period three
System Variations
notes
ARI. They are not, however, suggestions for good design practice for any given
Trends toward improved humidity control and
Low-Flow Systems
annual energyconsumption, kWh
750,000
600,000
450,000 |
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| chiller |
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300,000 |
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150,000 |
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| pumps |
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0 |
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| cooling tower fans | |||
basecase | lowflow | |||||||||
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Figure 71
Figure 71 shows the combined annual energy consumption of the chiller, chilled- and condenser-water pumps, and cooling-tower fans for these two system designs. In fact, a growing number of design engineers and utilities have published papers or manuals that recommend that system flow rates be reduced. A number of them have found that using lower flow rates can reduce both installed and operating costs.
“…there are times you can ‘have your cake and eat it too.’ In most cases, larger ∆T’s 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.”
(Source: Kelly, David W. and Chan, Tumin, “Optimizing Chilled Water Plants,” Heating/Piping/Air Conditioning, January 1999)
63 |
