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23-Chem-A3 Heat and Mass Transfer: December 2015

Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)

  1. Question 1 Knudsen and molecular diffusion of N₂ through a capillary
  2. Question 2 Oxygen mass transfer to fermenting microorganisms
  3. Question 3 Dimensional analysis of the spinning-disk mass-transfer coefficient
  4. Question 4 Dissolution of a NaCl cylinder — Chilton–Colburn analogy
  5. Question 5 Length of an aerated remediation trench (TCE stripping)
  6. Question 6 Gas-film coefficient on a spinning catalyst paddle
  7. Question 7 Packing depth for CO₂ absorption into water

Start with Question 1 →

National Exams — December 2015 — 04-Chem-A3 (Mass Transfer Operations). Three-hour, open-book exam; any non-communicating calculator permitted. Format: seven questions in three parts — answer one of Q1–Q2 (Part A), one of Q3–Q4 (Part B) and two of Q5–Q7 (Part C); four questions of equal value constitute a complete paper. All seven are solved below for completeness. Every property datum (diffusivities, Henry’s constants, solubilities, packing constants) is supplied in the question or its data table, so each answer is self-contained.

Reference texts: Geankoplis, Transport Processes and Separation Process Principles (4th ed., Prentice Hall) — Knudsen/molecular diffusion, convective mass-transfer coefficients, gas absorption in packed towers; Welty, Wicks, Wilson & Rorrer, Fundamentals of Momentum, Heat and Mass Transfer (6th ed., Wiley) — boundary-layer analogies and dimensional analysis; Bird, Stewart & Lightfoot, Transport Phenomena (2nd ed., Wiley) — Chapman–Enskog kinetic theory; Treybal, Mass-Transfer Operations (3rd ed., McGraw-Hill) — Sherwood–Holloway packed-tower correlation; supporting data from Perry’s Chemical Engineers’ Handbook (9th ed.).