On Wed, 22 Dec 2004, Josh Koffman wrote:

> Ok, so my thermodynamics knowledge isn't so great. I have a room,
> about 15' by 15', with a 10' ceiling. It's heated by a water filled
> radiator.
>
> My problem is this. Because the only air movement in the room is as a
> result of convection, there isn't a whole lot of movement, and warm
> air tends to congregate at the top of the room. I'd like to try and
> pull some of that back down to keep me warmer. Installing a ceiling
> fan isn't an option. I do have a few smaller (9") table top fans
> though.
>
> So the question is, would running these actually help? What would be
> the best setup? Have the fans sitting low, blowing up? Try and put
> them up on a shelf, even though they'll only be able to blow
> horizontally, not down?

Reverse flow is the most efficient way. This means finding out which way 
the air is moving where you put the fan, and arranging for the fan to 
blow against it. You can use a candle to find out the direction. You 
could locate a large cardboard tube and put a fan in it (hidden). The 
tube can stand vertically near the radiator or in a corner near it (it 
can be square or triangular or whatever section). Arrange for the fan 
volume to circulate the room air volume 2-3 times per hour. For example 
a 100cfm fan is all you need for a 10x20x8 room. The best thing you can 
do is to plate (temporarily) the exterior wall(s) with insulating 
material. 1 layer of carboard tacked on will already improve things (on 
account of the air space it forms behind it). Beware of fire proofing, 
not just the cardboard. A fan motor catching fire will make enough smoke 
to land you in hospital.

Peter
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