Understanding how thermal dispersion airflow measurements work is important to proper heating, ventilation, and air conditioning (HVAC) system management. Building managers with HVAC systems in their facilities must monitor and control airflows into and out of their buildings. Keep reading for a deep dive into how this technology works and how to get these measurements.
Know About Airflow Measurement
Airflow measurement devices are a fundamental component of building automation systems (BAS), which are used by controls contractors and mechanical contractors to monitor and control the performance of a facility. Whether for commissioning, monitoring, or control, airflow measuring stations are necessary for accurate control of ventilation rates, building pressurization, humidity, and energy use.
The Way That Thermal Flow Measurement Works
Thermal dispersion airflow stations, also known as thermal airflow stations or calorimetric airflow stations, are used to collect data about flow streams. A flow stream can transfer and remove heat from a source, cooling it in the same way air takes warmth from you as it flows across your skin. Each point of measurement in an airflow station utilizes two precision-matched thermistors for temperature measurement. One thermistor measures the temperature of the airstream, and the other is heated to maintain a set differential above that temperature. As the velocity increases, so does the rate of heat dispersion. The relationship between the mass airflow rate and power needed to maintain the temperature difference is used to calculate the flow rate.
The Challenges of Measuring Airflow
Thermal airflow measurement technology works well in ducted environments because the dimensions and characteristics of common upstream and downstream obstructions are well-defined and understood. There is enough straight run of ductwork upstream and downstream to condition the flow profile. Extreme variations of temperature are limited; the air is filtered, and the sensors are protected from moisture of any type.
This technology faces challenges when applied in environments that are outside of these environmental conditions—for example, when there is a limited straight run of duct. Another would be measuring outside air at a rain hood, where there is no straight run in a turbulent environment and the instrument is subjected to dirt, dust, rain, fog, sleet, and snow.
Find Solutions To Airflow Measurement Challenges
In the first example above, you can use our built-in three-point field characterization feature to reduce the errors introduced when factory-recommended installation requirements cannot be met.
In the second, a different technology is the best solution. Our OAM-IIb is specifically designed to work well in outside air applications.
We offer a variety of airflow measurement products that use different technologies so that we can meet the challenges of measuring flows in any environment. Airflow measurement devices are designed for large or small HVAC systems and fan types.
Applications of Airflow Measuring
Our thermal airflow measurement systems are designed to work in a wide variety of applications. Our ELECTRA-flo G5 is for stations mounted in ductwork, the ELECTRA-flo/SD is designed specifically for small ducts (16” or smaller), the ELECTRA-flo/FI is designed to be mounted in fan inlets, and the VOLU-trol/E is a combination airflow station and control damper.
Understanding how thermal dispersion airflow measurements work in real-world applications is important. Air Monitor’s airflow measurement systems are easier to install and place in real-world applications. Our technology requires a less straight run of duct to operate accurately and is more tolerant of misalignment in the field.
Contact us with your challenging airflow measurement needs and discover new ways to improve your facility. We have a network of local experts who are able to provide advice and support at no additional charge.