The refrigerant of choice
The use of ammonia for cooling applications dates back to the mid 1800’s. By the early 1900’s the use of ammonia as a refrigerant was largely perfected in a closed cycle of evaporation, compression and condensation. Since then, the entire food distribution chain has come to depend on the thermodynamic properties of this crucial refrigerant.
Today, ammonia remains the refrigerant of choice for industrial cooling applications. As noted by Professor William F. Stoecker, the preeminent academic authority on industrial refrigeration, the advantages of ammonia over various types of freon are numerous.
- Ammonia costs less. Not only is ammonia significantly cheaper than the least expensive halocarbons, but because the density of ammonia is half that of halocarbons, only half as much material needs to be purchased to charge a system.
- Ammonia is more efficient. Its mass flow rate for a given refrigerating capacity is 1/7 that of HCFC-22, meaning only 1/7 the liquid needs to be pumped for a given refrigerating capacity.
- Ammonia requires smaller vapor line pipe sizes for large systems spread over a large area due to less drop in saturation temperature compared to freon.
- Ammonia systems are more tolerant of water contamination than freon systems. Water concentrations of less than 100 parts per million cause no penalty to ammonia system operation.
- Ammonia has more favorable heat-transfer coefficients than halocarbons. Compared to HCFC-22, ammonia has the following advantages:
specific heat of liquid to vapor = 4:1
latent heat of vaporization = 6:1
liquid thermal conductivity = 5.5:1
viscosities = 8:1
liquid density = 5:1
Reference: Industrial Refrigeration Handbook
William F. Stoecker, McGraw-Hill Companies, Inc., 1998.
Links to other information on ammonia refrigeration:
- ARI (Air Conditioning and Refrigeration Institute)
- ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers)
- ASME (American Society of Mechanical Engineers)
- IARW (International Association of Refrigerated Warehouses)
- Institute of Refrigeration (UK)
- IIAR (International Institute of Ammonia Refrigeration)
- International Institute of Refrigeration
- RETA (Refrigerating Engineers & Technicians Association)
- RSES (Refrigeration Service Engineers Society)