A novel process has been proposed to create a composite palladium tube for use as a hydrogen separation membrane in order to produce high purity hydrogen. To fabricate the composite palladium tube, a gas containing palladium (species A) flows through a porous- walled tube, and the palladium deposits into the pores of the tube wall. The gas mass flow rate is iii and the inlet mass concentration of palladium is
(a) Building upon the convection mass transfer analysis presented in Section 8.9, derive an expression for the variation of the mean species density of palladium with distance from the tube entrance, and determine an expression for the local deposition rate (kg/m2 s) for a tube of diameter D. Neglect any leakage of gas through the porous tube walls.
(b) If the tube is too long, the variation in deposit thickness will be unacceptably large. What is the ratio of the deposition rates at x = L and x = 0?
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Fundamentals of Heat and Mass Transfer
- A l-mm sheet of FCC iron is used to contain nitrogen in a heat exchanger at 1200°C. The concentration of N at one surface is 0.04 atomic percent and the concentration at the second surface is 0.005 atomic percent. Determine the flux of nitrogen through the foil in N atoms/cm2's. Hint: The diffusion coefficient D is related to temperature by an Arrhenius-type еquation D = Doexp(-) RT For the diffusion couple N in FCC iron, the activation energy Q is 8.269 kJ/mol and Do is 0.34 mm²/s. R is the gas constant 8.314 J/mol·K.arrow_forwardProblem 1. A sheet of BCC iron 1 mm thick was exposed to a carburizing gas atmosphere on one side and a decarburizing atmosphere on the other side at 725°C. After having reached steady state, the iron was quickly cooled to room temperature. The carbon concentrations at the two surfaces of the sheet were determined to be 0.012 and 0.0075 wt%, respectively. Compute the diffusion coefficient if the diffusion flux is 1.4 × 10 -³ kg/m²-s.arrow_forwardDON'T COPY CHEGG. I NEED A NEW ANSWER!!!arrow_forward
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- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning