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fluidistic
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I would like to fully understand two parameters involved in convection heat transfer systems. I have read the document https://fenicsproject.org/pub/tutorial/sphinx1/._ftut1005.html, and I am interested in the parameters ##r## and ##s## in eq. 69.
As far as I understand, when one solves the heat equation in a solid and that there is convection occurring on some side(s) of the solid, then one can model this convection effect as a Robin boundary condition on the interfaces air/solid. They take the form ##-\kappa \frac{dT}{dn}=r(T-s)##.
Where ##s## seems the be the temperature of the fluid touching the surface and ##r## is the heat transfer coefficient. Is this correct?
I do not quite understand how to estimate or compute ##r##. I have seen tables on the Internet of values of heat transfer coefficient, for air and water for example, as if it has a fixed value. I would have thought that ##r## would represent something along the quantity of heat that air can remove/induce into that surface area element into which it is in contact (based on the units of ##r##). If that's the case then ##r## should not depend on the geometry of the solid, but it could depend on the relative humidity of air, for instance. Is that so?
Then in a real case, when we are blowing over a hot surface in order to cool it down, does ##r## change? If so, why? ##s## would change to near room temperature instead of being above room temperature. What about ##r##?
As far as I understand, when one solves the heat equation in a solid and that there is convection occurring on some side(s) of the solid, then one can model this convection effect as a Robin boundary condition on the interfaces air/solid. They take the form ##-\kappa \frac{dT}{dn}=r(T-s)##.
Where ##s## seems the be the temperature of the fluid touching the surface and ##r## is the heat transfer coefficient. Is this correct?
I do not quite understand how to estimate or compute ##r##. I have seen tables on the Internet of values of heat transfer coefficient, for air and water for example, as if it has a fixed value. I would have thought that ##r## would represent something along the quantity of heat that air can remove/induce into that surface area element into which it is in contact (based on the units of ##r##). If that's the case then ##r## should not depend on the geometry of the solid, but it could depend on the relative humidity of air, for instance. Is that so?
Then in a real case, when we are blowing over a hot surface in order to cool it down, does ##r## change? If so, why? ##s## would change to near room temperature instead of being above room temperature. What about ##r##?