Heat and Mass Transport Processes (CHEN30005)

AIMS

This subject aims to extend the fundamental concepts of heat transfer from that covered in CHEN20009 Transport Processes to include natural and forced convection and two phase systems. Mass transfer concepts are extended to unsteady state mass transfer and Fick's Second Law, prediction of diffusivity and of mass transfer coefficients. These fundamental concepts are then applied to the design of processes and equipment including shell and tube, air-cooled and plate heat exchangers, evaporator systems, membrane devices, binary distillation systems, gas absorbers and cooling towers. Experience in the use of appropriate simulation packages such as HYSYS for exchanger and distillation column design are included. This simulation work builds on the skills developed in CHEN20011 Chemical Process Analysis .

INDICATIVE CONTENT

• Forced Convection: Use of heat transfer correlations to predict coefficients
• Heat Exchange: concept of an overall heat transfer coefficient, fouling factors; determination of the area required for a given heat duty, Heat exchanger design. Use of simulation packages such as HYSYS and ASPEN
• Free convection: discussion and application of Grashof Number and other dimensionless groups
• Condensation and Boiling: Fundamentals. Evaporation: various evaporator types and their advantages and disadvantages (forced circulation, film types); multiple and single effects; backward and forward feed; boiling point elevation; mechanical recompression; evaporator energy balances
• Mass Transfer: Unsteady state mass transfer and Fick's Second Law; prediction of diffusivity; dimensional analysis and equations of change for mass transfer
• Distillation: single-stage separations, equilibrium flash, differential distillation; multistage separations, operating lines, reflux; binary distillation, varying reflux ratio, minimum reflux, total reflux, optimum reflux, feed plate location, side streams, open steam; tray efficiency via overall and Murphree efficiencies. Use of simulation packages such as HYSYS
• Gas absorption: basic mass transfer mechanism; material balances, co-current and countercurrent flow, limiting L/G ratio; multistage absorption and the absorption factor method; continuous contact, transfer units, height of a transfer unit, calculation of number of transfer units. Humidification and cooling tower height calculation
• Membrane Systems: Microfiltration, ultrafiltration, nanofiltration and reverse osmosis. Gas separation systems. Robeson’s bound. Electrodialysis and pervaporation. Membrane selection.