Learning objectives
At the end of the course, the student will have learnt the theoretical principles of thermofluidodynamics.
He will also have relatively specific applicative knowledge in particular on fluid flow, mass and heat transfer with reference to engineering applications.
The student must possess:
-Basic and applied knowledge of heat transfer phenomena with reference to conduction, convection even in the presence of phase change and also in the presence of complex rheological fluid behaviour;
- the basic tools to deal with the design choices aimed to heat exchangers sizing;
- the ability to clearly demonstrate the procedure used in the design of heat exchangers.
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 and non_Newtonian fluids.
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: " undamentals of Heat and Mass Transfer ", John Wiley & Sons, New York.
A. BEJAN: “Heat Transfer”, John Wiley and Sons, Inc.
R.K. SHAH, A.L. LONDON, “Laminar flow forced convection in ducts”, Academic Press, 1978.
Teaching methods
The theoretical part of the course is illustrated by frontal lessons. The part devoted to the exercise activity also involves an activity carried out by the students themselves, followed by the elaboration and discussion of the results. The notes and texts of the proposed exercises/tutorials will be uploaded to the Elly platform.
To download the material you need to apply to the online course on the same platform.
If conditions are favorable, seminars, held by R&D managers of companies, are additionally proposed to the students with the aim of reporting concrete experiences of real case studies in the field of the heat transfer apparatuses design.
Assessment methods and criteria
The exam is based on an oral test preceded by a written test requiring resolution of one or more exercises. The correct resolution of at least 50% of the exercises proposed in the test is an admission constraint to the oral exam. In the oral exam the correct and complete response to the theoretical questions and exposure property are evaluaterd.
In the written test, reference texts, thermodynamic tables and lessons notes can be consulted.
The results of the written test is communicated within a few days after the test itself, through publication on Elly Platform; The final vote shall be communicated immediately at the end of the oral exam before the registratrion.
The Laude is added in case of excellent score in each item (written test and oral exam) and in case of particular communicative and speaking ability with reference to the specific field.
Please note that online registration is compulsory for the written test; Different dates are proposed for the oral exam depending on the students' requests.
During the course, partial, formative tests are given, useful for monitoring the achieving of the learning goals and for providing feedback to students before the official call. The dates of the partial tests will be communicated by the teacher during the lessons.
Other information
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