boiling heat transfer ppt and advanced heat transfer ppt and heat and mass transfer powerpoint slides
A Short Course on Heat Transfer
Intended as a repetition from previous courses
Royal Institute of Technology, Stockholm Course Contents,
based on Holman’s book Heat Transfer
Chapter 1: Introduction
Chapter 2: Steady-State Conduction - One Dimension
Chapter 3: Steady-State Conduction - Multiple Dimensions
Chapter 4: Unsteady-State Conduction
Chapter 5: Principles of Convection
Chapter 6: Empirical and Practical Relations for Forced-Convection
Chapter 7: Natural Convection Systems
Chapter 8: Radiation Heat Transfer
Chapter 9: Condensation and Boiling Heat Transfer
Chapter 10: Heat Exchangers
(Chapter 11: Mass Transfer)
2 Part 1
What is heat?
Heat is energy transfer caused by temperature difference
The four laws of thermodynamics:
• Zeroth law:
If two bodies both are in thermal equilibrium with a third
body, they are also in thermal equilibrium with each other,
and they then are said to have the same temperature.
• First law: (Energy principle)
Energy cannot be generated or destroyed, only converted to
(”Energy consumption” is the transfer of ”prime” energy to
thermal energy in the surrounding)
6 • Second law:
Heat cannot by itself pass from one body to another body
with higher temperature.
(Entropy disorder strives to a maximum in a closed system.
Shows the direction of time.)
8 Third law:
The entropy of a pure, crystalline material takes its lowest
value at absolute zero temperature, where it is 0.
(There is a lowest limit to the temperature, 0K = -273.15°C.
World record: 0.00000017 K = 170 nanokelvin)
9 Three modes of heat transfer:
Through solid bodies and ”still” fluids hot cold
Through moving fluids
(also boiling and condensation)
Between surfaces, through gas or vacuum
What do we know about conduction?
11 Conduction, thermal conductivity, Fourier´s law:
q = -k⋅A⋅δT/δx
where, q = heat flow (W)
A = area perpendicular to heat flow (m )
δT/δx = temperature gradient in the direction
of heat flow(°C/m)
k = thermal conductivity (W/(m °C))
Fourier´s law is the defining equation for the thermal
12 Conduction, thermal conductivity, Fourier´s law:
For one-dimensional heat transfer (a plane wall,) with
constant thermal conductivity, Fourier´s law is simplified to
q = k⋅A⋅ΔT/δ
where ΔT = temperature difference (°C)
δ = distance or thickness (m).
14 Fig. 2 Heat transfer through a plane wall
15 Table 1
Thermal conductivity (20°), (W/m⋅°C)
Diamond, type IIa 2600
Iron, wrought, 0.5% C 60
Stainless steel, 18/8 16.3
Pine wood, 0.15/0.33 (cross/along fibres)
Glass wool 0.038
Mineral wool 0.04
Argon gas 0.018
Example to solve:
Calculate the heat flow per square meter (heat flux) through a
mineral wool insulation, 5 cm thick, if the temperatures on the
two surfaces are 30 and 200°C, respectively.
17 Heat transfer by convection, Newton’s law of cooling
Convection is a general term for heat transfer through a
Fig 3, Different types of convection heat transfer
What do we know about convection?