Sensing innovation co-developed by Fläkt Woods and VTT

Ventilation leader in search of better solutions

FläktGroup, originally established in Sweden in 1918, is now a European market leader for energy-efficient air technology solutions. FläktGroup, the indoor air comfort and fire safety division of the Group, employs 3,700 people in 65 countries, generating €680m in annual turnover. Fläkt Woods’s solutions improve air quality in offices, hotels, hospitals, airports and commercial construction projects, including specialist applications such as the pharmaceutical, marine, nuclear, oil and gas industries.

How to achieve correct ventilation based on room occupancy?

A healthy, comfortable and productivity-enhancing indoor climate can only be created by making sure ventilation accurately responds to the needs of the people occupying the space.

Current ventilation systems, based simply on estimated average occupancy, are not capable of adapting to changes in the use of indoor spaces. For example, the air in a conference room or a classroom quickly becomes stale if more than the predetermined number of people are present – or the ventilation may work at full speed even if the room is empty, wasting energy and money.

The biggest challenge in creating truly demand-controlled ventilation systems has been that suitable flow sensors are not available.

Ultrasound measurement – no pressure drop, no noise, accurate control

Fläkt Woods’s new OPTIVENT® ULTRA, developed in collaboration with VTT and coupled with modern control technology, achieves a high level of both indoor air quality and energy efficiency. VTT’s new, extremely accurate flow sensor based on ultrasound enables reliable measurement across the entire flow range, even at low flow rates.

“The collaboration between Fläkt Woods and VTT is a perfect example of needs meeting. We at Fläkt Woods saw the need for a better measuring solution and have the resources to productise it and fit it to solve our customers’ problems. Then again, few commercial companies have the time or budget for in-depth basic research – which is exactly what VTT brought to the table”, says Timo Kaasalainen, Product Manager, Fläkt Woods.

The airflow is guided by temperature or CO2 sensors installed in the room that detect changes in occupancy. An ultrasound pulse is transmitted radially across the air duct and the “bending” of the signal due to airflow speed is measured differentially using MEMS (Micro Electro Mechanical System) microphones. This measurement system eliminates several sources of error, such as turbulence after bends and T-joints, and obtains highly accurate measurements.

Because there are no objects in the flow channel, and no orifice plate is needed, no dirt-gathering or bulky measuring devices are needed. In addition, the absence of an orifice plate eliminates noise. The new maintenance-free, quiet, precise and intelligent sensor solution does not cause pressure losses as it does not physically interfere with the airflow.

VTT has been developing silicon-based MEMS sensors since the 1990s. This airflow measurement method can also be used in many novel industrial and automotive applications.

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