Tecnica del Freddo
Refrigeration Giovanni Di Nicola
Basic knowledge of Applied thermodynamics, Heat transfer, Fluidynamics.
KNOWLEDGE AND UNDERSTANDING:
The aim of the course is to enable students to acquire advanced knowledge on systems for the cold production and the foods storage. Such knowledge, integrated with the ones gained on the fundamentals of applied thermodynamics, heat transfer and fluid dynamics, will provide the insights that will increase the knowledge in the field of components and thermal systems by deepening the aspects specifically related to systems for the energy transformation, as well as the techniques for environmental impact assessment, so that the student could acquire a clear awareness of the wider multidisciplinary context of engineering, with a clear reference to the aspects specifically related to systems and technologies for the production, transportation and end-use of energy, and optimized design of components and energy systemsCAPACITY TO APPLY KNOWLEDGE AND UNDERSTANDING:
In order to address advanced design themes, even of considerable complexity, and treat the innovation and development of new products and new technological processes through the application of knowledge, the student will have to know how to design with optimization criteria the systems for the exchange and thermal energy conversion. This ability will be possible through a number of professional skills, such as: 1. ability to perform energy analysis on components and systems for the cold techniques; 2. ability to perform optimal choices in the design of systems for the cold production with particular attention to the foods storage aimed at saving energy and costs while minimizing environmental impact; 3. ability to apply alternative methods for the cold production also through the use of alternative energy sourcesTRANSVERSAL SKILLS:
The ability to solve numerical problems will help the student to improve the general degree of independence of judgment, the communication ability that comes from knowing his own skills, the ability to learn independently and to draw conclusions
Contents (42 hours).
Basic Thermodynamics. Reverse Carnot cycle. First and second Law efficiency. Thermodynamic charts. Vapour compression refrigerating cycle. Refrigerant fluids. Functional and environmental requirements for the working fluids. Synthetic and natural refrigerants. Application domains for the specific refrigerants. Liquid subcooling and suction superheating. Liquid/suction heat exchanger. Applicative limits of single stage cycles. Two stages cycles. Assessment of optimal intermediate pressure. Dual temperature cycles. Cascade cycles.
Main components for the vapour compression cycles. Dynamic and volumetric compressors; volumetric and isentropic efficiency. Modulation of the refrigaration capacity. Condensers and evaporators. Throttling valves.
Gas liquefaction. Linde cycle. Inversion temperature. Claude cycle.
Alternative reverse cycles. Absorption cycle: working fluids and their applicative domains; first law analysis. Air cycle. Adsorption cycle. Thermoelectric refrigeration.
Cooling Towers. The cold chain. Temperature influence in the deterioration of foodstuffs. Storage conditions for fresh products. Controlled atmosphere. Frozen and quick-frozen products. Assessment of freezing time. Freezing techniques. Thawing. Cold rooms. Thermal load of cold rooms.
Exercises (6 hours).
Exercises on the compressors. Design of cold rooms.
Development of the examination
LEARNING EVALUATION METHODS
The assessment of student learning consists of a test, consisting of a few questions of a theoretical nature and application regarding the topics covered in the course, to be completed in two hours. During the test the student is required to synthetically expose the theoretical basis and the main application topics of refrigeration.
LEARNING EVALUATION CRITERIA
To successfully pass the exam, the student must demonstrate, through the test described above, to have understood the concepts of refrigeration exposed during the course.
In particular, the student will have to know how to design with optimization criteria the systems for the exchange and thermal energy conversion. He will have to show the ability to perform energy analysis on components and systems for the cold techniques, the ability to perform optimal choices in the design of systems for the cold production with particular attention to the foods storage aimed at saving energy and costs while minimizing environmental impact, the ability to apply alternative methods for the cold production also through the use of alternative energy sources.
LEARNING MEASUREMENT CRITERIA
For each one of the questions of the test, it is assigned a score between zero and thirty. The overall grade, thirty, is the average of the marks obtained in the two tests, with rounding to the entire excess.
FINAL MARK ALLOCATION CRITERIA
Because the overall outcome of the evaluation is positive, the student must achieve at least eighteen points in the test described above. The highest rating is achieved by demonstrating a thorough understanding of the course content in the tests.
Lecture notes (available on-line at https://lms.univpm.it/enrol/index.php). Cavallini, L. Mattarolo, Termodinamica applicata, CLEUP, Padova, 1992; W.F. Stoecker, Industrial Refrigeration Handbook, McGraw-Hill, New York, 1998
- Ingegneria Meccanica (Corso di Laurea Magistrale (DM 270/04))