Another fact is a tangential muffler is a vortex generator.
This vortex is forced to flow aft out of the can due to exhaust
gas pressure build up in the front of the can.
Paul Lamar

"Robinson, Chad" wrote:

Could somebody please explain what the purpose of cooling the exhaust
 gases is? I understand the muffling aspects, but I don't understand 
why the cooling effect is valuable.

Regards,
Chad

It is not the exhaust gases we are interested in cooling. It is the
steel the muffler is made out of :) Cooling the gases does not reduce
the noise. Something like the opposite happens. Due to viscosity and friction
effects the steel is heated by the noise over and above the 1700 degree F 
temperature of the exhaust gases and the noise is reduced in the process.

In theory this design could reduce the noise by almost half exiting the can.
This is because of the concentric shape of the can doubling the steel
area the exhaust gases are rubbing against.

At the same time all the steel sheet exposed to the gas in the can would 
also be exposed to cooling air on it's opposite surface.

If this works it could be a revolution in low back pressure mufflers.

Paul Lamar
 
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