Trane trg-trc001-en Air Conditioner User Manual


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38 TRG-TRC001-EN
notes
period five
Tons of Refrigeration
Using the previous example for calculating supply airflow, the first step is to
determine the enthalpies of the air entering and leaving the cooling coil. This is
accomplished by lining up three points on the chart, including the entering-air
condition and identical points on the two enthalpy scales—one each on the left
and right edges of the psychrometric chart.
Using this method, the enthalpy of the mixed air entering the coil C is found to
be 32.7 Btu/lb. Similarly, the enthalpy of the supply air leaving the coil D is
found to be 23.5 Btu/lb.
The total refrigeration load, in terms of Btu per hour, is then calculated using
the following formula, where the supply airflow is expressed in cfm,
h
1
is the
entering-air enthalpy in Btu/lb, and
h
2
is the leaving-air enthalpy in Btu/lb.
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Figure 62
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Figure 63
Refrigeration Load (Btu/hr) 4.5 Supply Airflow×
h
1
h
2
–()×=
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