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 referred to food processing.
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. Inverse problem solution.
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.
Part of the practical activity is carried out in the computer lab and it is focused on the application of numerical analysis tools to heat transfer and fluid flow problems. In order to acquire an applicative knowledge this part of the course is based on practical lectures to be held with the use of the Matlab.
Full programme
1. Introduction
1.1. Conduction
1.2. Convection
1.3. Radiation
2. Heat conduction - basic equations
2.1. Basic equation
2.2. Boundary and initial conditions
2.2.1. Prescribed temperature
2.2.2. Prescribed heat flux
2.2.3. Convection boundary condition
3. One-dimensional, steady-state, heat conduction
3.1. The slab
3.2. The cylinder
3.3. The sphere
3.4. Composite medium
3.4.1. Composite slab
3.4.1.1. Series arrangement
3.4.1.2. Parallel arrangement
3.4.1.3. Parallel/series arrangement
3.4.2.Composite coaxial cylinders and spheres
3.5. Thermal contact resistance
3.6. Critical thickness of insulation
3.7. Finned surfaces
3.7.1. Long fin
3.7.2. Fins with negligible heat loss at the tip
3.7.3. Fin with convection at the tip
3.7.4. Fin effectiveness
3.7.5. Fin efficiency
3.7.6. Overall surface efficiency
4. Transient heat conduction: lumped-system analysis
4.1. Lumped-system analysis or global capacitance method
4.2. Lumped-system analysis for mixed boundary conditions
5. Transient heat conduction: analytical solutions for one-dimensional problems
5.1. Rectangular coordinate system
5.1.1. Finite medium
5.1.2. Semi-infinite medium
5.1.3. Multidimensional product solution
5.1.4. Non-dimensional graphical solutions
5.2. Cylinder and spherical coordinate systems: non-dimensional graphical solutions
5.2.1. Long cylinder
5.2.2. Sphere
5.2.3. Semi-infinite solid
6. Transient heat conduction: finite-difference methods
6.1. Fully explicit scheme
6.2. Fully implicit scheme
6.3. Crank-Nicholson method
6.4. Boundary conditions
6.4.1. Prescribed temperature
6.4.2. Prescribed heat flux
6.4.3. Convection
6.5. Initial conditions
7. Mass transfer by diffusion
7.1. Analogy between heat and mass transfer
7.2. Mass diffusion
7.3. Fick's law of diffusion: stationary medium consisting of two species
7.4. Generalized Fick's law: non-stationary medium consisting of two species
7.5. Boundary conditions
7.5.1. Specified species concentration
7.5.2. Specified species flux
7.5.3. Solid-liquid interfaces
7.5.4. Gas-liquid/solid interfaces
7.5.5. Evaporation and sublimation
7.6. Diffusion of vapor through a stationary gas: Stefan's flow
7.7. Constitutive equation of mass diffusion
8. Convection - introduction
8.1. Boundary layers
8.1.1. Velocity boundary layer
8.1.2. Thermal boundary layer
8.1.3. Concentration boundary layer
8.2. General conservation equations and non-dimensional numbers for steady flows
8.3. Boundary conditions and other non-dimensional numbers
8.3.1. Hydrodynamic boundary layer
8.3.2. Thermal boundary layer
8.3.3. Concentration boundary layer
8.4. Analogy between friction, heat transfer and mass transfer coefficients
8.4.1. Reynolds analogy
8.4.2. Chilton-Colburn analogy
8.5. Evaporative cooling
9. External forced convection
9.1. Convection equations for a flat plate - laminar flow
9.1.1. Fluid-dynamic solution
9.1.2. Heat transfer solution over an isothermal plate
9.1.3. Concentration solution over a plate with concentration fixed
9.1.4. Averaged parameters
9.1.5. Liquid metals and general equations
9.2. Turbulent flow over an isothermal flat plate
9.3. Mixed boundary layer over an isothermal flat plate
9.4. Flat plate with uniform heat flux
9.5. Flow across cylinders and spheres
9.5.1. Heat and mass transfer by convection
9.5.1.1. Hilpert correlation
9.5.1.2. Zukauskas correlation
9.5.1.3. General Zukauskas correlation
9.5.1.4. Churchill and Bernstein correlation
9.6. Flows across bank of tubes
9.6.1. Grimison correlation
9.6.2. Zukauskas correlation
9.6.3. Heat transfer rate
9.6.4. Pressure drop
10. Internal forced convection
10.1 Hydrodynamic considerations
10.1.1. Flow conditions
10.1.2. Mean velocity
10.1.3. Velocity profile in fully developed region (laminar)
10.1.4. Pressure drop in fully developed flow (laminar)
10.2. Thermal considerations
10.2.1. Mean temperature
10.2.2. Fully developed conditions
10.3. Energy balance
10.3.1. Constant surface heat flux
10.3.2. Constant surface temperature
10.4. Laminar flow in circular tubes: thermal analysis and correlations
10.4.1. Fully developed flow (laminar)
10.4.1.1. Constant surface heat flux
10.4.1.2. Constant surface temperature
10.4.2. Entry region (laminar)
10.5. Turbulent flow in circular ducts: convection correlations
10.5.1. Fully developed region (turbulent)
10.5.1.1. Colburn correlation
10.5.1.2. Dittus-Boelter correlation
10.5.1.3. Sieder and Tate correlation
10.5.1.4. Second Petukhov correlation
10.5.1.5. Liquid metals
10.5.2. Entry region
10.6. Non-circular tubes: laminar and turbulent correlations
10.6.1. Turbulent flow
10.6.2. Laminar flow
10.7. Annulus flow
10.8. Heat transfer enhancement
11. Heat exchangers
11.1. Types of heat exchangers
11.1.1. Double pipe or concentric tube
11.1.2. Cross flow
11.1.3. Shell-and-tube
11.1.4. Compact heat exchangers
11.2.The overall heat transfer coefficient
11.2.1. Fouling
11.3. Analysis of heat exchangers: the log mean temperature difference
11.3.1. Parallel flow heat exchanger
11.3.2. Counter-flow heat exchanger
11.3.3. Phase-changing flows
11.3.4. Multi-pass and cross-flow heat exchangers: correction factors
11.4. Analysis of heat exchangers - the effectiveness-NTU method
11.4.1. Definitions
11.4.2. Effectiveness-NTU relations
11.5. Final considerations
Bibliography
1.Ozisik, Heat Transfer: A Basic Approach, McGraw-Hill
2. Ozisik, Heat Conduction, John Wiley & Sons
3. Ozisik, Orlande, Colaço, Cotta, Finite Difference Methods in Heat Transfer, CRC Press
4. Incropera, Dewitt, Bergman, Lavine, Fundamentals of Heat and Mass Transfer, John Wiley & Sons
5. Cengel, Ghajar, Heat and Mass Transfer: Fundamentals and Applications, McGraw-Hill
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. Matlab and Comsol Multiphysics will be adopted
Assessment methods and criteria
The exam is based on an oral test consisting of a numerical exercise and two theoretical questions. The verification is so weighted: 50% correct resolution of a practical exercise), 50% correct and complete answer to theory questions and speaking ability). 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 and in case of particular communicative and speaking ability with reference to the specific field.
Other information
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