HEAT TRANSFER

IV YEAR I SEMESTER

AY: 2020-21
SYLLABUS:
Unit I
• Introduction: Modes and mechanisms of heat transfer – Basic laws of heat transfer –General discussion about
applications of heat transfer Conduction Heat Transfer: Fourier rate equation – General heat conduction
equation in Cartesian, Cylindrical and Spherical coordinates. Simplification and forms of the field equation
– steady, unsteady and periodic heat transfer – Initial and boundary conditions. One Dimensional Steady State
Conduction Heat Transfer: Homogeneous slabs, hollow cylinders and spheres – overall heat transfer coefficient
– electrical analogy – Critical radius of insulation, One Dimensional Steady State Conduction Heat Transfer:
Variable Thermal conductivity – systems with heat sources or Heat generation. Extended surface (fins) Heat
Transfer – Long Fin, Fin with insulated tip and Short Fin, Application to error measurement of Temperature.
Unit II
• One Dimensional Transient Conduction Heat Transfer: Systems with negligible internal resistance – Significance
of Biot and Fourier Numbers - Chart solutions of transient conduction systems- Concept of Functional Body
Unit III
• Convective Heat Transfer: Classification of systems based on causation of flow, condition of flow, configuration
of flow and medium of flow – Dimensional analysis as a tool for experimental investigation –Buckingham
Pi Theorem and method, application for developing semi – empirical non- dimensional correlation for
convection heat transfer – Significance of non-dimensional numbers – Concepts of Continuity, Momentum and
Energy Equations.
SYLLABUS:

• Forced Convection: External Flows - Concepts about hydrodynamic and thermal boundary layer and use of
empirical correlations for convective heat transfer -Flat plates and Cylinders. Internal Flows - Concepts about
Hydrodynamic and Thermal Entry Lengths
• Division of internal flow based on this –Use of empirical relations for Horizontal Pipe Flow and annulus flow.
• Free Convection: Development of Hydrodynamic and thermal boundary layer along a vertical plate – Use of
empirical relations for Vertical plates and pipes.

Unit IV
• Heat Transfer with Phase Change: Boiling: - Pool boiling – Regimes Calculations on Nucleate boiling, Critical Heat
flux and Film boiling. Condensation: Film wise and drop wise condensation – Nusselt’s Theory of Condensation
on a vertical plate - Film condensation on vertical and horizontal cylinders using empirical correlations.
• Heat Exchangers:
• Classification of heat exchangers – overall heat transfer Coefficient and fouling factor – Concepts of LMTD
and NTU methods - Problems using LMTD and NTU methods.

Unit V
• Radiation Heat Transfer: Emission characteristics and laws of black-body radiation – Irradiation – total and
monochromatic quantities – laws of Planck, Wien, Kirchoff, Lambert, Stefan and Boltzmann– heat exchange
between two black bodies – concepts of shape factor – Emissivity – heat exchange between grey bodies –
radiation shields – electrical analogy for radiation networks.
Course Outcomes:
• At the end of the course, the student will be able to

CO 1: Identify the mode of heat transfer and formulate the equation to calculate
temperature distribution.

CO 2: Compute the amount of heat dissipation during transient heat conduction using
lumped system/charts.

CO 3 : Calculate the rate of heat transfer by convection in the boundary/ potential flow regions

CO 4: Identify the heat exchanger required to transfer sensible/ latent heat between two fluids

CO 5: Interpret the concepts of radiation heat transfer between two bodies.

• Text Books:

1. Fundamentals of Engineering Heat and Mass Transfer, R.C. Sachdeva, 4th

Edition, New Age International, 2009.

2. Heat Transfer, P.K. Nag, 3rd Edition, TMH, 2012.

• References:
1. Heat Transfer, P S Ghoshdastidar, 2nd Edition, Oxford Higher
Education/Oxford University Press, 2012.
2. Heat and Mass Transfer: Fundamentals and Applications, Yunus A Cengel
and Afs Ghajar, 5th Edition, McGraw-Hill Education, 2015.
3.Heat and Mass Transfer, R.K. Rajput, S. Chand & Company Ltd., 1998.
Difference between Thermodynamics and Heat transfer
 Heat: The form of energy that can be transferred from one system to
another as a result of temperature difference.

 Thermodynamics is concerned with the amount of heat transfer as a

system undergoes a process, from one equilibrium state to another.

 Heat Transfer deals with the determination of the rates of such

energy transfers as well as variation of temperature.
• The transfer of energy as heat is always from the higher temperature
body to the lower-temperature body.

• Heat transfer stops when the two bodies reach the same
temperature.

• Heat can be transferred in three different modes:

Conduction
Convection
Radiation.

Note: All the three modes may occur simultaneously in practical life.
Applications of Heat Transfer
1. Many commonly used house appliances like:
• Air conditioning systems
• Refrigerators
• Water heater
• Iron box
• Computer, TV

• 2. Design of many Industrial devices like:

• Heat exchangers
• Boilers
• Condensers
• Furnaces
• Solar collectors
• IC Engines
3. Design of cooling systems for electric motors, generators and transformers

4. Energy efficient homes: Minimizing heat loss in winter and heat gain in
summer

5. Optimal insulation thickness in wall and roofs of the houses

6. Optimal insulation thickness of hot water and steam pipes.

7. Heating and cooling of fluids in chemical operations

8. Heat transfer application to human body:

The human body must maintain a consistent internal temperature in order to maintain
healthy bodily functions. Therefore, excess heat must be dissipated from the body to keep
it from overheating.
Conduction:

The transfer of energy from the more energetic particles of a

substance to the adjacent less energetic ones as a result of
interactions between the particles.

In gases and liquids, conduction is due to the collisions and diffusion
of the molecules during their random motion.

 In solids, it is due to the combination of vibrations of the molecules

in the lattice and the energy transport by free electrons.
Convection:
• The mode of energy transfer between a solid surface and the adjacent
liquid or gas that is in motion, and it involves the combined effects of
conduction and fluid motion.

• The faster the fluid motion, the greater the convection heat transfer.

• In the absence of any bulk fluid motion, heat transfer between a solid
surface and the adjacent fluid is by pure conduction.
Radiation:

• The energy emitted by matter in the form of electromagnetic waves

• Unlike conduction and convection, the transfer of heat by radiation does

not require the presence of an intervening medium.

• In fact, heat transfer by radiation is fastest (at the speed of light) and it
suffers no attenuation in a vacuum. This is how the energy of the sun reaches
the earth.

• In heat transfer studies, we are interested in thermal radiation, which is the

form of radiation emitted by bodies because of their temperature.