31393 - Fluid Mechanics and heat transfer

Learning outcomes

The aim of the Course is to provide a basic knowledge of fluid mechanics and heat transfer, in view of subsequent applications to the design of energy conversion, energy transfer and energy control systems.

Course contents

Fluid Mechanics

Basic definitions. Laminar flow and turbulent flow. Dynamic boundary layer. Viscosity. Newtonian and non-Newtonian fluids. Stresses in a flowing fluid. Time derivative and substantial derivative. Local mass balance equation. Local momentum balance equation. Fully developed laminar flow with constant density in a parallel-plane channel and in a circular tube. Flow with constant density past a cylinder or a sphere, drag coefficient. Integral equation of mechanical-energy balance. Head losses. Friction factor. Moody diagram. Measurements of velocity and of flow rate.

 

Heat conduction

Fourier law. Fourier equation. Steady heat conduction without generation in plane, cylindrical and spherical geometry. Thermal resistance, thermal resistances in parallel and in series. Heat equation. Example of steady heat conduction with generation, in cylindrical geometry. Measurement of thermal conductivity.

 

Heat convection

Forced, mixed and natural convection. Local equations of mass, momentum and energy balance. Boussinesq approximation. Convection coefficient and Nusselt number (Nu). Dimensionless equations of mass, momentum and energy balance. Reynolds number (Re), Grashof number (Gr), Prandtl number (Pr). Existence of a relation Nu = Nu(Re, Gr, Pr) for mixed convection. Thermal boundary layer. Forced convection: existence of a relation Nu = Nu(Re, Pr), special cases, examples. Natural convection: existence of a relation Nu = Nu(Gr, Pr), special cases, examples.

 

Heat radiation

Definitions. Black body. Laws of Kirchhoff, Stefan-Boltzmann, Planck, Wien, Lambert. Grey body. Radiation heat transfer between black bodies and grey bodies. Non-grey bodies. Radiation coefficient.

 

Composite heat transfer problems

Overall thermal resistance and overall heat transfer coefficient. Examples in plane and in cylindrical geometry. Heat exchangers: plots of fluid temperatures and logarithmic mean temperature difference for coaxial-tube heat exchangers; other kinds of heat exchanger; effective temperature difference; efficiency of a heat exchanger; examples of sizing and verifying heat exchangers.

Readings/Bibliography

1) E. ZANCHINI: DISPENSA DI MOTO DEI FLUIDI E TERMOCINETICA L, PER INGEGNERIA ENERGETICA.

Copies available at: Biblioteca della Facoltà di Ingegneria.

 

2) S. LAZZARI, B. PULVIRENTI, E. ROSSI DI SCHIO: “Esercizi risolti di Termodinamica, Moto dei Fluidi e Termocinetica” (Esculapio, Bologna, 2006)

Teaching methods

Lectures in classroom with the aid of audiovisual devices; exercises in classroom; discussions in classroom; measurements in the laboratory.

Assessment methods

The assessment method is an oral examination which includes the discussion of a topic of the theory and an exercise.

Teaching tools

Audiovisual systems; laboratory of Fluid Mechanics and Heat Transfer, Department DIENCA, Via Terracini 34

Office hours

See the website of Enzo Zanchini