Learning objectives
Knowledge and understanding:
At the end of the course the student will learn the basic principles of heat and mass transfer and fluid flow.
Applying knowledge and understanding:
The student will acquire knowledge about the application of transport phenomena principles to processes involved in engineering applications, with particular reference to the food industry.
Making judgments:
By the end of the course the student will have the tools to critically evaluate the design choices in the field of heat transfer apparatuses design.
Communication skills:
The student must possess the ability to present clearly the procedure adopted in the design of heat transfer apparatuses.
Prerequisites
To follow the course with profit requires knowledge of the basic concepts of Applied Physics.
Course unit content
The course is structured into two parts: theory and practical lessons. The theory lectures cover the following subjects: Steady and un steady heat conduction. Convection. Mass Transport. Analogy between the transport of energy, mass and momentum. Heat transfer in boiling and condensation. Convective heat transfer enhancement. Heat exchangers. Rheology. Computational fluid flow and heat transfer.
The practical lessons are integral part of the course and they are dedicated to numerical exercises that provide the opportunity to apply the skills and knowledge acquired in the course.
Full programme
Heat conduction.
Steady-state heat conduction in one-dimensional systems. Finned surfaces. Heat conduction in twodimensional systems. Finite difference formulation of the Fourier equation.
Unsteady heat conduction. Non dimensional form of the Fourier equativo and of its boundary conditions: Fourier number, Biot number; limitingcases for large and small Biot, any Biot case: infinite flat plate, infinite
cylinder, sphere, finite-dimensional solids: box and cylinder. Computational Thermal Fluid Dynamics
Convection.
Principles of convection. The boundary layers equations. External flow. The flat plate in parallel flow. The cylinder and the sphere in cross flow. Flow across banks of tubes. Internal flow. Hydrodynamic and thermal considerations. The energy balance: constant surface heat flux and constant surface temperature. Laminar flow in circular tubes. Convection correlations. Noncircular tubes.
Free convention
Physical consideration. The governing equations. External free convection: the vertical plate, inclined and horizontal plates, the long horizontal cylinder, the sphere. Empirical correlations. Free convention within channels. Vertical and inclined channels. Empirical correlations. Enclosures. Rectangular cavities, concentric cylinders and spheres. Empirical correlations. Combined free and forced convection.
Mass transfer
Fick's law. Mass diffusion coefficient. The conservation of chimica species. Dimensional analysis. Schmidt number. Diffusion through a stationary medium. Boundary conditions. Mass transfer coefficient.
Sherwood number.
Analogy between momentum, energy and mass transfer.
Reynolds analogy. Chilton-Colburn analogy. Simultaneous heat and mass transfer. Evaporative cooling. The wet-and dry-bulb psychrometer.
Boiling and Condensation
Dimensionless parameters in boiling and condensation. Pool boiling. The boiling curve. Pool boiling correlations. Nucleate pool boiling, critical heat flux, minimum heat flux, film pool boiling. Forced convection boiling. Condensation. Laminar film condensation on a vertical plate. Turbulent film condensation. Film condensation on radial systems. Dropwise condensation.
Heat transfer enhancement
Principles of enhanced heat transfer. The enhancement techniques. Passive techniques. Active techniques. Benefits of enhancement. Plate and fin extended surfaces. Externally finned tubes. Insert devices for
single-phase flow. Internally finned tubes and annuli. Integral roughness.
Heat Exchangers
Heat exchanger types. The overall heat transfer coefficient. Heat exchanger analysis. The log mean temperature difference method. The parallel and counter flow heat exchanger. Multipass and cross flow heat
exchangers. The effectiveness NTU method. Compact heat exchangers.
Rheology
General concepts of rheology. Generalized treatment of Non-Newtonian fluids. Non-Newtonian models: Bingham, shear thickening, shear thinning, power law. Rheological measurement. The capillary tube rheometer and the rotational viscometer. Laminar fully developed velocity profile of a power law fluid within a circular tube. Generalized Reynolds number. Turbulent flow regime. Dodge and Metzner correlation. Covective heat transfer to power law fluids.
Bibliography
F. P. INCOPRERA, D P DE WITT: " Fundamentals of Heat and Mass Transfer
", John Wiley & Sons, New York. Additional educational material available on the University web learning site “Campus Net”.
Teaching methods
The theoretical part of the course will be illustrated by means of lectures.
Part of the practical activity is carried out in the computer lab and it also includes an activity pursued independently by the students, followed by an elaboration and discussion of the results.
Assessment methods and criteria
The exam is based on a written/practical test, followed by an oral examination. The verification is so weighted: 50% written test (correct resolution of a practical exercise), 50% oral exam (correct and cmplete ansie to theoretical questions and speaking ability).
Other information
- - -
