Refrigeration System with Ammonia

[Samarjit Sen]

Could some one provide me with some information on the system designing of a refrigeration system for a temperature range of - 40 Deg C to -30 Deg. C. Will having a DX system be effective or a Flooded System. In case some e book on such applications or some web site where I can get these information, it may kindly be intimated.

I have worked mostly on R 404 A , R 22, R 23, R 134a and 124.

Your guidance and assistance shall be very mush appreciated as I find that most of you have an expertise in Ammonia systems. Also let me know if Screw Compressors would be suitable for such applications.

[US Iceman]

I would not recommend DX ammonia any lowe rthan about -10F (-23.3C). It is difficult to get a DX ammonia system to operate properly if the evaporating temperature is much lower than this temperature.

Flooded or liquid overfeed are very easy to use and operate. Selecting one of these over the over bascially depends on how many evaporators you will use.

A lot of evaporators used on a liquid overfeed system could be cheaper to install, rather than a lot of evaporators installed using a flooded coil arrangement.

Ammonia system designs can be quite a bit different than what you may be used to, since these systems tend to be very large. Because of their size and capacities you will mostly see liquid overfeed used when you have a lot of evaporators installed all over the facility.

There is a lot of good information right here on the RE forum.

You might find a couple of books about an ammonia system information, but not too much on design, since they are almost all custom engineered for a specific requirement.

[Samarjit Sen]

Thank you Iceman. The total refrigeration capacity shall be about 30 TR. There shall be in all 6 nos. of evaporators. 3 shall be maintaining a temperature of -40 Deg. C and 3 will be for -30 Deg. C inside the room. What would you recommend.

[winfred.dela]

I will try to find something and will send you.
Are you starting from scratch, I mean are you designing each component (condenser, liquid receiver, low receivers etc) piping, evaporator, cooling tower?

Your system is not small.
30TR @ -40Cte system needs around 2 or 3 units two stage compressor with 90KW motor drive.
This may vary depending on the design, room usage and safety factor you will consider.

I sugggest Flooded or Recirculation. If you have blast or contact freezers, recirc is better though a little bit more expensive.

[Samarjit Sen]

Yes I am starting from the scratch. The application is for an Ice Cream Factory. Rather there are two.

We have to provide the refrigeration plant for the Hardening Room at - 40 Deg. C and for the Storage Room at - 30 deg. C.

We had proposed to install the plant with R 404 A using two stage semi hermetic for hardening and single stage for the Storage room. The clients are now asking for ammonia as the rest of the refrigeration systems are going to be of ammonia.

What is your opinion about using semi hermetic screw compressors for the ammonia. Your advice will help me a great deal.

[winfred.dela]

NH3 Semi Hermetic compressor?
Please provide me a brand, model, etc.
I wanted to know if there is.
Have always use open type for NH3.

Have you made components for NH3 system?
Like oil separator, surge drum, S&T, low & high pressure receivers, etc.?

It will be a very daunting task to start designing all these components.

Why not buy above components from a supplier near you so you will just select compressors, unit coolers, controls, etc. and do the pipe sizing & other connection works?

[Samarjit Sen]

What I had referred was semi hermetic SCREW compressors.

No I am not going to make any component myself. I would like to procure these from the regular manufacturers.

Please let me know using screw compressors would be suitable and are they suitable for such applications. I am completely depending on you all to help me out, as I have always done good jobs and am known for the same. Till now I have worked on all refrigerant other than ammonia, and as such would like that in case I take it up, it has to be done in the best way.

[US Iceman]

What I had referred was semi hermetic SCREW compressors.

Are these Mycom compressors? I have heard they might be working on something like this for ammonia systems.

[Josip]

Hi,

http://www.refrigeration-engineer.co...ead.php?t=4944
http://www.mycomj.co.jp/eindex/mycorole.html


Best regards, Josip

[US Iceman]

Depending on the capacity required for each temperature level, it may be practical to use a single stage screw compressor with an economizer, instead of a two stage system.

An economized cycle will closely approximate the energy use of a two stage system and cost less also.

The economized cycle will also be less complex to work on and control for relatively untrained workers if that is a consideration.

[winfred.dela]

Thanks Josip, for the links.
It made my day. I learned something new today.

Have to interview my friend in Mycom and also ask him why he have not mentioned. . .
Maybe he also did not know . .

Am just a new member and still trying to siff thru all the previous threads/posts.
Need a lot of time to catch up with the originals.

I kind of enjoy the 2001 stuffs (chit chats), also trying to learn the ways of the Ref guys from West.

