90026 - Energy Conversion and Final Use T

Learning outcomes

To provide students with knowledge of the operating principles of the main machines and components used in fossil-fuel-based energy systems for the production of electrical and thermal power, with particular reference to steam generators, condensers, heat exchangers in general, and fluid machines operating with both compressible and incompressible fluids.

Course contents

MODULE 1
30 hours – for students enrolled in Chemical and Biochemical Engineering, course Fluid Machines T, and in Environmental Engineering, course Energy Conversion ed Utilisation T
Instructor: Prof. Saverio Ottaviano

Introduction and review of thermodynamics: Units of measurement for energy and related conversion factors: kcal, kJ, toe, kWh. The principles of conservation of mass and energy in open systems; the generalized equation of fluid motion in thermal and mechanical form. Ideal and perfect gases; the main transformations of an ideal gas — isentropic, polytropic, isothermal, isochoric and isobaric — and their representation on the temperature–entropy diagram.

Heat exchangers: The overall heat transfer coefficient and wall temperature. The counter-flow heat exchanger, exchanged heat rate, and the logarithmic mean temperature difference method. Heat exchange diagrams. Definition of heat exchanger effectiveness for counter-flow and parallel-flow configurations, as a function of the different heat capacities of the fluids.

Gas turbine power plants: Plant layout of a gas turbine unit operating on the Brayton cycle. Operating principles of the compressor, turbine and combustion chamber. For the case of constant specific heat capacity, analysis of the work output and efficiency of a gas turbine unit as functions of the cycle pressure ratio, polytropic efficiency and turbine inlet temperature. Real and isentropic cases. Representation of the Brayton cycle on the T-s diagram.

Combustion: Stoichiometric combustion reactions; calculation of the mass flow rate of stoichiometric oxygen and stoichiometric air. Definition of excess air and equivalence ratio. Definition of heating value; difference between higher heating value and lower heating value; calculation of the heating value as a weighted average; energy per unit volume. Energy balance in the combustion chamber.

Steam power plants: General aspects, operating principle and plant layout. Influence of lowering the condensation pressure on the thermodynamic efficiency of a steam power plant. Layout of a reheat steam power plant and T-s diagram. Layout of a steam power plant with three extraction points and T-s diagram. Heat balances in regenerative heat exchangers. Expression of the overall power output and efficiency.

Combined gas/steam cycles: Single-pressure-level combined cycle: plant layout, T-s diagram, expression of the power produced by the gas turbine and the power recovered in the heat recovery steam generator. Energy balances in the economizer, evaporator and superheater. Heat exchange diagram of the heat recovery steam generator. Expression of the overall efficiency of a combined cycle as a function of the gas turbine efficiency, the heat recovery steam generator effectiveness and the steam cycle efficiency.

Vapour-compression refrigeration systems: Plant layout and operating principle of a two-stage compression refrigeration system. Representation of the cycle on the pressure–enthalpy diagram and definition of the Energy Efficiency Ratio. Refrigerants and their environmental impact: Ozone Depletion Potential, Global Warming Potential and Total Equivalent Warming Impact.

For students enrolled in Chemical and Biochemical Engineering

MODULE 2
30 hours – Instructor: Prof. Saverio Ottaviano
Only for students enrolled in Chemical and Biochemical Engineering

Turbomachinery stages: The stage of a turbomachine. Equations of fluid motion in stationary ducts. Total quantities, speed of sound and flow regimes. Choking. Maximum mass flow rate and flow parameter. Hugoniot equations. Convergent and convergent–divergent ducts; h-s diagram. Euler equation for a turbomachinery stage. Kinetic energy difference equation. Degree of reaction. Impulse and reaction stages.

Axial steam turbines: Introductory concepts. Simple impulse De Laval turbine; two-row velocity-compounded turbine; pressure-compounded turbine; reaction turbine.

Gas turbine cycles with heat recovery: Layout and operating principle. T-s diagram. Heat exchange diagram in the recuperator. Limiting pressure ratio.

Organic Rankine Cycles: Plant layout, operating principle and T-s diagram. Working fluids and differences with respect to the water-steam Rankine cycle. Organic Rankine Cycle with heat recovery. Size range, performance and applications.

Reciprocating positive-displacement compressor: Indicator diagram and performance.

Centrifugal pump: Architecture and operating principle; characteristic curve.

Reciprocating positive-displacement pump: Layout and operating principle; indicator diagram and performance.

 

MODULE 2
30 hours – Instructor: Prof. Paolo Seri
Only for students enrolled in Environmental Engineering

Review of electromagnetism
Fundamental quantities of the electromagnetic field. Lorentz force. Electric polarization and magnetization. Electric displacement and magnetic field vectors. Constitutive relations of material media. Fundamental equations of electromagnetism.

