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

National Exams — May 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, vapour pressures, solubilities, humid-air heat capacities) is stated in the question, so each answer is self-contained.

Reference texts: Geankoplis, Transport Processes and Separation Process Principles (4th ed., Prentice Hall) — molecular diffusion, convective mass transfer, gas absorption and drying; Welty, Wicks, Wilson & Rorrer, Fundamentals of Momentum, Heat and Mass Transfer (6th ed., Wiley) — boundary-layer and transient diffusion; Incropera & DeWitt, Fundamentals of Heat and Mass Transfer — transient conduction/diffusion charts and the sphere in a stagnant medium; Treybal, Mass-Transfer Operations (3rd ed.) — packed-tower design; Crank, The Mathematics of Diffusion (2nd ed.) — series solutions for the sphere; supporting data from Perry's Chemical Engineers' Handbook (9th ed.).