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On 10 Jun 99, at 6:59, Erkson, Toby wrote: > Jim, that last sentence in your first paragraph is doing flips in my noggin. > What are other ways for the engine to get rid of heat [aside from radiation] > that are not conduction and convection, even though they "play an obvious > part" -- say what?! > >From: Jim Adney [mailto:jadney@vwtype3.org] > >This is the conventional wisdom, but, of these, only radiation > >applies directly to the case where heat is transferred from one > >material to another. There are obviously others ways for our engines, > >or any other hot body, to get rid of heat, but they are neither > >conduction nor convection, although those play an obvious part. The problem that I have is that both conduction and convection take place within a given medium over a finite distance: like heat conducted up a copper rod when you hold one end in a fire, or hot air rising off a hot road on a still day. Neither of these covers the case where heat transfers from one medium to another (magnesium case to air, or oil to case) across an interface which can be thought of as having zero thickness. Then there is the fact that convection plays little role because the air flow here is forced, not heat driven, as would be in the case of convection. Conduction explains how the heat works its way through the thickness of the case, but no one has concerned themselves with that here. This is rightly so, because the bottleneck is the case-to-air interface. Jim - ******************************* Jim Adney, jadney@vwtype3.org Madison, Wisconsin, USA ******************************* ------------------------------------------------------------------- List info at http://www.vwtype3.org/list or mailto:help@vwtype3.org