Ammonia Refrigeration – Myths and Facts

Ammonia is a reliable and fine alternate option for efficient refrigeration. There are some key facts, a comparison for the atmospheric life, ozone depleting potential and the global warming potential of different regions. It can be clearly seen that ammonia is having the best properties from the whole globe. If you come to know about the atmospheric life of ammonia, it will decompose in the air within few hours or within a day which is less than the duration of ozone depletion potential. Global Warming potential is less than one if you have a comparison with any of the other refrigerants. 

I think only CO2 is the one which matches its properties. Hence, in this case, I feel ammonia is a very good representative if you look at the coefficient performance of ammonia with respect to other refrigerants. At any evaporating temperature, you can see ammonia will have the highest coefficient performance. Talking about other physical properties – 

• Boiling point of ammonia is -330C which makes it very good to be used for low temperature as well as high temperature applications. 
• Looking at the ignition temperature, it is 650 degrees. 
• Flammability is very low for ammonia. 
• Flammable only when and if you want it to have flames under highest temperature. 

It can also be used for heat pump applications and other applications, as its explosion concentration is also very high with 16 percent to 28 percent by volume. With these properties, the chances of explosion become very low.

The detection threshold for ammonia is 5 PPM. It is a very pungent smell compound and naturally occurring compound which can be sensed during leaks, whereas some of the other refrigerants are colourless and odourless even during leaks.

Why ammonia is a natural choice? 

Like other refrigerants, Ammonia (R717) show no threat to the earth’s climate nor to the ozone layer. It has been used for a very long time and it can be used for any capacity for under temperature (from -50oC to +70oC). It’s a renown and well acknowledged refrigerant which has been safely used across the refrigeration applications for more than 100 years. 

• It’s efficiency levels and the C.O.P. is very high, it is heat transfer coefficient, cost compliant and it does not mix with the oil even if the density is higher.
• Pumping requirement is less and it is not a combination of requisites.
• Refrigerants composition doesn’t change even during any leaks
• It is very flexible for plant modifications and extensions. 

There are some myths and facts in understanding ammonia refrigerant.

There are various misconceptions about ammonia refrigerants. It is thought that ammonia is toxic, and it is; most of the refrigerants are colourless and odourless, but ammonia is pungent. So, most of the times even if 5 PPM leaks, it can be detected with its odour. Moreover, up to 25 ppm is allowed by international standards for 10 – 15 years. So, if it leaks also the operator goes and just shuts off the wall or the required equipment and repairs it. 

Ammonia, though is toxic at a certain concentration, but if handled properly with right equipment and used within the desired quality and design systems, it can never be harmful to any lives. Most of harm and the loss of lives takes place eitherdue to the explosion of equipment or because of inappropriate applications of equipment. These are the main reasons why most of the ammonia systems create problems. If there is no safe operation, if there is no leakage and there are leak detection systems, ammonia can be used very efficiently very safely. 

The effect of ammonia at five ppm it can be detected by our nose. At 25 PPM, it is so pungent that everyone nearby would know that ammonia is leaking and there is no health hazard for 10 to 15 years if you are under 25 PPM. At 100 PPM, irritation starts. And like if you go to higher concentration.

So, the systems need to incorporate ammonia leak detection sensors that can raise an alarm or give an indication to ensure safe operations. These procedures are missing in almost 90 percent of installations. 

Today, we are using proper ventilation techniques, proper techniques to remove the ammonia and put it into the water as it is miscible in water and not allow it to mix with the water even if it leaks. Ammonia is flammable, this is another myth, I would say ammonia is very hard to ignite. Why so, because it has an ignition temperature of 650 degrees and before that it breaks at 450 degrees to and N2 and H2 and for flammability, the concentration required for it to ignite or explode is very high. 

So, in a closed room maybe it is possible, but as ASHRAE said it is a B2L, which is very less flammable as compared with many hydrocarbons and other fuels which are used in day to day life. So, ammonia being a natural refrigerant, as per ASHRAE standards and other properties, is very less flammable and it has a high affinity to water. So, usually, the moisture that water takes in the ammonia and explosion is only due to pressure within a vessel not due to ammonia. 

There is this myth that ammonia is only being used in water-cooled applications but not in Ammonia cannot be used in air-cooled applications. But, as the picture shows ammonia is being used in air-cooled applications in Jammu and Kashmir for cold shortages. And this is an air-cooled condenser which is being used in that application. Even air-cooled chillers are being made by some international companies like Star Refrigeration.

Ammonia systems require a lot of refrigeration as compared to the other refrigerants. Now, what happens is to increase the efficiency of ammonia we use flooded systems in ammonia refrigeration. Usually pump systems are flooded systems, but it does not mean that it require additional ammonia to make a refrigeration system than any other refrigerant.

Low charge systems as defined is 1.3 kg per kilowatt of refrigerant and like the ammonia systems which are available have 0.06 kg per kilowatt of charge and if we use proper equipment like floats and we eliminate the HP receiver, then ammonia charge can be very less in a system. Even commercial level systems are now being developed. 

Small ammonia systems have also been developed, they are not there in India as of now, but up to seven-kilowatt compressor in ammonia has been developed in the world.

Ammonia cannot be used for air conditioning. Due to increased use of natural refrigerants and due to its excellent energy saving properties many countries are using ammonia with secondary fluids like water, brines and CO2in air-conditioning plants. 

Another myth is that ammonia plants cannot be automated and require a team of operators. 

So, today with Danfoss and many other good suppliers coming in many fully automated ammonia plants are being installed and some of them are:

• IPCL –BARODA-2300 Tons Refrigeration using 23No.  12 cylinder reciprocating compressors (fully automated)
• Asian Lacto Health Foods
• Mother Dairy

Chiller packages at many places which are fully automated and running with ammonia refrigerant. So, having talked about all this, I would say that ammonia as a refrigerant is very potent and if used properly with the right design, with the right safety, with the right products and brought into automation, so that operational problems are not there. It can be a very efficient refrigerant for our natural refrigerant sector.