[NSRCA-discussion] Cooling inlet/out sizes???

[Rcmaster199 at aol.com]

Tim:
 
Heat transfer from the cylinder's fins to the surrounding air flow is  
maximized when the cowling is shaped around the cylinder such that the air  becomes 
turbulent. For this to occur, the space betwen the shroud and the engine  
should be some minimal amount like 1/4" to 3/8". There are no cowls available in  
even the most expensive models that offer such shapes. In fact, some of the 
more  popular models with the huge cowlings offer nothing more in terms of  
cooling than large buckets up front where stagnant air collects, and it  matters 
little how large the exit opening is.
 
I would add to what Ed has stated that proper ducting around an engine  will 
keep it happier. The inlet doesn't really need to be terribly large as  long 
as it smoothly transitions the air flow from inlet to cylinder/shroud. Then  
turbulated air does its heat transfer most effectively. Exit area as Ed stated  
earlier. 
 
Matt
 
 
 
In a message dated 2/13/2006 6:07:34 PM Eastern Standard Time,  
ed_alt at hotmail.com writes:

Tim:
Good question - I don't know for sure what the  best inlet size is.  I always 
made an approximation that has about 2/3 to  3/4 the area of the cylinder 
behind the intake, then I apply the 2.5 or  greater rule of thumb for the outlet 
area.  BTW, that is 2.5 x the total  intake, so if you have something taking 
in air for colling the crankcase, add  that in too.  Not sure if this is 
optimal or not, but it has worked  for me so far.
 
Ed

----- Original Message ----- 
From:  _Tim Of Global Electronics,  Ltd._ 
(mailto:TJS at mail.global-electronics.com)  
To: _NSRCA Mailing List_ (mailto:nsrca-discussion at lists.nsrca.org)  
Sent: Monday, February 13, 2006 12:59  AM
Subject: Re: [NSRCA-discussion] Cooling  inlet/out sizes???


Thanks All!

But how do I calculate the minimum input  size?

Tim



 
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