Problem 2.252

The space between two large horizontal plates is filled with helium. The plate separation equals \(l=50 \mathrm{~mm}\). The lower plate is kept at a temperature \(T_{1}=290 \mathrm{~K}\), the upper, at \(T_{2}\) \(=330 \mathrm{~K}\). Find the heat flow density if the gas pressure is close to standard.

Reveal Answer

\begin{aligned} &\text { 2.252. } q=\frac{2 i R^{3 / 2}\left(T_{2}^{3 / 2}-T_{1}^{3 / 2}\right)}{9 \pi^{3 / 2} l d^{2} N_{A} \sqrt{M} \bar{M}}=40 \quad \mathrm{~W} / \mathrm{m}^{2}, \text { where } i=3, d \text { is the }\\ &\text { effective diameter of helium atom. } \end{aligned}

Transport Phenomena