Commercial Kitchen Exhaust 1

[Raj.S]

Hi

I am looking for design tips for a modication of commercial kitchen exhaust system . Without changing current duct , would like to know if more equipment can be added to extract smoke by enhancing exhaust fan.

This means: Keeping existing GI Rectangulatr duct as it is( Since there is no space ) to modify
Adding more powerful exhaust fan to pull out additional extract volumne


Appreciate your inputs

Thanks
Raj

 

[LittleInch]

Can't you figure this out yourself by now?
It's
Square area of the inside of the duct x max velocity (seems to be about 12m/sec). Hint - It's not close to 7,000 CFM





Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[nuuvox000]

SMACNA indicates a maximum velocity of 2500 feet per minute so you're looking at about 3400 CFM with that in mind.

 

[MedicineEng]

You need to be able to clean the duct from grease. So that needs access and, IMHO, you can't have turning vanes etc. since you can't clean them. Grease is very sticky.

You are absolutely right. Maybe my wording was not clear, apologies. I wasn't suggesting installation of turning vanes on KED. I was just highlighting the fact that being the duct already close to the recommended max speed, further increase would eventually create drumming noises that would be exacerbated by the fact that there were no turning vanes at the 90 degree elbows.

 

[MedicineEng]

Raj. S:

Clearly you need professional help on this one.
The help that we can give you in an open free forum has to be taken always with a grain of salt (pun intended)and is limited in nature.

People here will do their best to guide you in the right direction as we are all fellow engineers and engineering enthusiasts but either you train yourself by enrolling in a course on kitchen exhast duct design (ASHRAE, CIBSE or other professional association might have some online) or you hire someone that can design it for you.

Good luck.

 

[ProcessHVAC]

As others have mentioned, you need a qualified engineer to assist you and you won't find this in a forum. It worries me that you are basically asking how to size a duct for a given flow, one of the most basic hvac design skills. You might want to start determining which applicable codes and standards will apply to your jurisdiction. If something like NFPA-96 applies, you might have to do more upgrades to existing system.