HW 1 Assignment in Fundamentals of Mass Transfer - Molecular Diffusion and Fick\'s Law PDF

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This is about fundamentals of mass transfer and molecular diffusion in which Fick's law is also applicable...

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CHEMICAL AND PETROLEUM ENGINEERING UAE UNIVERSITY FALL 2021

HW Assignment 1 Mass Transfer CHME 421 Due date: September 16th 2021 Instructor: Kaushik Sivaramakrishnan Total Marks = 100 Weightage to final grade in course = 2% Note: Please submit 1 solution per group. Q1. Mass densities, concentrations, velocities and molar fluxes Consider a one-dimensional mass transfer for a mixture of O2 (A) and CO2 (B) at 294 K and 151.9 kPa. The mole fraction of A is 0.4. Discharge velocities (i.e., superficial velocities or velocities with respect to a stationary co-ordinate or mean velocities) of A and B are vA = 0.08 m/s and vB = -0.02m/s. Find: a. (5 marks) Mass concentration (density) of the mixture: , kg/m3 b. (8 marks) Mass concentration (density) of A and B: and , kg/m3 c. (5 marks) Molar concentration (density) of the mixture: C, kmol/m3 d. (5 marks) Molar concentration (density) of A: CA, kmol/m3 e. (5 marks) Mass fraction of A: wA f. (5 marks) Molar average velocity of the mixture: Vmol, m/s g. (5 marks) Mass average velocity of the mixture: vm, m/s h. (5 marks) Molar diffusion velocity of A: vAd, m/s i. (6 marks) Molar flux of A with respect to stationary point: NA, kmol/(m2 s) j. (6 marks) Molar flux of B with respect to stationary point: NB, kmol/(m2 s) k. (5 marks) Molar diffusive flux of A: JA*, kmol/(m2 s) (60 marks) Q2. Fick’s Law Maxwell-Stefan approach suggests that the difference in partial pressure of A (∆𝑝𝐴 ) over small distance ∆𝑧 is proportional to: a. Molar concentrations of A and B (i.e., cA and cB) b. Length of diffusion path (∆𝑧) c. Difference in velocities of A and B (𝑣𝐴 − 𝑣𝐵 ) Derive the expression for the molar flux of species A with respect to a stationary observer (NA) and hence, relate it to Fick’s first law from this relationship. (15 marks)

CHEMICAL AND PETROLEUM ENGINEERING UAE UNIVERSITY FALL 2021

Q3. Mass Transfer examples/separation agents/driving force - Conceptual a. What is the relationship between diffusivity and resistance in mass transfer? How do you separate 2 miscible liquid phases? What is the separating agent that you would use in this case? (10 marks) b. Would you think that centrifugation is a type of mass transfer? If not, why? (5 marks) c. Would an absorbing solvent be required to have: (i) Low vapor pressure; (ii) Low velocity; (iii) Low freezing point; (iv) None of these. (5 marks) d. Would you expect diffusivity to: (i) increase with a decrease in temperature?; (ii) increase with increase in molecular weight?; (iii) increase with the size of the individual molecule?; (iv) none of these. (5 marks) (25 marks)...