Heat and Mass Transfer

Overview

NAME CONTRIBUTION
Dr. M. Blesic Module Co-ordinator
m.blesic@qub.ac.uk Forced Convection (5 hours) ; Natural Convection (3 hours); Heat Exchangers (6 hours): Unsteady State Heat Transfer (6 hours); Tutorials: Forced and natural convection (2 hours);
Heat exchangers (3 hours);Unsteady state heat transfer (2 hours);
Mrs S. Evans - Email: s.evans@qub.ac.uk Labs (9 hours)
Dr. N. Gui,
M.Gui@qub.ac.uk Distillation (9 hours); Solvent Extraction (4 hours); Interphase and General Mass Transfer (3 hours); Gas Absorption (5 hours); Tutorials: 5.Distillation (3 hour);Solvent extraction (3 hour)
;Interface and general mass transfer (2 hour);Gas absorption (2 hour);
Dr E. Themistou
e.themistou@qub.ac.uk Radiative Heat Transfer (5 hours); Radiative heat transfer (2 hours);

Detailed Syllabus - Lectures:
Radiative Heat Transfer (5 hours):
 Modes of Heat Transfer.
 Emission and absorption of radiation.
 Definitions and laws of radiation.
 Photon gas
 Blackbody and real surface radiation.
 Effects of incident radiation - absorptivity, reflectivity and transmissivity.
 Radiative shape factors for simple and complex geometries.
 Radiation between surfaces – relations between radiative shape factors.
 Surface energy balance for opaque material – irradiation and radiosity.
 Radiation between non-black surfaces, electrical analogies.
 Insulated surfaces, surfaces with large areas infinite parallel surfaces

Forced Convection (5 hours):
 Physical mechanism of forced convection.
 Newton's Law of cooling.
 Convective heat transfer coefficient.
 Nusselt number.
 Velocity boundary layer.
 Boundary layer theory and friction and drag coefficients.
 Laminar and turbulent flows.
 The Reynold number.
 Thermal boundary layer.
 Thermal boundary layer theory.
 Prandtl number.
 Flow over flat plates.
 Flow across cylinders and spheres.
 Flow in tubes.
 Constant heat flux.
 Constant surface temperature.
 Logarithmic mean temperature difference.
 Pressure drop.
 Flow regimes in a tube.
 Hydrodynamic and thermal entry lengths.
 Laminar flow in tubes.
 Turbulent flow in tubes.

Natural Convection (3 hours):
 Physical mechanism of natural convection, volume expansion coefficient, Grashof number.
 Natural convection over surfaces, natural convection correlations, natural convection inside enclosures.
 Combined natural and forced convection.

Heat Exchangers (6 hours):
 Heat exchange.
 Applications and types of heat exchangers.
 Selection of heat exchangers.
 Temperature profile in heat exchangers.
 Basic equations in heat exchanger design.
 Overall heat transfer coefficient.
 Fouling factors.
 Log mean temperature difference (LMTD) – calculation for parallel-flow and counter-flow heat exchangers.
 LMTD - special operating conditions for condensers, evaporators/boilers.
 LMTD correction factors for multipass and cross-flow shell-and-tube heat exchangers.
 The heat exchanger effectiveness (ε) – number of transfer units (NTU) method for heat exchanger analysis for various types of heat exchangers.
 Shell-and-tube heat exchanger design.
 Design procedure, construction details and design considerations.
 Tube-side and shell-side heat transfer and pressure drop.
 Design methods: Kern’s and Bell methods.
 Gasketed-plate heat exchanger applications and design: Heat transfer area, mean flow channel gap, channel hydraulic diameter, heat transfer coefficient, total pressure drop, overall heat transfer coefficient, heat transfer surface area, thermal performance.
 Condensation and boiling.

Unsteady State Heat Transfer (6 hours):
 Introduction.
 Unsteady state conduction equation.
 Lumped capacitance method.
 Unsteady state heat conduction in various geometries: analytical method, semi-infinite solid, unsteady state in large flat plates.
 Charts for average temperature in plates, cylinders and spheres with negligible resistance.
 Numerical methods for unsteady state: finite difference, boundary conditions, selected applications.
 Boundary layer flow and turbulent conditions.
 0D to 3D transient problems.

Distillation (9 hours):
 Vapour pressure introduction: Vapour-liquid equilibria, Raoult’s law, Henry’s law, Dalton’s law, steam distillation, relative volatility, azeotropic systems.
 Flash distillation – material and energy balance equations, operating lines.
 Flash cascades.
 Isothermal flash configuration – multicomponent:
 Rachford-Rice equations.
 Newton’s iterative method for solving Rachford-Rice equations.
 Plate columns.
 McCabe-Thiele method for special equipment:
 Total and partial condenser.
 Sub-cooled reflux.
 Total and partial reboiler.
 Live steam injection.
 Multiple feeds.
 Side streams.
 Ponchon Savarit method for binary distillation.
 Enthalpy-composition diagrams.
 Equilibrium-stage calculations.

