However, I found that the room would just get hotter and sweatier - the fan was just moving the air around within the room.
If you stand in a doorway and move a hand gently inwards and outwards, with fingers spread, you can feel airflow in or out, and even get an impression of the speed of airflow, since cooling of the hand will be minimum when the speed and direction of the hand equals that of the air.
With no fan, I found that the air was almost always blown from South-East to North-West, or stage-left to stage-right (teacher's point-of-view), due to the UK prevailing South to South-West winds, and the shape of the buildings..
With the fan stage-right and blowing in, I found that very little air was coming in or going out of either fire-exit.
This can be understood because the outside wind was blowing air one way, but the fan was blowing the air the other way. The two tend to cancel out.
When I turned the fan round to blow outwards, away from the dancers, it helps the natural wind-blown airflow, so a really good airflow results, changing the air in the room every minute or so, preventing heat from building up.
We could put the fan the other side of the stage, where the wind is blowing inwards, so that a fan blowing inwards also assists the airflow instead of cancelling it. However, on that side, the cupboard is between the passage and the external wall, rather than between the passage and the stage. This means that the steps up to the stage are more accessible, so this side is used for teacher and DJ access. If we had a fan in the way, it would be very inconvenient. The DJ also usually stands this side of the stage, so being close to the fan would make it hard for him to hear the music !
So you get a gentler drift of the air towards the intake, rather than a violent jet of air on the 'out' side.
This means that plastic cups, leaflets, hair-styles etc will be affected less by the airflow.
It is much better to blow that heat outside, rather than inside : we are trying to cool the room !
To put that in context, a 3000W fan maybe generates 2000W of heat, which is equivalent to the heat given off by about another 10 dancing bodies.
We could put the fan the other side of the stage, where the wind is blowing inwards, so that a fan blowing inwards also assists the airflow instead of cancelling it. However, on that side, the cupboard is between the passage and the external wall, rather than between the passage and the stage. This means that the steps up to the stage are more accessible, so this side is used for teacher and DJ access. If we had a fan in the way, it would be very inconvenient. The DJ also usually stands this side of the stage, so being close to the fan would make it hard for him to hear the music !
Noise
I suspect the fan sends more noise 'downstream' than 'upstream'.Dust
Cripps can be a dusty venue : it is better to blow dust and grit outside, rather than towards the dancers.Airspeed
The airspeed downstream from the fan will be much higher than upstream, since the air output from the fan is a narrow unidirectional jet, not much wider than the fan itself, whereas the air is sucked into the fan from all directions on the intake side : a much larger area than the fan itself.So you get a gentler drift of the air towards the intake, rather than a violent jet of air on the 'out' side.
This means that plastic cups, leaflets, hair-styles etc will be affected less by the airflow.
Waste Heat
The fan motor and even the mains cable and 13-Amp plug get quite hot. Probably more of the electricity is converted to heat than to airflow - the fan is probably less than 50% efficient.It is much better to blow that heat outside, rather than inside : we are trying to cool the room !
To put that in context, a 3000W fan maybe generates 2000W of heat, which is equivalent to the heat given off by about another 10 dancing bodies.
Humidity
If air is not flowing in and out of the hall, sweaty bodies cause a steadily increasing humidity which gets unpleasant.
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