69156 - Applied Physics

Learning outcomes

The student will acquire the basic language of Physics and the essential concepts relative to heat transfer and fluid dynamics in food processing. The student will be able to understand and manage the physical parameters that describe foods, to understand the role of the governing parameters that rule the most important thermal and fluid treatments for foods, to understand the physical mechanisms underneath the measuring apparatus employed by food industry and catering sector.

Course contents

First Part

Introduction to applied physics: measurement units, international system, intensive/extensive/specific properties, vector quantities and scalar quantities, defining position, velocity, acceleration, force, pressure, energy and power, phases of matter.

Thermodynamics applied to closed systems: system definition, closed system, open system, isolated system, constituents of a system, property and status, transformation (or process) and cycle, stable equilibrium state, quasi-static process, mutually stable equilibrium, heat reservoir, mechanical apparatus, environment of a system, adiabatic process, the first law of thermodynamics, energy, heat, energy balance, simple systems and internal energy, enthalpy and specific heats. Heat engine, Carnot's theorem, efficiency of a heat engine.

Thermodynamics applied to open systems: fluid element, specific energy of a fluid element, control volume, energy balance for almost simple system in motion in steady state, examples: adiabatic turbine/compressor, heat exchanger, throttling valve.

Simple single-component systems: equation of state, critical point, diagrams (p, T) and (p, v), ideal gases, Joule's law, adiabatic and isothermal ideal gas processes, Carnot cycle, saturated vapor, refrigeration cycle.

Gas mixtures: mole fraction, mass fraction, partial pressure, partial volume. Mixtures of ideal gases: Dalton law. Water vapor-air mixtures (humid air): vapor quality, relative humidity, dew point, psychrometric chart and psychrometer.

 

Second Part

Elements of fluid dynamics: fluid element, trajectory, streamline, steady flow, viscosity, non-Newtonian fluids, internal/external flows, Poiseuille flow, average roughness, Reynolds experiment, hydraulic diameter, laminar regime, turbulent regime, transition regime, concentrated and diffused head losses, Moody diagram, total pressure drop.

Heat transfer: local thermodynamic equilibrium, temperature distribution, heat transfer, conduction, convection, radiation, flow, density of heat flow, thermal power, Fourier law, thermal conductivity. Steady conduction examples: single-layer flat wall, multi-layers flat wall, electrical analogy, thermal resistance for conduction; single-cylindrical layer, multi-cylindrical layers, electrical analogy.

Forced convection, natural convection, mixed convection, heat transfer coefficient, thermal resistance for convection, Nusselt number, Prandtl number, Rayleigh number, internal/external convection. Forced Convection: external flow on a flat plate, internal flow in a circular duct. Natural convection: horizontal/vertical flat plate, vertical cylinder.

Heat exchangers: shell and tube kind. Overall heat transfer coefficient. Sizing of a heat exchanger: heat capacity per unit of time, logarithmic mean temperature difference, efficiency of the heat exchanger, the Number of Transfer Units method.

Introduction to radiative heat transfer and to remote sensing techniques to monitoring the crop health.

Readings/Bibliography

Y. A. Çengel, Introduction to Thermodynamics & Heat Transfer, McGraw-Hill

Teaching methods

The course consists of lectures: both theoretical notions and exercises are presented.

Assessment methods

The notion acquired are assessed by two independent written tests, the first focused on verifying the knowledge relative to the first part of the course and the second focused on verifying the knowledge relative to the second part of the course.

Both tests are composed of questions designed to check the acquired theoretical knowledge and exercises designed to check the acquired probelm-solving knowledge. In particular, the exam is structured as follow:

- 3 multiple choices theoretical questions where every correct answer is worth 3 points, each incorrect answer is -1 points, each answer left blank is worth 0 points;

- 2 open answer theoretical questions where every correct answer is worth 4 points, each incorrect answer is 0 points, each answer left blank is worth 0 points;

- 3 exercises to be solved where every correct answer is worth 6 points, each incorrect answer is 0 points, each answer left blank is worth 0 points.

The mark on each written test can be: not sufficient if the total score is less than 18; sufficient if the total score is between 18 and 30, 30 cum laude ("30L") if every answer is correct. The ultimate mark will be the arithmetic mean of the marks obtained in the two test: the one relative to the first part of the course and the one relative to the second part of the course.

Every time the student partecipate to a written test, the mark obtained before, relatively to that part of the exam, will be erased.

Eligible students (laureandi and students far behind) can email the professor in order obtain an additional scheduled exam during the classes period.

Teaching tools

Lecture notes available on

https://iol.unibo.it

Office hours

See the website of Michele Celli