ammonia refrigeration system

[Lc_shi]

Hi Sir
Ammonia refrigeration system is new to me ,who like to give me a brief about it:
# how about the normal working pressure and temp;
# the compressor and other components is different from Freon system?
# the advantage and disadvantage in comparison with freon system
# application scope: if it possible to apply in AC area
# others

thx in advance

regards
LC:)

[Peter_1]

Hi Sir
Ammonia refrigeration system is new to me ,who like to give me a brief about it:
# how about the normal working pressure and temp;
# the compressor and other components is different from Freon system?
# the advantage and disadvantage in comparison with freon system
# application scope: if it possible to apply in AC area
# others

Some quick answers before starting to work:
Pressure and temperatures can be compared +/- to those of R12 (remember the good old times)

Compressor is always an open type (copper windings can't withstand NH3) mostly economically used starting at 250 to 300 kW, pistons or screws.

Steel lines you can't solder yourself unless you're qualified (at least in Belgium)

All the regulation devices are made out of steel, condensers and evaporators also.
Condensers mainly evaporating condensers....water threatening systems for these.

Seen never another system then a pump system with LP receivers, mostly 2 pumps/receiver.

System is necessary to provide oil return.

If NH3 is used for freezing systems, an air purger is often used.

For AC....?? If a secondary brine is used because you can't let flow NH3 through copper lines.

With the Bitzer software (German compressors), you can compare same compressors for different refrigerants and play a Little bit with same evaporating pressures and condensing pressures and compare once the different COP's.

[Brian_UK]

LC, also have a look at www.robur.com (http://www.robur.com) for a gas fired system, they have manuals for download if required.

Brian

[deepakrbhat]

Also there is a huge thread with regards to construction of a small capacity ammonia system....around 1.5years back
Definitely it has got a lot of insight....i guess it is in the refrigerants fourm
Regards

[US Iceman]

LC,

Copper or copper alloys cannot be used with ammonia. The usual materials of construction are: carbon steel (for valves, vessels, & piping), cast iron (for compressors), stainless steel (for vessels or piping).

All piping connections are either: flanged, threaded, or welded.

Insulation and vapor barriers are a critical aspect of ammonia systems since most of the components are carbon steel and rust very easy. The installation of the insulation must include vapor barriers to prevent moisture from reaching the cold pipes. Most of the corrosion found on ammonia vessels and piping is due to badly installed insulation systems.

The normal design condensing temperature is 35C (maximum). Slightly lower design condensing temperature help to reduce the required input power.

Instead of cap tubes to feed the evaporator in an ammonia system we use: thermal expansion valves (TXV's), hand expansion valves.

The evaporators can be designed for: flooded, liquid overfeed (liquid recirculation), or TXV's.

The condensers are almost always evaporative type or water-cooled.

Ammonia is normally less expensive than the other refrigerants.

Ammonia stinks and this creates a lot of panic. Ammonia liquid is very dangerous, since it absorbs a lot of heat. The liquid also produces a caustic chemical burn to skin. Ammonia is bio-degradable with no ozone depletion factor.

Leak checking is very easy. :D

Ammonia reacts with chlorine so these should never be mixed together.

Water will absorb large quantities of ammonia.

I have attached a vapor pressure curve for ammonia (also called NH3 or R-717).

To compare mass flow and volume flow rates you can easily develop these to see the differences.

For purgers I recommend these on all ammonia systems. As Peter said, when the system uses ammonia for freezing, the refrigerant vapor pressures are below atmospheric pressure (below -33.3C).

Air can leak into the system and increase the discharge pressure. Air can also get into the system during service and charging. I recommend purgers for any ammonia system to reduce the air in the system.

If you have the ASHRAE Refrigeration Handbook look in the chapter for ammonia systems for additional information.

I have also included a typical information sheet about ammonia as a refrigerant.

Hope this is helpful.

Regards,
US Iceman

[Lc_shi]

Thanks for all your input-:)
It seems ammonia system is not suitable in AC area, the discharge temp is much higher than R22 at similar pressure.

regards
LC　

[Cofreth]

Thought Ammonia refrigeration system was already outdated?? :confused: :confused:

[Lc_shi]

I don't think it's outdated. Ammonia is more environment-friendly. It should have more application.

[US Iceman]

Ammonia is still a viable refrigerant. Some of the issues relate to the safety aspects for it's use. Ammonia stinks, so anytime some leaks from a system instant panic occurs for persons unfamiliar with this refrigerant.

In almost all large refrigeration systems, ammonia is the refrigerant to use. There have been some occasions where large R-22 systems were used. This happens when the system is near a large population and the idea of a large ammonia system scares the population.

Ammonia can be used for AC systems. I have seen large central chilled water (and glycol) systems used for commercial buildings. When I worked for a manufacturer we had an ammonia water chiller for the office air conditioning. (In the center of town!)

I have also seen large thermal storage projects where ammonia is used. These have been located in cities also.

The higher discharge temperatures are due to the higher specific heat ratio of the ammonia vapor. This is not the reason why ammonia is not used for AC.

