# TRANSFER PROCESSES - 2021/2

Module code: ENG2109

## Module Overview

Mass Transfer: Mass transfer is essential knowledge for chemical engineers, governing the underlying operations in many industrial processes involving, for example, separation and reaction. The purpose of the module is to introduce students to mechanistic and semi-empirical descriptions of mass transfer, and to apply such understanding to the design of process such as gas absorption and drying.

Fluid mechanics: The main part of the syllabus concentrates on developing the student’s understanding of internal flows. Knowledge of turbulent flow is extended by the introduction of the Universal Velocity Profile. Furthermore, more complex flows, which may include multiple phases or compressibility, are introduced.  The issues of drag and terminal velocity of particles is tackled and the features and flow of some non-Newtonian fluids discussed.

A short introduction is given on the simulation of real-life Mass-Transfer and Fluid Mechanics problems using commercial software.

### Module provider

Chemical and Process Engineering

### Module cap (Maximum number of students): N/A

Independent Learning Hours: 93

Lecture Hours: 11

Tutorial Hours: 11

Guided Learning: 11

Captured Content: 24

Semester 2

None

## Module content

Indicative content includes:

Mass Transfer

Introduction to mass transfer

• Molecular diffusion: Fick's law

• General case of diffusion with bulk (convective) flow

• Stefan's law

• Diffusivity determination and prediction

• Mass transfer coefficients; mass transfer correlations

• Momentum, heat and mass transfer analogies; J-factor analogy

Mass transfer across interfaces

• Whitman two-film theory

• Gas-liquid equilibria; Henry's law

• Overall driving force and overall mass transfer coefficients

• Film control and design implications

Absorber and stripper design

• Industrial processes: staged vs. continuous contact equipment

• Absorber / stripper design equations: height and number of gas-transfer units; graphical and analytical solutions

• Other contact configurations: well-mixed flow; co-current flow; extension of concepts to liquid-liquid systems

Diffusion in solids

• Pore diffusion: molecular, Knudsen, configurational

• Effective diffusivity

• Diffusion through non-porous solids; membranes

Drying of particulate solids

• Drying principles, mechanisms and drying terminology

• Type of dryers; for solids, pastes, solutions, and slurries

• Drying rate curves and kinetics

• Characterisation of wet gas streams: humidity definitions; humid heat; enthalpy; humid volume; adiabatic saturation and wet-bulb temperatures; psychrometric ratio; psychrometric charts

• Basic design of dryers and drying time

• Simultaneous heat and mass transfer in dryers

Fluid Mechanics

Turbulent flow in a pipe

• Revision of 1/7th power law

• The universal velocity profile.

• Eddy viscosity and its link to eddy diffusivity

• Mixing of fluids

Two phase gas-liquid flow in pipes

• Flow pattern maps in horizontal and vertical flow

• Pressure differences (incl. Method of Lockhart and Martinelli)

Equipment for pumping gases

• Types and their characteristics

• Reminder of inter-cooling

• Surge and recycle

Compressible flow of gases

• Reminder of basic equations (Continuity, Ideal Gas law, adiabatic equations, steady flow energy equation)

• Isothermal compressible flow in pipelines (density changes, speed of sound, choking)

• Isentropic compressible flow through valves (density changes, speed of sound, choking, existence of shock waves). How to predict whether a valve is choked. Calculation of relief valve capacity

• When is a flow likely to be isothermal or isentropic? Mention of polytropic flows.

• Brief discussion of convergent-divergent nozzles.

Terminal velocity

• Drag coefficients for a sphere

• Force balance for a sphere in free fall

• Equations for terminal velocity

Non-Newtonian Fluids including Colloids

• Types of non-Newtonian behaviour

• Van der Waals’ forces and colloidal rheology

• Internal flow of non-Newtonian fluids

## Assessment pattern

Assessment type Unit of assessment Weighting
Coursework COURSEWORK 20
Examination Online ONLINE (OPEN BOOK) EXAM 80

N/A

## Assessment Strategy

The assessment strategy is designed to provide students with the opportunity to demonstrate the full range of learning outcomes though the balanced mixture of lecture and tutorial/problem classes coupled with the carefully graded tutorial problems which reflect current industrial practice.

Thus, the summative assessment for this module consists of:

• Examination – 80% (weighted 48% to Mass Transfer and 32% to Fluid Mechanics), 2 hours (LO1 – LO9)

• Coursework – 20% (Mass Transfer). Absorption column/dryer design calculations (LO2/LO5).

Formative assessment

• Mass transfer class test (LO1, LO2, LO4, LO5)

• Randomised multiple choice tests on SurreyLearn (LO6, LO7, LO8)

Feedback

• Weekly verbal feedback during tutorial classes (LO1 – LO9)

• Written feedback on Coursework (LO2)

• Verbal feedback at the end of the formative class test (LO1, LO2, LO4, LO5)

## Module aims

• Introduce the key concepts of mass transfer operations in Chemical Engineering, with a specific focus on gas-liquid and gas-solid systems.
• Provide the knowledge and skills to undertake the specification and design of absorption columns (i.e. continuous diffusional contact devices).
• Provide the knowledge and skills to undertake the specification and design of drying operations.
• Provide students further and deeper understanding of fluid flows in Chemical Engineering.

## Learning outcomes

 Attributes Developed 001 Describe the key principles of, and modelling approaches to, mass transfer in fluid-fluid and fluid-solid system. KC 002 Design absorption and stripping equipment based on continuous diffusional contact. KCP 003 Develop general mathematical models for mass transfer in different phase-contact and phase-flow situations. KC 004 Describe the drying mechanisms of particulate solids and the classification of drying operations. KC 005 Formulate, solve and use the governing equations for designing batch and continuous dryers. KCP 006 Explain the physics behind turbulent flow in a pipe and how that affects the velocity profile, the fluid friction at a pipe wall KC 007 Explain the physics behind non-Newtonian flows, describe the most common rheological models and describe colloidal suspensions KC 008 Describe the key steps involved in setting up a numerical simulation of real-life Mass-Transfer and Fluid Mechanics problems using commercial software. KP

Attributes Developed

C - Cognitive/analytical

K - Subject knowledge

T - Transferable skills

P - Professional/Practical skills

## Methods of Teaching / Learning

The learning and teaching strategy is designed to:

• Carefully cover in lectures the necessary fundamental material and analytical techniques, and demonstrate concepts with appropriate (and where possible practical) examples

• Allow students adequate time to practice the techniques using a large number of carefully selected tutorial problems.

The learning and teaching methods include:

• Lectures                                  3 hours per week for 11 weeks

• Tutorial/Problem Classes         1 hour per week for 11 weeks

• Independent learning                8 hours per week for 12 weeks (average)

Indicated Lecture Hours (which may also include seminars, tutorials, workshops and other contact time) are approximate and may include in-class tests where one or more of these are an assessment on the module. In-class tests are scheduled/organised separately to taught content and will be published on to student personal timetables, where they apply to taken modules, as soon as they are finalised by central administration. This will usually be after the initial publication of the teaching timetable for the relevant semester.