[Samarjit Sen]

Dear US Iceman,

Thank you very much. Since I would be doing this type of system using Ammonia for the first time, could you please provide me with some details of the system, which would be of great help to me. I would like to use Vilters compressors.

[winfred.dela]

Now that you have a compressor brand. . .
have you also decided the system you would use?
- Compound 2 stage or separate 2 stage?
- flooded or recirculation?
- water cooled or evaporative.

I suppose you have done all the necessary computations:
cooling load, ammonia flow rates,
water flow rates (if water cooled),
unit cooler capacities, etc. . .

It would be a lot easier for you if you could have a compressor selection software from manufacturers.
If you cannot find a software, send me your data and i will run them then send you the results.

Re materials i have mentioned, i finally found the Ammonia Refrigeration application manual published by AIRAH (90 pages).
Its an old issue but have helped me a lot.

[US Iceman]

Attached is a simple flow diagram for a basic liquid overfeed system with multiple evaporators.

I have shown three screw compressors, but this could just be one compressor also.

The liquid ammonia flows from the condenser into the receiver. From the receiver the liquid flows into a flash economizer vessel. The liquid expands from condensing pressure down to the pressure maintained in the vessel. The economizer pressure will be slightly higher than the suction pressure.

The gas that flashes off during the expansion process is piped into a side port on the screw compressors.

It is essentially a single stage system using cold, low-pressure liquid to feed the liquid overfeed package.

If you tell Vilter you want an economized compressor, they can provide you with additional details on the piping and control valves required. Please note I have only shown the basic components and piping.

If you want a separate system for the -40C load, then all you have to do is select an economized screw compressor that has sufficient capacity to match your cooling loads.

Of course there are many more details to consider as this is just for discussion purposes to help you understand how this type of system works.

I hope that helps.

Best Regards,
US Iceman

[Samarjit Sen]

Dear Winfred Dela,

I shall start working on the details shortly. I have softwares on Screw Compressors. I am first trying to understand the system and you guys have been a tremendous help. Slowly I am catching up. In case it is possible can you send the copy of the Ammonia Application manual to me.

Once I have worked out the details, I shall get back to you for necessary rechecking.

Thank you once again,

[Samarjit Sen]

Dear US Iceman,

Thank you very much for the drawing. This is going to be of great help to me. Would you advice me to go in for a single stage screw compressor or a two stage screw compressor for attaining - 45 deg. C Evap. temp. I would like to install two nos of compressors each of 50% load and maintain the two different Evap. temp. 0f -45 Deg. C and - 35 deg. C respectively. The load for the -45 Deg. C is 48 kw and the load for the -35 deg. C is 35 kw. What is your suggestion and advice.

Thank you.

[TXiceman]

I have to agree with US Iceman on the economized plant design for simplicity. As on another thread, I am not a supporter of the simgle screw compressor due to past experiences and also current operating history.

Since this is such a small plant, why not look at reciprocating compressors. If you go with a Mycom or Vilter, select the compressors so that they have an operating piston speed below 600 feet per minute and use a conventional two stage design. With the lower piston speed you can greatly improve the life cycle of the recip compressors.

A two stage recip will greatly improve your power consumption over an ecomonized screw system.

Ken

[US Iceman]

Since this is such a small plant, why not look at reciprocating compressors. If you go with a Mycom or Vilter, select the compressors so that they have an operating piston speed below 600 feet per minute and use a conventional two stage design. With the lower piston speed you can greatly improve the life cycle of the recip compressors.

A two stage recip will greatly improve your power consumption over an ecomonized screw system.

This is some very good advice. Since your system will be a relatively small capacity using recip compressors in a two stage system would be the best approach.

From a energy use & product simplicity & reliability veiw point this would provide maximum benefits.

Using this approach, a single recip. compressor could be piped into the system so that it can "swing" from the high stage to the low stage system by changing some valves.

Then you have equipment redundancy and less compressors to install.

[Samarjit Sen]

Will you please advice me as to who are manufacturing two stage ammonia recip. compressors. Generally what I have seen in our country, they use two seprate compressors one for the high stage and the other as the booster.
Since I am new in ammonia I shall follow the advises from you all of the forum.

[winfred.dela]

Grasso, Hasegawa, Mycom

Here in our place mostly Japanese: Mycom & Hasegawa.
Hasegawa is nice but much expensive than Mycom.

There are also some Grasso two stage compressors.
Grasso usually push a design for separate two stage system and not too keen on selling their two stage compressors.
Maybe because of the compressor body construction.

I've been pondering for quite sometime about the advantages of these two systems.
Hope you guys can share your comments.

