Low ambient conditions!!!

[Sergej]

Hi!
Can anybody help me?
I need to make the outdoor installation of heat exchanger in the heat-transfer system filled with ethylene glycol.
The outdoor temperature is -50 Deg.C!!!
Siberia, Russia...
Did you have experience in such installations?

Many thanx.

P.S. Sorry for my English... :)

[US Iceman]

Hi Sergej,

Welcome to the RE forums.

What type of questions do you have?

PS. Do not feel you have to apologize for the language skills. This is a worldwide forum.

Best Regards,
US Iceman

[Sergej]

Hi US Iceman!
Thanx for the reply!
We have a project mentioned units but we don`t have enough experience in it. May be somebody knows any features in works of such units at very low ambient temperature. May be we have to use some special additional devices (for example frost-protection) or special conditions (for example high speed of heat transfer medium) etc.

Thanks in advice.

[The MG Pony]

Why would you need a refrigeration plant at all?

I'd simply lay a heat exchanger a couple feet in the ground with a circulation pump, size the out door heat exchanger 1.5 times the expected load and that should keep every thing nice n chilled. Then for when and if it does get hot have an auxiliary phase plant that takes over, and when that must happen the ambients will not be so low so it can be built as per standard me thinks?

[US Iceman]

Sergej,

The use of any fluid to lower the freezing point of water should always be considered carefully.

Different terminology is used to describe several conditions that may be found in vey low temperature systems.

You generally have two issues; freeze protection or burst protection.

Burst protection is where you have a sufficient percentage of glycol added to the water to prevent the pipes from bursting from the expanding liquid when the temperature gets very low. In this instance, the percentage of glycol is lower than it would be for freeze protection. The glycol would have ice crystals (slush) in it, so the pumping may be more difficult.

Freeze protection requires a sufficient concentration of glycol to prevent the formation of ice crystals in the fluid when exposed to the lowest possible temperature.

If the fluid has to be pumped at low temperature operation, then you want the glycol concentration to be higher than you would for only burst protection.

To establish the minimum glycol percentage for freeze protection, you generally want to use a temperature slightly lower than the minimum expected temperature.

If your minimum temperature is -50C (-58F), the accepted practice is use a glycol concentration % that would provide freeze protection down to about - -52.7C (-63F). The use of the lower temperature provides some safety to allow for improper mixing with water, but you still have to watch this closely.

If the mixing you do is exact, the safety factor provides for lower than anticipated temperatures. You may have to decide exactly what you want to do. This is a general discussion only.

In cases where the system may shut down for some time in cold weather, you may want to provide heat tracing to improve your ability to get the system started again.

There may also be other fluids that are better suited to low temperature use. Some types of alcohol may also work, or potassium formate.

Does that help?

[Andy]

Hi!
Can anybody help me?
I need to make the outdoor installation of heat exchanger in the heat-transfer system filled with ethylene glycol.
The outdoor temperature is -50 Deg.C!!!
Siberia, Russia...
Did you have experience in such installations?

Many thanx.

P.S. Sorry for my English... :)

Hi Sergej:)

What about using a water cooled condenser and a fan coil unit to reclain the heat for a near by building, Iam sure at -50 deg c some spare heat would be welcome.
A water regulating valve on the unit would control the low ambient condensing and an electric heater for frost protection in the water loop, with the pump running all the time (or on a frost thermostat).

Kind Regards Andy:)

[NoNickName]

I'm upping this thread for a similar question. How would anybody cope with an ambient temperature similar to Sergej's, but for a remote air cooled condenser?
Here the problem is that liquid is so subcooled that all of it is in liquid phase and pressure is close to nil.
I thought of recirculating the discharge into the liquid line for 95% until liquid temperature is 35°C, and then 5% into the condenser to allow pressure to build up.
5% of gas at 80°C into the condenser will allow pressure to rise until liquid warms up (remote condenser fans are off, of course).
The problem is that I don't find any suitable valve for regulating the process.

Any thoughts?

[lana]

Hi there,

With ambient being -50°C why we need refrigeration?:D

Just kidding.
Cheers:)

[NoNickName]

I don't know. Ask my customers in Arkangelsk and Oimjiakon

[US Iceman]

How would anybody cope with an ambient temperature similar to Sergej's, but for a remote Air (http://www.refrigeration-engineer.com/forums/glossary.php?do=viewglossary&term=17) cooled condenser?


No doubt the -50°C is a severe duty. A couple of points I would make are:

The normal head pressure controls dump hot gas onto the receiver to pressurize the liquid quickly, but the volume of liquid refrigerant required would be about 100% of the condenser volume to block off the heat transfer surface. In this example I think you will need 100% of the discharge gas going onto the receiver to quickly warm it up.

The receiver should probably be insulated and heat traced for faster start-ups as I have had to do this before. However, I will say I have not encountered this low of a temperature for air-cooled systems.

A second point would be to use balanced port TXV's since they allow better control at lower pressure differentials, which would also help with the initial start-up problems.

A third point might suggest the use of condenser dampers to limit static convection air flow across the coil before any fans would start.

Besides the obvious problem of discharge pressure control and liquid feed pressure problems you will also need some sort of time delay to allow the compressor to continue operating until the suction pressure rises to a reasonable value.

Just some thoughts for consideration...;)

[momo]

Refrigeration must now include language, decoding and interpretation skills! Welcome!
Sergej, I think is looking at the following part:

(Evaporator:compressor: ) Condenser with liquid heat exchanger : outdoor heat exchanger liquid to air in other words: he needs to dump heat outside probably using a water (glycol) fan coil inside to collect heat ?
The issue then is identifying a pumping fluid that will not solidify/thicken at the design temperatures.
(Sergej: these details will help:
outdoor temperature variation
indoor target temperature (in /out),
how big is the system?
Is its size calculated for the heat load ?
if so with what fluid Specific Heat was used in calculations for heat transfer ?)

[Peter_1]

Perhaps a condensor with different sections which can be shut-off to reduce condensor surface?
Just a thought...
Indeed, at -50°C, you can have severe 'overcondensing' and pressures below atmospheric pressure.
Or use the condensor then as a dry cooler, perhaps with the pumped refrigerant itselves??

Is tehre anyhow an antifreeze which protects till these temperatures?

[NoNickName]

Is tehre anyhow an antifreeze which protects till these temperatures?

Bah! dry coolers can't be used, unless oil is circulated. There is no water-based brine at any concentration that will still be liquid at -50°C. But then again, what viscosity would oil have at -50°C? And what oil? :confused:

[US Iceman]

Is there anyhow an antifreeze which protects till these temperatures?


Methyl alchol gets pretty close to this, but I would have to check the exact numbers. It may be something where you have to heat trace the lines to prevent freezing in a shut down condition. But then, a power outage would be trouble also.

At -50C I would think a thermosiphon would work well, as then all you have to control is the process temperature.

[wineman]

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[US Iceman]

if you give me free flights at a seven star hotel with the best wine and food and surrounded by beautiful woman plus £90000 a month i may consider it you may wish to talk to roman abramovich about my offer


I'm not sure what this has to do with the topic being discussed?:confused: