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Tecnica del Freddo
Refrigeration
Giovanni Di Nicola

Seat Ingegneria
A.A. 2015/2016
Credits 6
Hours 48
Period II
Language ENG

Prerequisites
Basic knowledge of Applied thermodynamics, Heat transfer, Fluidynamics.

Learning outcomes
At the end of the course the student should know: -inverse thermodynamic cycles; -the phenomenology of components and systems for achiving temperatures below the ambient temperature; -the main methods for the technical-economic design and the evaluation of cooling systems and their components; -the main technologies alternative to vapor compression refrigeration; -the tecniques used for food storage; -the main methods for the technical-economic design and for the evaluation of systems for food storage and their components ; -the main technologies for cryogenics.

Program
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. Magnetic refrigeration. Thermoacustic refrigeration. Geothermal energy. 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. Insulation materials. Mathematical model for the evaluation of equivalent thermal conductivity. Poliurethans. Optimum insulation thickness. Cold rooms. Thermal load of cold rooms. Refrigerated transports.

Development of the examination
LEARNING EVALUATION METHODS
The assessment of student learning consists of a written 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.

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.

LEARNING MEASUREMENT CRITERIA
For each one of the questions of the written 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.

Recommended reading
Lecture notes (available on-line). Cavallini, L. Mattarolo, Termodinamica applicata, CLEUP, Padova, 1992; W.F. Stoecker, Industrial Refrigeration Handbook, McGraw-Hill, New York, 1998

Courses

• Ingegneria Meccanica (Corso di Laurea Magistrale (DM 270/04))