Recirculation recivers are 10m higher than fan coolers

[JERRYCOOL]

Hi ,
I have a system which require machine room higher than the cold stores. A pump recirculation system is required. I believe it will be a problem to pump the liquid back to receiver since the vertical piping is 10 m long. And if hot gas defrost system is applied, i can't imaging what will happen. Does anybody have experiences for that kind of application.

THANKS!!

[RANGER1]

JERRYCOOL,

How big is this plant?
How many aircoolers are on system chiller/freezer?
Will there be a chiller line suction nearby?

Assuming its ammonia & above questions are related to possible use of surge drums.

It can be done , but special design pipe work with double risers.

[JERRYCOOL]

RANGER 1

There will be about 12 air coolers and 4 tunnel freezers. The total capacity will be about 1800kw.
Ammonia will be applied.

Is it possible to solve the problem by higher discharge head pump?
It is good practise to use double riser for DX system. But for this kind of system, i am not sure.

Thanks!

[mbc]

What is your system ? wet or DX or floating system.

I think should be wet or float one ,normally use these system on tunnel ( have a more efficiency) .and with two stage system. ( -10 and -35) .
your problem is not your pumping liquid to evaporator( when your system is big and distance of room and machine room is too much your need more head pump -- we have to be careful and have a good attention about more head pressure in tunnel system--) .
your problem is oil returning from evaporator during defrosting time ,also in defrosting time returning liquid from evaporator to our separator(surge drum) ,
So you need good pipe design with loop system for pipes and high slop for pipes.
if your system is a DX .
what is a defrosting type ?
is it electric or hot water or hot gas. they have different design for oil return.

[RANGER1]

RANGER 1

There will be about 12 air coolers and 4 tunnel freezers. The total capacity will be about 1800kw.
Ammonia will be applied.

Is it possible to solve the problem by higher discharge head pump?
It is good practise to use double riser for DX system. But for this kind of system, i am not sure.

Thanks!

You can apply double risers for ammonia, the same as you would on ***** system
.
I don't think pump is your problem, its pressure drops in suction wet return line that you may pay a penalty on with surging & pressure drops if not designed properly.
Can you give us a bit more insight into this job!
I have seen it done, but at the end of the day, is it at all possible to instal remote vessel with pumps.
Do you really have to have it in plant room & not on ground level?

[Magoo]

I agree with Ranger, regarding vessels at low level and transfer pumps. Alternatively high pressure super sub cooled liquid supply to regenerating vessels at each cooler/ freezer and then the wet suction is fairly dry, but pipe sizing is critical as well.

[JERRYCOOL]

You can apply double risers for ammonia, the same as you would on ***** system
.
I don't think pump is your problem, its pressure drops in suction wet return line that you may pay a penalty on with surging & pressure drops if not designed properly.
Can you give us a bit more insight into this job!
I have seen it done, but at the end of the day, is it at all possible to instal remote vessel with pumps.
Do you really have to have it in plant room & not on ground level?

At the moment, I didn't see any other choice except to install the pump recirculation receiver at higher lever. To me, It is a challenge to do this kind of job. I'd like to figure out it.
Regarding the double riser design, I doubt the liquid will collect in the vertical pipe and the height can't be estimated thus the pressure loss can't be estimated.
Someone suggest to install another pump to make sure the vertical pipe empty. But I think the system is too complexity.

[Lodiev]

One of our plants are of the same layout and to solve the problem we did the following:
Wet suction: install a liquid trap in the suction line with a pump or two that pumps the liquid back to the main suction accumulator but still allowing the gas to go back to the main accumulator wit the main header going up.( Make sure that the pumps are correctly sized to accommodate defrost liquid returning)
Pump liquid: no problem with normal design.
Most important: The defrost cycles should be connected electrically in such a manner that at any time only one coil or room can defrost to prevent to much liquid flood back to liquid trap.

[JERRYCOOL]

One of our plants are of the same layout and to solve the problem we did the following:
Wet suction: install a liquid trap in the suction line with a pump or two that pumps the liquid back to the main suction accumulator but still allowing the gas to go back to the main accumulator wit the main header going up.( Make sure that the pumps are correctly sized to accommodate defrost liquid returning)
Pump liquid: no problem with normal design.
Most important: The defrost cycles should be connected electrically in such a manner that at any time only one coil or room can defrost to prevent to much liquid flood back to liquid trap.

Thanks for your information. This plan will work. I will think about that.

[mbc]

I did not get your system . could you put your designing diagrams ?Please

being liquid in suction line to liquid separator if our sloop is right it does not matter . only oil return and liquid return from evaporator during defrost time is very important, we should put right design U trap for that with right size .

if we have good sloop in piping system to liquid separator any liquid in suction pipe goes to liquid separator or it boils during system working time.

[shooter]

oke 10 m is very high, but is possible, the liquid will not boil in the evaporator but in the line that is vertical going to the receiver(separator), The difference in height should be kept to a minimum, to get circulation to the evaporator. In the evaporator(lowest point) a small line should go back for oilmanagment.
As the lines are long please be aware of the pressureloss in the pipes and evaporator, to get circulation.
If this could be a problem think of ejectors in the liquid line.
If the compressors are low, make a separator close to compressors as it is possible that condensation will happen in vertical pipe (the pressure will be a little higher, not 1 bar as it is a gascolumn.)

[mbc]

hi Shooter

In Evaporator wet and float system we have boiling of refrigeration
( changing phase of refrigeration in evaporator ) and in dry system (DX system ) we have changing phase in expansion valve.

In all systems piping is very important and proficient workers doing good job and they save system.( now we have a lot of software they can calculate your system with diagrams of pipe works but they can not tell you how you run your pipe ) in piping sloop of pipes is very very important and also U traps and connecting pipes to main pipe also putting drain of oil in receiver and separators and any where might you have collecting of oil and is not possible to return it to system.

[RANGER1]

One of our plants are of the same layout and to solve the problem we did the following:
Wet suction: install a liquid trap in the suction line with a pump or two that pumps the liquid back to the main suction accumulator but still allowing the gas to go back to the main accumulator wit the main header going up.( Make sure that the pumps are correctly sized to accommodate defrost liquid returning)
Pump liquid: no problem with normal design.
Most important: The defrost cycles should be connected electrically in such a manner that at any time only one coil or room can defrost to prevent to much liquid flood back to liquid trap.

JERRYCOOL, If you have room & can instal this suction trap with pump returning excess to main recirculation vessel, then why can't you position vessel & use this as main recirculation vessel in the first place?

As someone else suggested, please sen a sketch of layout, with a brief description.

[JERRYCOOL]

I am going to upload the plant plan layout drawings but the size is too big(1.5Mb) to be uploaded. Does anybody know how to upload a file bigger than 100kb?

[shooter]

Use wetransfer to for example shooter@home.nl
most forums can not handle this size without permission of the owner.
just send it to anybody who is asking for it like me via wetransfer in one go so you have to upload it only once.

[mbc]

Also could you send it to me might I help you
GHOLBEHAN@YAHOO.COM

[JERRYCOOL]

already sent!!

[mbc]

I saw your mail and I will come to you in 2-3 days
could you send your machine room lay out and your piping diagrams . please

[JERRYCOOL]

I saw your mail and I will come to you in 2-3 days
could you send your machine room lay out and your piping diagrams . please

We are not sure if the systme can work properly so we have not produce the machine room layout and piping diagram.