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50 C120-H007-05EN
CHAPTER 4 Air Conditioning
4.4.4 Convenient formulas for air conditioning capacities
Table 4.8 lists convenient formulas for the capacity of air conditioners installed in a
computer room. Because a proportion of the thermal load comes from sensible heat,
the capacity and number of air conditioners required can be determined by calculating
the flow rate requirement relating to sensible heat. Actual air conditioning design
should allow for air conditioner characteristics, building thermal load calculations,
etc.
Enthalpy of the air
coming out of the air
conditioner
i
5
=39.3 kJ/kg
(16.9 Btu/lb)
Determine the enthalpy at 18°C (64.4°F)
and 65% RH from the air-line diagram.
Air conditioner sensible
heat cooling capacity
(when calculated on the
basis of sensible heat
enthalpy difference)
95.9 MJ/h(90900 Btu/h) at a flow
rate of 220 m
3
/min (7770ft
3
/min)
(i
1
- i
5
) × Flow rate/Specific volume
=6.1(kJ/kg) × 220 (m
3
/min)
× 60 (min/h) / 0.84 (m
3
/kg)
=2.6(Btu/lb) × 7770 (ft
3
/min)
× 60 (min/h) / 13.5 (ft
3
/lb)
Table 4.8 Convenient formulas for air conditioner capacity
Air conditioning setup
Flow rate calculation formula
Room air conditioning
Underfloor ventilation
Table 4.7 Examples of underfloor-ventilation air conditioner cooling capacity
calculations (2/2)
Item Calculated value Calculation method
1.0/0.84 (24 C-11 C) 0.9 60
Thermal load (kJ/h)
0.24/13.5 (75.2 F-52 F) 0.9 60
Thermal load (Btu/h)
=
.
.
=
.
.
Flow rate (m /min)
3
Flow rate (ft /min)
3
1.0/0.84 (24 C-18 C) 60
Thermal load (kJ/h)
0.24/13.5 (75.2 F-64.4 F) 60
Thermal load (Btu/h)
=
.
.
=
.
.
Flow rate (m /min)
3
Flow rate (ft /min)
3