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  1. #51
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    Re: Flooded Ammonia Refrigeration



    Hi Josip,

    The way I have always considered side loads is based on screw compressors. The main suction load flows into the compressor suction flange. Any load operating at a higher pressure (greater than the main suction pressure), and connected to the side port is what I would call a side load.

    I think the side loads Andy was describing are similar. If you have a high temperature load (using an evaporator pressure regulator) that is connected to a lower main suction pressure, the high temperature load could be called a side load to the main suction line.

    Quote Originally Posted by Josip
    We can install complete compressor or more to work at eco pressure and here we call it economizer system.
    I have seen these also. If the system is large enough you can use separate compressors for the flash gas when flash tanks (flash economizers) are used.

    Quote Originally Posted by Josip
    There are some good ideas and designs but believe me very few....
    I very much agree. I have seen some very crazy systems where someone has tried to reinvent refrigeration principles. Heat recovery for warming water is one problem that some still seem to have difficulty with.

    How large are the systems you work on?



  2. #52
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    Re: Flooded Ammonia Refrigeration

    Hi, US Iceman

    Yes, I can see that we are speaking about same thing. Sometime language can make a big mass.

    I agree with you about exact problem to get warm or cold water. It is sometime unbeliveable what they can put on paper...

    Sorry, becuse I forgot to put quotation marks to "warm water" to make it more clear. In my country we use this ironical expression for "bright" designers. What are you using for?

    Those days, I saw one new design where young designer is going to use glycol water, PHE and pumps for oil cooling instead to use ammonia thermosyphon oil coolers. He has not too much expirence with thermosyphon oil coolers and he is going to make it on old fashioned way.

    I'm working mostly with ammonia from 1MW up

    Industrial plants like: slaughter houses, cold stores, breweries, food process plants - ice cream, milk, petrochemical industry. Very few with *****s mostly with ammonia. I'm ammonia guy like you

  3. #53
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    Re: Flooded Ammonia Refrigeration

    In my country we use this ironical expression for "bright" designers
    Over here we would say they are not the brightest light bulb in the box. (as in dim!).

    On the thermosyphon oil cooler subject... If the young person has never designed one of these systems he should have someone to show him how to design it.

    If he has designed a gravity flooded system for evaporators, he has a good chance of success for a thermosyphon system, don't you think?

    You are working on some good sized systems. I have a fun one to look at next week. About 12 MW total for a slaughter house. Nice little system...

  4. #54
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    Re: Flooded Ammonia Refrigeration

    Quote Originally Posted by US Iceman
    Over here we would say they are not the brightest light bulb in the box. (as in dim!).
    Nice

    On the thermosyphon oil cooler subject... If the young person has never designed one of these systems he should have someone to show him how to design it.

    If he has designed a gravity flooded system for evaporators, he has a good chance of success for a thermosyphon system, don't you think?
    Agree with you but many times for some reason they are untouchable I don't understand that! I have quite a lot of expirience but still ready to listen and accept any good idea or solution even from younger people.

    You are working on some good sized systems.
    Yes, working mostly on large industrial plants.

    I have a fun one to look at next week. About 12 MW total for a slaughter house. Nice little system...
    New or old one? Share some good ideas with us

  5. #55
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    Re: Flooded Ammonia Refrigeration

    The system is an old one. The building is probably over 100 years old. It is the original facility. Most of the original equipment has been replaced by now.

    Some of the system is liquid overfeed. Some of it is using a controlled pressure receiver for liquid feed.

    Other areas use what we call pumper drums (liquid draining by gravity into a small vessel. When the vessel fills up with liquid, high pressure gas is used to displace or "pump" the liquid out to the system).

    There about 26 screw compressors of various sizes connected to about 4 suction pressure systems. Two stage compression.

  6. #56
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    Re: Flooded Ammonia Refrigeration

    Quote Originally Posted by US Iceman
    The system is an old one. The building is probably over 100 years old. It is the original facility. Most of the original equipment has been replaced by now.
    Yes, let's say that is normal after so many years of exploitation, ha? For chicken or some other "4leg birds" I believe it is not for chicken becuse in that time that meat was not so popular

    Some of the system is liquid overfeed. Some of it is using a controlled pressure receiver for liquid feed.
    If I understand this, you have a part with pumps (or this one is with pumper drums) and a part with direct expansion with TEX or with orifices?

    There about 26 screw compressors of various sizes connected to about 4 suction pressure systems. Two stage compression.
    How old they are, brand, condition? What kind of air purger, new electronic one or "home made".

    Other areas use what we call pumper drums (liquid draining by gravity into a small vessel. When the vessel fills up with liquid, high pressure gas is used to displace or "pump" the liquid out to the system).
    This is something I believe many fresh designers never see. I like this. Most important thing is flap NRV. We have one here working now for 30 years without problem. Designed by STAL Sweden.

  7. #57
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    Re: Flooded Ammonia Refrigeration

    This facility has always been used for pork.

    The areas where the controlled pressure liquid is used is difficult to sort out right now. I have been in the facility twice before.

    The liquid at some controlled pressure is used to feed the liquid level control valves and some evaporators. When the controlled pressure liquid is used, a hand expansion valve is used to meter the refrigerant into the coil. Some coils may have a distributor, some may have orifices. The new coils being installed with controlled pressure liquid normally use refrigerant distributor, otherwise you have to many problems with the flash gas.

    The screw compressors are: Howden, Sullair, Mycom, and Dunham-Bush. Most of these are at least 20 years old, and all run very well.

    The one thing I do not like about the pumper drums is that you have to maintain a minimum gas pressure for pumping the liquid. Otherwise they are very simple to understand. You are exactly right about the NRV's.

