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Fans are key components of ventilation systems, providing ventilation, cooling, drying or pneumatic transport. For optimum design of such systems, it is important to know the characteristic variables of a fan.
HM 210 investigates a radial fan. This trainer determines the interdependencies between the head and volumetric flow rate as well as the influence of the fan speed on the head and volumetric flow rate.
The radial fan aspirates the air in axially from the surrounding environment. The high-speed rotating rotor accelerates the air outwards. The high velocity at the outlet from the rotor is partially converted into pressure energy in the spiral housing. The vertical pipe section is connected to the spiral housing. A Venturi nozzle to measure the volumetric flow rate and a throttle valve to adjust the volumetric flow rate are inserted into the pipe section. An iris diaphragm can optionally be used. Its variable cross-section enables simultaneous adjustment and determination of the volumetric flow rate. The effective pressures to calculate the volumetric flow rate are read from liquid column manometers. The head of the radial fan is likewise measured by liquid column manometers. U-tube manometer, single tube manometer and inclined tube manometer with graduated measuring ranges are available.
A frequency converter is used to adjust the fan speed. The speed, torque and electric power capacity are digitally displayed. This permits energy analyses, and enables the efficiency of the fan to be determined.
The system characteristic curve is determined by recording the characteristic variables at a constant throttle setting but at variable speed. The interaction of the fan and system at the operation point – the so-called system dimensioning – is investigated.
Learning Objectives / Experiments
- setup and principle of a radial fan
- plotting fan and system characteristics
- volumetric flow rate measurement methods based
on the differential pressure method using:
* iris diaphragm
* Venturi nozzle
* comparison of both measurement methods
- familiarisation with various differential pressure gauges
- determining efficiency