Several connotations may come to mind and which direction are we going in today?
I was inspired to write by an uninspiring hot, sweaty and uncomfortable evening at a dance locally, where halfway through my second dance I was sodden with sweat. I stopped dancing, left early and contemplated the following.
- Dancers generate heat, but how much?
- In any given space how fast does the temperature increase?
- Could this information help organisers?
A quick search gave me the basic science needed. Now before I get into this too deep a word of warning. This is a worst-case scenario, it does not take into account the thermal losses of the building, air conditioning, or other building properties, which involve some complex calculations.
The average person generates around 100W (one hundred watts) of heat when sitting down at rest.
Moderate dancing generates between 250-300W
Full out fast swing dancing somewhere around 400W
Therefore 4 couples ‘moderately’ dancing generates the same heat as a two kilowatt (2KW) fan heaters
Ramp up the energy to full out dancing and 5 couples generate the same as two, 2KW fan heaters.
On this night
A quick headcount revealed about 100 couples dancing and 70 people watching.
Moderate dancing: 50KW (25 heaters) plus 7KW standing still.
Full out dancing: 80KW (40 heaters) plus 7KW standing still.
That’s a lot of heat!
How long to raise the temperature?
On this evening the room was approximately 20m x 20m x 6m. A new build room with no open windows, the air conditioning was off and a single set of double doors in and out. Effectively a sealed, well-insulated box.
Applying some simple thermo-dynamic calculations reveals:
Mass of air @ 20 deg C = 1 Kg m3
Specific heat capacity Cp = 1.012 KJ/Kg
Q = mCp(Delta)T
Energy = mass x Specific heat capacity x temp change
The energy needed to increase the room temperature by 10 deg C
Q = (20x20x6x1.2) x 1.012 x 10
Q = 24,288 KJ
Power = work / time, rearranging time = work / power
Time (s) =24,288KJ / 57KW (moderate dancing)
Time= 426 s or 7.1 minutes
10 deg change in 7 minutes!
For full out dancing that 10 deg C change happens in 4.7 minutes.
Now as I said earlier worst-case scenario with no other heat losses but also no other heat gains either from lighting or equipment. It takes no account of the humidity change from all the sweaty dancers either.
Hopefully, it illustrates that the temperature change in a room can happen quite quickly. And that it will keep rising until an equilibrium is reached or the air con kicks in. But even then the air con has to remove roughly 60KW of heat just to maintain the temperature.
How does this help?
When considering a room thinking that for every four couples dancing moderately is approximately a fan heater in a room? Much easier to visualise what would happen then if you put in multiple heaters.
- Are there opening windows?
- What’s the outside temperature?
- What’s the outside temperature?
- Is there air conditioning or a ventilation system?
- Do you need a bigger venue?
- Should you limit numbers?
There are a lot of variables!
Hopefully, this gives you an insight into the how’s and why’s of why swing dancing is hot, and some things to consider when selecting venues.
Badminton court with 6m ceiling height, 50 dancers. 10 deg C increase
Moderate dancing, no heat losses = 9 minutes
Moderate dancing, assuming 75% heat loss to walls and windows = 32 minutes
Tennis court with 6m ceiling height, 50 dancers. 10 deg C increase
Moderate dancing, no heat losses = 21 minutes
Moderate dancing, assuming 75% heat loss to walls and windows = 1 hour 24 minutes