Courses

Food Engineering I – Mass and Energy Balances

General

Course Contents

Unit 1: Mass and Energy Balances

  • The concept of balance on steady-state or transient system. The principles of mass and energy conservation.
  • Formulation and solution of mass balances in simple and complex processes with or without reactions.
  • Phase diagrams and phase equilibria. Gibbs rule.
  • Humidity and psychometric charts.
  • Internal energy, enthalpy, heat and work. Steam tables. Energy balances.

Unit 2: Fluid Mechanics

  • Hydrostatic equilibrium. Absolute and manometric pressure
  • Flow phenomena. Viscosity and Newton’s law. Types of rheological behavior. Laminar and turbulent flow, Reynolds number. Boundary layers in walls.
  • Flow equations. Average velocity, momentum and energy in unidirectional flow. Continuity, momentum and mechanical energy (Bernoulli) equations. Flow from orifice.
  • Incompressible flow in pipes. Wall friction, friction coefficient Fanning. Non-circular pipes. Velocity profiles in laminar and turbulent flow. Equation Hagen-Poiseuille. Calculation of friction coefficients in smooth and rough pipes. Friction due to cross section reduction or enlargement and the presence of valves etc. Pump power.
  • Types and categories of pressure, flow and tank level sensors.

Unit 3: Heat Transfer

  • Heat transfer mechanisms. Conduction and Fourier’s law. Thermal conductivity. Convection, Newton’ law. Heat transfer coefficients.
  • Steady-state Conduction. Unidirectional conduction in planar, cylindrical and spherical geometry. Conduction through multiple layers. Combined conduction-convection in fluids.
  • Non-steady-state Conduction. The Biot number. Thermal Diffusivity. The Fourier Number. Lumped capacity analysis. Charts for transient heating/cooling in planar, cylindrical, spherical and complex geometries.
  • Forced Convection. The Nusselt and Prandtl numbers. Thermal boundary layer. Heat transfer equations for laminar and turbulent flow over slabs and through pipes. Natural convection. The Grashof number. Convection with phase change: condensation and evaporation.
  • Heat transfer devices: heat exchangers and their types. Heat transfer equation for double-pipe heat exchangers. Correction factor for composite heat exchangers. NTU method. Heated tanks: calculation of heating/cooling time.
  • Types and categories of temperature sensors. Steam networks and steam traps.

Titles of Laboratory Exercises

  • Non-steady state heating of a can
  • Flow meters – Pressure drop
  • Heat exchangers
  • Spray Dryer

Educational Goals

The course aims to achieve the following learning outcomes for students:

  • acquiring knowledge in the basic engineering principles that govern the physical processes during food processing
  • recognizing, understanding and interpreting the physical phenomena govern these processes
  • the ability to describe mathematically and evaluate the contribution of each phenomenon or parameter to the evolution of the process
  • acquiring experience in applying the above knowledge and analytical skills to industrial-scale processes

General Skills

  • Analyzing, interpreting and synthesizing empirical data obtained from experimental setups
  • Searching and analyzing information using information and communication technologies
  • Promotion of analytical, productive and inductive thinking
  • Working in an interdisciplinary environment
  • Autonomous work
  • Teamwork
  • Decision making

Teaching Methods

Face to face:

  • Lectures (theory and exercises) in the classroom.
  • Laboratory exercises in groups in a pilot plant laboratory.

Use of ICT means

  • Lectures with PowerPoint slides using PC and projector.
  • Notes, solved and unsolved problems in electronic format.
  • Use of videos and web-applications in lectures.
  • Posting course material and communicating with students on the Moodle online platform.
  • Use of electronic devices for retrieving and recording experimental data (data logging) in the laboratory.

Teaching Organization

ActivitySemester workload
Theory and practical exercises60
Laboratory exercises27.5
Independent Study100
Total187.5

Students Evaluation

Evaluation methods:

  • Compulsory attendance at (at least) 80% of the laboratory exercises.
  • Written final exams in the theoretical part of the course with problem solving (80% of the final grade).
  • Final written exams in the laboratory part of the course with multiple choice, short essay and problem-solving questions (20% of the final grade).
  • Optional written assignments in laboratory exercises.

The evaluation criteria are presented and analyzed to the students at the beginning of the semester and are available at the course website.

Recommended Bibliography

  1. McCabe W., Smith J., Harriott P., Βασικές Φυσικές Διεργασίες Μηχανικής, 6η Έκδοση, Μετάφραση: Εκδόσεις Τζιόλα, Θεσσαλονίκη, 2003.
  2. Pitts D., Sissom L., Μεταφορά Θερμότητας, Σειρά Schaum, 2η Έκδοση, Μετάφραση: Εκδόσεις Τζιόλα, Θεσσαλονίκη, 2001.
  3. Himmelblau D.M., Riggs J.B., Βασικές Αρχές και Υπολογισμοί στη Χημική Μηχανική, 7η Έκδοση, Μετάφραση: Εκδόσεις Τζιόλα, Θεσσαλονίκη, 2006.
  4. Fryer P.J, Pyle, D.L., Reilly C.D., Chemical Engineering for the Food Industry, Chapman & Hall, 1997.

Related Research Journals

  1. Journal of Food Engineering.
  2. Journal of Food Processing & Technology.