Air Curtain

Nope.

The air curtain is typically more for flying insect control than it is for thermal control. But as for recovering energy from the airflow I would have to say that the basic requirement of near laminar airflow for proper operation of an air curtain would eliminate any reasonable installation of a power generation device in the air stream.

Hi Richard,

You have got in partly wrong. There are 2 types of air curtains low air velocity for acting as a thermal barrier and high velocity for insect control. Of course the latter acts as a thermal barrier as well in addition to the insect control capability.

Insect control type will have some residual energy left (kinetic enregy in air), but i believe it is practically impossible to harness same.

Kapoor idea... when i first had a look, I thought is stupid but later reading through the forum responses i started respecting his line of thinking. He must have seen an insect barrier type air curtain.

air curtains are full width squirrel cage fans and simply pull air from a plenum above it to separate the cold or hot out side air. They are too small to really save energy and create it at the same time as they are direct drive units with high rpms.

the air curtains are simple means of regulating the air temperature by creating a thermal barrier holding either cold or hot ventilating air inside a structure and avoiding temperature swings in the building by doing so.

the curtains are using waste energy in a way to regulate the interior temperature of a building.

It doesn't much matter what you are using the air curtain for - the position remains the same - if there is sufficient waste energy in the air curtain for you to harness without compromising its effectiveness, you would do better to reduce the amount of energy you put into the curtain in the first instance.

That's just what I was thinking! I suppose there is a point where this isn't true, though, but it would depend on how strong the air flow had to be to do its primary job... if it was really strong then maybe some of that energy could be recovered.

When the hoods in the kitchen of the snack bar are drawing several cubic meters of air per minute out of the kitchen, you have to replace it. You should not replace it with the expensively heated or cooled air in the dining room. Often the hvac technicians bring in outside air to do this job. The architect should have some idea that this needs to be done, and will assign the correct technician to do this. A really complex building, like a shopping mall, will need an engineer to figure out how to balance the air coming in with the air going out. Sounds easy...until you have to do it! When you fail, you get situations like here in Ottawa when the main doors to the mall were stuck closed with the suction whenever the food courts flashed up their vent fans. Smaller restaurants sometimes have this problem as well, especially smaller ones whose owners do the work. It could even be dangerous, especially when you have hot water heaters and stoves which cannot ventilate dangerous combustion products due to negative pressures in the wrong place!

I think the idea of an air curtain separating the dining room from the kitchen of a restuarant is an excellent idea, and my hat is off to tpkapoor's hvac engineers!

A properly designed air curtain for a pedestrian size doorway between a conditioned space to ambient will use very little energy to operate i.e. some where around .5 kW. The typical air curtain in use is a downblast non-recirculatory device which does very little good in stopping infiltration/exfiltration. A properly engineered air curtain such as a horizontal flow recirculatory type will yield efficiencies as high as 80%. The .5 kW consumed is very little compared to the energy saved by the reduction of the effective area of the doorway by 80%. For air curtain info go to hcr-inc.com.

Pete