Fan types and blade efficiency

Fan types and blade efficiency

Fans, while technically a machine designed to keep people feeling cool, don’t actually cool a room. Rather, they work to improve the air circulation in a room by creating a breeze effect to make you feel cooler. The principle is very simple - the increased air flow passes across the moisture and perspiration on your skin and evaporates it.

 

Fan performance factors

The effectiveness of a fan can fairly simply be evaluated in terms of how good a job it does of circulating air through a room. As far as ceiling fans go, there are a number of different factors that will affect this ability.

These include:

  • the size of the fan
  • the size of the room
  • the distance the fan is from the ceiling
  • the tilt of the blades, and
  • the speed at which the fan is rotating.

It would be easy to go into great detail about how the shape and tilt of different fan blades affect airflow patterns and so forth but in reality, provided that the fan (or fans) are big enough for the size of the room and installed at a minimum of 30cm from the ceiling, the only difference you really need to worry about is fan speed - which can almost always be controlled at the switch.

Tip:
  • For small to medium rooms (up to 4m x 4m) such as kitchens, dining rooms, kids bedrooms and home offices, you should choose a fan of 122cm or smaller.
  • For large rooms (bigger than 4m x 4m) such as family rooms or master bedrooms, choose a fan with a blade of 132cm or larger.
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Practical differences between different fan types

The blades in ceiling fans come in various forms. While these factors are fairly basic in their effect on cooling performance, they can make a bit of a difference in terms of the noise they generate.

Metal or timber fan blades?
Ceiling fans with metal fan blades tend to produce more noise than their timber counterparts. As a result, you may prefer to use timber blades in the bedroom.

Three, four or five bladed fans?

The number of blades on a ceiling fan doesn’t really impact a ceiling fan's performance. That being said, four-bladed fans are the most common and three-bladed fans are typically only available in metal, and for that reason alone they may generate more noise. The difference between these different fans is mostly cosmetic.

 

Fans that don’t go on your ceiling

Not all fans are ceiling mounted - and in these cases the same logic normally applies in terms of the things that affect their performance. The stronger and wider the air flow they can supply, the more effective they are for cooling purposes.

  • Pedestal/oscillating fans – Available in single or multi-speed varieties, pedestal fans allow you to angle the fan’s head to face in any given direction. Bigger fans (and oscillating fans) are more effective at cooling.
  • Tower fans – Oscillating in a similar way as pedestal fans, tower fans produce a wider area of air circulation.
  • Box fans – Designed to sit low to the floor, box fans can also sit in front of windows to draw air in straight from outside. Because these fans don't oscillate and are limited in size, they may not be as effective as pedestal fans.
  • Air multipliers – An air multiplier is technically not a conventional fan, although it cools using the same basic principle. These coolers also oscillate, and are more effective at larger sizes.
  • Whole-house fans – Whole-house fans operate on a different principle. These fans, while they do promote airflow, help to cool a house by ventilating the hot air pooled at the top of the house out through the roof. Larger fans in general are able to push the same amount of air than smaller fans, albeit at lower speeds, which can reduce the amount of noise they produce.
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