Push-Pull Ventilation Hood 1

[butelja]

Where can I find design guidelines for a push-pull exhaust hood? I have a filter press that is located on the ground, and the bottom of the ventilation hood will be about 10' above grade. Due to access requirements and large standoff requirments, a normal overhead ventilation hood requires excessive flow. Enclosing the filter press is not an option. It is desired to use a perimeter plenum with slot blowing upward from floor level to act as an air curtain and reduce the main hood airflow requirement.

It all sounds good in theory, but I'm lacking any design guidelines for such a ventilation system. Any help is appreciated.

 

[ChasBean1]

butelja, your application sounds unique as compared to standardly-published info regarding hoods with makeup flow that prevent excess removal of conditioned air from a building. A typical rule for hoods with makeup air is that an excess of 70% makeup air messes up your hood's capture velocity characteristics. You could run into the same situation if you have makeup air with excessive throw coming from the floor, up around the ventilated equipment, toward the capture intake. If you use the perimeter capture you desire, ensure the throw is low from the makeup source (by use of large grilles or multiple diffusers).

Other than these recommendations, standard design guidelines might be those for kitchen hoods, i.e., hood open area hangs over equipment by XX inches for an XX sized piece of equipment. I'm not at the office now and don't have access, but the standards might be ASHRAE, SMACNA, ACGIH, or NFPA, I can't remember. I'll repost if I get the time, until then I hope some of the thought process helps. -CB

 

[ChrisConley]

For guidelines concerning the design of push-pull hoods and other issues I recommend Industrial Ventilation - A Manual of Recommended Practice 21rst Edition (or later). The manual is released by the Amercian Conference of Governemental Industrial Hygienists. The manual contains some excellent introductory material as well as more specific information.