What about infrared heat vs convection.

[BTDretire]

I'm trying to help someone that has a Palapa (thatched roof) restaurant eating area.
 They want to provide heat over the North Florida winter. It has clear plastic drapes on the walls. It has a high ceiling, which I think will gather most of the heat so it will be wasted. I'm wondering if Radiant heat ( infrared) would be a better method. The downside I see is it may require many Infrared heating elements, essentially one per table.
 Anyone have experience with Infrared heating?

[bigblock440]

I've never used them to heat people, but I have used them to dry paint.


These are the ones I used in the paint booth, cures paint in 10 minutes at a 25-50% duty cycle.  http://infratech-usa.com/products/w-series/  They have a few different options.  They definitely throw the heat down though, the floor of the paint booth would be 110-120 degrees just a minute or two after turning them on.


Edit: supposed to be pictures, but post was blank.  Here's the links to the coverage area:

http://infratech-usa.com/wp-content/uploads/w-coverage-area-1.png

http://infratech-usa.com/wp-content/uploads/w-coverage-chart-1.png

[lutorm]

Many restaurants have these gas-fueled infrared heaters that look like kind of like round street lights (the "lamp shade" acts as a big reflector that directs the infrared down.) They're quite effective, but obviously can't heat your legs under the table. As for where you'd get them, no idea.

[AlexK]

I was a thermal engineer in my previous working life. If the curtains are sealed pretty good heating the air might work but if there are gaps in the curtains and there is a breeze it will blow the warm air away. It would definitely be warmer at the top but that's OK if the roof doesn't leak much air. If it does, forget it, the hot air will rise right through it. Radiant heat seems like a good choice to heat bodies directly and that is what I see most outdoor restaurants using, the stand up propane type with a cone reflector on top. I always feel like it's a big waste to try to heat the outdoors with fossil fuels and use warm clothes instead but they are popular nonetheless.

[lthenderson]

We have infrared heating in our farm shop and it works well but takes some getting used too. It doesn't so much heat you the person but everything you touch. The tools, machinery, etc. will all feel much warmer and thus I feel warmer. However in a restaurant situation where you really aren't touching much, I suspect that it might leave the person feeling cold if the warmth of the seat isn't enough.

[Just Joe]

Be careful. A neighbor was using infrared heaters in their garage to keep their pets warm. Burned down the house when some cardboard boxes caught fire. Lost several of the pets too.

My be perfect for a restaurant though.

[BudgetSlasher]

Radiant has its perks. It heats objects not air, which means it doesn't rise (until an object is heated and that heat is transferred to the air), wind doesn't impact it (it is essentially a form of light we cannot see), it is a quite common source of heat in the NE.

It does have its drawback as it doesn't always feel as warm as heated air (the air stays cold except of the bit of heat emitted from the warmed objects), and it is limited to line of sight.

Places that get colder than FL (I grew up in NE FL) have or used to have plenty of IR heaters, like cafes in Paris.