FISICA TECNICA A - L

The course is designed to provide skills and knowledge in the following areas:

• basic principles and laws of thermodynamics and related applications to plant components, thermodynamic and reversed cycles and air conditioning systems;
• three modes of heat transfer and their engineering applications, including models for the description and characterization of heat transfer in simple geometries and heat exchangers.

Lessons and exercises are carried out in the classroom using teaching materials and courseware (slides, exercises, etc.) made available to students on the Studium platform at the beginning of and during the course. Should teaching be carried out in mixed mode or remotely, it may be necessary to introduce changes with respect to previous statements, in line with the programme planned and outlined in the syllabus.

The verification takes place through a written and an oral examination. For the admission to the oral examination, it is required to pass the written test. Both the written and oral tests aim at verifying the student’s capability of both arguing about the theoretical thermodynamics and heat transfer aspects and resolving practical problems and exercises. The written test consists in both theoretical questions and exercises to be resolved. Learning assessment may also be carried out online, should the conditions require it.

If the course has been held in presence and for all students who have attended the course (i.e. with at least the 70% of participation), two intermediate tests will be proposed, one at the end of the applied thermodynamics part and the other one at the end of the course. Passing both tests is equivalent to passing the written test and students have to take the oral exam within the academic year. The intermediate tests will not take place in case of remote lessons.

Applied Thermodynamics

1. BASIC CONCEPTS OF THERMODYNAMICS

The classical thermodynamics and energy; heat transfer; International System of Units. The thermodynamic system: control mass and control volume; state and equilibrium; the state postulate or Gibbs phase rule; the zeroth law of thermodynamics; pressure, volume and temperature; transformation and cycles.

2. POINT AND PATH FUNCTIONS

Energy and its forms: internal energy, kinetic and potential energy; energy transfer by heat and work.

3. PROPERTIES OF PURE SUBSTANCES

Pure substances and physics of the phase-change processes of pure substances; compressed and saturated liquid; saturated vapour and superheated vapour; property diagrams for phase-change processes. The ideal-gas equation of state and other equations of state; deviation from ideal-gas behaviour.

4. ENERGY ANALYSIS OF CLOSED AND OPEN SYSTEMS AND FIRST LAW OF THERMODYNAMICS

Energy balance for closed systems; moving boundary work; specific heats at constant volume and at constant pressure. Definition of enthalpy. Mass and energy analysis of control volumes. The first law of thermodynamics for closed and open systems. Flow work and energy analysis of steady-flow systems and thermodynamic behaviour of steady-flow engineering devices.

5. THE SECOND LAW OF THERMODYNAMICS AND ENTROPY

Definition of thermal energy reservoirs; heat engines; refrigerators and heat pumps. The second law of thermodynamics: Kelvin-Planck and Clausius statements. Reversible ad irreversible processes. The direct and reversed Carnot cycle. The Carnot principles; the thermodynamic temperature scale. Entropy, isentropic processes and property of diagrams involving entropy. Entropy change of liquids, solids and ideal gases. Entropy balance.

6. TECHNOLOGICAL COMPONENTS

Technological devices; isentropic efficiency of thermodynamic devices; energy, mass and entropy balances for thermodynamic components.

7. GAS POWER CYCLES

The Carnot gas cycle; air-standard assumptions; the Brayton-Joule cycle and deviation of actual gas-turbine cycles from idealized ones; the Brayton-Joule cycle with regeneration; basics of ideal jet-propulsion cycles and other engineering applications; basics of Otto and Diesel cycles.

8. VAPOUR AND COMBINED POWER CYCLES

The Carnot vapour cycle; the Rankine cycle and deviation of actual vapour power cycles from idealized ones; how to increase the efficiency of the Rankine cycle; the ideal reheat Rankine cycle; the ideal regenerative Rankine cycle; cogeneration and combined gas-vapour power cycles.

9. REFRIGERATION CYCLES

The reversed Carnot cycle; refrigerators and heat pump; ideal vapour-compression refrigeration cycle; actual vapour-compression refrigeration cycle.

10. GAS-VAPOUR MIXTURES AND AIR-CONDITIONING

Ideal- and real-gas mixtures and properties; dry and atmospheric air; the psychrometric chart; main air-conditioning processes.

HEAT TRANSFER

11. BASIC CONCEPTS OF HEAT TRANSFER

Heat transfer mechanisms: conduction, convection and radiation. Simultaneous heat transfer mechanisms.

12. HEAT CONDUCTION

The Fourier heat conduction equation; thermal conductivity; solution of steady one-dimensional heat conduction problems; thermal resistance concept and thermal resistance network; thermal contact resistance. Steady heat conduction in plane walls, cylinders ad spheres; multi-layered cylinders and spheres and critical radius of insulation.

13. EXTERNAL AND INTERNAL FORCED CONVECTION AND NATURAL CONVECTION

Classification of fluid flows; non-dimensional parameters for the forced convection; parallel flow over flat planes; flow across cylinders and spheres; flow across tube banks; internal forced convection; laminar and turbulent flows in tubes; physical mechanism of natural convection; equation of motion.

14. THERMAL RADIATION AND RADIATION HEAT TRANSFER

Thermal radiation; blackbody radiation and laws; radiation intensity; radiative properties. Radiation heat transfer; the view factor and relations; black surfaces and diffuse, grey surfaces.

15. HEAT EXCHANGERS

Types of heat exchangers; the overall heat transfer coefficient; the fouling factor; analysis of heat exchangers; the log-mean temperature difference method; the effectiveness-NTU method.

16. MIXED CONDUCTION-CONVECTION PROBLEMS

Heat transfer from finned surfaces; fin equation; fin efficiency and effectiveness. Transient heat conduction and lumped system analysis and Heisler diagram.

Y. A. ÇENGEL – Thermodynamics and Heat Transfer, McGraw-Hill

J. MORAN, H.N. SHAPIRO, B.R. MUNSON, D.P. DE WITT – Introduction to Thermal Systems Engineering: Thermodynamics, Fluid Mechanics, and Heat Transfer, McGraw Hill