    This thread is getting very long. Perhaps we should start a new one??

  8. #58
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    Re: Flooded Ammonia Refrigeration

    I forgot to answer on of your questions. I am not sure about the purger. I think I remember seeing an old manual refrigerated purger mounted in a corner somewhere.

  9. #59
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    Re: Flooded Ammonia Refrigeration

    Hi US ICEMAN, What make of air purger ?? We use 4Armstrong H370 on the 3 plants that we have on this site. We have set them up to work on auto with Danfoss EVRA 3 valves and on a timer unit, Two of them working on 4 condensers with two take off points on each condenser. They work well and keep the head pressure down to about 160 Psi on a 17 ton charge ammonia plant. What type do you like to fit on your systems.
    all the best Arthur.

  10. #60
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    Re: Flooded Ammonia Refrigeration

    The one I remember seeing looked like the old Armstrong single point purger. I do not know how it was connected to the system, or if this is the only purger.

    When I was last at this plant we were looking for other issues and I just happened to notice the old purger attached to a wall (in the shadows).

    I suspect that whatever they have, it is probably too small. This system has over 300,000 pounds of ammonia in it.

    The purgers I have used in the past are the Hansen multiple point purgers. They seem to do a very good job of removing the noncondensable gas.

  11. #61
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    Re: Flooded Ammonia Refrigeration

    hi thanks for the info will have to look up Hansen and see how they work.

  12. #62
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    Re: Flooded Ammonia Refrigeration

    Hello guys,

    hansen multiple point purger is good. Have some expirience with, more or less positive. With proper maintenance can work for long time. On another hand possibility to purge couple of points is very important for big plants. Power reduce cost is significant becuse here we have almost always very big el. motors with high power consumption. I think that is a must device for such a plant.

    aawood1 please check this link for Hansen purgers:

    http://www.hantech.com/products/purge.asp

    hope you can find something there

    I agree to start a new thread becuse this one has a long beard

  13. #63
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    Re: Flooded Ammonia Refrigeration

    Hi Josip, Had a look at the site will have to see if the man will spend some of the companey pounds. Have not worked out what we save on the main plant system, But did on a small ammonia system and we reduced the power cost by £ 1,180 last year. Reduced the working head pressure down from 180 psi (12.5 bar) to 150 psi
    (10.5 bar) on two Grasso RC11 9 cylinder units with a 4.5 Ton charge in the system working at -38oC. Must change the pressure gauges and stop useing psi.

  14. #64
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    Cool Re: Flooded Ammonia Refrigeration

    Quote Originally Posted by Andy
    Hi Peter
    it would be common to have at least one HT drum along with the LT drum, running at a intermediate pressure of say -12 deg C, pumps fitted below to feed the liquid to the HT rooms.
    It is also possible to have a number a various HT drums commoned on a HT dry suction header, with evaporator pressure regulators controlling the various drum pressures.
    Drum evaporations could be.

    Blast chilling -18 deg c (common to header)

    Cold room 0 deg c, with -10 deg drum pressure

    Chilled water 3 deg c with a drum pressure of 0 deg C.

    It is further possible to have a different HT drums and compressors which are only linked to their own HT load (say the 0 deg c and the -18 deg C) which do not handle any LT intermediate load, their only link is to the HT condenser. This would be the example Latent heat is talking of.

    Kind Regards. Andy
    Thread this is latent heat and what I would like to make clear is that the main fuction of a intercooler is to remove superheat reduceing the thermal load on your second stage of compression as I said before I run a two stage system with rotary screw compressors and the booster compressors (or 1st stage compressors) have a suction pressure of 5 inches of hg. and discharge pressure of 37 psig. but during the compression stage (of the first stage)the suction vapor coming in to the compressor at its saturated temperature will have about about 140 degrees F. of superheat after being compressed and will then be sent to the intercooler which is a vessel that remains at the intermediate pressure containing liquid nh3 about 30% of vessels capacity so when superheated vapor enters this vessel the superheat will be drawn to the saturated liquid nh3 causeing the liquid to flash into vapor and reducing the super heat. as vapor enters into the second stage (on our system) we usally have only 1 to 2 degrees of superheat.

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    Re: Flooded Ammonia Refrigeration

    Quote Originally Posted by Peter_1
    At different pressures to reduce energy consumption you said. This surprises me.

    But allways higher pressures then the pressure on the main drum.

    So, the main drum must work under the lowest pressure needed somewhere in the system. So the main drum is running verry unefficient because compressors has to evaporate constantly low or very low because one place needs a low pressure.

    So I don't see the benefit of this statement.

    Intercoolers reduce energy consumption between first and second stage. It's mainly because cooling the interstage gasses is needed for the compressors discharge valves instead of energy reduction.
    Even more, the energy taken out of the interstage flow has also to be removed by the compressors, so you gain it perhaps at one point but you loose it back in another point.
    Your main receiver will always be at a higher pressure but liquid can be drawn from your low side receiver, intercooler, or your high side or main receiver.

  16. #66
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    Re: Flooded Ammonia Refrigeration

    Quote Originally Posted by latent heat
    Your main receiver will always be at a higher pressure but liquid can be drawn from your low side receiver, intercooler, or your high side or main receiver.
    Quite true. However, when the liquid is drawn off of any low side vessel containing liquid, the additional flash gas load will have to be picked up by the compressor connected to that vessel pressure.

    The more liquid drawn from a low pressure vessel also requires additional higher pressure liquid flowing into the vessel to maintain a constant level. This adds load to the compressor.

    It is not free.

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