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Re: type3-d Digest V2003 #79


On 10 Apr 2003 at 8:40, manish  tiwari wrote:

> Read some interesting comments on the issue of oil coolers . Correctly
> said that the main  cooling factor  is the flow of air . That is why
> it is important that the engine be kept clean from grime and mud
> deposits รถ  a much neglected aspect . It helps in better dissipation
> of heat .

I never see mud accumulation in engines which have been in use. I think the 
engine vibration breaks these up and the airflow blows it out. Grime made of 
oil and dirt is certainly a problem, however. I see a lot of oil coolers which 
need to have their airflow passages cleaned out. When you first get the engine 
apart it doesn't look like the cooler could have been doing much, but I've 
never seen one that was actually completely blocked.

> Also read in some VW related FAQ on the Web  that  painting the
> cylinder fins black ( not the block ) helps in better dissipation of
> heat . Though there is no scientific justification provided ( perhaps
> concept of black body ) 

Right, it's the black body concept that a good radiant absorber is also a good 
radiator, but this has to be balanced against the problem that any paint 
coating there will also be an insulator, so it's not clear how to get the best 
result. I just leave them bare and let them rust. A nice brown layer of surface 
oxide is a pretty good radiator, and we have to realize that very little of the 
heat dissipation is by radiation. Most of it is by direct conduction from the 
fins to the air.

-- 
Jim Adney
jadney@vwtype3.org
Madison, WI 53711-3054
USA


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