Chapter 14: Problem 31
Using solubility data of a gas in a solid, explain how you would determine the molar concentration of the gas in the solid at the solid-gas interface at a specified temperature.
Chapter 14: Problem 31
Using solubility data of a gas in a solid, explain how you would determine the molar concentration of the gas in the solid at the solid-gas interface at a specified temperature.
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Get started for freeIn transient mass diffusion analysis, can we treat the diffusion of a solid into another solid of finite thickness (such as the diffusion of carbon into an ordinary steel component) as a diffusion process in a semi-infinite medium? Explain.
Air flows in a 4-cm-diameter wet pipe at \(20^{\circ} \mathrm{C}\) and \(1 \mathrm{~atm}\) with an average velocity of \(4 \mathrm{~m} / \mathrm{s}\) in order to dry the surface. The Nusselt number in this case can be determined from \(\mathrm{Nu}=0.023 \mathrm{Re}^{0.8} \mathrm{Pr}^{0.4}\) where \(\mathrm{Re}=10,550\) and \(\operatorname{Pr}=0.731\). Also, the diffusion coefficient of water vapor in air is \(2.42 \times\) \(10^{-5} \mathrm{~m}^{2} / \mathrm{s}\). Using the analogy between heat and mass transfer, the mass transfer coefficient inside the pipe for fully developed flow becomes (a) \(0.0918 \mathrm{~m} / \mathrm{s}\) (b) \(0.0408 \mathrm{~m} / \mathrm{s}\) (c) \(0.0366 \mathrm{~m} / \mathrm{s}\) (d) \(0.0203 \mathrm{~m} / \mathrm{s}\) (e) \(0.0022 \mathrm{~m} / \mathrm{s}\)
When the density of a species \(A\) in a semi-infinite medium is known at the beginning and at the surface, explain how you would determine the concentration of the species \(A\) at a specified location and time.
The basic equation describing the diffusion of one medium through another stationary medium is (a) \(j_{A}=-C D_{A B} \frac{d\left(C_{A} / C\right)}{d x}\) (b) \(j_{A}=-D_{A B} \frac{d\left(C_{A} / C\right)}{d x}\) (c) \(j_{A}=-k \frac{d\left(C_{A} / C\right)}{d x}\) (d) \(j_{A}=-k \frac{d T}{d x}\) (e) none of them
The pressure in a pipeline that transports helium gas at a rate of \(5 \mathrm{lbm} / \mathrm{s}\) is maintained at \(14.5\) psia by venting helium to the atmosphere through a \(0.25\)-in-internal-diameter tube that extends \(30 \mathrm{ft}\) into the air. Assuming both the helium and the atmospheric air to be at \(80^{\circ} \mathrm{F}\), determine \((a)\) the mass flow rate of helium lost to the atmosphere through the tube, (b) the mass flow rate of air that infiltrates into the pipeline, and \((c)\) the flow velocity at the bottom of the tube where it is attached to the pipeline that will be measured by an anemometer in steady operation.
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