HVAC Tools Information & Reviews

HVAC Ultrasonic Flow Meters

Did you know that there are some sounds, which are beyond human hearing range? Ultrasonic sounds are some of those. They travel at frequencies higher than the normal sound waves but thanks to technology and an HVAC tool called an HVAC ultrasonic flow meter, the ultrasonic sounds can be exploited and put to use. For instance, they are used to determine the rate of flow of liquids and air.

Ultrasonic flow meter definition


When a bat produces ultrasonic sound, the waves spring back as echoes from the surrounding grounds and objects; and depending on the speed of the echo, the bat knows how close or far an object is. It is quite intriguing how the bats are able to produce ultrasonic sounds but for now, our main concern is the technology behind ultrasonic sounds and how they can be utilized to determine the rate of flow inside the HVAC pipework. To determine the flow of gas or liquid being transmitted by an encased industrial pipe, ultrasonic flow meters come in handy. Outside the pipes, ultrasonic receivers and transmitters are attached to the pipe exterior and since the ultrasonic sound waves travel through the pipe, they are harnessed by the transmitter. Like a bat, which determines the landscape of the surroundings using ultrasonic echoes, special software can scrutinize the tendency of the ultrasonic sound waves to calibrate the flow of the fluid inside the pipe as well as the volume.

The 3 kinds of Ultrasonic Flow Meter tools


The type of fluid and how it is transmitted dictates the kind of ultrasonic flow meter to be employed. That said, three types of flow meters can be used: Time transit, Doppler shift, Open channel.


Time Transit


What if it a baseball could be thrown at a speed of 100 miles per hour? Wouldn’t everyone be playing baseball? Actually, we would use the high-speed throwing ability to figure out how the ultrasonic flow meters work. Suppose you threw a baseball in a room and the radar gun registered 100MPH. Assume that a wind tunnel is introduced in the room such that the throwing speed increases to 110MPH and 90MPH when throwing the ball against the direction of the wind. Let’s assume that these variables are constant. In that case, the speed of the wind would be 10MPH. in this hypothetical case, take the baseball speed as the ultrasonic wave speed and the wind to be the fluid traveling through the pipe. If the ultrasonic wave moves from the transmitter at a speed of 100MPH and registers 90MPH when it reaches the destination, you can finally determine the speed and direction of the fluid. Since the total speed reduces instead of increasing, it means that the fluid is moving against the transmitted signal’s direction. If we get the difference between the initial transmission speed (100MPH) and the end speed of the sound wave (90MPH), we can finally conclude that the fluid was traveling at 10MPH against the transmitted signal.


Doppler Shift


This technique is synonymous with the ability of a bat to figure out its way irrespective of the fact that it cannot see. It is also similar to the use of SONAR by a dolphin as it moves inside the waters by bouncing off the ultrasonic waves of the surrounding environment. The application of the Doppler shift method requires the medium in question to have suspended materials e.g. bubbles and particles in order for the ultrasonic sound to spring back.


Once the transmitter releases the ultrasonic waves, they hit the suspended elements inside the enclosed pipe and bounce off. Note that the signal that returns has varied frequencies that are used to calibrate the speed of the flow plus other specifications with respect to the flow of the fluid.


This method is rarely used in HVAC mechanisms because the systems don’t always have suspended elements but it is applicable in the healthcare industry whereby it is used to calculate such things as blood pressure during diagnoses.


Open Channel


The right way to determine the flow of a medium is by taking measurements from a utility line filled with a fluid such as the water pipes inside the house. But when it comes to draining systems that use gravity e.g. sewers, the method of calculating the flow is a bit complicated this is where open channel ultrasonic flow meters come into play. A transmitter is mounted over an open channel of a fluid. The transmitter bounces off the ultrasonic sound waves from the fluid surface to obtain a consistent rate with regards to the height of the fluid. It is worth noting that temperatures can alter the velocity of the sound and so the open channel meters are furnished with temperature sensors that adjust automatically. As the water height falls or rises in the channel, the volume and continuity can be determined in addition to geometric information of the channel.

Reasons HVAC professionals require ultrasonic flow meters


Chilled and cooling water units in commercial buildings utilize the flow of water to operate i.e. to convey heat in and out of the building. During routine checkups of these systems, ultrasonic flow meters are used to diagnose common issues, which are often related to lack of flow. Inside the chilled water and cooling water systems are several switches that can hamper the smooth running of the system if the flow of the fluid is too low.


For the switches to function as intended the flow must be at its appropriate range and that’s why an HVAC technician needs an ultrasonic meter to figure this out. As such, the professional will save time in determining whether there is a bad switch or not; whether a component is dysfunctional or if there is an obstruction. For this matter, the time taken to troubleshoot a problem is greatly reduced through the comprehensive and quick mechanism, which doesn’t necessitate disassembling of the entire piping or the prohibited areas.


In summary


The science of ultrasonic flow meters is such a spectacular HVAC tool that every HAVC professional needs to know, particularly those who deal with industrial units. Sometimes back when this technology never existed, the only means that could be used to measure the flow was by accessing the enclosed systems and it was still hard to take measurements in the actual operation.


Hopefully, you have enjoyed checking the scientific side of the HVAC tools as highlighted in this post. Use the insights on ultrasonic flow meters to become a better HVAC technician.