Anemometer.pptx

Anemometer Ms. Dipali Pandya Assistant Professor Mechanical Engineering, SET

Made by: Mihir patel(16103358) Asim jujara(16103374)

Anemometer • An anemometer is a device to measure the wind speed and direction. Wind measurement is significant for detecting wind in industrial field. Besides, wind measurement can be applied in environment monitoring and controlling systems, air conditioning systems and so on . • Additionally – • Temperature measurement. • Pressure measurement. • Wind direction.

Types of anemometer • Cup anemometer • Vane anemometer • Hot wire anemometer • Laser doppler anemometer • Sonic anemometer • Ping-pong ball anemometer

Cup type anemometer • A simple type of anemometer was invented in 1845 by Dr. Jhon Thomas Romney Robinson, of Armagh Observatory. It consisted of four hemispherical cups mounted on horizontal arms, which were mounted on a vertical shaft. The air flow past the cups in any horizontal direction turned the shaft at a rate that was roughly proportional to the wind speed. Therefore, counting the turns of the shaft over a set time interval produced a value proportional to the average wind speed for a wide range of speeds. It is also called a rotational anemometer.

Advantages and disadvantages of cup type anemometer advantages

disadvantages

• Low price • Flexible design • Simple installation • Most technicians understands operating principles and necessary connections

• Moving parts wear outs • Without provision of heating , they don’t work well in snow or freezing rain • They don’t work well in rapidly fluctuating winds

applications : -this type

of device used in open air position for example on towers, weather stations etc.

Vane anemometers • One of the other forms of mechanical velocity anemometer is the vane anemometer. It may be described as a windmill or a propeller anemometer. Unlike the Robinson anemometer, whose axis of rotation is vertical, the vane anemometer must have its axis parallel to the direction of the wind and therefore horizontal. Furthermore, since the wind varies in direction and the axis has to follow its changes, a wind vane or some other contrivance to fulfill the same purpose must be employed. • A vane anemometer thus combines a propeller and a tail on the same axis to obtain accurate and precise wind speed and direction measurements from the same instrument. The speed of the fan is measured by a rev counter and converted to a wind speed by an electronic chip. Hence, volumetric flow rate may be calculated if the cross-sectional area is known.

Advantages and disadvantages of vane type anemometer Advantages

Disadvantages

• ➨It is used to measure wind speed, wind pressure, wind velocity, and wind direction. ➨It delivers precise measurement with very low power consumption. ➨It is available in variety of shapes and sizes.

• ➨Strong winds might damage the instrument, which should be taken care during installation.

Applications :These anemometers have great use in mines in which it is in gob holes to measure the speed of methane releases from the mines

Hot wire anemometer • Uses very fine wire (on the order of several micrometers) • Electrically heated up to some temperature above the ambient • Air flowing past the wire has a cooling effect on the wire • The electrical resistance of most metals is dependent upon the temperature of the metal • Using above a relationship can be obtained between the resistance of the wire and the flow speed

Probe specifications Tungsten or platinum filament is used as a probe for hot wire anemometer • ~1 mm long • 4-10 mm diameter Benefits • Good spatial resolution • Flat frequency response Limitations • Fragile • Requires clean flow • Cost (starts at $ 300-400) Applications: To measure the velocity of turbulent flow of gases To determine relative concentration of mixing of two different gases

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