X

Glossary

A

C

EF

HI

M

O

S

V

a
Axial Fan

means a fan that propels gas in the direction axial to the rotational axis of one or more impeller(s) with a swirling tangential motion created by the rotating impeller(s). The axial fan may or may not be equipped with a cylindrical housing, inlet or outlet guide vanes or an orifice panel or orifice ring;

c
Centrifugal backward curved fan without housing

means a centrifugal fan where the outward direction of the blades of the impeller(s) at the periphery is backward relative to the direction of rotation and which does not have a housing;

Centrifugal backward curved fan with housing

means a centrifugal fan with an impeller where the outward direction of the blades at the periphery is backward relative to the direction of rotation and which has a housing;

Centrifugal fan

means a fan in which the gas enters the impeller(s) in an essentially axial direction and leaves it in a direction perpendicular to that axis. The impeller may have one or two inlets and may or may not have a housing;

Centrifugal forward curved fan

means a centrifugal fan where the outward direction of the blades of the impeller(s) at the periphery is forward relative to the direction of rotation;

Centrifugal radial bladed fan

means a centrifugal fan where the outward direction of the blades of the impeller(s) at the periphery is radial relative to the axis of rotation;

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e
Efficiency category

means the fan gas output energy form used to determine the fan energy efficiency, either static efficiency or total efficiency, where:

  • ‘fan static pressure’ (p sf ) has been used to determine fan gas power in the efficiency equation for fan static efficiency; and
  • ‘fan total pressure’ (p f ) has been used to determine fan gas power in the efficiency equation for total efficiency.
Efficiency grade

is a parameter in the calculation of the target energy efficiency of a fan of specific electric input power at its optimum energy efficiency point (expressed as parameter ‘N’ in the calculation of the fan energy efficiency).

f
Fans total pressure

means the difference between the stagnation pressure at the fan outlet and the stagnation pressure at the fan inlet.

h
Housing

means a casing around the impeller which guides the gas stream towards, through and from the impeller;

i
Inlet guide vanes

are vanes positioned before the impeller to guide the gas stream towards the impeller and which may or may not be adjustable;

m
Measurement category

means a test, measurement or usage arrangement that defines the inlet and outlet conditions of the fan under test.

Measurement category a

means an arrangement where the fan is measured with free inlet and outlet conditions.

Measurement category b

means an arrangement where the fan is measured with free inlet and with a duct fitted to its outlet.

Measurement category c

means an arrangement where the fan is measured with a duct fitted to its inlet and with free outlet conditions.

Measurement category d

means an arrangement where the fan is measured with a duct fitted to its inlet and outlet.

o
orifice panel

means a panel with an opening in which the fan sits and which allows the fan to be fixed to other structures;

Orifice ring

means a ring with an opening in which the fan sits and which allows the fan to be fixed to other structures;

Outlet guide vanes

are vanes positioned after the impeller to guide the gas stream from the impeller and which may or may not be adjustable;

Overall efficiency

is either ‘static efficiency’ or ‘total efficiency’, whichever is applicable.

s
Static efficiency

means the energy efficiency of a fan, based upon measurement of the 'fan static pressure' (p sf ).

v
Variable speed drives (vsd)

means an electronic power converter integrated — or functioning as one system — with the motor and the fan, that continuously adapts the electrical power supplied to the electric motor in order to control the mechanical power output of the motor according to the torque-speed characteristic of the load being driven by the motor, excluding variable voltage controllers where only the supply voltage for the motor is varied.

Variable speed drive


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