Chapter 6 Introduction to Refrigerants
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Safety Note
Working with Ammonia
Wear a tight-fi tting respirator when working with
R-717 and related equipment. Always stand to one side
when operating an ammonia valve because a small stem
leak can burn and damage the eyes. An excessive leak
can cause an almost instant loss of consciousness. Use
a sulfur candle or sulfur spray vapor to detect R-717 leaks,
which form smoky white fumes in the presence of sulfur.
R-717 attacks copper and bronze in the presence of
moisture. However, it does not corrode aluminum, iron,
or steel. The use of ammonia presents no special prob-
lems related to lubrication unless extreme temperatures
are encountered. R-717 is lighter than oil, and there is
no separation of the two. Excess oil in the evaporator
may be removed by opening a valve in the bottom of
the evaporator. R-717 is used in large compression sys-
tems with reciprocating compressors and also in many
absorption-type systems. Condensers for R-717 are usu-
ally water-cooled. Proper training and safety protocols
should be followed when working with ammonia.
Working with Ammon ia
Wear a tight- fi tting respirator when working with
R -717 an d related equipment. Always stan d to one s id e
when operatin g an ammonia valve because a small stem
leak can burn and damage the eyes. An excessive leak
can cause an almost instant loss of consciousness. U se
a sulfur candle or sulfur spra y vapor to detect R-717 leaks,
which form smok y white fumes in the presence of sulfur.
The International Institute of Ammonia Refrigera-
tion (IIAR) publishes numerous guidelines that
technicians can reference when working with R-717.
These publications provide guidance for the safe
installation, repair, and operation of ammonia-based
mechanical refrigeration systems. They also detail the
safety precautions that must be followed when han-
dling or working with ammonia.
6.6.2 Cryogenic Fluids
Many large food processing plants use cryogenic
fluids, such as liquid nitrogen or carbon dioxide, to
rapidly freeze foods. These liquid refrigerants are
often called freezants, and they range in temperature
from –250°F (–157°C) to nearly absolute zero (–460°F or
–273°C). This is called the cryogenic range. Common
cryogenic fluids are R-702 (hydrogen), R-704 (helium),
R-720 (neon), R-728 (nitrogen), R-729 (air), R-732 (oxy-
gen), and R-740 (argon).
Figure 6-17 lists the boiling temperatures of vari-
ous refrigerants and cryogenic fluids. Cryogenic fluids
Goodheart-Willcox Publisher
Figure 6-16. Pressure-enthalpy table showing the temperature, pressure, volume, and heat content of R-717 (ammonia). Note the
high latent heat, which is calculated by subtracting the liquid heat content from the vapor heat content.
R-717 Saturation Properties
Temperature
(°F)
Pressure (psia)
Vapor
Volume
(ft3/lb)
Liquid
Density
(lb/ft3)
Enthalpy (Btu/lb)
Latent Heat
(Btu/lb)
Liquid Vapor
–100 1.24 182.40 45.52 –63.3 572.5 635.8
–75 3.29 72.81 44.52 –37.0 583.3 620.3
–50 7.67 33.08 43.49 –10.6 593.7 604.3
–35 12.05 21.68 42.86 5.3 599.5 594.2
–25 15.98 16.66 42.44 16.0 603.2 587.2
–20 18.30 14.68 42.22 21.4 605.0 583.6
–15 20.88 12.97 42.00 26.7 606.7 580.0
–10 23.74 11.50 41.78 32.1 608.5 576.4
–5 26.92 10.23 41.56 37.5 610.1 572.6
0 30.42 9.12 41.34 42.9 611.8 568.9
5 34.27 8.15 41.11 48.3 613.3 565.0
10 38.51 7.30 40.89 53.8 614.9 561.1
15 43.14 6.56 40.66 59.2 616.3 557.1
20 48.21 5.91 40.43 64.7 617.8 553.1
25 53.73 5.33 40.20 70.2 619.1 548.9
35 66.26 4.37 39.72 81.2 621.7 540.5
50 89.19 3.29 39.00 97.9 625.2 527.3
75 140.50 2.13 37.74 126.2 629.9 503.7
100 211.90 1.42 36.40 155.2 633.0 477.8