Ammonia is the Future
Ammonia has been an established, pre-eminent industrial refrigerant for over 125 years. Ammonia has been used in industrial refrigeration applications such as food production. CFCs, such as Freon, became popular in the 1930s due to their low toxicity. The chlorine in the refrigerant was found to have caused a hole in the ozone layer. Therefore, they have now been phased out. Non-chlorine, low toxicity, HFCs were developed to replace the CFCs. HFCs, however, have a high global warming potential, so they too are being phased down to 21% by 2030
Between now and 2030 ammonia will become increasingly popular in non-industrial applications, such as, the cooling of data centres and the air conditioning of buildings. Systems with a low refrigerant charge have been developed and rigorously field tested, so the application of cooling a small office with ammonia is becoming more and more common place. New ammonia chillers are simpler in design, therefore competitive in price to HFC chillers. The higher initial cost is paid back in electricity savings within 2 years- then they become cheaper. They use less electricity because ammonia has a latent heat bubble 5 times bigger than other refrigerants- more refrigeration effect and less gas. The range of smaller, non-industrial applications will become more common place during the HFC phase down
There are no concerns, now-a-days, by the end user as regards the toxicity of the refrigerant. The refrigerant is contained within the system. Similar to electricity being contained within plastic in your home. The low charge refrigeration plant shuts down in the event of a leak. You can stand next to a leaking ammonia system and tolerate the gas. The machine brings a fan on which disperses the small amount of ammonia into air. The ammonia then absorbs into the moisture in the air. Particularly in North Europe and to an increasing extent in the UK, ammonia is used in domestic or residential locations
Pipework used for Industrial Refrigeration
Ammonia corrodes various metals and alloys. Steel, however, works well with ammonia. The use of steel makes the maintenance different as opposed to HFC chillers. HFC chillers are prone to leaks on the copper pipework. On the condenser, the copper expands and contracts- eventually rubbing through against the steel frame. Vibration related leaks are also common. On an ammonia system, steel that is freezing then thawing on defrost or off cycles creates rapid rust formation and can lead to catastrophic failure of the pipework. Steel that is permanently frozen creates slower rust formation as the ice slows the oxidisation process. Our engineers carry out metallurgic testing to gauge the integrity of the steel
Industrial Refrigeration Compressors
A popular compressor type is the Screw compressor, right and below, which has two rotors running together. The Reciprocating compressor, in the above video, is another popular Ammonia compressor. NH3 compressors are open drive.
Oil used to lubricate the compressor and ammonia are non-miscible. That is to say: the refrigerant does not carry the oil round the system and back to the compressor. Oil return is achieved by various methods of oil return
Manual oil recovery
When there are oil return issues, the engineer has to work out where oil is not returning from and use his experience to resolve the issue. Otherwise, the machine will experience low oil return problems
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