Today’s industrial facilities rely on power distribution systems to maintain stable and efficient operation. Plant systems have greater power demands than ever. In most cases where electric installations and devices shut down or malfunction, the problem is thermal.
Ultrasonic flow measurement can be used to optimize hydronic cooling of integrated power distribution systems. Ultrasonic meters monitor flow conditions throughout the system and provide data to help determine if fluid volumes are consistent and meet the necessary coolant demand.
Increasing awareness of limited energy resources, coupled with the drive to minimize operational costs, has focused attention on energy management. For industrial organizations, enhanced power distribution systems are necessary to keep pace with technology improvements and support a fully integrated solution that maximizes the efficient use of installed power generation.
Electrical power is used in every aspect of plant operations. A constant power supply is crucial for plants to operate safely and economically. A shutdown or malfunction of the electrical installation can have major—even catastrophic—repercussions.
Need for Effective Cooling
Plants use distributed power technologies to ensure a robust energy supply and increase productivity. However, heat generated by electronic devices and circuitry must be dissipated to improve reliability and prevent premature failure. Traditional techniques for heat dissipation include heat sinks and fans, as well as other forms of automated cooling such as liquid cooling.
Hydronic cooling (i.e., the use of water as a heat-transfer medium) is commonly employed to keep plant power systems within the proper temperature range. Water has a high thermal conductivity, meaning it absorbs heat easily—more so than air. It is effective for cooling power supply equipment.
Water cooling transfers heat from each part to a radiator that dissipates the heat and cools the liquid—similar to a car’s radiator.
In any hydronic cooling application, the liquid medium must flow at designed flow rates within the system.
It is also important to assess load variations. Load is calculated by using the flow rate as well as the associated supply and return fluid temperatures.
Hydronic cooling systems can be difficult to balance because of the presence of multiple system branches, changes in cooling demand, and pressure differences among the various supply and return lines. Inclusion of balancing valves and flow meters at each terminal or branch circuit facilitates balancing. To help reduce the cooling system’s energy requirements, system designers also seek to minimize the cooling system pressure drop.
Measuring the bidirectional flow of liquid circulating in the hydronic system is critical in order to monitor proper cooling performance. Flow measurement instruments are used to detect reduced flow rates, leakage and other conditions affecting the robustness of cooling equipment.
Selecting the Right Flow Meter
Companies that design power distribution systems for industrial facilities count on precise flow measurement instrumentation to monitor flow through hydronic system piping and ensure that coolant volumes remain consistent.
Flow readings are needed at strategic locations to give a general overview of coolant supply and demand. This often necessitates a non-invasive metering solution that can easily attach to piping to gather flow data without disrupting the system’s configuration and normal operation.
Certain flow metering techniques lack the accuracy and/or responsiveness to optimize hydronic cooling operation. Poor meter performance can lead to large fluctuations in the coolant flow rate. This, in turn, results in excessive energy consumption at pumps because of continuous loading and unloading.
Mechanical meters used in liquid flow measurement applications face an increased likelihood of deteriorating accuracy caused by wear and tear on the device. Additionally, the need for mechanical meters to be periodically tested, recalibrated and repaired means they have to be removed from service, forcing the user to replace the meter with a temporary device.
Some power system designers focus on transit time ultrasonic flow measurement as an alternative to in-line metering. Externally mounted, clamp-on ultrasonic meters are suited for use with coolant distribution lines. They are quick, easy and less expensive to install than in-line flow meters because there is no need to cut the line, interrupt service or drain the pipe. The meters do not require the installation of bypass piping and valves for removal, and there is no pressure drop as with some other technologies.
Unlike Doppler-type ultrasonic flow meters that depend on large particles or bubbles in the flow path to read a flow rate, ultrasonic devices employing a transit-time measurement method provide an accurate output without modifying the coolant flow.
Putting the Solution to Work
For a wide range of power distribution applications, the use of clamp-on, solid-state ultrasonic flow meters meets key accuracy and bidirectional measurement criteria with an installation approach that satisfies cost, reliability and uninterrupted operation needs (see Figure 1).
A transit-time ultrasonic meter uses two transducers functioning as both ultrasonic transmitters and receivers. It operates by alternately transmitting and receiving a frequency-modulated burst of sound energy between the two transducers. The burst is first transmitted in the direction of fluid flow and then against fluid flow (see Figure 2).
Because sound energy in a moving liquid is carried faster when it travels in the direction of fluid flow (downstream) than it does when it travels against fluid flow (upstream), a differential in the times of flight will occur. The sound’s time of flight is accurately measured in both directions and the difference in time of flight calculated. The liquid velocity (V) inside the pipe can be related to the difference in time of flight (Δt) using Equation 1.
V = K * D * (Δt) Equation 1
V = liquid velocity
K = a constant
D = the distance between the transducers
Δt = the difference in time of flight
Transit-time ultrasonic flow meters have no moving parts to maintain or replace, making fluid compatibility and pressure head loss a non-issue. Their rugged aluminum enclosure also promotes a long service life. The meters have a large measuring range that enables reliable readings at all designed alternating-current integrated fight-through power (AC IFTP) system flow rates.
Integrated in the cooling apparatus for an industrial power distribution system, the ultrasonic meters provide an analog 4-20 milliamps (mA) output to a data acquisition system that corresponds to the instantaneous volumetric flow rate of the coolant. The meters offer low energy consumption, and their accurate measurement data is used to help reduce cooling system variability and maximize operational efficiency.