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A Comparison Of Pump Operating Costs
Energy-and-economic-analysis software can help engineers quickly and accurately assess the appropriateness of alternative designs. In this case, we used Trane’s System Analyzer™ software to compare the energy and related operating costs of three pumping strategies.
As the analysis results show, a "decoupled" (constant primary–variable secondary) or VPF system can yield substantial savings when compared with a constant-flow design.
Design Criteria
- Medical office building in Atlanta, Georgia (USA)
- Design load is 470 tons of cooling (1560 kW refrigeration)
- Two air-cooled helical-rotary chillers piped in parallel
- One pump per chiller
- Alternative pumping strategies: constant flows; constant primary–variable secondary flows; and variable flows
| Annual Analysis Results |
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| System Flow Alternatives |
Pumping
Energy
Consumed |
Operating
Costs,
US Currency |
|
| Constant primary, constant secondary |
52,588 kWh |
$4,522 |
|
| Constant primary, variable secondary ("decoupled") |
32,819 kWh |
$2,822 |
|
| Variable primary, variable secondary (VPF) |
26,614 kWh |
$2,289 |
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