Learning objectives
Knowledge and understanding:
Development of the ability to design and select the fluid machinery used in food industries.
Applying knowledge and understanding:
The student should be able to set the design of fluid machinery
Making judgments:
At the end of the course, the student should be able to evaluate, with critical mind, the best solutions in the field of fluid machinery used in the food industry.
Communication skills:
The student should be able to clearly present the knowledge acquired by the course.
Prerequisites
Course unit content
The purpose of the course is to present a review of the main fluid machines which found applications in the food industries.
Full programme
Presentation of the course.
Mass balance. Energy equation of fluid motion in enthalpy and mechanical form for fixed and mobile observer. Equation of conservation of momentum.
Work in turbomachinery. The speed triangles. The Euler equation.
The architecture of centrifugal pumps. The work of the impeller in centrifugal pumps. The losses. The characteristic curve of the pump. Hydraulic, mechanical and total efficiency.
The similarity in turbomachinery.
Choice of pumps. Operating point: characteristic curve of the pump and the circuit. Priming. Cavitation. NPSH required and NPSH available: effect of fluid temperature. Pumps in series and in parallel.
Architecture of axial pumps, the work of the impeller and the law of the free vortex. Speed triangles at the hub and tip of an axial pump blade.
Positive displacement pumps.
Correction of the performance of a turbopump as a function of the viscosity of the fluid for high viscosity Newtonian fluids and for non-Newtonian fluids.
Fan architectures and performances.
Elements of gasdynamics. Total thermodynamic properties. Mass balance equation for compressible fluids. Motion in simply convergent and convergent-divergent nozzles.
Compressors. Turbocompressors. Analysis of thermodynamic transformations in an axial compressor stage. Characteristic indices of turbocompressors.
Dimensionless performance maps of turbocompressors (psi vs phi, psi_p vs phi, eta vs phi).
Dimensional performance maps (compression ratio vs correct flow rate with reduced speed parameter).
Stall, surge and choking.
Positive displacement reciprocating compressors: representation of real transformations on p-V diagram. Clearance volume and limiting compression ratio. Intercooling.
Positive displacement rotary compressors. Internal compression and external compression.
Performance maps of reciprocating compressors and regulation strategies.
Steam generators: historical evolution and scheme of the radiant boiler. Analysis of the radiant boiler (configuration of the exchangers and wall temperature, effect of irradiation, heat exchange diagram). Graphic method for determining the fictitious average combustion temperature. Direct and indirect method for calculating the efficiency of the steam generator.
Bibliography
Dossena, Ferrari, Gaetani, Montenegro, Onorati, Persico - Macchine a fluido - Città studi Edizioni
For further information:
Sistemi energetici e macchine a fluido / Giorgio Negri di Montenegro, Michele Bianchi, Antonio Peretto
Bologna: Pitagora, 2009
Acton O. & Caputo C. - Collana di Macchine a fluido, 4 voll.- UTET, Torino
These books are all available in the University library.
Teaching methods
Frontal lectures.
Educational material will be periodically uploaded to the Elly platform to support the lessons and to deepen their contents.
To access these contents (which are an integral part of the course) it is necessary to register for the on-line course.
Assessment methods and criteria
The exam consists of
- a written test consisting of a numerical exercise and five structured questions;
- an oral test consisting of two questions.
Admission to the oral test is subject to passing the written test.
The written test is passed if the exercise is correctly solved and a minimum score of four is obtained in the structured questions.
Other information
Some numerical exercises are presented.
Lectures attendance is highly recommended.
Non-attending students are invited to consult the Elly platform on which the topics actually presented in class will be periodically listed.