When would it be advantageous to use a Two Stage compressors instead of the Separate two Stage (1 high stage + 1 booster) ?

[TXiceman]

Are you runnig just the low temp suctions of do you have a need for an intermediate level arounf 0 dF or +10 dF. If you need an intermediate, you would naturally go with a conventional 2-stage system. If you do not need the intermediate level for refrigetaion, no real reason not to use a 2-stage compound machine.

The separate 2-stage compressors may provide a lower operating horsepower than a compound machine.

For a long lived machine, I'd still insist on rating no higher than 600 feet per minute piston speed.

I personally prefer separate two stage machines, but they will be more expensive to buy as you have to install bases, starters, controls and so forth for two machines instread of just one.

If your owner is more worried about low lower cost, then he will want a single compound machine and will run the machines on up to 900 feet per minute of more.

Ken

[US Iceman]

Vilter makes an internally compound two-stage compressor also. If you get it with the integral intercooler and subcooler you pick up a little capacity over the base model with just an intercooler.

TXiceman's suggestion about low piston speed is a well founded fact. Of course, it does require a larger compressor to accomplish the same capacity since the rotational speed is lower. However, this is the best way to gain a longer life expectancy for recip compressors.

If you do not have any intermediate loads (between the evaporating and condensing temperatures) then an internally compounded compressor might be the way to approach this project.

I also prefer two separate compressors (booster & hi-stage), but if you are trying to get a project and still provide a good design, this compressor should work just fine.

Talk to your Vilter representative for more information on the compressors. They should be able to send you a PDF.

[Samarjit Sen]

There is not going to be any intermedite load . This project is for an Ice Cream Factory, where we are to provide the refrigeration system for only the Hardening and Storage Chambers.

Cost is an important factor. In our country the competition is not clean. However I have always worked with good equipments and the best designs. I am sure that if the system is good and power saving, my clients would not mind paying more for the plant.

I would love to install Vilter recip. Unfortunately they are in India being represented by Frick India who will also be quoting and will not provide the compressor. They are not handling Vilter Screw. Any way I shall enquire from Vilters.

Could any one provide me with the Japanese Hasegawa Compressors website address.

[Darshi]

Mr. Sen, Hi
I think mycom has an office in Gurgaon.I met there local manager in Feb-2006.
They have semi hermatic screw compressors and should be able to help you in design too.Mycom was also represented earlier by Frick and you are right about their response.
I had their business cards somewhere.
Another possible semihermatic screw for ammonia is from a GEA owned company perhaps from netherland.
your best bet is Mycom india at Gurgaon

[Darshi]

and you could try Grasso (GEA company) too

[Samarjit Sen]

I would prefer to contact Mycom at Gurgaon. In case you are able to locate their business card kindly let me know their e mail address. Thank you very much.

[US Iceman]

Marcus,

You need to make a request to a gent using the name of Webram on this forum. He would be happy to discuss advertising rates with you for your purposes.

Otherwise, do not be surprised if your post is deleted.

[Josip]

Hi,

There is not going to be any intermedite load . This project is for an Ice Cream Factory, where we are to provide the refrigeration system for only the Hardening and Storage Chambers.

Cost is an important factor. In our country the competition is not clean. However I have always worked with good equipments and the best designs. I am sure that if the system is good and power saving, my clients would not mind paying more for the plant.

I would love to install Vilter recip. Unfortunately they are in India being represented by Frick India who will also be quoting and will not provide the compressor. They are not handling Vilter Screw. Any way I shall enquire from Vilters.

Could any one provide me with the Japanese Hasegawa Compressors website address.

Please take a look:

http://www.hasegawa-usa.com/indexb.html
http://www.mycomj.co.jp/eindex/kaigai/adress3.htm
http://www.hasegawa-jpn.com/Whasegjp...n/index05.html

Best regards, Josip

[Samarjit Sen]

Thanks Josip,

I have downloaded the compressor details from Hasegawa web site. Since much details were not providedtherein, I have sent a mail to them requesting the required information.

[anand]

If need aany information control selection, hot gas defrost system design please mail me. My personal email address is anand_joshi@satyam.net.in
In India Kirloskar Pneumatics make 2 stage reciprocating compressors which are msot popular. They sale around 2000 reciprocating machines per year.
Accel India in Ahemdabad also make 2 stage ammonia reciprocating compressor equivalent to sabore make SMC 104L, 106L, and 108L.
However, if you are interested in imported compressors you can talk to Haresh Rupchandani of Mycom India on 9960049990 or Mr. Mangalani of IDMC for Grasso Compressors on 9824442498 or Mr. Subramaniam for Vilter Compressor 9322407701
If you plan to use Screw Compressors you can contact Bitzer India Mr. Deshpande on 9833889734
In India Cooling system Delhi also make low cost ammonia screw compressors equivalent to sabroe compressor range of SAB 128, 163, and 202. You can talk to Mr. Saxena or Pravin Kumar on 9818023111 or 01294073491.

