Stationary Engine Heat Recovery - velocity

[oexit]

I am designing a heat recovery system for the exhaust from engine-generator sets. My question is, "what is the appropriate velocity for the duct between the engine and the heat recovery unit?" Engine exhaust appears to be around 12,000 feet per minute at the engine manifold discharge. Industrial air handling standards are at about 4000 feet per minute.
Does anyone know what the industry standard (velocity) is for energy recovery from engine exhasut?

 

[btrueblood]

Talk to the people who build IC-engine-powered carpet cleaning machines, they have been building such recovery systems for years.

http://www.hydramaster.com

http://www.prochem.com

are two of the larger firms.

The velocity of the exhaust gas needs to be fairly high to help promote turbulent flow and improve heat transfer on hx surfaces. At the same time, heat removal from exhaust is dropping the temperature & therefore density, thus velocity drops too. Like everything else, it's a trade off.