Heat transfer in food industry processes

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Technical Physics
Second semester
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Learning outcomes of the course unit

- Knowledge and understanding:
At the end of the course the student will learn the theoretical principles of energy processes applied to the food industry. The student will therefore have to possess knowledge related to the heat transfer phenomena with reference to conduction and convection even in the presence of complex rheology fluids.

- Applying knowledge and understanding:
The student will acquire applicative knowledge, in relation to transport processes in the food industry field and will acquire the basic tools to deal with autonomy and critical sense the choices that support the sizing of heat transfer equipment.

- Making judgments:
By the end of the course the student will have the tools to critically evaluate the energy processes that occur in the food industry.

- Communication skills:
Through the frontal lessons and the assistance of the teacher, the student acquires the specific vocabulary inherent to energy processes. The student must possess the ability to clearly present the procedure
adopted in the evaluation of transport processes in the food industry.

- Learning skills:
The student who has attended the course will be able to deepen his knowledge in the field of energetics in the food transformation industry through the autonomous consultation of specialized books, scientific journals, even outside the topics explained during lectures also in view of the entrance in a job environment or in a third level course.


To follow the course with profit requires knowledge of the basic concepts of Applied Physics

Course contents summary

The course aims to provide the students with basic and applicative knowledge on energy processes of the food industry. During the course theoretical lessons are coupled to exercise activity. The theory lectures cover the following subjects: Heat Transfer Mechanisms. Steady and unsteady heat conduction. Mass Transport. Convective heat transfer. Analogy between the transport of energy, mass and momentum. 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 exercises that provide the opportunity to apply the skills and knowledge acquired in the course.

Course contents

Heat Transfer mechanisms.
Energy equation and its dimensionless form. Dimensionless numbers and Buckingham theorem.
Steady-state and unsteady heat conduction. Non dimensional form of the Fourier equation and of its boundary conditions: Fourier number, Biot number; limiting cases for large and small Biot; Semi-infinite solids. Convection:
Principles of convection. External flow. Internal flow. Hydrodynamic and thermal considerations. The energy balance: constant surface heat flux and constant surface temperature. Laminar flow in circular tubes. Convection correlations.
Mass transfer:
Fick's law. Mass diffusion coefficient.
Analogy between momentum, energy and mass transfer.
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.
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. Convective heat transfer to power law fluids.

Recommended readings

The notes of the lectures and exercises, and all the supporting material are available to students and shared on Elly platform. In addition to the shared material, the student can personally study some of the topics discussed during the course in the following books:F. P. INCOPRERA, D P DE WITT: " Fundamentals of Heat and Mass Transfer ", John Wiley & Sons, New York.
S. Yannotis: Solving Problems in Food Engineering - Springer

Teaching methods

The course counts 6 CFUs (one CFU, University Credits equals one ECTS credit and represents the workload of a student during educational activities aimed at passing the exams), which corresponds to 42 hours of lectures. 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 energy processes in the food industry.

Assessment methods and criteria

The exam is based on a written test requiring the answer to 10 questions regarding both exercises and theory questions. The results of the written test is communicated within a few days after the test itself, through publication on Esse3 Platform. The final vote, that considers the vote of the written test (1 point for each question) is normalized in a scale in thirtieths. The Laude is added in case of excellent score in each item (3 point for each question).
Please note that online registration is compulsory for the written test.