Convective Heat Transfer Questions & Answers  
Question by Student 201883332
Dear professor. I am hard to understand the meaning of "starting at x=x0" : "Restrictions" of the 7th "Flow regime", "Summary of Equations for Flow over Flat Plates" on page 4 of "Convective Heat Transfer Tables". If we are talking about the starting point of the integral when we get the average Nusselt number, we can not acquire integral value at that point. I have one more question. When I asked about the relationship between thermal layer thickness and velocity layer thickness, professor answered that velocity layer thickness is larger than thermal layer thickness. After that, I saw "Unheated starting length" in the book. Does 'velocity layer thickness is larger than thermal layer thickness' means that velocity layer thickness is equal to thermal layer thickness plus unheated starting length? Oh, I think x0, "starting at x=x0" in the first question, is where heat transfer starts.
Yes $x=x_0$ is the location where the thermal layer starts while $x=0$ is where the momentum layer starts. In the derivation we did in class, I mentioned to you that $\delta_t<\delta$ at $x=0$ not that $\delta_t<\delta$ at any $x$. This is because the thermal layer is assumed to start just a bit downstream of the momentum layer. Whether $\delta_t$ is smaller or larger than $\delta$ for a large $x$ depends on the Prandtl number.
Previous   1 ,  2   •  PDF 1✕1 2✕1 2✕2