I am sure all these people will help you.

[Samarjit Sen]

Dear Anand,

Thank you for your offer. You see I have been in this line for quite some time and had not used ammonia for low temperature application. With ***** of 404A I am fine. I am aware that Kirloskars are making ammonia compressors in India, but when you have the option of using better imported units then why not use them.

It is very nice of you to send me the contact numbers which I shall definately use.

With best wishes,

[Bocko]

Hello! Best regards from Ice Factory Nestle/Serbia! We using R 717, ammonia 1 stage Hall screw UK. Suction is minus o,6 bar in tunell, for minus 42 C, and minus 0,2 bar in storage room for minus 30 C. Discarge is about 10-12 bar! Feeding separator it is over economiser , system is floated!

[US Iceman]

Welcome to the RE forums Bocko. It's always nice to see another industrial refrigeration person on here.

Please feel free to contribute or ask questions.

[Josip]

Hi, Bocko

Welcome to RE.

Hello! Best regards from Ice Factory Nestle/Serbia! We using R 717, ammonia 1 stage Hall screw UK. Suction is minus o,6 bar in tunell, for minus 42 C, and minus 0,2 bar in storage room for minus 30 C. Discarge is about 10-12 bar! Feeding separator it is over economiser , system is floated!

Where is your plant?

Best regards, Josip

[f4760249]

Hi Sen

For designing any compressor pakage you must know the operating conditions and capacity required but you didn't mentioned capacity

please send all details

Could some one provide me with some information on the system designing of a refrigeration system for a temperature range of - 40 Deg C to -30 Deg. C. Will having a DX system be effective or a Flooded System. In case some e book on such applications or some web site where I can get these information, it may kindly be intimated.

I have worked mostly on R 404 A , R 22, R 23, R 134a and 124.

Your guidance and assistance shall be very mush appreciated as I find that most of you have an expertise in Ammonia systems. Also let me know if Screw Compressors would be suitable for such applications.

[f4760249]

Dear samar jeet

For -30/+40 as pre my calculation i prefer J & E HALL SCREW(HSO-3220) WITH ECONOMISED OPERATION.


FOR FURTHER ASSISTANCE MAIL ME


f4760249@yahoo.co.in

[Samarjit Sen]

Hi Bocko,

I would be grateful if you could please give me an idea and some details of the plants for -42 and - 30 installed in your factory.

Sorry to be so late in welcoming you, the reason had been that I have been kept a bit busy with some projects.

[Samarjit Sen]

Hello f4760249,

Sorry for replying to your posts. I have been kept busy with some of our outstation projects and had hardly been in office for quite a while.

First I would like to know about the system. My client are yet to decide on the size of the room. Once they finalise then I can work out the heat load.

In the meanwhile we have installed a Hardening Room for Ice Cream at a room temperature of -40 Deg. C with R 22. We had used Dorin Semi Hermetic with DTC.

For my Ammonia projects which I am yet to start, I would prfer to use Vilter Screw, as they have been helping with lots of facts and figures and technical supports.

[Kawaljeet Singh]

It is very simple to design the system you are looking for. I am in meat freezing industry and temerature of -40 & -30 are common. I have also designed and installed few ice cream hardining and storage chambers.

[Samarjit Sen]

Dear Mr. Kawaljeet Singh,
Thanks for your assistance. We have just completed a couple of rojects wherein we are maintaining - 40 Deg. C Room Temperature and in another - 35 Deg. C Room Temperature. All our plants are either with R 22 or 404A. The compressors are single stage compressors.

What I am interested is in knowing about Ammonia Systems with the latest technology. We are importing all the equipments.

[Sinke]

Your guidance and assistance shall be very mush appreciated as I find that most of you have an expertise in Ammonia systems. Also let me know if Screw Compressors would be suitable for such applications.[/QUOTE]

...You must try ammonia if you use them in industrial purpose...
...and try Sabroe screw compressors 202LF or 283L...

[US Iceman]

...You must try ammonia if you use them in industrial purpose...

I'm not sure I understand what you mean by this. Screw compressors can work with almost any gas or refrigerant if applied properly.

[Samarjit Sen]

Screw Compessors are suitable for any refrigerants and conditions. There are a large manufacturers of good screw compressors.

