APPLIED THERMO-FLUID DYNAMICS (UNIT 1)
Learning outcomes of the course unit
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 the 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.
The student must possess the ability to present clearly the procedure adopted in the design of heat transfer apparatuses.
To follow the course with profit requires knowledge of the basic concepts of Applied Physics.
Course contents summary
The course is structured in two parts: theory and practical lessons. The theory lectures cover the following subjects: 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. The exercise activities are an integral part of the course and they are dedicated to numerical exercises intended as a moment of verification and clarification of the theoretical knowledge acquired in the lectures.
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.
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.
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.
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 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.
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.
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”.
The theoretical part of the course will be illustrated by means of lectures. The part devoted to the lab training 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 test followed by an oral examination. The verification is so weighted: 50% written test (correct resolution of a practical exercise), 50% oral exam (theoretical questions and speaking ability).
Lecture attendance is highly recommended.