Ammonia can not be used as a direct refrigerant. Let's say you have an air handler that has a refrigerant coil for cooling. R-22 can be used for cooling, but not ammonia.

Indirectly, ammonia can be used to cool water or glycol. The water or glycol can be circulated through the coil for cooling.

This is part of the safety code for refrigeration systems here in the US.

Anytime ammonia leaks from a tank or system, the news reporters try to tell everyone that the gas is poisonous and the people will die.

Ammonia is dangerous, but then so are all of the refrigerants. ;)

[US Iceman]

Found something you guys may be interested in reading...

On the continent, ammonia air-conditioning systems are already commonplace. The SAS Radisson Hotel in Denmark, a high occupancy building in the heart of Aarhus town centre, has been successfully guaranteeing its guests’ comfort through the operation of water-cooled ammonia chillers for over five years. In the UK, four 6.6 MW ammonia chillers have been installed in the energy centre at Heathrow Airport to provide chilled water for the air conditioning system in the new Terminal 5 building.

There is no doubt that ammonia has now been firmly re-born into air conditioning. Its future-proof potential and environmental advantages will ensure this is not just a passing vogue but represents a long term, viable alternative to HCFCs and, even, HFCs.


This was taken from this link:
http://www.modbs.co.uk/news/fullstory.php/aid/1067/New_commercial_opportunities_for_ammonia_chillers.html

You may be seeing more ammonia equipment as the trend catches on! :D

[Lc_shi]

very interesting topic--ammonia water chiller for AC area.
i know there is absorption ammonia chiller or heat pump but i'm not sure if there is compression type ammonia water chiller or heat pump. need do some research-:)
thx for all your valuable comment--it's a free lesson-:p

rgds
LC

[willie]

if you are not experienced or have'nt worked on ammonia leave it to those that are experienced, that way no one gets hurt or system gets damaged

[US Iceman]

A refrigerant is a refrigerant. Ammonia, R-22, or CO2.

The use of any refrigerant for a particular application must be carefully selected for the desired operating conditions, type of equipment, and equipment limitations.

Compression systems for ammonia are only limited to imagination and in some cases, local safety codes. I have heard of ammonia heat pumps up to about 100C, and ammonia compression for chilled water production.

One of the biggest differences between a commercial "Freon" system and an industrial ammonia system is the type of equipment and how the equipment is used.

Persons working on an ammonia system must be familiar with the technology and components. Processes done in an ammonia system might be totally different from what may be expected in a "Freon" system.

willie raises a good point! If someone does not fully understand the system, walk away from it.

Sulphur dioxide was also used as a refrigerant. This smells worse than ammonia. Since most of the "new" refrigerants do not exhibit a strong smell, does not mean they are totally safe.

All refrigerants can cause death. Treat all of them with respect and understanding.

[frank]

i know there is absorption ammonia chiller or heat pump

Not a type of installation I've heard of :confused:

But I would be interested in reading any info available.

Ammonia is not something I have worked with so I'm up for being educated, although I have seen ammonia plant working.

[iceman007]

Ammonia is the most efficient refrigerant. 3% more than R22 and 10% or so more than R134a. Like any refrigerant it has it's good and bad points, on the plus side it's thermodynamically stable and will condense and evaporate pretty much at constant temperatures, the valves and other componenets are usually smaller than standard CFC HCFC systems because of the high latent heat capacity and thermal transfer characteristics. Moisture if it gets in has to be removed because it usually gets to the coldest part (evaporator) and needs to be removed, but on the whole the components are reliable, and less refrigerant is necessary to achieve the same degree of heat transfer than halocarbons. The plant is different and it sometimes in the past has intimidated some of our guys, but like anything else it's knowledge of how it all works. My opinion is that you need to know what you're doing with it, but a good refrigeration technician can learn it with time. I think ASDA have used ammonia/CO2 systems in one or two of their sites.

James
(PS I might be able to forward something on to you Frank-if I find it I'll send you a message)

[botrous]

Not a type of installation I've heard of

But I would be interested in reading any info available.

Ammonia is not something I have worked with so I'm up for being educated, although I have seen ammonia plant working.

A hotel here have an ammonia chiller that have the heat source comming from an oil burner (fuel oil # 2 ) and i think it's the only one in the country as an ammonia chiller . . . went to see it once with a fellow friend but never worked on it myself . . . so if there is more information about this subject i will be glad to see it

Regards

[Frosty]

Hello US Iceman

'Ammonia can not be used as a direct refrigerant. Let's say you have an air handler that has a refrigerant coil for cooling. R-22 can be used for cooling, but not ammonia.'
Is that really the case in the US? Over the pond (UK) NH3 is frequently used as a direct refrigerant - coldstores, distribution centres etc. It's also being used as the high stage refrigerant in CO2 cascade systems more and more frequently. Take a look at the following web site
www.star-ref.co.uk I think the hyperlink has gone pear-shaped! Type it in manually, there's lots of interesting stuff in here.

