Sierra Instruments, Inc.

Flow Energy Management: 3 Killer Apps to Lower Energy Costs

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Courtesy of Sierra Instruments, Inc.

More and more, buzz words like “flow energy” or “flow energy management” have become prevalent as companies grapple to control costs, reduce energy use, and comply with government regulations—all while trying to increase profitability. But what are flow energy and flow energy management? Why should you care?

In this three-part series, we will:

  • Explore what flow energy is
  • Discuss the applications and flow meters that really impact the bottom line
  • Give tips and tricks for using flow meters to improve energy efficiency
  • Look at real-world examples of managing flow energy and how they have benefited from this practice

3 Killer Apps to Lower Energy Costs With Efficient Flow Energy Management
Flow energy is defined as flows that are critical to your facility’s every day operation. In other words, continuous flows that cost money. These flows include natural gas, compressed air, water, and steam.

Facilities managers often have the challenging task of managing all the flow energy in their facility. Since none of these commodities are “free,” they must strive to measure their “energy” usage accurately, determine the processes that use the most energy, and make them more efficient. These initiatives contribute directly to the bottom line.

The challenge is deciding which flow meter technology should be used for each fluid. In this first part of our blog series, we look at the best measurement applications (or “killer apps”) for optimal flow energy management for gas, liquid, and steam measurement and explore the best flow meter technology for each.

Killer App #1: Natural Gas And Compressed Air Measurement
Natural gas and compressed air measurement hit the top of the list for “killer apps” that almost every facility must measure and manage. Many facilities use natural gas for burner control in manufacturing or to fire boilers to produce steam or hot water. Facilities may require tracking of gas distribution, allocation, and billing.

All images courtesy of Sierra Instruments

Regardless of the application, facilities managers must have precise natural gas measurements to efficiently manage flow energy and thus lower energy costs.

Compressed air is another expensive flow energy, requiring energy-intensive compressors to produce it. Facilities managers are often tasked with conducting compressed air usage audits to determine compressor efficiency, find leaks in the system, and balance distribution and allocation.

In the past, facilities have used insertion turbine meters for compressed air measurement, but turbine meters don’t work well with low compressed air flows. Alternatively, insertion pitot tubes could be an option, but they don’t measure direct mass flow. Both technologies are prone to clogging.

The mass flow advantage
Thermal mass flow meters are ideal for natural gas combustion and allocation applications because mass flow rate, not volumetric, is the quantity of direct interest. For example, the optimal fuel/air ratio for efficient combustion is calculated on a mass basis. Natural gas is also billed on a mass basis.

Measuring compressed air presents its own challenges. In many facilities, usage varies widely throughout the day from very heavy at times of peak manufacturing to small flows (perhaps due to leakage) when most production is on standby. Thermal flow meters have a very wide turndown (100:1) to handle these fluctuations. Further, they have little to no pressure drop. The facility has already paid to have the air compressed, so needless pressure drop is wasted money.

Because thermal mass flow meters count the molecules of gas, they are immune to changes in inlet temperature and pressure. In a thermal flow meter’s simplest working configuration, fluid flows past a heated thermal sensor and a temperature sensor. As the molecules of the fluid flow pass the heated thermal sensor, heat is lost to the flowing fluid. The thermal sensor cools down, while the temperature sensor continues to measures the relatively constant temperature of the flowing fluid.

Figure 1. Thermal mass flow principle of operation

The amount of heat lost depends on the thermal properties of the fluid and the flow rate of the fluid. Thus, by measuring the temperature difference between the thermal and temperature sensors, the flow rate can be determined (Figure 1).

New developments in four-sensor thermal technology, coupled with stable “dry sense” sensor technology and advanced thermodynamic modeling algorithms, enable some thermal flow meters to attain +/-0.5 percent of reading accuracy, rivaling the accuracy of Coriolis flow meters at a fraction of the cost (Figure 2). On board, software apps also enable gas mixing capability, in-situ validation, and dial-a-pipe.