A large Midwestern university found a significant chiller performance improvement through proper air elimination in the circulating chilled water piping system. Best of all, the project carried a sub-two year simple payback.Youngstown (Ohio) State University studied one of their chilled water systems with an eye toward reducing energy consumption. The system included 3 -1,200 ton York chillers fed by 3 -250HP chilled water pumps. While the pumps maximum design flow was 8,640 GPM the variable frequency drives were locked at 6,500GPM for constant flow operation. The chillers were operated under a variable output control plan.
The study zeroed in the installed air separator which was a common centrifugal design. The 16” line size separator was rated for 8,000 GPM maximum flow however, at maximum flow its’ removal efficiency was only 40%.
The physical plant operator investigated the impact of a new, high efficiency coalescing air and dirt separator built by Spirotherm and customized for the project. The recommended unit was a 20” line size, selected for optimum air elimination at the maximum flow rates. Even at maximum flow conditions the selected unit:
- · Eliminated 100% of the free air
- · Eliminated 100% of the entrained air
- · Eliminated up to 99.6% of the dissolved air
The dirt separator function of the Spirotherm unit removed 80% of all dirt and sediment 30 microns and larger within 100 passes. This feature eliminated the need for additional sidestream filtration and the associated maintenance it would require.
The new Spirotherm air and dirt separator was installed in a very short time window – 24 hours over a holiday - and was started up without a hitch. The results of the new separator were apparent almost immediately:
- Chiller output went from 2,300 tons to 2,700 tons; a 15.9% increase
- ΔT at the chiller increased from 8.5°F to 10°F
- Delivered air temperature at the furthest point on the campus went from 65°F to 58.5°F
So what can this advanced separator actually save in energy costs? A lot it, turns out. When the control scheme is altered to a variable pump flow and constant chiller output plan, the required chiller output (2,300 tons) can be met with only 5,543GPM – a 14.7% reduction in pump flow from the original 6,500GPM. Couple that with head reduction to only 72.7% of the initial conditions, pump power consumption drops to only 62.1% of initial conditions – a 37.9% KWh savings.
Put into dollar amounts, the Youngstown State plant engineer calculates that the previous system’s pump energy consumption cost the school $94,650.00 per year. At 62.1% of the initial conditions (as outlined above), the new pump energy consumption will be $58,778.00 – an annual savings of nearly $36,000.00.
The project cost was $70,300.00 which included a contractor’s premium for overnight installation on a very tight schedule. The project’s simple payback was just under two years – savings that will continue to accrue over time.
Marspec Technical Products can help you select the right Spirotherm air and dirt separator for your unique needs. For complete details – and a demonstration – of this technology, call us at 1-800-233-1394.
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