Simple Hot-Air Exhaust Mechanism

Find out the direction of the prevailing wind, make a flue with a venturi top that swivels in the wind. Connect that to the downwind side of the building. To collect the warm kitchen gases make a plenum across the room(round tube with holes every 2 feet to draw in the hot air from the top of the room. Connect the plenum to the flu with a fan inside and up and out.

When a wind blows it will help

Sir,

It is better to provide a chute at the top of each equipment, connect them together by a common duct, lead it outside the building above the roof with a rain cap at the top. An ID blower is preferred and it can be positioned in such a way that the oil fumes emnating from the items being cooked will be directly exhausted to the atmosphere without affecting the blower. I can design the system for you, if you give me the details of no. & type of cooking equiments, type of fuel (electricity/gas), capacity of each equipment and no. of working hrs./day. The blower capacity will be only 1 HP.

M. N. Mahadevan

(n_mahadevan2002@yahoo.com)

Yes, Here in Canada, by law you have to create these ducts for exhaust fumes, especially deep frying pans. Here they must have CO2 fire suppressors.

I got the impression that the system was to be economical and simple and it was also a warm country with not much in the way of a manufacturing base, as such imported blowers and exhaust ducts could be very costly.

You will have to update yourself about India. Fans and ducts are available in India.

Dear Mr Govinda,

Why do you want to go for 2 fans? i have not seen the place of your application. But i am sure one high capacity exhaust fan at one end will be sufficient. If the length of the pipe is coming more with multi inlet then you can give one more booster fan for that working in the same direction. the pipe materials can be MS or plastic anything but one care should be taken that there should not be any leakage.

rajesh

If this is not a commercial kitchen, then I'd simply put one or two box fans in one or two windows, blowing out. Fresh air would come the other open windows. It could hardly be simpler or cheaper. (I used this "system" to extract welding fumes from my shop.)

If it is a commercial kitchen, then you must consider grease in the discharged air, which makes things much more complicated and, if ducting is involved, potential dangerous.

Your simplest and cheapest solution is probably a thru-the-wall
propeller fan, mounted as close to the peak of the roof as practicable,
at the end of the hall nearest the kitchen area.
(W.A.G. - about 1/2 HP. - 36" Dia. should do it).

Convection should direct most of the kitchen heat and vapors up to
this area,so thats where they are best removed. You can 'design` the
air flow pattern by selecting which windows to open.

Duct work and hoods for a kitchen area, especially if frying is involved,
require fire-proof duct, filters, and maybe supression systems for safety,
and it can be expensive to to it right, dangerous if you skimp.
(Consider the possiblility of accumulated grease catching fire under
the condition of a forced air stream.)

A couple of rules of thumb and a formula:

Suggested air changes for an assembly hall is 3-10 minutes per air change. For a kitchen it is 1-3 minutes per air change. Take the room volume and divide by the number of minutes for desired air volume. In your case, my mental math suggests 3000CFM. 30x25x12/3minutes = 3000 CFM (it is a bit late here so double check my numbers.)

For heat removal, CFM is equal to BTU/hr removed divided by 1.10 time temperature difference. (CFM=(BTU/hr)/(1.10x delta T in F degrees))