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skhan855
22-07-2016, 01:53 PM
Hi,

I am planning to install Solenoid on Evaporators to control liquid flow to evaporator thus controlling temperature.

Temperature required is +3.0 C

Pipe size to and from Evaporator is 19 mm (3/4 inches) and 102 mm (4 inches)

I have checked from suppliers of solenoid and I selected danfoss PWM valve AKVA 15 068F5020 for liquid side but for Suction side I couldn't find such big valve of 102 MM. Maximum I could get it 32 MM.

My question is:
1) Did supplier properly designed evaporator having connection size of 102 mm at suction side, considering temperature of +4.0 C cooling around 200 tons of fruit?

2) should I reduce line size from 102 MM to 64 MM and install two valves in parallel 32 mm each?

3) Any other alternate?


Regards
Salman Khan

RANGER1
22-07-2016, 07:51 PM
Salman,
What refrigerant, ammonia?
what is refrgeration capacity required.
What type of valve do you require for suction.
Why are you using AKVA, as it's not a solenoid, it's a pulsing expansion valve to control superheat.

skhan855
23-07-2016, 07:34 AM
Hi

Thanks for quick reply
Yes, refrigeration is ammonia.
Capacity: 100 Kw.
I am looking for solenoid valve which should turn off suction when temperature is achieved, this means liquid valve would be closed along with suction valve.

I believe AKVA would be better option as its PWM and I can control temperature easily by opening / closing this valve.

I am attaching a sketch for better understanding.

Regards
Salman14208

cduque
25-07-2016, 09:50 AM
Hi Salmon,
I'm a little bit confused with your scheme since with ammonia DX systems, manual expansion valves are very dangerous and normaly not used. The danger is to have liquid in the compressor suction and eventually break the compressor.
You can use the AKVA since it already is a PWM expansion valve, what you do need is a correct control system of the superheating in the evaporation side.
For the dimensions, AKVA 15 is adequate for 100 kW, 3/4" in liquid line also, 4" in suction line is very generous, you could use a smaller line (thinking the evaporating temperature is around -10ºC) but you can use the 4" line anyway.
But why use a solenoid suction valve? Do you have hot gas defrosting system? If thats the situation you can use a Danfoss ICS+EVM 65. But otherwise I think you don't need it.
If you use a consulting or installation service they might advise you to economise and have a better system in operation.
Regards,
CDuque

skhan855
25-07-2016, 10:33 AM
Hi

Thanks for reply,

Situation is like this, I have whole system design and everything is manual, all compressor, condenser and evaporators are manual.

I am starting from Evaporator first to control temperatures, for that I am planning tom install AKVA 15 on liquid side and suction solenoid valve on suction side.

Reason I am using suction solenoid valve is that if AKVA 15 is close when temperature achieved than compressor would keep suction on evaporator causing continuous suction which could cause damage to evaporator !!!. Correct me if my fundamentals are correct.

Defrost system is water.


Regards
Salman

skhan855
26-07-2016, 05:02 AM
so whats the suggestion?

RANGER1
26-07-2016, 11:33 AM
Salman,
I have a few questions & comments, hopefully I am understanding your set up.

Is this system as per sketch
1/ high pressure liquid ammonia from liquid receiver to AKVA
2/ AKVA controlling superheat on evaporator, distributor used to supply refrigerant to each circuit.
3/ suction of evaporator going directly into compressor.
4/ water defrost on 3-4 deg C room


2/ AKVA required strainer up stream, you could also install solenoid upstream of it for safety.
3/ Requires suction slop pot on suction of compressor to protect it against liquid flood back.
High pressure liquid line normally has a coil piped through suction trap to boil off any excess liquid that could return from evaporators.
This in turn cool liquid line before AKVA.
Circuiting of evaporator has to be specifically designed for AKVA or TX valve operation.