Solvent Extraction (4 hours):
 Liquid-liquid extraction introduction.
 Examples of ternary systems and ternary phase diagrams.
 Review of processes and applications.
 Review of equipment.
 Totally and partially immiscible systems.
 Stagewise contact:
 Single-stage extraction.
 Multistage crosscurrent extraction.
 Continuous countercurrent multistage extraction.
 Cascade efficiencies.

Interphase and General Mass Transfer (3 hours):
 General introduction to turbulent mass transfer.
 Film theory and surface renewal.
 Two-film theory.
 Individual and overall mass transfer coefficients.
 Steady state co-current and counter-current processes (operating and equilibrium lines).
 Mass transfer with continuous contact: height equivalent to a theoretical plate, the transfer unit, determination of the number of transfer units, determination of the number of transfer units, height of a transfer unit.
 Mass transfer with discontinuous contact.

Gas Absorption (5 hours):
 Gas-liquid equilibria.
 Choice of solvent for absorption.
 Counter-current and co-current flow.
 Minimum liquid-gas ratio for absorbers.
 Number of plates using absorption factor.
 Absorption columns.

Detailed Syllabus –Tutorials (19 Hours):
The students are provided with tutorial and worked examples of the above lecture material. Tutorial classes are an integral element of the module.

 1.Radiative heat transfer (2 hours) – Dr E. Themistou
 2.Forced and natural convection (2 hours ) - Dr. M. Blesic
 3.Heat exchangers (3 hours) – Dr. M. Blesic
 4.Unsteady state heat transfer (2 hours ) - Dr. M. Blesic
 5.Distillation (3 hour) - Dr. N. Gui
 6.Solvent extraction (3 hour) - Dr. N. Gui
 7.Interface and general mass transfer (2 hour) - Dr. N. Gui.
 8.Gas absorption (2 hour) - Dr. N. Gui.

Detailed Syllabus – Labs (9 Hours):
 Students will be divided into groups. Each group will carry out experiments based on:

 1. Boiler Heat Transfer Unit (2 hours)
 2. Turbulent Flow Counter-Current Heat Exchanger (2 hours)
 3. Distillation column (2 hours)
 4. Liquid/liquid extraction (2 hours)
 5. Gas absorption column (1 hour)

 Both an individual pre-lab report and an individual post-lab report will be submitted for each experiment as indicated in the lab manual (to be handed out at the beginning of the term).

Learning Objectives

On completion of this module a learner should be able to:
 General Learning Outcomes:
 Develops an understanding of how heat transfer is accomplished in chemical engineering process operations and applies the concept of mass transfer to specific unit operations such as distillation and solvent extraction.
 Specific Learning Outcomes:
 On completion of this module the student should:
 Understand the concept of heat, interphase and mass transfer;
 Be able to calculate heat transfer rates using correlations of non dimensional groups, analytical techniques or numerical techniques;
 Understand the compromises between effectiveness and cost inherent in the design optimisation of heat transfer equipment;
 Understand in depth the unsteady state heat transfer which is essential in start-up and transient processes;
 Acquire basic knowledge of radiation heat transfer which is essential for the design of higher temperature systems.
 Develop and apply the concept of mass transfer to specific unit operations including distillation, solvent extraction, absorption and adsorption.
 Recognise, analyse, compare and choose from various cases of distillation design such as flash distillation, multiple feeds, side streams and live steam injection.
 Design azeotropic distillation processes.
 Apply the concept of mass transfer in extraction processes.
 Design crosscurrent and countercurrent multistage extraction processes.
 Use the concept of interphase and general mass transfer.
 Solve problems on mass transfer with continuous contact.
 Explain the concepts of mass transfer in gas absorption and adsorption processes.
 Design methods for gas absorber analysis.
 be able to apply mass transfer in leaching processes;
 Design of cocurrent and countercurrent leaching processes.
 Improved understanding of basic chemical engineering (heat transfer, vapour pressure, bubble points, distillation, heat exchange etc.) through specific test questions.
 Obtain a greater understanding of overall heat and mass balances and conceptual process flow (PF) diagrams.

Skills

Learners are expected to demonstrate the following on completion of the module:
 Application of the concepts of heat transfer and design to heat transfer systems.
 An appreciation of the design and operation of mass transfer process.
 Improved mathematical and problem solving skills.
 An ability to use specific and general computer packages for solving chemical engineering design problems.
 Ability to utilise specific chemical engineering application software in solving chemical engineering problems, such as Matlab.

Assessment

MODULE CREDIT:
The module is assessed by Examination (50%) and continual assessment (50%).
The mark breakdown of the continuous assessment is as follows:
• 4 Class tests 30%
• Labs 20%

Course Requirements:
 Lab attendance 80 %
 Practical report submission 80 %
 Examination mark veto 40% (20% from each section)
 Laboratory mark veto 40 %
 Heat transfer Class tests mark veto 40 %
 Mass transfer Class tests mark veto 40 %
 Module pass mark veto 40 %