Fan: criteria for its selection

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superadmin

March 20, 2017

In this article, we present the different types of fans available in the market, the measures that can be adopted to reduce the energy demand of ventilation systems, and what are the requirements of the RITE in the energy efficiency of that fundamental element in a ventilation system, which is the fan.rn

Measures to reduce energy demand

rnTo reduce energy demand of your ventilation system, it is important to consider system optimization. This can be achieved in two ways:rn
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  • Through the optimization of the air flow rate.
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rnThe installation should transport only the necessary air flow. To achieve this, during the design phase of the installation, the optimal nominal flow rate must be determined, and in the execution, maintenance, and use phases, actions must be taken to ensure that the propelled flow is nominal.rn
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  • Optimization of load loss.
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rnConsidering that the load loss in the duct network of the ventilation system is approximately 0.05 mm c.a. - 0.07 mm c.a. per linear meter, it is not advisable, under any circumstances, to design duct networks with load losses that exceed 0.1 mm c.a. per linear meter.rn

Delving into types of fans

rnThe Thermal Installations Regulations in Buildings emphasizes the obligation to choose the fan of our ventilation system in such a way that its efficiency, under the calculated operating conditions, is maximum. Let’s see what the market offers. rn

Axial fans

rnThese are the ones in which air flows in the direction of the axle of the impeller. Their design allows for the achievement of high flows with low load losses. In both ventilation and air conditioning installations, two types of axial fans are often used: wall-mounted and tubular. While the former, with a diameter of 400 mm and rotating at 1450 r.p.m., can deliver a flow rate of 3000 m3/h with a static pressure of 8 mm c.a., the latter propel flow rates between 2000 and 100,000 m3/h, and generally provide static pressures below 40 mm c.a.rn

Centrifugal fans

rnThese are capable of providing higher pressures. Normally, they are used in ventilation and air conditioning installations with duct networks. According to the static pressure produced, they can be classified into low pressure, medium pressure, and high pressure fans.rn

Helico-centrifugal fans

rnRarely used, these fans have flow entering the rotor in an axial direction and exiting the rotor in a radial direction.rn

Requirements of the RITE for the energy efficiency of fans

rnTo achieve the maximum energy efficiency of ventilation systems, the regulation establishes different requirements:rn
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  • Choose those fluid propulsion equipment that operate as close as possible to the point of maximum efficiency.
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  • When the ventilation system is a variable flow system, the requirement of the previous point must also be met for average operating conditions throughout a season.
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  • It must be justified for each of the circuits the specific power of the pumping systems, to establish the power that the fan consumes per unit of air flow that passes through it.
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  • The category of each system must be indicated, considering the supply and return fans. Thus, the ventilation and extraction systems are classified as SFP 1 and SFP 2, while the air conditioning systems are classified as SFP 3 and SFP 4.
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  • The specific power absorbed by each fan that is part of an air conditioning system will depend on the classification of the previous point. Thus, the specific power of a fan in a category SFP 1 system must not exceed 500 W/(m3/s); that of the SFP 2 category should be between 500 and 750 W/(m3/s); that of the SFP 3 category should be between 750 and 1250 W/(m3/s); that of the SFP 4 category should be between 1250 and 2000 W/(m3/s); and that of the SFP 5 category can exceed 2000 W/(m3/s).
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Siber Ventilation

Manufacturer of High Energy Efficiency Ventilation Systems. Siber provides a set of high energy efficiency solutions in wind and mechanically intelligent ventilation, improving the Health, Hygiene, and Comfort of people, being respectful of the environment.

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