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AER423 Lab - Thermal Conductivity and Contact Resistance (1).docxFull description
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Electrical Conductivity Lab Report -Example for Physics lab report
Abstract:The objective of this experiment is: To evaluate evaluate the thermal conductivity of copper experimentally using “Thermal “ Thermal Conduction System-Model 9!"# $xperimental results %ere compared %ith the theoretical results& There %as difference in theoretical and experimental results& Theoretical value of thermal conductivity %as ' ()m * and experimental value %as '+"&9' ()m *& This difference is due to experimental errors&
Introduction: Conduction ,
convection and radiation are basic modes of heat transfer& (hen a temperature difference exists in a stationary medium, %hich may be in solid, heat transfer occurs due to conduction across the medium& y conduction conduction heat spontaneously spontaneously flo%s from a body at a higher higher temperature to a body at a lo%er lo%er temper temperatu ature& re& .n the absenc absencee of extern external al drivin driving g fluxes fluxes,, temperat temperature ure differ difference encess disappear over time and the body approaches thermal e/uilibrium& e/uilibrium& Convection Convection is the major mode of heat transfer in the fluids& .n our experiments experiments %e had both convective and conduction heat transfer,
Apparatus:-
Experimental procedure:The follo%ing experimental procedure should be follo%ed %hile conducting this experiment: $stablish constant and steady cooling %ater flo%& Turn on heater of unit ' in given arrangement and set to 0 (& 1llo% the
system to reach steady-state conditions& Start recording temperatures using a digital thermometer& 2ote that selector
s%itch on the apparatus allo% you to select %hatever thermocouple you %ish to read& Measure cooling %ater flo% rate& 3ecord data at least once every " minutes, and continue until steady conditions have reached& 4ou may have to %ait for about an hour and nearly + min after setting up the apparatus to allo% the unit to reach the desired state conditions&
(hen the readings do not change in t%o consecutive readings then record the data&
Observations and Calculations
Observations: 5iameter of Copper ar 6 !&7cm 8ength of Copper ar 6 8 6 0cm .nlet temperature of %ater 6 +!C utlet temperature of %ater 6 0'C .nlet eat;olume ?lo% 3ate 6 >@ 6 +&++ ml)sec
Calculations:Cross-Sectional Area:-
A =
A =
πd
2
4
−2 2
(
3.1416 x 5.08 x 10 4
)
−3
A = 2.0268 x 10 m
2
Calculations of Mass Flow Ratem!" b# $olume Flow Rate$!":'
V =
'
V =
V t
2.2 ml
s
100 ml
'
V =
'
V =
=1 x 10− m 4
1 x 10
−4
3
3
m
45 s
−6 m 2.22 x 10
3
s
'
m = ρ w x V '
m
'
=
0.9956502 x 10
−3
'
m =2.210 x 10
3
kg m
3
3
x 2.22 x 10
6
−
m s
kg sec
Where density of water is calculated at average value of temperature of inlet and outlet water. T avg=
¿
25
T 1 + T 2 2
+ 34 2
¿ 29.5 c ρ = 0.9956502
g cm
0
at 29.5 c 3
0
Calculations of %eat Ener&# 'ransferred (":-
( ) 2
π d ∆ T m c p ∆ t = k ∆ X 4 '
q ¿ m c p ∆ t =( 2.213 x 10
−3
'
q =0.0832
) x ( 4.1814 ) x (9 )
kJ sec
Calculation of rate of c)an&e of temperature w*r*t distance ∆ T ∆ X
: −¿
∆ T =−97.288 ∆ X
Calculations of
0.0832
Distance(m)
Temperature('C)
.!"#
%$.&#"
$#
."$
$
."
%
.!&$
%%
.&
%
."$"
%
.%
!
.!$
!$
.&
!!
+:-
( ) 2
q=
π d ∆ T k 4 ∆ X
= k x 2.0268 x 10− x 97.288
k =421.94
3
W m K
Result and discussion:There are fe% problems that may cause problems and had caused problem in our results& The t%o main reasons are given belo%&
?irst problem is in our assumption that %hen there is a steady state, then all the heat
generated %ill be taAen up by the %ater coolant& 1s there is a lot of heat loss through the copper bar in the surrounding atmosphere& 1lthough %e have applied a lot of insulation around the insulating bar but still some heat %as being %asted a%ay in the surrounding environment& There might be the calibration problem in the thermocouples %hich are installed on
the on the copper rod& 1ll the thermocouples may not respond uniformly& So the graph bet%een temperature and distance %ill change and the accordingly slope %ill also change, affecting the thermal conductivity& There is human error in calculation of volume flo% as there %as no proper
measurement device %as not installed& .nlet %ater temperature %as too high to conduct significant heat through copper bar&
