This preview shows pages 1–3. Sign up to view the full content.
INTRODUCTION
heat transfer accrue in three ways conduction ,convection ,and radiation. Heat transfer by
conduction is best done in solids where the thermal conductivity is high. Heat
transfer
by conduction
accrue as a result of temperature difference between two bodies in contact with each other. So , heat
moves from the higher temperature to the lower temperature object. It result from molecular
interaction between adjacent molecule. Also, there another mechanism which is caused by free
electron which accrue in free metallic solids.
THEORETICAL BACKGROUND
Heat transfer by conduction is described by fourier’s law.
Q
x
/A= kdT/dx
 1)
where k is the thermal conductivity of the material which
is a function of temperature for the case of
solids. and Qx is the rate of heat transfer
K = k
o
(1+
β
T)
2)
It is known that any two materials can not have a perfect contact between them , so when heat moves
through this empty space
there must be a temperature drop because of the resistance of air which has
lower thermal conductivity than the solid material . this is called the barrier resistance which is
defined as
q
x
/A =
∆Τ
b
/
1
/h
c
3)
where
∆Τ
b
is the barrier temperature gradient and 1/ hc is the resistance
the cross sectional area A will be a function of position x as in the eq. 4
q
x
/A(x)=kdT/dx4)
the area of
a circular cone r =.5(x=0) ,r=1(l=14)
is
A(x) =
π{.5/
12 +.5x/14
}
2
5)
for
a circular cone
qx =(9.35e3)*k(T
h
T
c
)6)
and
for the cylinder
unit 4 with diameter 2”
qx =(.0187)*k(T
h
T
c
)7)
PROCEDURE
This preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentIn this exp. One end of the conducting bar was heated at the same time the heat was removed
from the other end in the heat sink. The temperature was recorded for each unit and the inlet and
This is the end of the preview. Sign up
to
access the rest of the document.
 Fall '09
 M.Elgaily

Click to edit the document details