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The volumetric flow rate (often referred to as volume flow rate or flow rate) is a physical variable from the field of flow mechanics. It specifies the volume of a medium (e.g. air) that is conveyed through a defined cross-section in a certain time period.
The volumetric flow rate Q thus describes the displaced volume V over the time t: Q = V/t
The unit used to specify the volume flow varies depending on the underlying reference variable, e.g. m³/s, m³/h, l/h, etc.
Which fan offers the optimum volume flow for your application? Use the selection software FANselect from ZIEHL-ABEGG to find out.
The volumetric flow rate quantifies the movement of media (e.g. air) within a technical application and thus represents a performance factor for ventilation systems, such as fans.
The volumetric flow rate depends on the flow velocity of the medium and the cross-sectional area of the flow channel. A higher flow rate or a higher cross-sectional area leads to a higher volumetric flow rate.
The continuity equation states that the volumetric flow rate at constant density in the unbranched system is constant at every point.
This results in the formula Q = A1 x c1 = A2 x c2 = A3 x c3 ...
Q = A x c = constant
In practice, this means a negative correlation between the cross-sectional area A and the air velocity c: If the cross-section of an unbranched air duct increases, the air flow slows down. If the cross-section narrows, the air is accelerated.
This relationship is particularly important when designing a system depending on the specific installation situation. Optimum air routing and dimensioning of the air ducts can have a considerable influence on the efficiency and aerodynamic noise development, caused by friction effects between the flowing air and the air duct, of certain applications.
The volumetric flow rate indicates how much air or other gaseous media a fan can convey within a given unit of time. If a fan can achieve a particularly high volume flow rate, it can move more air per unit of time and thus operate particularly effectively. If the fan achieves a certain volume flow rate with low energy consumption at the same time, it is considered to be particularly efficient.
Design characteristics of the fan, such as design, number and design of blades and wings, surface finish, inclination angle, etc. can significantly influence the achievable volume flow rate and thus the efficiency of the fan. Optimum adjustment of all system components to the respective use case is crucial for the energy efficiency of the system.
ZIEHL-ABEGG fans stand for optimum performance with maximum energy efficiency
When designing ventilation systems, the volume flow in relation to the pressure must meet the specific requirements of the application. The more precisely the performance parameters are matched in line with the given installation conditions (e.g. length and cross-section of the air duct, installation dimensions, etc.), the easier it is to find the most efficient combination of impeller, motor technology and other system components. The sum of all pressure losses in the system in relation to the volume flow is shown in the system characteristic curve.
The higher the pressure loss (e.g. due to obstacles in the air duct, friction or dimensional resistance) in a system, the more energy the fan needs to adequately fulfil the purpose of the application. From the point of view of the user, the pressure loss should therefore be as low as possible for efficient operation.
Structural measures, such as larger heat exchangers, shorter air ducts, larger cross-section of pipes, etc. can reduce the pressure loss. Although this increases the space requirement and, in part, the construction costs of the system, the fan can be operated with significantly lower energy and also with lower noise levels. The more efficient design of the system thus reduces the operating costs over the entire operating time, which in practice usually leads to a higher overall saving for the user.
Conclusion: In order to achieve the most efficient operation, optimum acoustics and the highest economic efficiency of a system over its service life, numerous factors must be taken into account. Often, the best compromise between the given underlying conditions and the system configuration must be found from the point of view of the user.
ZIEHL-ABEGG is happy to help you create the ideal design for your system. Please get in touch!