4/ Not sure why you would need water defrost on a 3-4 deg C room, as if you close liquid line solenoid valve & keep evaporators fans on, then it's called off cycle defrost if it reaches temperature.
Otherwise just turn solenoid off in your manually operated plant.

To have a suction solenoid is not really necessary unless suction pressure is lower than required.
In that case a back pressure regulator would be required to avoid excess ice build up on evaporator.
This to my knowledge cannot damage evaporator.

skhan855
27-07-2016, 08:38 AM
Hi,

I understand the setup,
2) I would be needing strainer
3) Slop pot is already installed to prevent liquid going into receiver, I forgot to mentioned in diagram
4) Defrost is not really needed as we run this system some months ago but since its water defrost system therefore lines are already there..

I googled around and saw back pressure valve / EPR

What I want to know how auto system works?
a) does system have solenoid valve at suction side between evaporator (Suction side) and compressor?
b) or have a back pressure valve?
c) just a hand valve?

Thanks for kind support.

Regards
Salman

RANGER1
27-07-2016, 09:20 AM
Hi,

I understand the setup,
2) I would be needing strainer
3) Slop pot is already installed to prevent liquid going into receiver, I forgot to mentioned in diagram
4) Defrost is not really needed as we run this system some months ago but since its water defrost system therefore lines are already there..

I googled around and saw back pressure valve / EPR

What I want to know how auto system works?
a) does system have solenoid valve at suction side between evaporator (Suction side) and compressor?
b) or have a back pressure valve?
c) just a hand valve?

Thanks for kind support.

Regards
Salman

b&c would be best as "b"you can control evaporator pressure to prevent unecassary frosting of evaporator by raising evaporator pressure.
If you can control suction pressure by unloading compressor to suit that is Ok, but back pressure regulator gives you more options to adjust things.
"c" so you can service "b"

skhan855
31-07-2016, 05:21 PM
Hi

This forum is awesome and I am learning a lot from this forum, I get many suggestions and I follow and results are great.

If I go for option "c", manual hand suction valve than:

Scenario is that expansion valve is closed and manual suction valve is open and compressor is still vacuuming than could it cause damage to Evaporator having aluminum pipe thickness of 2 mm with diameter 19 mm??

Regards
Salman

skhan855
31-07-2016, 05:23 PM
14227

Diagram to above post attached

RANGER1
31-07-2016, 09:26 PM
14227

Diagram to above post attached

No damage will occur to aluminium evaporator, even under vacuum.

Evaporator has to be specifically designed for TX valve, for correct circuiting.

Suction slop pot in suction line , normally high pressure liquid line runs through a coil inside it to boil off any refrigerant that gets carried over.
If no coil heater, coil is best.
Should have oil drain point on bottom of it as well as high level float switch to protect compressor.
Size it adequately to hold enough liquid from all evaporators if practical.

Evaporator piping is critical as well so each suction on each evaporator should go in the top of a main header above or below evaporator, sloped towards suction slop pot back in plant room.
You want to avoid liquid from other evaporators entering each other.

skhan855
31-07-2016, 10:21 PM
Hi,

Thanks for prompt reply. Really appreciate it.

What I understand from your reply is that you are focusing on liquid coming back to compressor.
By suction slop pot you mean Accumulator?

And there should be coil / coil heater to turn liquid into gas.

Further there should be a float switch to stop liquid going back to compressor.

About Evaporator piping, I understood the idea that liquid from one Evop should not enter into other. I will think of having more than 1 accumulator so 1 set would be for those evop on ground level and 1 set for those on upper level !!?

Regards
Salman

skhan855
12-08-2016, 06:11 PM
Hi,

Do I need to consider concept of superheat on Evaporator?
or just solenoid to be operated based on temperature on "liquid switch" on accumulator?

I consult one of automation expert, he told me no need to consider super heat, just focus on liquid at accumulator and shut off solenoid when liquid level cross safety level.

Need to double check,

RANGER1
12-08-2016, 09:49 PM
Hi,

Do I need to consider concept of superheat on Evaporator?
or just solenoid to be operated based on temperature on "liquid switch" on accumulator?

I consult one of automation expert, he told me no need to consider super heat, just focus on liquid at accumulator and shut off solenoid when liquid level cross safety level.

Need to double check,


From your previous post showing diagram & the fact that you want to use Danfoss AKVA pulsing solenoid, then superheat is required at each evaporator.
Evaporator has to be specifically designed for this or expect problems.
If any liquid does return to suction slop pot/accumulator then high pressure liquid line from liquid receiver running through coil will boil it off.
If level in slop pot to high Danfoss AKS38 or similar float switch will activate shutting compressor down to protect it.
This is as simple as it gets on ammonia, there are other ways of doing it but more expensive., like flooded evaporator with surge drum or accumulator above unit/s.

skhan855
13-08-2016, 11:24 AM
Hi,

Every time I speak, I learn new things from you. Thanks. Now I realized that there should be a coil inside accumulator to boil liquid. This practice is not being adapted here, I checked from other installers also. But I remember I saw coil when I cut down an old accumulator.

Your idea for AKS 38 is good, I am searching for this kind of equipment. But I am still struggling to get AKVA 15 as lead time from local supplier is too high,

Coming back to topic, if concept of superheat to be applied than I would be needing pressure controller also at suction line to get super heat calculations. Correct me if I am wrong.


Regards
Salman

RANGER1
14-08-2016, 12:01 AM
skhan855,
I would strongly advise you contact Danfoss representative for full advice.
If you give all your design information they should be able to give you a shopping list of things to include as well as valve sizing.
That would be the case in my part of the world, maybe yours is different.
To me you would require superheat controller, temperature sensor & pressure transducer.
Danfoss recommend their advice when installing AKVA on chiller duty, also solenoid upstream of AKVA which would be EVRAT for extra protection.
Liquid line has to be sized for AKVA not evaporator & also subcooling of liquid line required for AKVA or any other type of TX valve to work effectively.
Good luck

RANGER1
14-08-2016, 12:11 AM
Hi,

Do I need to consider concept of superheat on Evaporator?
or just solenoid to be operated based on temperature on "liquid switch" on accumulator?

I consult one of automation expert, he told me no need to consider super heat, just focus on liquid at accumulator and shut off solenoid when liquid level cross safety level.

Need to double check,

Automation expert must be thinking of something else, as once level in accumulator/slop pot how to get level down again continuously?
System has to be balanced perfectly.
Why not simple automation, this plant could run by itself with a few controls.

skhan855
15-08-2016, 08:06 PM
Hi,

In my area Pakistan there is no Danfoss here, only distributors here who ask most expensive prices from world. I am still struggling getting AKVA 15, probably I will look alternatives. System automation is not common here. Either I buy whole system including compressors / condenser and Evaporator from one good company and they do everything, but this would be very expensive.

Alternate is to buy from different regions and fit myself which would be cheaper option but in this case its DIY.


Automation expert must be thinking of something else, as once level in accumulator/slop pot how to get level down again continuously?
System has to be balanced perfectly.
Why not simple automation, this plant could run by itself with a few controls.

Above raise my eyebrow, maybe you can elaborate.

RANGER1
15-08-2016, 09:23 PM
Hi,

Do I need to consider concept of superheat on Evaporator?
or just solenoid to be operated based on temperature on "liquid switch" on accumulator?

I consult one of automation expert, he told me no need to consider super heat, just focus on liquid at accumulator and shut off solenoid when liquid level cross safety level.

Need to double check,

skhan855, this was statementI was referring to that did not make any sense.
How many evaporators are you going to install on this system?

Also you have access ti internet, can you contact a Danfoss head office in your country or region.

skhan855
15-08-2016, 09:43 PM
Hi. There would be 7 evaporators