This module consists of two organically integrated components: (a) a comprehensive and rigorous treatise of heat conduction, convection and radiation, the three basic modes of heat transfers; and (b) modern engineering applications of heat transfer.
Part I: Fundamentals
1.1 Introduction:
1.2 Heat conduction:
a. Simple 1d steady state: from Fourier’s law to differential equation, infinite slab and other 1d geometries (thin wire/rod, cylinder and sphere), boundary conditions and boundary value problems, nonlinear conduction and composite materials, equivalent circuits, thermal resistances including convection boundary condition, critical radius of cooling/heating;
b. Heat diffusion equation and applications: derivation, introduction to 3d and transient conduction, longitudinal and radial conduction with heat generation, extended surface and fin optimisation;
c. Transient heat conduction: qualitative behaviour and the influence (Biot number) of boundary conditions and material properties, lumped heat capacity analysis (characteristic length, criterion, time constant of cooling), analytical solution of transient heat conduction by separation of variables for general temporal solution (thermal diffusivity, Fourier number and time constant of diffusion) and specific spatial solution in 1d slab with mixed boundary conditions), extension to cylinder and sphere and approximate forms (Heisler’s charts and one-term solutions);
d. Numerical solutions: finite difference schemes for transient 1d and steady state 2d with implementation in Matlab, problem solving in Ansys.
1.3 Convection
a. Concept of boundary layer and flow over flat plate: similarity (Prandtl number) between hydraulic (part II fluid) and thermal boundary layers, Reynolds’ integration, temperature profile and heat transfer coefficient, boundary layer development over flat plate and Nusselt number correlations;
b. External flows: differences streamlined and bluff bodies, heat transfer by flow across a cylinder and sphere, correlations for various geometries and configurations;
c. Internal flow: fully developed laminar flow in a circular pipe (temperature profile, definition/calculation of bulk average temperature, heat transfer coefficient and pressure drop, Nusselt correlations), non-circular pipes and enhancement of heat transfer by narrow channels, boundary conditions (uniform heat flux or constant temperature on the tube wall), turbulent flow, entry zone;
d. Free convection: driving force and Grashof/Raleigh number, boundary layer of free convection, correlations;
e. Condensation and boiling: laminar condensation film, pool boiling characteristics (convection, nuclear and film boiling).
1.4 Radiation
a. Blackbody radiation: general characteristics (Wien’s displacement law) and Stephan-Boltzmann law;
b. Heat exchange between two bodies at different temperature: thermal equilibrium of a radiation body (radiation, reflection, transmission), solid angles and viewing factor.
Part II Applications
2.1 Heat exchangers
a. Type of heat exchangers and overall heat transfer coefficient;
b. Log-mean temperature differences: concentric tube heat exchange, parallel and counter flows and temperature profiles along the flow, correction factors for other types (multi-pass tube-shell, cross-flow);
c. Effectiveness ε of heat exchangers and the ε-NTU method: maximum possible heat transfer and effectiveness, ε-NTU relation for concentric tube heat exchangers, other types of heat exchangers, comparison of heat exchanger performances;
d. Sizing and rating problems: Independent variable and typical heat exchanger problems, methodology using forward and inverse ε-NTU relations;
2.2 Thermal management of electronic components and equipment:
a. Electronics cooling specifics: Heat transfer at different length scales from chips to system, non-uniform and non-steady heat generation, high heat flux and low temperature excursion;
b. Cooling of micro-chips: conduction and heat dispersion at micro-scales, material properties and chip design/packaging, transient heat load and thermal stress;
c. Heat flux and thermal management strategy for electronic equipment: selection of cooling method (effectiveness, cost and environment), optimal distribution of components/units and routing for forced flow;
d. Management of very high heat flux (>50 W cm–2): liquid cooling, heat pipes.
2.3 Heat transfer in energy systems:
a. Heat recovery and steam generators: Recuperation, boiler efficiency and selection of the pinch-point;
b. Combustors and turbines: Radiation from flames; film and effusion cooling technology for combustor walls and for turbine blades;
c. Cryogenic heat transfer.