Circuit theory
Lumped-parameter circuit model. Definition of electric circuit, node, branch and loop. Voltage and current. Passive and active sign conventions. Kirchhoff’s laws. Electric power and energy. Power balance.

Electrical components
Definitions and constitutive relations of two-terminal components. Linear resistor, inductor and capacitor. Series and parallel connections. Star and delta connections. Independent voltage and current sources. Real sources. Two-port networks and n-port networks. Controlled sources. Linearly coupled inductors.

Elements of graph theory
Graph associated with a circuit. Tree and cotree. Fundamental loops and fundamental cutsets. Independent cutset and loop equations.

Circuits with memory
Initial conditions and continuity of energy variables. Analysis of first-order transients in an RC circuit. Natural response and forced response. Time constant.

Sinusoidal steady-state operation
Periodic and sinusoidal quantities. Average value and root mean square value. Representation using complex numbers and phasors. Steinmetz transform and its properties. Transformation of Kirchhoff’s laws and constitutive relations into symbolic form. Symbolic method for the analysis of circuits in sinusoidal steady-state operation. Impedance and admittance. Impedance connections. Resonance and antiresonance.

Power in sinusoidal steady-state operation
Instantaneous, active, reactive, apparent and complex power. Power conservation theorem. Power factor. Effects of a low power factor on electrical lines. Power factor correction of ohmic-inductive loads.

Three-phase systems
Definitions and properties of symmetrical three-phase systems. Phase and line-to-line voltages. Balanced and unbalanced systems. Star and delta load connections. Three-phase systems with and without neutral conductor. Power in three-phase systems.

Magnetostatics and magnetic circuits
Properties of diamagnetic, paramagnetic and ferromagnetic materials. Hysteresis loop. Lumped-parameter magnetic circuits. Magnetic flux, magnetomotive force and reluctance. Hopkinson’s law. Hysteresis and eddy-current losses.

Single-phase transformer
Transformer electromotive force. Operating principle of the single-phase transformer. Ideal transformer and transformation ratio. Real transformer, leakage fluxes, winding resistances and core losses. Equivalent circuit and power balance.

Electrical systems and rotating machines
Introductory concepts on electrical energy generation. General structure of transmission and distribution systems. Voltage levels and role of power lines and transformers. Motional electromotive force. Operating principles of the direct-current machine, synchronous machine and induction machine. Rotating magnetic field, synchronous speed and slip. Introductory concepts on inverter-based drives and brushless machines.

Operation and control of electric power systems
Balance between generation and load. Relationship between grid frequency, number of poles and speed of synchronous machines. Effects of power imbalances on frequency.

Readings/Bibliography

For Fluid Machines T, and Energy Conversion ed Utilisation T - Module 1

"Sistemi Energetici" 1 – MACCHINE A FLUIDO, G. Negri di Montenegro, M. Bianchi, A. Peretto – Pitagora Editore

"Sistemi Energetici" 2 – COMPLEMENTI, M. Bianchi, F. Melino, A. Peretto – Pitagora Editore

"Sistemi Energetici" 3 – IMPATTO AMBIENTALE, M. Bianchi, A. De Pascale, A. Gambarotta, A. Peretto – Pitagora Editore

 

For Energy Conversion ed Utilisation T - Module 2 - Only for students enrolled in Environmental Engineering

-‘Circuiti elettrici’ di Charles K. Alexander, Matthew N. O. Sadiku

-‘Elettrotecnica: Principi e Applicazioni’ di G. Rizzoni

-'Elettrotecnica: elementi di teoria ed esercizi' di M. Repetto e S. Leva

- 'Elettrotecnica 1 e 2' di G. Chitarin, F. Gnesotto, M. Guarnieri, A. Machio, A. Stella

Teaching methods

Lectures and exercise sessions.

Assessment methods

For Fluid Machinery T and for Module 1 of Energy Conversion and Utilisation T:

The knowledge acquired by students will be assessed through a written test consisting of two parts, taken consecutively on the same day. The first part consists of a multiple-choice quiz administered through the EOL platform, while the second part consists of an open-ended question.

 

For Energy Conversion ed Utilisation T - Module 2 - Only for students enrolled in Environmental Engineering

The knowledge acquired by students will be assessed through an examination consisting of two parts, one written and one oral, taken consecutively on the same day.

Teaching tools

Slides and lecture notes prepared by the instructors will be made available on the Virtuale platform after each lecture.

Office hours

See the website of Saverio Ottaviano

See the website of Paolo Seri