does not know how to do.

I have get an answer from the consultant, he's from France, than you can see the answer in french and the translation to english:

"veuillez trouver ci-dessous mes réponses=
- les économiseur ne fonctionne pas actuellement
- de plus ces économiseurs ne sont pas utile à ce régime de T° (il ne font qu’augmenter la puissance frigorifique tout en augmentant proportionnellement la puissance absorbée = le COP reste constant)
- les compresseurs à vis qui ne sont pas équipés d’aspiration d’économiseur, sont équipés d’une bride avec un partie usinée qui rentre dans le piquage d’aspiration. cette partie permet d’éviter les fuites au passage des lobes de la vis.
- en conclusion = il vaut mieux remettre cette bride usinée, que de laisser à l’arret l’économiseur."

Translation:
"Please find below my answers =
- the screensaver does not currently work
- moreover these economizers are not useful to this regime of T ° (they only increase the cooling capacity while proportionally increasing the power absorbed = the COP remains constant)
- Screw compressors not equipped with economizer suction are equipped with a flange with a machined part which goes into the suction pipe. This part makes it possible to avoid leaks when passing the lobes of the screw.
- in conclusion = it is better to replace this machined flange, than to leave the economizer at the stop."

Even with the answer I remain in doubt ... or I was left with more doubts ...

RANGER1
08-08-2017, 09:30 PM
Renata,
I think consultant theoretically correct with blanking flange.
With Mycom you can only install a basic blanking flags like when they are manufactured.
Sometimes if economized off, the same gas trapped in port can continually get re-compressed causing heat build up & possible oil breakdown.
So install standard blanking plate.
From what I posted, minimal capacity gains, but also some absorbed power if it is actually doing the work 10- 12kw.
If you are sure you are not going to use economized, decommission, blank off.

Segei
09-08-2017, 12:19 AM
Actually, it make sense. When lobe of the screw pass economizer opening and economizer doesn't work, part of the gas will go around the lobe from one cavity to another. Blanking flange will stop this internal bypass. I'm not sure about 3% energy savings.

Renata
28-08-2017, 01:48 PM
now, it make sense for me too. I will do this service, but it would be nice to mesure de sanving to prove this theory, any sugestion about how to mesure this sanving?

RANGER1
28-08-2017, 09:39 PM
now, it make sense for me too. I will do this service, but it would be nice to mesure de sanving to prove this theory, any sugestion about how to mesure this sanving?


To me makes no sense, blanking flange externally installed still leaves internal port.
If bypass happening internally, then all Mycom screws would do it & impossible to measure.
But you can try, somehow.

Renata
30-08-2017, 01:22 PM
Ranger,
the ideia is to manufacture a special piece to enter the compressor and avoid the bypass.
I have talked with mycom and they don't have this kind of flange, but I find an alternative supplier, who can manufacture this piece.
In this case, I would mesure the compressor performance before and after the intervention, with the objective to prove the saving and viability of this kind of intervention, but I would like sugestion about how to mesure compressor performance.

Many thanks,

Renata

RANGER1
30-08-2017, 09:25 PM
Renata,
The economizer port & liquid injection port go in side & top of discharge housing.
They then change direction 90 degrees into discharge port.
I think impossible to blank off & if you went to the trouble liquid injection would have to be blanked as well.
To do it, machine would have to be dismantled & plugged permanently at discharge end face.
The area where ports enter rotors is at a pressure above suction pressure after that rotor thread closes.
There would be next to no bypass in this area, otherwise Mycom would be onto it if it effected efficiency (you would think).
The only real test would be on Mycom test rig where they test run each machine, as we are talking miniscule amounts, if any bypass.
They use nitrogen on test rig & can monitor flow rate at a fixed position.
You could probably achieve more by installing oil return float on oil separator oil return, instead of cracking a valve in my opinion.
There is only so much you can practically do, but if you have the time go for it.

Segei
31-08-2017, 01:31 AM
I'm not sure how to do it practically but idea is to install the flange with thick rubber gasket. Initially it should be minimal tightening of the gasket and will be gap between flange and rotor. When gasket tightened to max, will be no gap between flange and rotor. Compare energy use before and after.

Renata
31-08-2017, 01:49 PM
Renata,
The economizer port & liquid injection port go in side & top of discharge housing.
They then change direction 90 degrees into discharge port.
I think impossible to blank off & if you went to the trouble liquid injection would have to be blanked as well.
To do it, machine would have to be dismantled & plugged permanently at discharge end face.
The area where ports enter rotors is at a pressure above suction pressure after that rotor thread closes.
There would be next to no bypass in this area, otherwise Mycom would be onto it if it effected efficiency (you would think).
The only real test would be on Mycom test rig where they test run each machine, as we are talking miniscule amounts, if any bypass.
They use nitrogen on test rig & can monitor flow rate at a fixed position.
You could probably achieve more by installing oil return float on oil separator oil return, instead of cracking a valve in my opinion.
There is only so much you can practically do, but if you have the time go for it.

Ranger1,

Do you have any project with details about this port on Mycom screw compressor? I couldn't find on internet or with Mycom.

Thanks,
Renata

RANGER1
31-08-2017, 09:29 PM
Renata, please download V series 160 to 320 (SCV) manual refer to pages 2-11 to 13 & 7-3 to 5.
I will send a picture in the flesh later today of 250VLD discharge end housing.

http://www.mayekawausa.com/techdata/index.html

RANGER1
01-09-2017, 09:58 AM
Renata, as you can see it's a bit hard to block off the ports you are referring to
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