Quote:
Originally posted by myv65
Lest anyone think I'm slinging mud, Scott and I have talked long before his article was posted and have talked since. What I say now I've already talked about with him.
Scott made a point of comparing "thermal differential", a ratio of a fluid's conductivity vs its specific heat, to determine the effectiveness of a particular fluid. While not unrelated, the simple fact is that flowrate (largely a function of viscosity) matters more than either fluid conductivity or specific heat when determining convection. If specific heat drops by 50%, that doesn't mean much considering pure water will care 75 watts in 1°C delta-T at only 23 gph. At any reasonable flow, the specific heat of water is overkill. The fluid's conductivity will impact overall convection rate as conductivity plays a role in heat transfer through the boundary layer. Viscosity and velocity, however, determine the thickness of the boundary layer, which then dictates just how important conductivity really is. At our typical flow rates, conductivity just doesn't mean much compared to viscosity and flow velocity.
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Hell, Sieder-Tate proves your point.
Nu=0.023* Re^0.8 * Pr^0.33
Where
Re = (V*D*rho/mu)
Pr = (Cp*mu/k)
Nu = (h*D/k)
Clearly the viscosity (mu) has a larger influence on the convective heat transfer coefficient (h) when compared to specific heat over conductive coefficient (Cp/k).
Alchemy
Reynolds number (density*length*velocity/viscosity)