70
less than evaporative
condensers not
equipped with a desuperheater.
One method of calculating evaporation and
bleed in gallons per minute (gpm) is shown
as follows:
Evaporation Rate
=
Total Heat of Rejection via Evaporation
h
fg
btu lb
⁄ ×ρ lb gal
⁄
×60 min hr
⁄
=
Total Heat of Rejection via Evaporation
525,000 (Btu hr
⁄
gpm)
⁄
Bleed Rate
=
Evaporation Rate
Cycles of Concentration − 1
Example:
A unit has 100 ton cooling capacity with a
compressor EER = 15
Total Heat of Rejection
= Unit Capacity in Tons × 12000 ×
(1 +
3.413
EER
)
= 100 × 12000 ×
(1 +
3.413
15
)
= 1,473,040 Btu/hr
Total Full Load Heat of Rejection via
Evaporation
= Total Heat of Rejection ×
(1 – fraction of heat rejected by desuperheater)
= 1,473,040 Btu/hr × (1 – 0.22)
= 1,148,971 Btu/hr
Note that approximately 22% of the total heat of
rejection is accomplished with the desuperheater
at full load. So, the fraction of heat rejected by the
desuperheater (in the equation above) is
approximately 0.22 at full load and increases as
the ambient dry bulb decreases.
Evaporation Rate
=
1,148,971 (Btu hr
⁄
)
525,000 (Btu hr
⁄
gpm
⁄
)
= 2.19 gpm
Assuming 4 cycles of concentration:
Bleed Rate
=
2.19
4−1
= 0.73 gpm
Summary of Contents for RZ Series
Page 2: ......
Page 31: ...31 Figure 4 4 Point Lift RZ Series Air Cooled Condenser Unit ...
Page 90: ...90 Gas Heater Operating Instructions ...
Page 108: ...108 Maintenance Log E Coated Coil ...
Page 110: ...110 ...
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