302042 Heat Transfer
Teaching scheme : (hrs/week)
Lectures: 4
Practical: 2
Examination scheme
Paper: 100 marks
Practical: 50 Marks
Unit I
Introduction: Applications of Heat Transfer in different fields of engineering. Modes
of heat transfer, Fourier’s law of conduction, Newton’s law of cooling. StefanBoltzmann’s law of radiation. Isotropic and anisotropic materials. Three dimensional
heat conduction equation in Cartesian coordinate for anisotropic material for unsteady
state condition, thermal diffusivity and reduction to Fourier equation. Laplace
equation and Poisson’s equation. Three dimensional form of heat conduction equation
in cylindrical and spherical co-ordinates (no derivation).
One dimensional steady state heat conduction: - One dimensional steady state heat
conduction through a plane wall, cylindrical wall and sphere, Analogy between Heat
flow and electricity, heat conduction through a composite slab, cylinder and sphere,
overall heat transfer coefficient, Concept of thermal resistance and conductance,.
Unit II
Critical radius of insulation, thermal contact resistance. Economic thickness of
insulation.
Physical interpretation of Thermal conductivity and its variation with temperature for
metals, non metallic solids, gases and liquids. One dimensional problems of variable
thermal conductivity.
One dimensional steady state heat conduction with heat generation:Symmetrical and asymmetrical boundary condition in plane wall, Conduction in solid
and hollow cylinder and sphere. Practical problems of heat generation.
Unit III
Extended Surfaces: Heat transfer through extended surfaces .Fins of different
shapes. Derivation of differential equation for fins with constant cross section with
different boundary conditions. Effectiveness and efficiency of a fin. Error in the
measurement of temperature in a thermowell. Heat sinks- types and applications.
Unsteady state Heat Conduction: System with negligible internal resistance. Biot
and Fourier numbers. Criteria for neglecting internal temperature gradient.
Unit IV
Convection: Introduction to hydrodynamic and thermal boundary layer .Laminar and
turbulent flow over and inside a surface.
Convective heat transfer coefficients and their order of magnitude, Dimensional
analysis of free and forced convection. Physical significance of the dimensionless
parameters – Nusselt’s number, Reynold’s number, Prandtl’s number, Grashoff’s
number, Stanton number, Rayleigh number.
Forced convection: Empirical correlations for heat transfer in laminar and turbulent
flow over a flat plate and in a circular pipe .Concept of hydraulic diameter.
Natural convection: Empirical correlations for free convection heat transfer over
horizontal, vertical plate and cylinder.
Unit V
Thermal Radiation: Fundamental concepts, Black body radiation, Kirchoff’s law,
Planck’s distribution law, Wien’s displacement law and Stefan Boltzmann’s law.
Surface emission, radiative properties of a surface .Grey, black, white and real
surface. Solid angle and intensity of radiation, Lambert’s cosine law. Heat exchange
by radiation between two finite black surfaces .Radiation shape factor, use of shape
factor charts.
Irradiation, radiosity, electrical network method of solving problems.
Heat exchange between non-black bodies, Heat exchange between two infinitely
parallel planes, cylinders and spheres.
Radiation Shields, Gas radiation (elementary treatment only). Solar radiation.
Unit VI
Condensation and boiling: Film and drop wise condensation .Derivation of heat
transfer coefficient for Laminar film condensation on vertical and inclined plate,
correlations for condensation on and inside tubes.
Regimes of pool boiling and pool boiling curve and critical heat flux.
Forced Convection boiling.
Heat exchangers: Classification, Applications of heat-exchangers.
Heat Exchanger analysis – Logarithmic Mean Temperature Difference for parallel
and counter flow heat exchangers. LMTD correction factors, fouling factor.
The Effectiveness –NTU method for parallel and counter flow heat exchangers.
Design considerations for heat exchanger. Introduction to compact heat exchanger
and heat pipe heat exchanger.
List of Practicals:
The term Work shall consist of any “eight’ experiments out of the following:
Note: One of the experiments listed below must have computer interfacing.
1.
Determination of thermal conductivity of insulating powder
2.
Determination of thermal conductivity of metal rod.
3.
Temperature distribution through a composite wall.
4.
Temperature distribution along the length of a fin and determination of fin
effectiveness and fin efficiency.
5.
Natural convection heat transfer from a heated vertical cylinder.
6.
Heat transfer in forced convection for a pipe losing heat to air flowing through it.
7.
Determination of emissivity of a metal surface.
8.
Determination of Stefan-Boltzmann constant.
9.
Determination of critical heat flux in pool boiling.
10.
Performance of a parallel flow and counter flow heat exchanger.
Reference Books :
1. J.P. Holman, ”Heat Transfer”, McGraw hill.
2. Frank P Incropera, David P De Witt, (1990), “Fundamentals of Heat
Transfer”, Wiley, Eastern Limited.
3. Sachdeva, R.C,(1988),”Fundamentals of Engineering Heat and Mass Transfer
,Wiley Eastern Limited IIIrd Edition.
4. Sukhatme S.P.(1989), “A text book on Heat Transfer “,III rd Edition, Orient
Longmans Ltd,New Delhi.
5. Arora S C and Domkundwar.S. (1994),”A Course in Heat and Mass
Transfer”, Dhanpat Rai & Sons, IVth Edition.
6. Gupta and Prakash, (1994),”Engineering Heat Transfer”, Nemchand and
Brothers.
7. Karlekar & Desmond,”Principles of Heat Transfer “, Prentice hall of India
Ltd, New Delhi.
8. M. Necati Ozisik, “Heat Transfer”.