[US Iceman]

Hi Frosty,

Ammonia can not be used as a direct refrigerant. Let's say you have an air handler that has a refrigerant coil for cooling. R-22 can be used for cooling, but not ammonia.

You are correct also.

The ASHRAE safety code for refrigeration lists both direct and indirect systems. A direct system would be an air handler for comfort cooling with people. You can use chilled water (indirect, & cooled by ammonia, if you follow the safety codes and the correct guidelines), but you cannot use an ammonia coil in the air handler (direct).

For cold storage or food processing, etc. the use of ammonia is OK. The difference is the type of occupancy, and the refrigerant type.

Ammonia can be used for industrial occupancy, but not commercial (more people).

Everything you have written I agree with. What I should have said in my earlier post was, " Ammonia can not be used as a direct refrigerant in some types of applications".

It is a safety issue.

When I was talking about air handlers, I meant the very large sizes you see in commercial office buildings. Not ceiling hung cooling units.

Nice catch on a subtle point. ;)

US Iceman

[TXiceman]

The only place I have seen ammonia absorption used is in process cooling. While is is similar to Li-Br absorption, it is totally different. Where a Li-Br sytem used the water as the refrigerant and the Li-Br as a transport agent, the NH3 absorption system uses the ammonia as a refrigernat and the water as a transport agent. Since the NH3 is the refrigerant, you run run much colder evaporator temps (double and triple effect systems) and not limited to the freeze point of water.

The last time I saw a NH3 absortion unit here in the states was for a project in California for a refinery. These things are huge built up process plants and typically cost 5 to 10 times the cost of a mechanical plant of equivalent capacity.

As for mechanical units, I have built several NH3 screw water chillers for chemical plants with capacites ranging from 100 HP up to 2500 HP, both electric drive and steam turbine drive. Personally I prefer to use ammonia in the larger systems over the "Freons".

In the states, if you are interested in NH3 systems, two excellent organizations to coantact are IIAR and RETA. RETA offers a PSM accepted Ammonia Operator training courses .

As noted above, if you are not familar with NH3 and it safety practices, you need to get someone that is familar with NH3 to take care of the problem. Likewise, propane (R-290) is a good refrigerant. It is a safe refrigerant and can be used in a lot of applications. It is all in knowing how to handle it.

Ken

[frank]

Hi frosty

Long time no speak - what brings you back to the forum :)

If you still need some one to one training in Fridge give me a ring

Frank :D

[Lc_shi]

TXiceman,
propane(R-290) is a safe refrigerant? It is ignitible.How about its application?

rgds
LC-:)

[US Iceman]

Hi LC,

R-290 is very similar to R-22 performance. Yes, the propane is flammable and requires the use of explosion proof electrical components.

All electrical components must be "spark-proof". The control panels are usually made from cast aluminum enclosures, or use water-tight control panels that are purged at a positive pressure with dry nitrogen.

The facilities where a propane refrigeration is used will be familiar with these requirements.

Like R-22, propane has some oil solubility issues and the oil used must be carefully selected for the operating conditions.

I'm sure TXiceman will have some good information to share also.

[TXiceman]

Any refrigerant can be unsafe if not handled properly. A lot of chemical plants and refineries use propane as they have it on hand as a feed stock. They usually have a propane grade that is lower than refrigerant grade and contains some light end and heavy end hydrocarbons.

It is fairly comparable to R-22 in properties and efficencies, but does have the requirement of a Class 1, Group D, Division 2 area in the states. I believe in Europe requires an IP54 area. All sparking devices have to be contained in a cast NEMA 7 box or in a purged enviroment.

There are oil solubility problems with the hydrocarbon refrigerants and nearly everyone uses a snythhtic based oil now. The one use most of the time is a polyglycol based oil.

With the oil and it's affinity for the refrigerant, it is very critical to keep the oil warm during operation and during all off cycles.

Propane does not have a large tendency toward high discharge superheat and therefore does not produce very high discharge temsp and can create problems with oil injected screw compressors and over cooling of the oil.

Some companies and local authorities require the use of a cast steel compressor case inlieu of the more common cast iron compressor case. This feature alone can double or triple the cost of the compressor. Most plants will want B-31.3 piping as a minimum and all steel body valves for the propane service. Generally when comparing an R-22 system to a propane system, the initial cosr will be a minimum of 20% higher on the larger systems and it can approach 50% more on a smaller system.

Ken

[frank]

Hi Ken

This may be of interest http://www.protectingpeople.co.uk/fire_tech/ip_explained.htm

[knudo]

Could you elaboarate on the different type of evaporator designs. How does each work ???
Regards - Kevin

[bigtwin]

Hi guys, my first post here so let me introduce myself. My name is Bob and the nic' "bigtwin" thats cos I ried and build hogs. It is important to consider that the carbon foot print created per / ton refrigeration is approximately 20% less using ammonia when compared with R507 etc.....

[TXiceman]

Could you elaboarate on the different type of evaporator designs. How does each work ???
Regards - Kevin

Which type of evaporator designs?
Flooded
Thermosiphon
DX
Spray
Shell and tube
plate and frame or brazed plate?

Ken