Heat Transfer |

1. Introduction

Concept
of heat transfer, Difference between the subject of “Heat Transfer” and
its parent subject “Thermodynamics”. Different modes of heat transfer -
conditions, convection, radiation.

2. Conduction

Fourier’s
law of heat conduction, coefficient of thermal conductivity, effect of
temperature and pressure on thermal conductivity of solids, liquids and
gases and its measurement.

Three-dimensional
general conduction equation in rectangular, cylindrical and spherical
coordinates involving internal heat generation and unsteady state
conditions. Derivation of equations for simple one dimensional steady
state heat conduction from three dimensional equations for heat
conduction though walls, cylinders and spherical shells (simple and
composite), electrical analogy of the heat transfer phenomenon in the
cases discussed above.

Equivalent
areas, shape factor, conduction through edges and corners of walls and
critical thickness of insulation layers on electric wires and pipes
carrying hotfiuids. Internal generation cases along with some practical
cases of heat conduction like heat transfer through underground
electrical cables, simple model of heat conduction through piston crown
and case of nuclear fuel rod with cladding. Influence of variable
thermal conductivity on conduction through simple cases of walls I
cylinders and spheres. Introduction to unsteady heat transfer, Newtonian
heating and cooling of solids; definition and cxplanation of the term
thermal diffusivity.

3. Theory of Fins

Straight
rod type of fins of uniform cross-section; e.g. of circular,
rectangular or any other cross-section). Straight fins with varying
cross-sectional area and having triangular or trapezoidal profile area,
circunerential find of rectangular cross section provided on the
circumference of a cylinder.

Optimum
design of straight find of rectangular and triangular profile
cross-sections; fin effectiveness and fin efficiency for straight rod
fins of rectangular and circular cross-section. Application of fins in
temperature measurement of flow through pipes and determination of error
in its measurement.

Convection
Free and forced convection, derivation of three-dimensional mass,
momentum and energy conservation equations (with introduction to Tensor
notations)

Boundary layer formation, laminar and turbulent boundary layers (simple explanation only and no derivation)

4. Theory of dimensional analysis as applied to free and forced convective heat

transfers

Analytical
formula for heat transfer in laminar and turbulent flow, flow over
vertical and horizontal tubes and plates. Newton’s law of cooling.
Overall coefficient of heat transfer. Different design criterion for
heat exchangers. Log mean temperature difference for evaporator and
condenser tubes, and parallel and counter flow heat exchangers.
Calculation of number and length of tubes in a heat exchanger.

Convection with Phase Change (Boiling and Condensation)

Pool
boiling, forced convection boiling, heat transfer during pool boiling
of a liquid. Nucleation and different theories of nucleation, different
theories accounting for the increased values of h.tc. during nucleate
phase of boiling of liquids; different phases of flow boiling (theory
only)

5. Radiation

Process
of heat flow, definition of emissivity, absorptivity, reflectivity and
trarismissMty. Concept of black arid grey bodies, Plank’s law of
non-chromatic radiation. Kirchoff’s law and Stefan Boltzmann law.
Interchange factor. Lambert’s Cosine law and the geometric factor.
Intensity of Radiation (Definition only), radiation density,
irradiation, radiosity and radiation shields..

Derivation
formula for radiation exchange between two bodies using the definition
of radiosity and irradiation and its application to cases of radiation
exchange between three or four bodies (e.g. boiler or other furnaces),
simplification of the formula for its application to simple bodies like
two parallel surfaces, concentric cylinders and a body enveloped by an
other body etc.

Error in Temperature measurement by a thermocouple probe due to radiation losses.

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