View Full Version : Designing Accumaltor

18-08-2016, 09:03 PM

I need some advise and basic fundamentals on designing accumulator for R717 flooded Evaporator.

Previously I designed accumulator had no coils and I am seriously thinking to modify and make some new.

I have evaporator of 77 KW rated, so based on my idea 5 feet (1.5 Meter) x 2 feet (0.6 meters) should be sufficient.

The problem is coil. I made some research and I am not sure if "hot line" coil could be inside of accumulator or outside.
See below link:

There are some more accumulators I saw which is U type but that one I saw mostly for freeon.

I would appreciate if someone can help me with design and share with me their existing14279 designs.

18-08-2016, 11:20 PM
what is the evaporator SST., are you designing for?. High pressure liquid feed to coil?. Pumped liquid feed, gravity feed ?.
Horizontal accumulators have a larger surface area reducing surge levels, plus adding a serpentine sub cooling circuit in bottom of vessel is ok. Add oil trapping and drain as well. Add high level alarms.

18-08-2016, 11:41 PM
Evoperator temperature is +3.0 C
High pressure I am plannint to feed to could
No Pump would be installed
Gravity feed yes.

plus adding a serpentine sub cooling circuit in bottom of vessel is ok.

I did not understand what is serpentine sub cooling circuit.
Should it be inside accumulator?
or just wrap around outside accumulator?

20-08-2016, 08:32 AM
Would appreciate if some one can shed expert opinion on above.

20-08-2016, 10:08 AM
Hi skhan855,
I canīt understand why you pretend to use a suction accumulator with heat exchanger to feed a NH3 evaporator. I can't see any usefull purpose. Those kind of apparatus are used for compressor suction protection with halogenated fluids, not NH3.
For NH3 gravity feed evaporators I only know basic separators, they can be horizontal or vertical, but without any heat exchanger.

20-08-2016, 10:17 AM
The reason for this is that icing occurs in suction accumulator.
The safety float switch would trip occasionally when it reach safety level.

Wouldn't heat exchanger would improve performance of system?

20-08-2016, 01:20 PM
Dear S Khan
you are trying to work with Accumulator with Flooded system, Please find enclosed a P&I diagram of the same, it is orignally a diagram for hot gas defrost system, and not to confuse you I have cut the hot gas line. Difference in this diagram and what you are doing is that in diagram an ACU has been shown and you are using a Coil which will be filled with R717 and a Thermosiphon is created. coil shall be kept in the cylindrical14282 drum, which would have liquid (Water/brine/gyclol) which you wish to cool

20-08-2016, 02:56 PM
I could not study diagram as file size is too small to read, I see you are new to forums and there is a way attaching a image file. you need to click on third last icon where it says insert a image (on mouse hover) and attach file.

21-08-2016, 12:22 AM
I could not study diagram as file size is too small to read, I see you are new to forums and there is a way attaching a image file. you need to click on third last icon where it says insert a image (on mouse hover) and attach file.

I am confused, which type of system are you designing

1/ Liquid recirculation with liquid pump
2/ AKVA type expansion valve with accumulator(slop pot, suction trap) in plant room with boil of coil in it (serpentine coil, high pressure liquid line to evaporators running inside suction accumulator in a separate coil
to boil off any refrigerant that returns from evaporator for any reason to protect compressor).
3/ gravity feed surge drum mounted over the top of evaporator/s using thermosyphon principle.

1/ most expensive liquid recirculation
3/ less expensive used with 1-6 separate evaporators approximately
2/ cheapest

You mention long lead time of 6 weeks for AKVA valves, what is lead time on the rest of the equipment?

21-08-2016, 10:17 AM
Situation is like this.

System is gravity mode

I am planning to install hand expansion valve without concept of Super hear / AKVA. However
Solenoid valve would be installed for each evaporator.

Excess liquid coming from Evaporator would be stored in its own Accumulator; this means each evaporator will have its own accumulator.

Each accumulator will have its own AKS 38 or similar float switch which will signal respective evaporator solenoid to shut off despite target temperature achieved. Further solenoid will be switched off through a temperature controller once temperature achieved.

Now to avoid frequent tripping signals from AKS38 or similar, I want to install serpentine coil so that excess liquid evaporates.

I don’t know how to make accumulator with serpentine coil, but I can make it because I make condenser and evaporators and accumulators without serpentine coil.

I am attaching a diagram based on my understanding; please check if I am on right track. Please pay attention to 1 and 2 on receiver connecting serpentine coil is it OK?

AKVA in Pakistan costing me USD 740 which is too high compare to international price of USD 550 + lead time too high. I think hand expansion is ok

21-08-2016, 10:36 PM
I don't think this will work at all.
Firstly liquid line should leave liquid receiver, go through coil in accumulator to potentially boil off any liquid that returns from evaporator., then to expansion device on evaporators.
Also you need an expansion device on each evaporator to control superheat.
If you return to much liquid to accumulator, your in trouble as how to transfer it back to liquid receiver!
In this case accumulator helps boil off excess liquid ammonia & protects compressor.
There are ammonia TX valves like Danfoss,Sporlan, Parker to name a few, which are cheaper than AKVA, but control in not as good as electronic valve.

21-08-2016, 11:18 PM
I have run system for some months with manual expansion valve and without AKS 38, everything manually and all worked fine.

The problem I am facing with existing scenario is that too much liquid coming to Accumulator. For that there would be two options.

1) install AKVA or similar expansion along with AKS 38 on accumulator, but I spoke with some installers and technicians, they advise me that since system is in flooded mode therefore I don't know TXV or AKVA.
Hand valve is more than enough. This practice is normal in India and Pakistan. I am confused between your method and what I got suggestions from Indian and Pakistani technicians.

2) Install a Solenoid and AKS 38 that turns off Solenoid as soon as accumulator reached dead level. This is Indian method.

but in any case I need to install serpentine coil and I am not clear with connections of it. So far I understand from you that:
Liquid Line -> serpentine coil -> Expanssion valve -> Evoperator

Please find correct attached diagram marked as 1 and 2

I myself is good in electronics and do basic programming, and could control AKVA + pressure transducer.

22-08-2016, 05:23 AM
hansen have pulse ammonia liquid expansion valve suitable for each evaporator, to eliminate excessive carry over, search Hantech PXVW 60.
and make surge vessel horizontal with sub cooling coil in the bottom

22-08-2016, 01:45 PM
Hi, I got solution to install actuator on expanssion valve, which I can control through PLC, this will open close hand valve to 90 Degree, that is half turn of 1 round.

Any particular reason to make horizontal accumulator?

22-08-2016, 08:46 PM
I have never seen horizontal one, only vertical.
Vertical takes up less space & easier to run liquid line boil off coil inside.
Horizontal one with coil in bottom a lot more work to fit as much pipe as possible.

22-08-2016, 08:53 PM
Are connection ok? 1 and 214286

23-08-2016, 07:28 AM
Looks OK to me, evaporator regulating valves are a concern, as never seen them used in that way.
Do evaporators have a distributor set up for TX valve?

23-08-2016, 08:59 AM
Evaporator regulator valve, you mean Expansion valve?

23-08-2016, 10:49 AM
Evaporator regulator valve, you mean Expansion valve?

Yes sounds unreliable to me, needs to control superheat on suction of evaporator. Hand expansion valve closed to much poor performance, if open to far flood back of liquid ammonia to accumulator.

24-08-2016, 10:50 AM
I am working on actuator, to control expansion valve. we will have results in dry test how much it can open / close.

14-02-2017, 08:32 AM
Hi, what is the alternative for the accumulator to store liquid refrigerant in the fridge?