The mission of a fan is to enforce the flow of a given gas volume through a more or. less complicated system. This system can comprise diverse elements such as pipes, elbows, transition pieces, filters, coils, silencers and valves, among others. The fan is the component integrated in the system which delivers the required power to surmount the resistance that all the other system elements oppose to the flow.

The ratio of the useful energy added by the wheel to the gas stream to the brake horsepower measured at the fan shaft is the EFFICIENCY of the fan.

The STATIC EFFICIENCY takes into account that it is in the static pressure developed by the fan where rests the potentiality to overcome the resistance of the system.

The following formula gives, as a percentage, (when no very high pressures are involved) the value of the static efficiency:

The static efficiency can be plotted in a graphic (RE curve) in which the developed pressure versus volume flow is also depicted and must be considered when selecting a fan.
The value of the static efficiency reach its maximum in a point halfway across the characteristic of the fan (PE curve) and it is in this point were the optimally selected fan should cut the system resistance curve.

To achieve the maximum energy savings, a fan has to operate in the point of highest efficiency of its characteristic curve. But it is also necessary that the design of the selected type of fan is the one which gives the best possible efficiency when operating in such a point.

The efficiency of a fan is affected by the following factors:

• The selection, made by the user, of a suitable supplier for the intended application.
• The shape and proportions of the impeller, the number and curvature of its blades, the type of the gas inlet cone and inlet ring, etc.
• The dimensions and constructive form of the fan casing and the air outlet.
• The fabrication process of all the assembly, maintained within the required tolerances to guarantee the desired efficiency of the design.
• The perfect finish of every component, mainly in the case of the impeller wheel, which should allow the smooth flow of the gas reducing losses to a minimum.

The centrifugal fans of our H SERIES has been carefully checked in our modern laboratory equipped with precise instruments. All variations have been considered:

• Testing every possible scroll and wheel type in each fan prototype
• Individual contrast of blade types (airfoil, backward curved, backward inclined, etc...)
• Study of such variables as number of blades, inclination angle, thickness and blade width , etc.

All these possibilities are conveniently reflected in the characteristic curves of each fan: pressure - absorbed power - efficiency versus volume flow.
We can offer notable energy savings to the user of these fans, due to the absolute certainty that the machine quoted in each occasion is the right one to obtain the best efficiency in its operating point.

Every model in this series is of the backwards inclined blade type. This means a non overloading characteristic power curve.

In accordance to the fan application, blades can be :

• Hollow airfoil blade, of profile similar to an aircraft wing.
  Efficiency up to 90%
• Single thickness blade of high backwards curvature.
  Efficiency up to 88%
• Single thickness blade of moderate backwards curvature.
  Efficiency up to 86%
• Single thickness flat blade, inclined backwards
  Efficiency up to 85%

The fact that customers would carry out the analysis of the total investment involved in the purchase of a fan is of special interest for GRUBER HERMANOS :

• Considering the initial purchase price, high efficiency fans are slightly more expensive that their counterparts of lower efficiency, due to the fact that their casings and wheels are bigger.
• The overall operating price, in terms of demanded electric energy, is noticeably lower.
• The analysis of both these prices of acquisition and operation will clearly show that the purchase of a high efficiency fan, as those offered in our H series, is a very sensible election.