Chilled-Water-System Options
SYS-APM001-EN
25
Figure 7 System energy comparison (no pipe)
Energy consumption for the chiller, condenser-water pump, and cooling-tower
fans is shown in Figure 7. Note that only at full load does the total power of the
chilled-water plant increase. Recall that this is with absolutely no pressure drop
through the condenser-water piping, valves, or fittings. It is interesting to note
that the break-even point at full load is approximately 8 feet of head (water)
[23.9 kPa]. Also note that at all part-load conditions, the total power of the low-
flow system is less than that of the base system. It is easy to see that even for
short piping runs, reducing flow rates can improve plant energy consumption.
Misconception 2--Low flow only works for specific
manufacturers' chillers.
Demirchian, et al.
3
, Eley
4
, and Schwedler and Nordeen
6
independently showed
that system energy consumption can be reduced by reducing flow rates. It is
interesting to note that in the systems studied, three different chiller
manufacturer's chillers were examined, yet the energy savings only varied from
2.0 to 6.5 percent. In all cases, regardless of which manufacturer's chillers were
used, the system energy consumption was reduced. In addition, Demirchian, et
al.
2
, and Schwedler and Nordeen
6
also noted reduced first costs.
0.0
50.0
100.0
150.0
200.0
250.0
300.0
350.0
25%
50%
75%
100%
System Load
System Energy C
onsumption (kW
h
)
3.0 gpm/ton
2.0 gpm/ton
Summary :
Chilled-Water-System Options SYS-APM001-EN 25 Figure 7 System energy comparison (no pipe) Energy consumption for the chiller, condenser-water pump, and cooling-tower fans is shown in Figure 7. 0.0 50.0 100.0 150.0 200.0 250.0 300.0 350.0 25% 50% 75% 100% System Load System Energy C onsumption (kW h ) 3.0 gpm/ton 2.0 gpm/ton
Tags :
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