As commonly known in the HVAC industry, the precision of airflow measurement is important for most industrial working environments.
It will essentially affect the general operational performance of the airflow and HVAC systems.
However, it is less commonly known that better precision can save big on the budget! According to research, buildings annually contribute 30% of the total energy usage and 60% of the total use of electricity in the United States.
In addition, running HVAC system in buildings constitutes about half of a building’s energy cost. Accurately measuring and controlling the outdoor air intake flow rate and building pressure are options that should be considered for reducing HVAC energy consumption and improving performance.
Indoor Air Quality, known as IAQ, is also one of the most important aspects of HVAC performance. The potential annual savings and productivity gains from improved IAQ in the United States are estimated as high as $14 billion from reduced respiratory disease, $4 billion from reduced allergies and asthma, $30 billion from reduced sick building syndrome, and $160 billion from direct improvements in worker performance that are unrelated to health. Therefore, modest investments toward improved IAQ would generate substantial returns by installing proper and precise outdoor airflow measurement stations in order to manipulate the incoming air.
Airflow measurement systems used for ventilation rate control or volumetric tracking to control building pressure require a primary element to measure the flow and a transducer to convert the raw signal to velocity. The preferred method of measuring airflow is the Pitot-tube; the primary standard which most other technologies are tested against.
Pitot-tube arrays have an accuracy of ±2%. However, the overall airflow measurement accuracy is only as good as the transducer being used to interpret the differential between the total and static pressures measured by the Pitot-tube array. Transducer accuracies must be examined to ensure that adequate tolerances are maintained. Most transducers accuracies are rated as a percent of full scale (F.S) span; the larger the span, the greater the inaccuracy.
Therefore, transducers should be ranged based on the design maximum velocity plus 10% to allow for field adjustment. To reduce error, the square root function of converting the measured velocity pressure into velocity should also be done prior to analog-to-digital signal conversion. Additional sources of error include transducer drift for low velocity applications, changes in air density associated with ventilation rate control in climates with large temperature variances, and signal noise. As a result, it is necessary to choose the right transducer for the sake of getting the best performance and accuracy.
Sales engineers at Belnor Engineering are experienced and fully proficient to give you any professional advice on your options for your particular case with our well-known partner in airflow measurement industry, Paragon Controls.
Paragon's engineering and manufacturing managers have more than 150 years combined experience in designing both commercial and industrial airflow and pressure measurement and control systems and their products are proven as trust-worthy, reliable, and affordable.
In conclusion, in order to improve the general performance of HVAC system and IAQ, as well as cost efficiency, the appropriate airflow measurement station and transducer needs to be chosen for its very special case. Consult with us today to know more about the importance of airflow measurement in a building.