Introduction to ArtificiaI Intelligence in Higher Education
Lee’s disk method
1.
2. To determine the coefficient of thermal conductivity of
bad conductors by using Lee’s disk method .
Now here two question arises that what is lee’s disk , and what is
the coefficient of thermal conductivity?
The answer is not complicated, lee’s disk is an apparatus consist
of metallic cylindrical chamber and a disk.
While coefficient of thermal conductivity is the quantity of heat
flow in one second through a meter cube of a substance the
opposite faces of which are maintained at a difference of 1 degree
C .
3. 1.Vernier Caliper
2. Lee’s disk apparatus
3.Thermocouples
4. Stop Watch
5.Heating Mantle
6. Insulator to find the value of K .
4. We have set the apparatus ,then we calculated the
thickness and diameter of insulator with the help of
venire caliper.
Insert the insulator b/w the disk and the cylindrical vessel.
Place the thermocouple at T1 and T2 position.
Then by using heating mantle pass the steam from the
inlet of the vessel, then wait till the temperatures T1 and
T2 reached at steady state, note down the temperatures.
Then remove the insulator to rise the temperature of disk
almost 15 degrees above the steady state.
Then allow it to cool down and note the temperature
interval of about 90 seconds .
Then plot the graph b/w temperature and time.
5. The coefficient of thermal conductivity is denoted by K, which
is equal to
K=-mcd/pi.r^2(t2-t1) *dT/dt ---------(1)
Here
m=mass of the lee’s disk
c= specific heat of iron
d=thickness of the insulator
r= radius of the insulator
t2-t1= steady temperatures of thermocouples
dT/dt= change in temperature/change in time
6. m= 1700 g
c=1.08*10^-1 cal/g.C
d=1.94 cm
r=5.5 cm
t2=79 C
t1=32 C
dT/dt= -0.01C/s
Putting all these values in eq. (1) we get
K= 7.9*10^-4 cal/cm.s.C
7. In this experiment we concluded that this method is good
for calculating the values of bad conductors .
If we want to find the coefficient of thermal conductivity
for good conductors this method fails , because of very
little difference between the values of t1 & t2, for
calculating K for good conductors the conductors must be
long enough to get the reasonable difference between t1 &
t2.