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SYS-APM001-EN Chiller System Design and Control 39
Figure 23. Annual system operating costs (absorption chillers)
Kelly and Chan
10
compare the operational costs of chilled-water system
designs in site locations. Their summary states:
In conclusion, there are times you can ’have your cake and eat it too.’
In most cases, larger Ts and the associated lower flow rates will not
only save installation cost but will usually save energy over the
course of the year. This is especially true if a portion of the first cost
savings is reinvested in more efficient chillers. With the same cost
chillers, at worst, the annual operating cost with the lower flows will
be about equal to “standard” flows but still at a lower first cost.
Misconceptions about Low-Flow Rates
Some common misconceptions about low-flow systems include:
1 Low flow is only good for long piping runs
2 Low flow only works well for specific manufacturers’ chillers
3 Low flow can only be applied to new chilled-water systems
Let’s discuss each of these three misconceptions.
Misconception 1—Low flow is only good for long piping
runs.
One way to examine this claim is to use our previous example, but to
concentrate on the condenser-water side. We’ll start with the example
covered on pages 30-32. Using the same chiller, but a smaller cooling tower
$-
$5,000
$10,000
$15,000
$20,000
$25,000
$30,000
$35,000
$40,000
4.45 gpm/ton 3.60 gpm/ton 3.09 gpm/ton
Condenser Water Flow