TRG-TRC001-EN 39
period five
Tons of Refrigeration
notes Realize that 4.5 is not a constant! It is the product of density of air and the
conversion factor of 60 minutes per hour. The density of air at “standard”
conditions (69.5°F DB dry air at sea level) results in the value 4.5. Air at other
conditions and elevations will cause this factor to change.
Using the supply airflow calculated during Period 4 and the enthalpy values
read from the psychrometric chart:
Converting to the more common units of tons:
Density 0.075 lb/ft3
=
0.075 60 min/hr×4.5=

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Figure64
Refrigeration Load (Btu/hr 4.5 3,430 cfm×32.7 23.5–()×142,000 Btu/hr==
142,000 Btu/hr
12,000 Btu/hr/ton
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