The course aims to broaden some of the topics developed in thermodynamics and heat transfer that are used for the design of thermal systems as distribution networks, heat generators (boilers, combustion chambers and waste-to-energy plants). Both theoretical and application aspects are considered, as well as the techniques for numerical analysis.
Large part of the course is focused on the design of combustion systems, in particular the boilers. For these systems, the possible configurations are considered, with the aim to discuss the thermal, mechanical, technological, environmental, economic and safety aspects. The energy balance, the efficiency and the possible losses are discussed, depending on the nominal load and the control operation. Practical examples are introduced to evaluate the performances and costs. A mathematical model able to relate the energy performances and the control parameters is also presented.
From the theoretical viewpoint, the radiation heat transfer is analyzed in detail. In particular, the grey body hypothesis and the participation of gases to the radiation heat transfer are presented. The zone method is used as a numerical technique for such problem. This method is widely used in the analysis of boilers. The proposed application consists in the numerical design of a fire tube boiler. This consists in the thermal analysis of the fire tubes, where the convection and radiation heat transfer occur. In addition, the hotbed is analyzed using the zone method.
Once the production of process fluids is considered, their distribution is considered. The design and operation of fluid networks are proposed. Starting from the governing equations (mass, momentum and energy), that are recalled, the fluid dynamic and thermal problems are formulated and a numerical solution is proposed. An application to a district heating network is proposed in order to allow the student the familiarization with the nodal technique.

The student is expected to know the technical, economic and environmental aspects if the main industrial thermal plants and the characteristic issues in the design process related with the system complexity and the physical phenomena that occur in these plants. In addition, the student should know the numerical techniques that are used for the design of thermal plants, as the fluid networks and steam generators.

The prerequisites for this course are the subjects on thermodynamics and heat transfer, chemistry and advanced engineering thermodynamics.

Introduction to the course.
Primary Energy use in Italy and in the World. Environmental impact of the primary energy use. Reduction of the environmental impact. General model for a combustion plant. Energy and continuity equation. Main characteristics of the process fluids. Gas turbines, combined cycles, cogeneration plants. Description of the various types of boilers: superheated water, oil, hot water. Combustion chambers and waste-to-energy plants. Calculation of losses and efficiencies. Control systems. Relation between efficiency, losses, load and control. Calculation of the nominal performances and seasonal efficiency. The completely mixed reactor model and its application.
Main concepts related with radiation heat transfer: geometrical quantities, emission, incidence radiation, interaction between radiation and materials, Beer’s law, black body, emissivity, gray body. Heat transfer between black bodies. Direct exchange surface. Heat transfer between gray bodies. Net heat transfer between surfaces.
The zone method and the radiosity in a gray surface cavity. The total heat transfer surface. Heat transfer with gray participating medium. Heat exchange between surfaces, gases, gas and surface. Participating real gases. The total energy balance.
The concept of network. Models and methods for the analysis of real system through the application of numerical models. Models for network: constraints, objectives, typo of problem, calculation method. The graph theory and the one-dimensional analysis of complex systems. Topological model. The nodes and branches. The incidence matrix. The main topological relations. The physical model. Fluid dynamic and thermal analysis.

Monographic reports on the use of gaseous fuel and heat recuperators are proposed to the students. In addition two applications are proposed to the students. These are focused on the application of the theoretical aspects to two design problems.
The first application is focused on the design of a steam generator. This consists in the application of the numerical approach to the analysis of the combustion, the temperature distribution in the combustion chamber and the fire tubes, considering both the radiation and convection heat transfer. Different detail levels will be considered for the radiation heat transfer. The design of the necessary fan is also proposed.
The second application consists in the design of a district heating network. The design problem consists in the choice of the pipe diameters and the adjustment of the valves required to supply the necessary heat load to the users. In addition, the simulation of a looped network is proposed in order to analyze the advantages with respect to a tree configurations.
In the laboratory, the evaluation of the efficiency of a boiler using the direct and indirect methods is proposed. Two technical visits to a company producing thermal plants and to a power plant are proposed.

The notes constitute the main material for the exam. The slides used at the lessons will also available on the website of the course.
As for the reference textbooks:
Borchiellini R., Caĺ M., Torchio M., Fisica Tecnica, Esercitazione di Termocinetica. Politeko.
Hottel Sarofin, Radiative transfer. New York : McGraw-Hill, 1967.

The exam is in the oral form and it is based on the theoretical aspects and the proposed application.
A written report is requested for the proposed applications.