www.heatingandventilating.net T
he role of facilities managers mean they are usually masters of many trades, and for core building services, such as ventilation,
they need to know all the variables that can affect performance. One of these variables is Indoor air quality (IAQ) which is at now acknowledged as a critical component of building management. This recognition has also led to a greater focus on ventilation, especially with the return of higher occupancy levels in public venues. Although many companies may previously have relied on natural ventilation alone, like opening windows, there is now an awareness that more sophisticated solutions are needed to provide healthy air. With an improved understanding comes an even
more significant challenge for facilities managers, as they are tasked with ensuring appropriate levels of airflow in a building, as well as considering other key factors such as ambient temperature, running costs and performance of ventilation systems. Many of these considerations relate back to the fan
itself, with specification, positioning and maintenance of the fan key to ensuring good IAQ.
Mixed, centrifugal and axial flow: a comparison
Common ventilation systems will use either axial fans or centrifugal fans. Axial flow fans are typically cost-effective, compact,
and are easy to install. Due to ongoing improvements in their design since their introduction, axial fans may also provide a more efficient service and less noise than their previous counterparts. They are also adaptable, making them suitable for many uses. It’s important to note that air flows straight through the fan - in an axial direction. Centrifugal fans impart energy on the air itself, leading it to flow in a radial direction. They tend to provide more pressure than axial fans, and depending on the design, they may be backward curved or forward curved. Mixed flow fans still utilise some features of axial
flow fan, such as volume flow and axial direction of airflow. However, they incorporate features from backward-curved centrifugal fans too, like pressure development. When it comes to how efficient they are,
Ventilation
Enhancing ventilation: a facility manager’s role
David Millward, group product manager at Elta Group, provides some top tips and considerations for fan ventilation, including specification, installation, and ongoing maintenance
mixed flow fans are usually rated more favourably than the axial flow fan. They also tend to outperform axial fans in terms of noise level and pressure development. They typically offer better airflow and more of a compact design than the centrifugal fan too. It is necessary to make sure the right fan is used, so it meets the needs of the location, as this will help to improve the system’s effectiveness. An open dialogue between facilities managers, contractors and building designers is vital to improve existing systems.
Where to place fans
The location of fans is another factor in maximising effectiveness. A detailed knowledge of building layout, including which rooms may be busier (and when), will be crucial in establishing the best areas for ventilation. For example, the optimal solution may be a roof
fan, which is designed to give ventilation through roof outlets. There are models created to provide high levels of flow or pressure in centrifugal, mixed and axial flow configurations. Effort should be made to allow a gap equivalent to the diameter of one fan between the fan intake and nearby locations for internal locations. Without this, the impeller can become deprived of air, which increases resistance and lessens air flow. Minimising vibration and noise levels Efficiency and overall performance will always be the most important factors for facilities managers to consider. However, issues like noise and vibration should also be accounted for. Ensuring neither of these are too disruptive to building occupants is crucial to providing a comfortable space. While sound cannot be avoided, it can be reduced.
For instance, airborne and duct-borne noise can be limited by using attenuators, while structure-borne noise can be lessened by isolating the fan from the structure or the duct itself. Additionally, using lined fan types and duct lining may alleviate duct-borne noise. Vibration is another inevitable side-effect, as fans
cause the structure on which they are mounted to vibrate. Vibration isolators should be chosen to provide the minimum deflection required. They should also be appropriate for the fan and the environment in which it will be operating.
Maintaining equipment
Facilities managers will be aware of the need for ongoing maintenance and servicing across all types of equipment. Ventilation is no different, and regular checks on a system help ensure IAQ remains as high as possible. Maintenance schedules will vary, as they depend on which fan type is being used, the atmosphere within which it operates, and other variables. Those in charge of the upkeep of fans should consult the manufacturer and create a detailed maintenance schedule.
Facilitating healthy air, facilitating healthy buildings
Considering their role in ensuring a comfortable and safe building, facilities managers need to appreciate the importance of delivering good IAQ. This requires them to stay aware of updates to key technologies in ventilation design. They must also make sure that the aspects mentioned above are factored in when making improvements to existing systems.
DOWNLOAD THE HVR APP NOW
March 2022
27
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36
