2.1 Explain the physical mechanisms governing thermal diffusion? 2.2 Heat transf
ID: 2116781 • Letter: 2
Question
2.1 Explain the physical mechanisms governing thermal diffusion?
2.2 Heat transfer problems are classified according to the variables influencing temperature. Briefly explain the following in terms of heat transfer and temperature:
a. Transient
b. Steady-state
c. One-dimensional
d. Three-dimensional
2.2.1 Explain the physical meaning of each term in equation 2.6.
2.2.2 Define the physical meaning of the Fourier number. What is its use in heat transfer analysis?
2.3.1 Define a plane wall, and then explain how to reduce the conduction equation for a plane wall without heat generation. Detail reasoning behind elimination of any terms.
2.3.2 Using Example 2.2 as a starting point, explain how the conduction resistance equation changes for cylindrical coordinates and provide a brief explanation as to why.
2.3.3 Mathmatically, how does the presence of heat generation affect the complexity of the conduction equation solutions?
2.4.1 Explain how a fin enhances heat transfer.
2.4.2 Describe two different types of fins and what resources you would use to evaluate them. Be specific.
Explanation / Answer
The primary mechanism behind diffusion is the thermal gradient leading to density gradient and hence movement of particles.
Thermal diffusion is the thermal motion of all (liquid or gas) particles at temperatures above absolute zero. The rate of this movement is a function of temperature, viscosity of the fluid and the size (mass) of the particles
Transient heat is the process in which transfer of heat is varying with time.
Steady state heat is the process in which transfer of heat is not varying with time.
One dimensional heat transfer is when heat transfer is along only one axis.
Thre dimensional heat transfer is when heat transfer is along all three axes.
In heat transfer analysis, three dimensional heat equations can be solved only using fourier transformations
A fin enhances heat transfer due to the fact that it has more area thsn just a normal, so more heat is lost to the surroundings.
For 2.3.1 check this : www.core.org.cn/NR/rdonlyres/Materials-Science.../1d_heat.pdf%u200E
There are different type of fins like circular fins, cylindrical fins
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