Focus

The course is focused on an advanced treatment of heat transfer and it is aimed at providing knowledge and know-how for the solution of heat transfer and thermal control problems, particularly for space applications.


Detailed description of the topics

1. Heat conduction.
The Fourier hypothesis and the thermal conductivity. The heat diffusion equation; initial-, boundary- and interface- conditions. Steady-state conduction: one-dimensional solutions; thermal resistances and equivalent circuits. Transient conduction: lumped-capacity solutions; analytical solutions in a semi-infinite medium with constant or periodic temperature boundary condition; thermal waves.

2. Convective heat transfer.
The governing equations, dimensionless version of the thermo-fluid dynamics equations and dimensionless groups of interest for convection. Free and forced convection in external flows: laminar and turbulent boundary layers, micro- and macro- scales, velocity profiles; some relevant heat transfer correlations for flows over flat plate, cylinders, spheres and bluff bodies. Forced convection inside ducts: the bulk temperature, the fully developed region and the Graetz problem; some relevant correlations for the friction factor and the heat transfer coefficient; the logarithmic mean temperature difference.
Boiling and condensation: evaporation; introduction to capillary and interface phenomena; metastable states; pool boiling, the boiling curve, critical and minimum heat fluxes, factors affecting the boiling curve; introduction to two-phase flow, forced-convection boiling inside tubes; film condensation on vertical flat plates and inside/outside tubes, dropwise condensation.

3. Radiative transfer.
Overview about radiation and radiation-matter interaction. Thermal radiation, radiation intensity, directional, spectral and total quantities, irradiation and radiosity. Blackbody radiation: Planck distribution, Stefan-Boltzmann law, Wien displacement law, band emission. Emission, absorption, reflection, transmission for real, diffuse and gray emitters; selective surfaces; Kirchhoff law. Radiation exchange between gray surfaces, view factors and their relationships, radiation exchange between gray surfaces in an enclosure. Radiation in gases: emission, absorption, scattering. Solar and environmental radiation.

4. Thermal analysis.
Introduction to thermal control. Operative and survival limits. Internal and external thermal sources. Heat sinks, cooling/insulating devices for electronic/space equipment: fillers, thermal bridges, cold plates, heat pipes, Peltier cells, coatings and clothing, primary and secondary surface mirrors, space radiators.

5. Thermal modeling.
Design of heat exchangers and extended surfaces. Lumped-capacity approach: arithmetic and diffusive nodes, mesh types, thermal resistances. Introduction to numerical methods and codes to solve thermal equivalent circuits for space applications; steady and transient multidimensional conduction by means of finite difference approximation, basic forms, explicit and implicit schemes, direct and iterative solving methods; FEM and FVM numerical codes; ray-tracing and Monte Carlo methods for radiation.

Course organization and exams

The course is structured in lessons, exercises and laboratories. Exercises are devoted to the solution of problems related to heat transfer analyses and thermal design, focused both on general applications and on space and propulsion topics. Laboratories are devoted to the use of suitable software for the solution of thermo-fluid dynamics problems.

Exams are scheduled only after the course end (no intermediate test is offered). They consist of a written test including theoretical questions and numerical exercises on the course topics.

The textbook can be dowloaded from the given Web page