Writing in Consulting-Specifying Engineer, Fedele says that flow meters allow facility managers to measure HVAC systems’ performance and make the best decisions to optimize efficiency.
In one example, a commercial real estate company designing a four-tower complex in New York City installed a central district cooling plant of 10 chillers to provide cooled water for all four buildings, instead of using individual HVAC systems for each tower. With clamp-on ultrasonic flow meters, the company was able to keep track of how much water was flowing from chillers to tenants, and the temperature differential between supply and return water.
With this data, facility managers could calculate how much energy each tenant was using, and they could also use the system to monitor flow between pumps and chillers, enabling energy efficiency and performance evaluations.
Today’s market offers a variety of flow meters that provide the basic information necessary to evaluate efficiency, Fedele says. Four types that should be considered are:
Differential pressure: The most traditional type of flow meter can be used with natural gas boilers, boiler stacks, air ducts, combustion intakes and chilled water systems.
Electromagnetic: This can provide a greater range of functions, and can be used with most hot and chilled water systems.
Vortex: These systems work well in HVAC systems with fluctuating temperatures or pressures, including boilers, burners and compressed air systems.
Clamp-on ultrasonic: These meters are ideal for systems that experience periods of low flow, and for retrofit projects. They can be used a wide variety of systems including condenser water, potable water, thermal storage, river and lake water, and chemical feed.
GE has installed ultrasonic flow meters at select sites as part of its long-term goal to cut fresh water use 25 percent by 2015, using 2006 as a baseline.