The purpose of the study of Heat Transfer is to provide the initial background for the study of energy transport phenomena, which are becoming scientific and technological subjects of a growing concern and importance, not only for mechanical and electrical engineers but also in a broad range of different scientific disciplines. Among these vital disciplines are geophysics, meteorology and earth sciences as well as studies dealing with heat and pollutant dispersion in the biosphere. The study of Heat Transfer with an impressively expanding number of applications in the contemporary technology begins with the teaching of the basic physical principle that energy in the form of heat is transferred as a consequence of a temperature difference or under the effect of a temperature gradient, according to the pioneering work developed by Fourier. The aim of the program is to introduce and familiarise the undergraduate students with the three fundamental thermal energy transport processes  conduction, convection, and radiation, where the former represents a heat transfer process carried out in solid materials through diffusion phenomena under the influence of a temperature gradient. When conduction occurs within a fluid in motion the process becomes convective heat transfer, in absolute contrast with the radiative heat transfer which involves energy transfer phenomena caused by electromagnetic waves. The introduction of quantitative laws and mathematical models allows the students to proceed to simple and more advanced engineering calculations involving combined heat transfer phenomena occurring in practice, in various fields of energy technology like heat transfer from the building envelope, extensive use of heat exchangers for energy conservation applications, maximum current loading of power cables and lines etc.

Course Description 

Theory: Introduction to the fundamental heat transfer processes, Structure of matter and thermal conductivity, Multi dimensional and one dimensional heat transfer by conduction under steady state conditions, thermal resistance and U value of simple and composite plane wall structures, simple and composite cylindrical wall structures,  simple and composite spherical walls with convective boundary conditions, Optimum insulation thickness in cylindrical walls, thermal contact resistance and its influence on energy conservation. Transient heat transfer by conduction, the general three dimensional transient heat conduction equation with heat generation, Differential equations of Poisson, Laplace etc, Transient heat transfer applications and solutions using the Heisler Diagrams, Cooling fins, their importance and significance, Cooling fin design and calculations. Heat exchangers, their scope and taxonomy, Concentric tube, Shell and tube, Compact, Plate etc heat exchangers, Energy balance and calculation of heat exchangers using the Logarithmic mean temperature difference and the NTU methods. Natural and forced Convection, Physical interpretation of mechanisms and phenomena involved. The significance of dimensionless numbers and the development and significance of the thermal and hydrodynamic boundary layers. The calculation of the convective heat transfer coefficient for various forced and free convection characteristic cases and configurations. Thermal radiation, the concept of Black body, Laws of thermal radiation, Plank’s law, Stefan-Boltzmann’s and Wien’s laws. Radiative properties of real surfaces, Selective and Grey surfaces, spectral and total emissivity, absorptivity and reflectivity of real surfaces, Kirchhoff’s law. Radiative heat transfer between two surfaces, the definition and calculation of the View Factor, Net radiation heat exchange between any two surfaces, Equivalent sky temperature.

Laboratory: Following an extensive recent modification, the programme  is currently based on 16  laboratory exercises among which 12 different are selected for presentation during every teaching term. The laboratory exercises are properly designed for the two hours duration of the class and they are dealing with different objectives aiming to familiarise students on issues first dealing with the temperature measurement using both thermocouple and NTC thermistor temperature sensors. They also deal with the study of one dimensional transient conduction phenomena and the approach to steady-state condition, along with measurements of thermal conductivity of standard geometry metallic samples. Also the study of the conduction heat transfer through cylindrical walls, the measurement of the (free and forced) convective heat transfer coefficient based on the lumped capacitance method valid for Bi<<0.1. The study of steady-state heat balance of cylindrical and spherical heaters under the influence of combined conduction forced and free convective and radiative heat transfer. The programme also deals with the investigation of the heat balance and the study of the influence of various Heat Exchanger parameters on their operational behaviour and performance as well as involves various exercises aiming to study the Thermal Radiation laws and their effect on the radiative heat exchange between real surfaces.

All participating students are obliged to proceed into the class of the followimg week  having previously studied thoroughly the aim, the background theory and the procedure that will be followed by the exercise. During each class and following a brief outline of the procedure, practical measurements are carried out using the specific equipment of the laboratory exercise. The derived measurements are employed for the appropriate calculations aiming to derive results, plots and comments which are formally submitted at the end of the session or at maximum before the attendance of the subsequent exercise in the following week, as the required handouts for the evaluation of each participating student. At the end of the semester all the registered students should participate in a written evaluation test for the overall laboratory course. The final results are derived based on the combined effect of the overall performance during sessions and the score in the final evaluation test.

Expected Course Outcome

 

Bibliography

Greek:

1. Σημειώσεις από τις παραδόσεις του μαθήματος ΜΕΤΑΔΟΣΗ ΤΗΣ ΘΕΡΜΟΤΗΤΟΣ, Π.Θ.Τσιλιγγίρης, ΤΕΙ Αθήνας, 2007.
2. Σημειώσεις εργαστηρίου ΜΕΤΑΔΟΣΗΣ ΘΕΡΜΟΤΗΤΟΣ, Π.Θ.Τσιλιγγίρης, ΤΕΙ Αθήνας, 2005
3. ΜΕΤΑΦΟΡΑ ΘΕΡΜΟΤΗΤΑΣ, D.Pitts, L.Sissom, (Ελληνική μετάφραση σειρά Schaum, Έκδοση Τζιόλα,Θεσσαλονίκη, 2001.

English: