surge tank on racks

[frozen ocean]

hello i am from canada where the winters get pretty cold.my question is the true operation of a surge tank.why have a surge tank instead of a standard reciever.is the tank there to store refrigerant when the txv's start satisfying.i have also came across recievers with surge bypass.i understand the surge bypass is for ambient subcooling.but what makes the gas bypass the tank and go directly to the liquid manifold.is it differential pressures?i'm trying to understand the true operation of supermarket refrigeration rack systems.i thank u for your time,looking forward on some replys also what temps or setpoints need to be achieved on these type of controls for recievers.

[Peter_1]

What do you mean with a surge tank?
Bottom feed?
Perhaps a little schematic can clarify your question.

[frozen ocean]

the surge tank only has a feed at the bottom of the tank which is teed one line comes from condenser,one line goes to tank and other line goes to liquid manifold.there is a hotgas line which feeds the top to dump pressure on the tank for a full column of liquid going to txv.that control is called the attron valve.

[US Iceman]

The receiver you describe sounds like a surge type receiver. Any liquid draining from the condenser flows into the surge receiver when the volume flow of liquid to the TXV's is reduced. This allows the liquid to backup into the surge receiver.

The other receiver, which is more common, is called a flow-tru receiver. This should have a diptube which supplies the liquid to the TXV's.

For most aspects the surge receiver allows any subcooled liquid coming from the condenser to flow to the TXV's.

The flow-thru receiver is just that; the liquid flows into the receiver, through the receiver, and out the diptube. You could normally expect the flow-thru receiver to dissipate any subcooling, if the receiver is cooler than the room in which it is installed.

Dumping hot gas on top of the liquid in the surge receiver could be for a couple of reasons;

1) the high pressure gas is used to maintain a constant liquid supply pressure to the TXV's, or

2) the high pressure gas increases the liquid pressure (same as above), however, the higher pressure could provide additional subcooling of the liquid, or

3) the high pressure gas is used to equalize the pressure of the surge receiver.

I've heard of this attron valve before, but I cannot remember what it does or who the manufacturer is.

A piping sketch would be very helpful to clear up the details for you.

[Peter_1]

Never heard of an attron valve, did a serarch on it an 0 hits.
Therefore, it's allways necessary to describe as clear as possible your set-up.
Sometimes , you're perhaps using different words for the same component and also many posters native language is not the English. So....

It was like I thought it was, a bottom feed receiver.
Is the attron valve really a valve or just an equalising line from top of surge drum to hotgas? I think it's there to ensure a flow in the surge drum.
When liquid is entering the surge drum, some means must provided to let escape the gas in it, otherwise the liquid can't enter the drum unless the pressure can rise in it.

Perhaps it's only a valve which opens when pressure becomes larger then condensing pressure.

What brand name is it and eventually type?

[frozen ocean]

the atrron valve senses flash gas in the liquid line with a electronic eye,which then energizes a solnoid to dump hot gas into the reciever which prevents flashing at your txv.i was just woundering if anyone could point out to me the different methods of reciever/surge on racks.or what you use to control on your type of racks.where i am we use hussman,hill pheonex,and kysor warren racks.

[Peter_1]

Is Attron the brand name and correct spelled of me?

I think - but that's my vision - that using such a valve is remedying the consequences (results?) but not the cause of the flashgas.

You mentioned that you have cold outside temperatures.
Well, it should energetically seen be a much better to subcool the liquid with the low ambient temperatures.

Removing flashgas by increasing the pressure is a bad tactic.
*
* *
We use packs from different brands. Profroid (France in the Carrier group) is often seen here but there each wholesaler here (+/- 10) has his own brand.

The previous director (Jan Menten) of Bitzer Europe (which is located in Belgium) started some months ago a new division - again Bitzer Germany linked - in the UK and they manufacture now Bitzer packs.

Control, I should say keep it as simple as possible.
HP control is switching off the condenser fans or controlled with a VFD.

In your country, the most economic way I can think on is to cut off the outside condenser and use the heat to reheat the store or use it for preheating the water.
I think you need a lot of heat in winter to heat the building itselves.

I can imagine that if it's becoming real cold outside, then even switching off all the fans is not enough to hold the HP on a sufficient high level.

Some controls must then be installed so that the refrigerant is not migrating to the very cold outside condenser.

Just thinking, don't they use condensers with 2 parallel coils in it, 2 besides each other?
Switching 1 off when outside temperatures drops enough.

Mechanical louvers under the condenser which encapsulate the coil a little bit.

Compressors here are mostly with unloaders, very rare VFD's seen on it.
Oil floats, one main oil separator, ...

Almost never seen a way to prevent flashgas, no subcool section in the condensers.

We even installed once (Carrefour) a pack (+/- 300 kW) with a condenser +/- 70 ft high on the roof. The pack was in the cellar at -2 level, so +/- 90 ft high discharge lines and liquid lines.
The store was at ground level.

My intention was to install the receiver right under the condenser and use the liquid column down to subcool it enormous.

Conclusion of the engineering office: it will rust there and this will not give you such a great benefits.
I even argued that underneath the condenser it's mostly dry, warm, even proposed a stainless steel tank...
It's installed now in the very warm cellar besides the pack and liquid lines goes up again two levels to the cabinets.
Can you imagine this

[US Iceman]

My intention was to install the receiver right under the condenser and use the liquid column down to subcool it enormous.

Conclusion of the engineering office: ... and this will not give you such a great benefits.

The stainless receiver was a great idea, but it sounds like the engineering office could use a course in refrigeration theory.

Did the liquid line going to the cabinets have any subcooling?

I run into refrigeration people all the time who say the liquid lines going up are OK with no subcooling. And if the liquid flashes a little bit, it's OK.

The subcooling created by pressure increase does not improve the COP, it just maintains a constant liquid quality. I think this is all that is being done on the rack/surge tank frozen ocean is talking about.

[Peter_1]

The person who said this was the head engineer of the engineering office.

There was no additional subcooling of the liquid and some lines were +/- 150 ft long.

It's indeed no real subcooling because you only go straight ahead in the log/P graph.

[US Iceman]

It's indeed no real subcooling because you only go straight ahead in the log/P graph.

Exactly...

Using static head to maintain liquid quality is a cheap way to get the effects of subcooling. And as Peter_1 correctly points out, the best time to consider it is during the installation.

Even if the flash gas is only a few percent by mass (kg), the difference on a volume basis ( cubic meter) can significantly impact the liquid line pressure drop.

When the long liquid lines are installed, it can be helpful if the liquid and suction lines are run in an area where the ambient air is cooler than the liquid line temperatures.

My preference is to oversize the liquid lines so that the piping has a larger surface area, which exposes more surface to help to cool the liquid lines. The larger inside diameter also helps.

When the liquid line goes up, subcooling by temperature reduction of the liquid is the only way to prevent this. Or, you can use a refrigerant pump too for those inclined to do so.

[Peter_1]

Was? Is the product that bad Marc?
What do you mean by 'talking down the lines'?

[chillin out]

What do you mean by 'talking down the lines'?

What he means is, we all seem to be talking about a similar (if not the same as), the link provided.

Chillin

[ARtech]

the atrron valve senses flash gas in the liquid line with a electronic eye,which then energizes a solnoid to dump hot gas into the reciever which prevents flashing at your txv.i was just woundering if anyone could point out to me the different methods of reciever/surge on racks.or what you use to control on your type of racks.where i am we use hussman,hill pheonex,and kysor warren racks.

The attron valve is not manufactured anymore by anyone that I can find. The manufacturer shut down. No one picked up the patent because of lack of distribution. I am interested in knowing if anyone else has ran into this problem. If anyone has knowledge of a replacement valve or series of valves to take its place please respond. I have several scenarios in my mind but want more input from other techs. This is a hill rack. Have taken care of this rack for 16 years. Attron has been replaced 2 times but unable to buy this product at this time.

[displaced paddy]

you need a LOT of ***** in those things because they have a stacking valve that backs the ***** up into the condenser. The best thing to do would be to have a welder put a threaded fitting in the side of the receiver and pipe the dropleg into it or if you put a differential check from the hot gas into the top of the receiver, even if you have to take out a sight glass to do it (sporlan ori-10) and set the stacking valve around 225 it should be ok. Those things always run out of liquid when they go into defrost.

[displaced paddy]

Hussmann used to have a control they called Koolsurge that did essentially the same thing but I dont know if they're still available either