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. The preeminent 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 one 1/7 the liquid needs to be pumped for a given refrigerating capacity. Consequently, the mechanical pump and pumping power will be less in an ammonia system. |
| |
|
|
Ammonia requires smaller vapor line pipe sizes for large systems spread over a large area due to less |
| |
drop in saturation temperature compared to halocarbons. |
| |
|
|
Ammonia systems are more tolerant of water contamination than freon systems. However, this is only a |
| |
relative advantage for small amounts of water contamination, as concentrations greater than 100 ppm create problems in ammonia systems. |
| |
|
|
Ammonia has more favorable heat-transfer coefficients than halocarbons. Compared to HCFC-22, |
| |
ammonia has the following advantages: a.specific heat of liquid to vapor = 4:1 b.latent heat of
vaporization = 6:1 c.liquid thermal conductivity = 5.5:1 d.viscosities = .8:1 e.liquid density = .5:1 |
| |
|
| |
|
|
| |
|
