Page 31 - Uninterruptible Power Supplies

Standby Power Generating Sets
Standby Power Generating Sets 29

planning or design stage it is necessary to use the heat loss figures from
the manufacturers or installers.)
Assume that the entering air is at 15°C and a 10°K rise is permissi-
ble, the specific heat capacity of air may be taken as 1.005 kJ/kg°K, and
3
the density as 1.22 kg/m .
From Eq. 1.2
100 kW 0.247
Air mass flow
10°K 1.005 kJ/kg°K
2.46 kg/second

From Eq. 1.3

Air volume flow 2.01 m /second
3
Where the radiator is mounted within the engine room and takes
its cooling air from within the room, it will invariably be the case
that the radiator air flow exceeds the room ventilation requirements.
The standard radiator fan fitted to an engine will have some surplus
power and will probably overcome a total external pressure drop
of 250 Pa (2.5 mbar). However, if room inlet or outlet louvers or
acoustic attenuators are to be fitted, the total external pressure drop
should be ascertained and the set manufacturer consulted. If neces-
sary a supply fan should be installed. Figure 1.11 indicates a typical
arrangement for a local radiator cooled diesel engine driven generat-
ing set.
Where the radiator is mounted away from the engine, engine room
ventilation will be essential and Fig. 1.12 indicates a typical arrange-
ment for a remote radiator-cooled diesel engine–driven generating set.

Direct Air–Cooled Diesel Engines
Air is extracted from the engine room to cool the engine but this will
not be sufficient to remove the heat gained from the engine cladding.
Engine room ventilation will be required as discussed in the preceding
paragraphs; Figure 1.13 indicates a typical arrangement for a direct
air–cooled diesel engine–driven generating set.

Gas Turbine Ventilation
The ventilation requirements for a gas turbine are calculated in a man-
ner similar to that discussed in the preceding paragraphs. The heat
loss data will be required from the manufacturer. Turbines are sensi-
tive to any restrictions of flow of the air inlet or of the exhaust outlet

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