The subject aims to present and discuss some advanced topics in the field of engineering thermodynamics and heat transfer. Both theoretical and applied aspects are considered. In particular, modeling and numerical methods are presented and applied to relevant systems in engineering thermodynamics. This course is designed to broaden the student’s background required for the analysis and design of real systems and devices involving fluid flow and heat transfer phenomena.

Knowledge of the physical, technical and design aspects of some typical energy systems. Basic knowledge of the design aspects of fluid distribution networks and steam generators. Knowledge of the numerical techniques that can be applied for modeling fluid networks. Knowledge of the numerical techniques for the analysis of energy systems involving radiation heat transfer Knowledge of the numerical techniques for the optimization of energy components Ability to calculate the energy demand of a building and the energy provided by the heating system and equipment. Ability to implement the numerical techniques necessary to model fluid distribution network. Ability to implement a numerical model for the description of radiative heat transfer in engineering systems

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

Generality. The subject is structured on theoretical lessons and practical applications. In particular, a district heating system (pipe network + thermal plant + thermal storage system) is considered as the application of the numerical methods that are introduced. The first part of the course is focused on the simulation and optimization of energy components using continuum mechanics. The a pplication to relevant energy components, such as heat exchangers, Thermal storage units, etc. is proposed using a commercial software. The second part of the course is focused on fluid distribution networks. On the basis of conservation equations introduced in previous courses fluid distribution networks are theoretically characterized. Computational techniques are introduced to numerically solve the fluid dynamic and thermal problems typical of a fluid distribution network. Then the student is required to apply the methods illustrated during the lectures to a district heating network. In the last part of the subject , convection and radiation heat transfer are considered. Radiation exchange between gray bodies and radiative behavior of participating media, such as gases, are presented. The zonal model is presented as numerical technique to solve radiative heat transfer problems involved in engineering systems. An application of the zonal model to a steam generator is proposed. In such analysis both convective and radiative heat transfer are numerically modeled in order to compute the temperature field in the system and the radiative heat transfer rate. Topics. Introduction to the subject. Introduction to numerical techniques and its relevance in the field of the field of engineering thermodynamics. Radiative exchange between gray surfaces. Net radiative heat flux. Introduction to radiative heat transfer: geometrical definitions, emitted radiation, incident radiation, interaction between radiation and matter. Black and gray body concepts. Radiative heat transfer between black surfaces. Introduction to zonal model and radiative heat transfer in a cavity of grey surfaces. Total interchange areas and adiabatic surfaces. Radiative heat transfer in the presence of a participating media. Gas-surface and surface-surface radiative exchange. Real gas model and direct flux surfaces. Energy balances. Recall of the continuum mechanics. Continuity, momentum and energy equations. Initial and boundary conditions. One dimensional form of the equations. Introduction to networks. Numerical models for the analysis of fluid distribution networks. Constrains, objectives, type of problem and methodologies involved in the analysis of typical real networks. Graph theory and mono-dimensional models of complex systems. Topological model, branch and node concept. Definition of graph, tree, co-tree, cut-set and loop. Incidence matrix an major topological correlations. Physical models and conservation equations. The steady-state fluid dynamic problem for a fluid distribution network. SIMPLE algorithm for the solution of the fluid-dynamic problem. Upwind method for the solution of the thermal problem.

During an application to a district heating system is proposed to the students. The application is composed of various parts, each corresponding to the application of a numerical method to a portion of the system. The first part concerns the revision of continuum mechanics (conservation equations, boundary and initial conditions). The aspects related with numerical implementation are also discussed. In addition, the use of optimization approaches for the design of energy components is discussed. The application to relevant energy components is proposed. Second part consists in the detailed design of a waste-to-energy cogeneration system which supplies heat to the network. A numerical model is developed to study the combustion process and the heat transfer phenomenon taking place in the system. Specifically the zonal model is used to model radiative heat transfer in the combustion chamber considering the interaction between radiation and combustion products. The results are then compared with those obtained applying a continuum model implemented through a commercial software. Then the analysis of the heat recovery steam generator is performed. Possible advantages in integrating a thermal storage unit are also examined Last part of the practice consists in the design of a district heating network. The problem consists in the choice of pipe diameters and the evaluation of mass flow rates and pressure drops along the network. Two configurations of the network are examined.

A textbook covering the program of the course is available. Notes of the lectures available online on the "Portale della Didattica". Textbooks: A. Sciacovelli, V. Verda, R. Borchiellini. Numerical Design of Thermal Systems, Clut, 2015 A. Bejan, "Advanced Engineering Thermodynamic" John Wiley & Sons 1997. F.P. Incropera, D.P. DeWitt, Fundamentals of Heat and Mass Transfer, John Wiley & Sons, 2002. H.C. Hottel, A. F. Sarofim. "Radiative Transfer" McGraw – Hill, Inc. 1967. M. F. Modest, "Radiative heat transfer" Academic Press 2003. R. Siegel, J.R. Howell, "Thermal radiation heat transfer". CRC Press, 1992.

Modalità di esame:

Exam:

... The exam consists of three parts: 1) evaluation of the practices (this part contributes for about 40% to the final mark). This part aims at providing the students the opportunity to apply the theoretical aspects to real engineering problems; 2) written exam based on the theoretical aspects discussed during the course and their applications to the proposed application. The written exam is composed by 4 questions (two on theoretical aspects and two on the practices) and lasts about 2 hours. Text or notes are not allowed during the exam. This part aims at checking the specific knowledge and abilities of the students; (this part contributes for about 50% of the final mark); 3) an optional oral integration mainly with the aim of integrating the evaluation provided by the written exam and check both theoretical knowledge and the ability to apply these concepts to practical cases (this part contributes for about 10% to the final mark). The oral exam lasts about 20 minutes.

Gli studenti e le studentesse con disabilità o con Disturbi Specifici di Apprendimento (DSA), oltre alla segnalazione tramite procedura informatizzata, sono invitati a comunicare anche direttamente al/la docente titolare dell'insegnamento, con un preavviso non inferiore ad una settimana dall'avvio della sessione d'esame, gli strumenti compensativi concordati con l'Unità Special Needs, al fine di permettere al/la docente la declinazione più idonea in riferimento alla specifica tipologia di esame.