23-Chem-A3 Heat and Mass Transfer

Questions by sitting

December 2019

1. Question 1: Cooling-Crystallisation Heat Load (Na₂SO₂·10H₂O)
2. Question 2: Free vs. Forced Convection from a Vertical Plate
3. Question 3: Restoring Duty on a Fouled Tube Condenser
4. Question 4: Evaporation Time in a Stefan Diffusion Tube
5. Question 5: Mass-Transfer Coefficient by the Chilton–Colburn Analogy
6. Question 6: Benzene–Toluene Distillation (McCabe–Thiele)

December 2018

1. Question 1: Ordering of Two Insulation Layers on a Steam Pipe
2. Question 2: Tube Length to Heat Water with Condensing Steam
3. Question 3: Radiation Heat Leak into a Liquid-Oxygen Dewar
4. Question 4: Diffusion of HCl through a Stagnant Water Film
5. Question 5: Gas Absorption in a Laminar Liquid Jet (Higbie)
6. Question 6: Differential (Rayleigh) Distillation of Methanol–Water

May 2018

1. Question 1: Part A: Steam Temperature for Maximum Boiling Rate
2. Question 2: Part A: Local Free-Convection Coefficient on a Vertical Plate
3. Question 3: Part A: Pipe Length in a Cross-Flow Tube-Bank Gas Heater
4. Question 4: Part B: Diffusion of Trichloroacetic Acid Through a Stagnant Methanol Film
5. Question 5: Part B: Differential (Rayleigh) Distillation of Acetic Acid–Water
6. Question 6: Part B: Minimum Liquid Rate and Diameter of a Packed Absorber

December 2017

1. Question 1: Part A: Free-Convection Heat Loss from a Pipe, Horizontal vs. Vertical
2. Question 2: Part A: Heat Loss Through Two Insulation Layers on a Pipe
3. Question 3: Part A: Number of Tubes in a Steam-Heated Water Heater
4. Question 4: Part B: Vapour–Liquid Equilibrium of Benzene–Toluene
5. Question 5: Part B: Mass-Transfer Coefficient in an Ammonia Scrubber, and by the Chilton–Colburn Analogy
6. Question 6: Part B: Evaporation of Water into Air Flowing Over a Flat Surface

May 2017

1. Question 1: Critical Radius of Insulation on a Pipeline
2. Question 2: Length of a Cube-Packed Gas Heater
3. Question 3: Copper Tube — Free Convection and Fins
4. Question 4: Flash and Differential Distillation of Heptane / Ethyl Benzene
5. Question 5: Sublimation of a UF₆ Cylinder in Cross-flow
6. Question 6: NO₂ Adsorption on Silica Gel — Counter- vs Co-current

December 2016

1. Question 1: Evaporation into a Closed Chamber (Stefan Diffusion)
2. Question 2: Evaporative Cooling from an Open Bowl
3. Question 3: Ethanol Evaporation from a Falling Film into a Cross-flow of Air
4. Question 4: Overall Gas-Phase Coefficient for CO₂ Absorption in NaOH
5. Question 5: Distillation of Ethanol–Water with a Liquid Side Stream
6. Question 6: BET Surface Area from a Nitrogen Isotherm
7. Question 7: Batch Ultrafiltration — Membrane Area

May 2016

1. Question 1: Diffusivity by the falling-level (Winkelmann) method
2. Question 2: Fall time of an acetone / dibutyl-phthalate level
3. Question 3: Non-equimolar diffusion in a distillation vapour film
4. Question 4: Effective gas-film thickness; water then ethanol
5. Question 5: Benzene / toluene distillation (McCabe–Thiele)
6. Question 6: Steam stripping of a paraffin (number of stages)
7. Question 7: Adsorption of acetone vapour on activated carbon

December 2015

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

May 2015

1. Question 1: Leaching caffeine from coffee beans — stagnant vs. stirred solvent
2. Question 2: Salt dissolving from a pipe wall — effect of tripling the flow
3. Question 3: Sublimation of a naphthalene rod in cross-flow air
4. Question 4: Humidifying air bubbles — transient diffusion into a sphere
5. Question 5: Packed-tower height for amine CO₂ absorption
6. Question 6: Carburizing a steel roller — semi-infinite diffusion
7. Question 7: Rotary drier — air rate and exit humidity

December 2014

1. Question 1: Water-vapour concentration above an open tank
2. Question 2: Diffusion-limited combustion of a carbon sphere
3. Question 3: Dissolution of a polymer film into a flowing solvent
4. Question 4: Fraction of mass transfer in the laminar zone of a flat plate
5. Question 5: Overall gas-phase coefficient for a packed absorber
6. Question 6: Bulk-solution concentration for diffusion into a biofilm
7. Question 7: Wetted-wall absorption of ammonia — film coefficient and rate

May 2014

1. Question 1: Gas-Film Thickness for Ammonia Scrubbing
2. Question 2: Sublimation Rate from a Falling Iodine Sphere
3. Question 3: Time to Dissolve a Pipe Deposit
4. Question 4: Evaporation Rate from a Water Pool
5. Question 5: Height of a Cyanogen Absorption Column
6. Question 6: Psychrometrics and Cooling-Tower Design
7. Question 7: Wetted-Wall Stripping of TCE from Water

December 2013

1. Question 1: Evaporation of a Gasoline Spill Through a Stagnant Air Film
2. Question 2: Water Vapour Diffusing Through a Conical Stack
3. Question 3: Unsteady-State Leaching from a Porous Slab
4. Question 4: Overall Mass-Transfer Coefficients for a Gas Absorber
5. Question 5: Height of a Natural-Draft Cooling Tower
6. Question 6: Mean Mass-Transfer Coefficient over a Flat Plate

May 2013

1. Question 1: Ammonia Diffusing Through Stagnant Nitrogen
2. Question 2: SO₂ Diffusion Through a Tapering Conduit
3. Question 3: Humidification of Air Over a Water Container
4. Question 4: Oxygenation of a Deep Mountain Lake
5. Question 5: Height of a Packed Ammonia Absorption Tower
6. Question 6: Cooling-Tower Sizing and Air/Make-up Balances
7. Question 7: Case Hardening of a Steel Rod

Undated paper

1. Question 1: Conduction with Temperature-Dependent Conductivity
2. Question 2: Length of a Double-Pipe Cooler — Countercurrent and Cocurrent
3. Question 3: Single-Effect Evaporator — Steam Economy and Area at Two Feed Temperatures
4. Question 4: Diffusion of Acetic Acid through a Stagnant Water Film
5. Question 5: Two-Film Interphase Transfer in SO₂ Absorption
6. Question 6: n-Heptane / n-Octane Vapour–Liquid Equilibrium from Raoult’s Law