I'm currently having a bit of an intuitive problem understanding the Prandtl number effect on boundary layers and I'm hoping that someone can explain it better than what I've read in some heat transfer books.(adsbygoogle = window.adsbygoogle || []).push({});

According to various HT books, a low Prandtl number means that heat diffuses quickly (predominantly via the conduction mechanism) whereas momentum does not diffuse as quickly. This results in a large thermal BL relative to the hydrodynamic BL. I am having trouble understanding why this occurs? Why is the thermal BL "thick"? My current thinking is that if the heat (thermal energy) diffuses/spreads through the fluid quickly (through molecular collisions between adjacent fluid laminae) the free-stream temperature would be approached more quickly, resulting in a thinner thermal BL. Basically,I would have thought that if heat diffuses quickly through the fluid that the thermal BL would be "thin" as the heat quickly reaches the free-stream temperature.

I know my understanding is flawed but if someone can explain to me why I'm wrong, I would appreciate it!

Cheers

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# Effect of Prandtl Number on Thermal Boundary Layer

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