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From: Arild Jensen (no email)
Date: Fri Jul 18 2003 - 02:31:06 EDT
Larry Brown wrote - off list
Stipulating that the engines do suck in great quantities of air when in
operation and to some extent "cool" the engine room by pumping heat out with
the raw water, how effective do you find engine room blowers that run after
the mains are shut down and continue to radiate heat? In an average twin
engine 44' trawler, how many cfm would it take to do any good?
What kind of forced ventillation do the big guys use? Is it on even under
way? At anchor?
My solution, however inelegant was to bump up the ac. Get the boat cooled
off and then shut down units as needed. The 16.5k on the 34' marine trader
just never could catch up with a hot Ford Lehman in a FL summer.
Regards.
Larry
REPLY
Most of the "big boats" use Delta T brand name air handlers.
Company is located in Florida. These are typically around 24" diameter fans
powered by a 5 Hp electric motor.
One inlet and one outlet. The inlet is always larger than the outlet and they
are usually run when the engines are running.
Most engine manufactures are very particular about maintaining atmospheric
pressure in the engine room at all RPM.
Therefore the fans must deliver more air than the engine can pump at full speed.
The input CFM is therefore a function of engine displacement, max RPM and
exhaust CFM rating.
There is no such thing as an "average" twin engine 44' trawler when it comes
to this particular design aspect.
You must know the numbers, do the math and recheck with manometers when the
system is checked out.
cheers
Arild
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