Natural Refrigerant Cooling – Low-content Ammonia Technology

The ammonia chillers are more efficient than traditional CFC based chillers for two main reasons.
The first one is the use of ammonia as a refrigerant: the heat necessary for the vaporization of ammonia is very high, therefore less quantity of refrigerant is required to provide the same cooling capacity: consequently the size of the chiller can be reduced, the electric consumption will then be less and the COP higher.

The second reason is the use of high technologies compressors that can function at variable speeds, often from 100 to 10%.

Ammonia properties

 

Ammonia

R134a

Normal boiling point, 1013 hPa (°C)

-33.3

-26.1

Critical temperature (°C)

135.3

101

Heat of vaporization (kJ/kg)

1262

199

GWP (based on CO2=1)

0

1300


Future of ammonia cooling plants lies in the use of low-content ammonia chillers.

Considering technical, legislative and market points of view:

  • Using ammonia as a refrigerant enables high efficiency plants with short returns on investment and high energy savings.
  • The low-content ammonia chillers don't fall under the safety legislation: as the charge of refrigerant contained is low, there is no risk of flammability. Moreover, the principles on which the laws are based where laid down 50 years ago: technology has changed beyond recognition since then.


Considering today’s political trend that is to reduce the use of HFC gases, Ammonia is a natural refrigerant which does not have any impact on the environment and it will not be subject to carbon emission based taxation or price increases.

  • Finally, while the world is facing increasing costs of energy, low-content ammonia chillers provides huge reliable possibilities for commercial application.

Safety and risks

Two significant safety issues while using ammonia are the toxicity of the gas and the flammability under certain circumstances. However, the odour makes ammonia immediately apparent when present, enabling appropriate measures to be taken.

For low-content ammonia chiller, there could be no health and safety risks. 

nature_refrigerantFlammability:

  • Lower limit: 15 % of total volume
  • Upper limit: 28 % of total volume


Toxicity:

  • 100-200 ppm (70-140 mg/m3): eyes irritated
  • 500 ppm (348 mg/m3): no permanent eye damage even to permanent exposure.
  • 1700 ppm (1182 mg/m3) : cough


Example: Low-content chiller with 73 kg of ammonia (2.2 MW cooling), size: 6.4 x 2.4 x 2.8 m. Considering worst case: ventilator of technical room broken & all refrigerant leaks into the room.

  • To avoid flammability, a room of 8.8 x 5 x 4,2 meters is sufficient to be in any case below the lower limit (141 m3 of air). About toxicity, a leakage of 19.6 g of ammonia will correspond to eyes irritation and 165 g to cough. Consequently, indoor ammonia units should be maintained with extreme care; whereas units located on roof present very limited risks.

For more information about ammonia as a refrigerant, please consult the following document :

About Ammonia

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