Learning objectives
To make the students acquainted with the application of transport phenomena principles to the processes involved in engineering applications,, with particular reference to the food industry .
Prerequisites
Technical Physics
Course unit content
The course cover a large number of different topics, ranging from the fundamental alws of mass transfer (Fick's law), to almost any kind of heat transfer, including two-phase, and even covers the behaviour of non-newtonian fluids.
Full programme
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 convection
Physical consideration. The governing equations. External free convection: the vertical plate, inclined and horizontal plates, the long horizontal cylinder, the sphere. Empirical correlations. Free convection within channels. Vertical and inclined channels. Empirical correlations. Enclosures. Rectangular cavities, concentric cylinders and spheres. Empirical correlations. Combined free and forced convection.
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 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.
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.
Mass transfer
Fick's law. Mass diffusion coefficient. The conservation of chemical species. Dimensional analysis. Schmidt number. Diffusion through a stationary medium. Boundary conditions. Mass transfer coefficient. Sherwood number. Convection. Forced convection in laminar boundary layer flow. Other external forced convection configurations.
Analogy between momentum, energy and mass transfer
Reynolds analogy. Chilton-Colburn analogy. Turbulent flow in smooth pipes. Cylinder in cross flow. Infinite plate in parallel flow. Simultaneous heat and mass transfer. Evaporative cooling. The wet-and dry-bulb psychrometer.
Rheology
General concepts of rheology. Generalized treatment of Non-Newtonian fluids. Non-Newtonian models: Bingham, shear thickening, shear thinning, power law. Analysis of capillary flow without Newtonian assumption. Rheological measurement. The capillary tube rheometer and the rotational viscometer.
Bibliography
F. KREITH: “Principi di trasmissione del calore” - Liguori Editore, Napoli, 1976
F. P. INCOPRERA, D P DE WITT: " Fundamentals of Heat and Mass Trasfer ", John Wiley & Sons, New york, 1985.
Teaching methods
Most of the material is presented in the traditional way, employing the dashboard and slides. In some cases, a beamer is employed with various types of computation sofwtare. At the end of the course, two training sessions are made in the lab, where students can develop their own computer program for simulating transient heat transfer, and use a commercial FEM program.
Assessment methods and criteria
The examination is oral, but it can happen that nuemricla exercises are to be solved, so the s=tudnet must be equipped with a calculator and evry data neeede, such as tables, charts, formulas, etc.
Other information
Since academic year 2009/2010, each lesson is transcribed by one or two students, which create a document made available on the course's web site.
