cooling principals

[Bill Verburg]

There are 4 methods of heat transfer[list=1][*]radiation which is dependant on surface area and temperature differential between the radiating surface and its environment, a great example is the radiative cooling of my yard on a clear night. A poor example is a cool collar because it has a small surface area(though it is larger in area than a naked oil filter) and the temperature differential between it and its environment is also small[*]conduction which is dependant on material, aluminum conducts better than iron, and temperature differential between the source of heat and the cooler parts, in the case of bolted up pieces the contact area is crucial, this is why in electroncs when conduction is needed a thermal paste is used to increase the contact areas. The cool collar has relatively poor contact with the filter and thus scores poorly on this issue[*]convection which must be further broken down into 2 sub catagories natural and forced[*]natural convection can be seen in a boiling pot of water, or in a room in your house, it's always warmer near the ceiling, there is probably a small amount of natural convection from the cool collar especially at idle[*]forced convection is exhibited by the water pump in a car or house, or by any of the fans in a Porsche or the heating fan in a house. Another example is a front mount oil cooler where the amount(volume) of air which is forced over the cooler determines the cooling effect. Of course temperature differential is also a factor here. My favorite example of forced convection is a bicyclist who is generating a tremendous amount of convective cooling[*] lastly evaporation the sweat evaporating from the bicyclist above evaporates further cooling him, unfortunately there is very little inthe way of evaporative cooling going on in a Porsche unless one has installed a mister.[/list=a]
So to sum up for any amount of cooling, temperature differential, surface area, and a source of cooler tranfer medium are all required. The more of each, the more cooling will take place.

As far is the cool collars effectiveness I guess we have to take the word of the folks who are actually using it. We can quote theory all day but it is results that we are all after. Unfortunately double blind unbiased controlled results are hard to come by in this imperfect world.

Personally I never believed in band aids and if oil temp was an issue I would put a properly sized and ducted forced convection cooler in place and forget about it.


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Bill Verburg
My Home Page My Pelican Gallery page My Porsche Owners Gallery Page

[island911]

Concise as usual, Bill
You can lance them with logic all day long, but people will believe what they want, as they buy a solution to a problem they did not know they had.

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'81 Platinum Metalic SC COUPE

[wckrause]

You forgot to mention how important blind faith and consumer gullability is to the cooling of a 911.

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Bill Krause
'79 911SC Euro
MY PELICAN GALLERY

[Bill Verburg]

I also used the wrong principle and am quite embarrased. I shall immediately do 50 mi, enjoying every moment of forced convection, as pennance.