The document describes heat conduction through plane walls, cylinders, and spheres under steady-state conditions. It introduces the concepts of thermal resistance, resistance networks, and one-dimensional heat transfer. Equations are presented to calculate heat transfer rates and temperature distributions based on thermal properties and surface temperatures for multi-layered systems with conduction and convection. Special cases like contact resistance and critical insulation thickness are also covered.
Heat transfer due to emission of electromagnetic waves is known as thermal radiation. Heat transfer through radiation takes place in form of electromagnetic waves mainly in the infrared region. Radiation emitted by a body is a consequence of thermal agitation of its composing molecules. The underlying mechanisms and the concepts involved are discussed in the ppt
Heat transfer due to emission of electromagnetic waves is known as thermal radiation. Heat transfer through radiation takes place in form of electromagnetic waves mainly in the infrared region. Radiation emitted by a body is a consequence of thermal agitation of its composing molecules. The underlying mechanisms and the concepts involved are discussed in the ppt
Introduction to transient Heat conduction, Lamped System Analysis, Approxiamate Analytical and graphical method and Numerical method for one and two dimensional heat conduction by using Explicit and Implicit method
heat conduction and its mechanisms ,thermal conductivity,Fourier law,variation of thermal conductivity with temperature in metals and solids,steady and unsteady states,biot and Fourier numbers and their significance, Lumped heat analysis
Lectures on Heat Transfer - Introduction - Applications - Fundamentals - Gove...tmuliya
This file contains Introduction to Heat Transfer and Fundamental laws governing heat transfer.
The slides were prepared while teaching Heat Transfer course to the M.Tech. students in Mechanical Engineering Dept. of St. Joseph Engineering College, Vamanjoor, Mangalore, India.
Recognize numerous types of heat exchangers, and classify them.
Develop an awareness of fouling on surfaces, and determine the overall heat transfer coefficient for a heat exchanger.
Perform a general energy analysis on heat exchangers.
Obtain a relation for the logarithmic mean temperature difference for use in the LMTD method, and modify it for different types of heat exchangers using the correction factor.
Develop relations for effectiveness, and analyze heat exchangers when outlet temperatures are not known using the effectiveness-NTU method.
Know the primary considerations in the selection of heat exchangers.
One dim, steady-state, heat conduction_with_heat_generationtmuliya
This file contains slides on One-dimensional, steady-state heat conduction with heat generation.
The slides were prepared while teaching Heat Transfer course to the M.Tech. students in Mechanical Engineering Dept. of St. Joseph Engineering College, Vamanjoor, Mangalore, India, during Sept. – Dec. 2010.
It is hoped that these Slides will be useful to teachers, students, researchers and professionals working in this field.
Introduction to transient Heat conduction, Lamped System Analysis, Approxiamate Analytical and graphical method and Numerical method for one and two dimensional heat conduction by using Explicit and Implicit method
heat conduction and its mechanisms ,thermal conductivity,Fourier law,variation of thermal conductivity with temperature in metals and solids,steady and unsteady states,biot and Fourier numbers and their significance, Lumped heat analysis
Lectures on Heat Transfer - Introduction - Applications - Fundamentals - Gove...tmuliya
This file contains Introduction to Heat Transfer and Fundamental laws governing heat transfer.
The slides were prepared while teaching Heat Transfer course to the M.Tech. students in Mechanical Engineering Dept. of St. Joseph Engineering College, Vamanjoor, Mangalore, India.
Recognize numerous types of heat exchangers, and classify them.
Develop an awareness of fouling on surfaces, and determine the overall heat transfer coefficient for a heat exchanger.
Perform a general energy analysis on heat exchangers.
Obtain a relation for the logarithmic mean temperature difference for use in the LMTD method, and modify it for different types of heat exchangers using the correction factor.
Develop relations for effectiveness, and analyze heat exchangers when outlet temperatures are not known using the effectiveness-NTU method.
Know the primary considerations in the selection of heat exchangers.
One dim, steady-state, heat conduction_with_heat_generationtmuliya
This file contains slides on One-dimensional, steady-state heat conduction with heat generation.
The slides were prepared while teaching Heat Transfer course to the M.Tech. students in Mechanical Engineering Dept. of St. Joseph Engineering College, Vamanjoor, Mangalore, India, during Sept. – Dec. 2010.
It is hoped that these Slides will be useful to teachers, students, researchers and professionals working in this field.
PERFORMANCE ANALYSIS OF GAS LUBRICATED CYLINDRICAL JOURNAL BEARING USING FS...Venkata Sai Teja Gunuputi
To choose the best suitable lubricant for different eccentricity ratio and L/D ratio combinations of journal bearings by considering the pressure, deformation and stress results obtained in analysis.
This file contains slides on One-dimensional, steady state heat conduction without heat generation. The slides were prepared while teaching Heat Transfer course to the M.Tech. students.
Topics covered: Plane slab - composite slabs – contact resistance – cylindrical Systems – composite cylinders - spherical systems – composite spheres - critical thickness of insulation – optimum thickness – systems with variable thermal conductivity
Numerical methods in Transient-heat-conductiontmuliya
This file contains slides on Numerical methods in Transient heat conduction.