I myself am learning a lot about ammonia from this forum. If I could be of any help to you, please do put in a post so that the experts in this forum will also be able to guide you.

[gwapa]

Hello Samarjit Sen

I just finished a project for an Ice Cream Plant using ammonia as refrigerant.
The projets has three suction temperature levels
-10°C,-35°C and -45°C.

-10°C is used for a water IceBank and Chilled water. The Icebank are flooded

-35°C is used mainly to keep the temperature in store room and some proces machines. The Ice Cream should be kept at -28°C so you should evaporate the ammonia at -34°C and 1°C temperatura loss to the compressor. The evaporator in the Freezer are overfeeded 5:1.
-45°C is maily to hardener tunnel They are also overfeeded 5:1

We used to have two stage Recip commpressor and with the new project we move to open screw compressor. The compressor oil is cooled by thermosifon.
The plant will handle 400Tr at -45°C, 350Tr at -35°C and 1400Tr at -10°C.
The plant will work in two stage with intercooler.

I hope this comments will be helfully for you

[US Iceman]

Hi gwapa,

That seems like a nice project.

Are you using the -10°C as your intercooler temperature?

Also, if I may ask... why did you use a 5:1 circulation rate?

[Samarjit Sen]

Hello Gwapa,

Thank you for the information. I shall be more than grateful if you could please give me more information on the system. We have executed similar projects with R 22. Now I am interested to use Ammonia, and as such your informations would be of great help.

[gwapa]

Hi Us Iceman
It is nice to greeting you all
Yes ,I am using the -10 °C as intercooler temperature. This is a flash intercooler. It also has an sideload conection to handle the load coming from -10°C .That is the Ice Back and water Chiller. So the intercooler works as a knock down vessel too.

The truth is that 5:1 overfeed is a mean value. There are some process machines using 6:1 and evaporators 4:1.
My expirence is that when we have several evaporator in paralle operation in diferentes applictions one has to pump ammonia for the installed load and not to the pick calculated load. Let me explain my self. If you have a pick load of 100Tr. but you have installed evaporator for 120Tr then one should pump ammonia for 120Tr.What do you think?

By the way US Icemann and all the experts in the forum, the intercooler is a big tank 2,00 m x 4,5 m. It is horizontal shape
I ask to the provider in order to make the diameter smaller,but I have not had any lock . Do you have the designg parameter for an intercooler?. That is the residence time of the ammonia hot gas bubbles into the liquid.
What will be the gas speed leving each hole in the distribution pipe?
Again nice to hear from you all

[gwapa]

Hello Samarjit Sen
It is glad to help you in any question regarding the Ice Cream Plant project using ammonia
Best regards

[TXiceman]

Gwapa, size the intercooler based on the gas velocity per ASHRAE or use Stokes equation. I never exceed 80% of the calculated velocity for an intercooler of suction side vessel.

As for the distribution of the hot gas under the liquid, I use a perforated plate in the bottom of the I/C and distribute the gas under this plate. I use a total hole area that is about 50% of the area of the vessel (vertical vessel). For the liquid out of this vessel, I leave a portion of the plate without perforations and build a weir About 12" high and let clear liquid settle there and take this liquid to the rest of the system.

Since the liquid level will lift from the gas distribution in the bottom at start up, you need to make sure you have enough height between the operating level and safety shut down level.

Another way to do this is to take your discharge pipe to the bottom and cap it. Them use perforations in the side of the pipe....about 2 times the pipe area for the total hole area.

In either case, you will need to have a anti-siphon hole in the top of the inlet elbow inside the vessel. This will equalize the pressure and keep liquid from backing up in the discharge pipe at shut down conditions. Usually about a 3/8 to 1/2" hole will do OK.
Ken

[US Iceman]

Horizontal intercoolers are more involved for design requirements than a vertical vessel I think. The depth of the liquid pool in a vertical vessel tends to be higher than what is found on a horizontal vessel (if you do not want loose your surge volume).

This problem becomes worse if you try to install refrigerant pumps under a vessel being used as an intercooler also.

It can probably be designed around to work OK, but I would prefer to use a vessel for separation and do the intercooling in the booster discharge line prior to the vessel.

On the horizontal intercoolers I used a similar approach to TXiceman, but on the sparge pipe I used a 45° arc of holes across the bottom of the pipe. This allows a lot of the surface area of the pipe to be used and it places the holes closer to the bottom of the vessel.

The perforated plate is critical. This should be a mandatory requirement to prevent jets of liquid being pushed up into the vapor space.