Scroll compressor for Freezing application

[georgedvf]

Hello everybody!

Have you used Scroll compressor/s for Freezing applications???

I have this project where the client needs to freeze mango nectar, it should be ready like in 15 hrs (from +85ºF to -28ºF), the thing is that after those 15 hrs they will turn off the system; the next load of product could be in 2 or 3 days, they will turn on the system and after 15hrs turn off again, and the process repeats again and again...

Some fellows have advice me NOT TO USE Scroll compressors for this project, (but whit not good technical reasons, they heard that from other fellows), they say it's such a heavy duty the Scroll will not withstand.

What do you think?? Scroll compressors have issues working in this conditions??

Greetings!

[Brian_UK]

Danfoss seem happy with it...

http://www.ra.danfoss.com/TechnicalI...-001-A1-02.PDF

[ernestlin]

Copeland ZF scrolls with DTC set work well under this condition, but R404a refrigerant should be used.

[ucesmik]

Hello all,

I am looking at plant sizing for industrial application i.e. cooling and freezing.

Could you let me have spreadsheet or calculator for plant sizing.

Thank you

[Brian_UK]

Hello all,

I am looking at plant sizing for industrial application i.e. cooling and freezing.

Could you let me have spreadsheet or calculator for plant sizing.

Thank you

Perhaps if you started your own thread for this question you might get a better response as it has nothing to do with this thread.

[smpsmp45]

Ingersoll Rand used to sell Refer units for cold stores with Scroll Compressors. & they were working nicely. Except Ingersoll Rand could not find enough business in India for them on sustainable basis & hence did not continue with that.

[georgedvf]

Thanks to all, I guess then there's no technical reasons to not to use scroll compressor in this application.

I got another suggestion from a fellow (sorry, this is the first time I work with this kind of application), he says I must use a TXV with MOP (maximum Operating Pressure) but again, he couldn't explain me well the reason....

Could you explain me why should I use this TXV with MOP???

[Brian_UK]

Download the Sporlan TEV book 10-9, it will explain the reasons and effects of using MOP valves.

http://www.sporlanonline.com/tevs.shtml

[georgedvf]

Thanks Brian_UK, I read Sporlan's 10-9 bulletin, but I'm still confused, If i get it, they recommend those valves for applications where during the pulldown pressure goes up and compressor doesn't work at that pressure. But there's a sentence I don't understand:

"The pressure limiting charge causes the TEV to remain closed until the system evaporator pressure is reduced below the MOP of the charge, permitting rapid pulldown"

The question is: how is it that closing the valve until the system evaporator pressure is reduced permits rapid pulldown????

[NoNickName]

Of course there is a technical reason for not using scrolls for freezing, and it's inherent to the efficiency of the scrolls under heavy compression ratios.
Infact Danfoss will soon present a new product optimised for refrigeration, which would not be the same product used in air conditioning.

[Brian_UK]

Thanks Brian_UK, I read Sporlan's 10-9 bulletin, but I'm still confused, If i get it, they recommend those valves for applications where during the pulldown pressure goes up and compressor doesn't work at that pressure. But there's a sentence I don't understand:

"The pressure limiting charge causes the TEV to remain closed until the system evaporator pressure is reduced below the MOP of the charge, permitting rapid pulldown"

The question is: how is it that closing the valve until the system evaporator pressure is reduced permits rapid pulldown????

If a normal (sic) TEV was used then at start up the TEV would be fully open feeding the coil at it's maximum rate.

The suction pressure/temperature would be high with possible compressor overload.

With the MOP working the evaporator pressure/temperature is keep to a maximum limit and providing a controlled cooling and compressor crankcase pressures. With the lower evaporator temperature at start up the pull down rate will be improved.

[nike123]

http://www.acr-news.com/news/news.asp?id=685

I fitted few days ago some control box for commercial freezers (six of them) connected to pack that has two of these in it. Some Italian company in blue boxes.

What was funny to me is that in same engine room is pack (from same manufacturer) for refrigerators which is driven by 2 Bitzer semi-hermetic!

[georgedvf]

Of course there is a technical reason for not using scrolls for freezing, and it's inherent to the efficiency of the scrolls under heavy compression ratios.
Infact Danfoss will soon present a new product optimised for refrigeration, which would not be the same product used in air conditioning.

Could you explain me a little bit more about what happens to the efficiency of scrolls under heavy compression ratios?

With the lower evaporator temperature at start up the pull down rate will be improved.

Do you mean that using a normal TEV evaporator temperature at start up is higher than usign a MOP TEV? Is it because suction temperature is higher? Doesn't the TEV should be able to give same evaporator temperature even if suction temperature is higher?

Thanks!

[NoNickName]

Scrolls are optimised for compression ratio typically found in hvac systems, but it's a well known fact that their efficiency drops considerably at higher compression ratio, because of the blow by factor between the scrolls.

[norseman]

Hi all from cold Norway

I have good experience with scroll's working under harsh deep cooling condition on plasma rapid cool down freezers. It is a kind of pockets in them and some weight load to make a solid contact between the blood bags and the pockets to make a fast pull down. The Copeland scroll in this case is running down to almost -60c on the suction to make a lower than -55c in the pockets. The units runs most of the days and get a hard load of ambient blood bags.
The bags have to reach -30c in less than 25 minutes.
The units are running on 404A so the sytem goes below zero on the suction every cycling of the (plasma) To make this low suction, the original inject of liquid on the suction port of the compressor is removed and a simple capillary tube is feeding a little liquid all time to make some extra suction cooling. Most of those units have been running for at least 6 Years without any brake down. I have only seen two disasters and that due to that the control valve did not open since the voltage to the solenoid was missing from a slave contact on the main contactor.
Without any suction gas, the scroll's kill themself pretty fast.
The worst scenario I have seen was on -140c
autocascade freezers and they did last for a Year at the best. On those units they had to handle R50 in the mix gas and such refrigerant is hard to get into condensing before the hx is at a very low temperature. The discharge pressure was to wild high for the scroll's to handle over time.

[georgedvf]

Thanks norseman, if you don't mind, could you tell me the model/family of compressors?

[norseman]

Thanks norseman, if you don't mind, could you tell me the model/family of compressors?

Hi george.

On those units it is used ZF 09 K4E mostly for 400volt 3 phase+N. We also got some for 230volt 3 phase (No N) The expansion valves is of electronic style from Carel so it is easy to make a set up to this fast powerful cooling system.

[georgedvf]

Thanks norseman.

That's the family of copeland compressors I intend to use for this project.

See you.

[Gary]

Hi all from cold Norway

I have good experience with scroll's working under harsh deep cooling condition on plasma rapid cool down freezers. It is a kind of pockets in them and some weight load to make a solid contact between the blood bags and the pockets to make a fast pull down. The Copeland scroll in this case is running down to almost -60c on the suction to make a lower than -55c in the pockets.

Are these cascade systems?