The slides were prepared while teaching Heat Transfer course to the M.Tech. students in Mechanical Engineering Dept. of St. Joseph Engineering College, Vamanjoor, Mangalore, India, during Sept. – Dec. 2010.
Contents: Finite difference eqns. by energy balance – Explicit and Implicit methods – 1-D transient conduction in a plane wall – stability criterion – Problems - 2-D transient heat conduction – Finite diff. eqns. for interior nodes – Explicit and Implicit methods - stability criterion – difference eqns for different boundary conditions – Accuracy considerations – discretization error and round–off error - Problems
NUMERICAL METHODS IN STEADY STATE, 1D and 2D HEAT CONDUCTION- Part-IItmuliya
This file contains slides on NUMERICAL METHODS IN STEADY STATE 1D and 2D HEAT CONDUCTION – Part-II.
The slides were prepared while teaching Heat Transfer course to the M.Tech. students in Mechanical Engineering Dept. of St. Joseph Engineering College, Vamanjoor, Mangalore, India, during Sept. – Dec. 2010.
Contents: Methods of solving a system of simultaneous, algebraic equations - 1D steady state conduction in cylindrical and spherical systems - 2D steady state conduction in cartesian coordinates - Problems
This file contains slides on Transient Heat conduction: Part-I
The slides were prepared while teaching Heat Transfer course to the M.Tech. students in Mechanical Engineering Dept. of St. Joseph Engineering College, Vamanjoor, Mangalore, India, during Sept. – Dec. 2010. Contents: Lumped system analysis – criteria for lumped system analysis – Biot and Fourier Numbers – Response time of a thermocouple - One-dimensional transient conduction in large plane walls, long cylinders and spheres when Bi > 0.1 – one-term approximation - Heisler and Grober charts- Problems
Heat transfer from extended surfaces (or fins)tmuliya
This file contains slides on Heat Transfer from Extended Surfaces (FINS). The slides were prepared while teaching Heat Transfer course to the M.Tech. students in Mechanical Engineering Dept. of St. Joseph Engineering College, Vamanjoor, Mangalore, India.
Contents: Governing differential eqn – different boundary conditions – temp. distribution and heat transfer rate for: infinitely long fin, fin with insulated end, fin losing heat from its end, and fin with specified temperatures at its ends – performance of fins - ‘fin efficiency’ and ‘fin effectiveness’ – fins of non-uniform cross-section- thermal resistance and total surface efficiency of fins – estimation of error in temperature measurement - Problems
Study on Natural Convection in a Square Cavity with Wavy right vertical wall ...IOSRJMCE
In the present study, natural convection problem has been solved in a cavity having three flat walls and the right vertical wall consisting of one undulation and three undulations. The two vertical and bottom walls are cold walls maintained at a fixed temperature whereas the top wall is heated with spatially varying temperature distribution. Air has been taken as the working fluid with Pr =0.71. This problem is solved by SIMPLE algorithm with deferred QUICK scheme in curvilinear co-ordinates. A wide range of Rayleigh number (103 to 106 ) has been chosen for this study. For small Ra, the heat transfer was dominated by conduction across the fluid layers. With increase of Ra, the process began to be dominated by convection. In the presence of undulation the peak point of the heat rejection (negative local Nusselt number) in the right wall increases by 5.54% than left wall for Ra = 104 . The three undulations case had maximum heat transfer to the uppermost undulation compared to that of the one undulation case
GATE Mechanical Engineering notes on Heat Transfer. Use these notes as a preparation for GATE Mechanical Engineering and other engineering competitive exams. For full course visit https://mindvis.in/courses/gate-2018-mechanical-engineering-online-course or call 9779434433.
1. Heat and Mass Transfer: Fundamentals & Applications
Third Edition
Yunus A. Cengel
Chapter 3
STEADY HEAT CONDUCTION
2. STEADY HEAT CONDUCTION IN PLANE WALLS
Heat transfer through the wall of a house can be
modeled as steady and one-dimensional.
The temperature of the wall in this case depends
on one direction only (say the x-direction) and
can be expressed as T(x).
for steady operation
In steady operation, the rate of heat transfer
through the wall is constant.
Fourier’s law of
heat conduction
2
3. The rate of heat conduction through
a plane wall is proportional to the
average thermal conductivity, the
wall area, and the temperature
difference, but is inversely
proportional to the wall thickness.
Once the rate of heat conduction is
available, the temperature T(x) at
any location x can be determined by
Under steady conditions, the
replacing T2 by T, and L by x.
temperature distribution in a plane
wall is a straight line: dT/dx = const.
3
4. Thermal Resistance Concept
Conduction resistance of the
wall: Thermal resistance of the
wall against heat conduction.
Thermal resistance of a medium Analogy between thermal and electrical
depends on the geometry and the resistance concepts.
thermal properties of the medium.
rate of heat transfer electric current
thermal resistance electrical resistance
Electrical resistance temperature difference voltage difference
4
5. Newton’s law of cooling
Convection resistance of the
surface: Thermal resistance of the
surface against heat convection.
Schematic for convection resistance at a surface.
When the convection heat transfer coefficient is very large (h → ),
the convection resistance becomes zero and Ts T.
That is, the surface offers no resistance to convection, and thus it
does not slow down the heat transfer process.
This situation is approached in practice at surfaces where boiling
and condensation occur. 5
6. Radiation resistance of the
surface: Thermal resistance of the
surface against radiation.
Radiation heat transfer coefficient
Combined heat transfer
coefficient
Schematic for
convection and radiation
6
resistances at a surface.
7. Thermal Resistance Network
The thermal resistance network for heat transfer through a plane wall subjected to
convection on both sides, and the electrical analogy.
7
8. Temperature drop
U overall heat
transfer coefficient
Once Q is evaluated, the
surface temperature T1 can
be determined from
The temperature drop across a layer is
proportional to its thermal resistance.
8
9. Multilayer
Plane
Walls
The thermal resistance
network for heat transfer
through a two-layer plane
wall subjected to
convection on both sides.
9
11. THERMAL CONTACT RESISTANCE
Temperature distribution and heat flow lines along two solid plates
11
pressed against each other for the case of perfect and imperfect contact.
12. • When two such surfaces are pressed against each other, the peaks
form good material contact but the valleys form voids filled with air.
• These numerous air gaps of varying sizes act as insulation because
of the low thermal conductivity of air.
• Thus, an interface offers some resistance to heat transfer, and this
resistance per unit interface area is called the thermal contact
resistance, Rc.
12
13. The value of thermal
contact resistance
hc thermal contact depends on:
conductance • surface roughness,
• material properties,
• temperature and
pressure at the
interface
• type of fluid trapped
at the interface.
Thermal contact resistance is significant and can even dominate the
heat transfer for good heat conductors such as metals, but can be
disregarded for poor heat conductors such as insulations. 13
14. The thermal contact resistance can
be minimized by applying
• a thermal grease such as silicon oil
• a better conducting gas such as
helium or hydrogen
• a soft metallic foil such as tin, silver, Effect of metallic coatings on
thermal contact conductance 14
copper, nickel, or aluminum
15. The thermal contact conductance is highest (and thus the contact
resistance is lowest) for soft metals with smooth surfaces at high pressure. 15
17. Two assumptions in solving complex
multidimensional heat transfer
problems by treating them as one-
dimensional using the thermal
resistance network are
(1) any plane wall normal to the x-axis is
isothermal (i.e., to assume the
temperature to vary in the x-direction
only)
(2) any plane parallel to the x-axis is
adiabatic (i.e., to assume heat transfer Thermal resistance network for
to occur in the x-direction only) combined series-parallel
Do they give the same result? 17
arrangement.
18. HEAT CONDUCTION IN CYLINDERS AND SPHERES
Heat transfer through the pipe
can be modeled as steady
and one-dimensional.
The temperature of the pipe
depends on one direction only
(the radial r-direction) and can
be expressed as T = T(r).
The temperature is
independent of the azimuthal
angle or the axial distance.
This situation is approximated
in practice in long cylindrical
Heat is lost from a hot-water pipe to
pipes and spherical
the air outside in the radial direction,
containers.
and thus heat transfer from a long
pipe is one-dimensional.
18
19. A long cylindrical pipe (or spherical
shell) with specified inner and outer
surface temperatures T1 and T2.
Conduction resistance of the cylinder layer
19
20. A spherical shell
with specified
inner and outer
surface
temperatures T1
and T2.
Conduction resistance of the spherical layer
20
21. for a cylindrical layer
for a spherical layer
The thermal resistance
network for a cylindrical (or
spherical) shell subjected
to convection from both the
inner and the outer sides.
21
22. Multilayered Cylinders and Spheres
The thermal resistance
network for heat transfer
through a three-layered
composite cylinder
subjected to convection
on both sides.
22
23. Once heat transfer rate Q has been
calculated, the interface temperature
T2 can be determined from any of the
following two relations:
23
24. CRITICAL RADIUS OF INSULATION
Adding more insulation to a wall or
to the attic always decreases heat
transfer since the heat transfer area
is constant, and adding insulation
always increases the thermal
resistance of the wall without
increasing the convection
resistance.
In a a cylindrical pipe or a spherical
shell, the additional insulation
increases the conduction
resistance of the insulation layer
but decreases the convection An insulated cylindrical pipe exposed to
resistance of the surface because convection from the outer surface and
of the increase in the outer surface the thermal resistance network
area for convection. associated with it.
The heat transfer from the pipe
may increase or decrease,
depending on which effect
dominates. 24
25. The critical radius of insulation
for a cylindrical body:
The critical radius of insulation
for a spherical shell:
The largest value of the critical
radius we are likely to
encounter is
We can insulate hot-water or
steam pipes freely without The variation of heat transfer
worrying about the possibility of rate with the outer radius of the
increasing the heat transfer by insulation r2 when r1 < rcr.
insulating the pipes. 25