Lab Report: Unsteady State Heat Transfer you Will find everything you need in the Attached files. IT IS IMPORTANT TO READ THEM CAREFULLY. will be repo repo

Lab Report: Unsteady State Heat Transfer you Will find everything you need in the Attached files. IT IS IMPORTANT TO READ THEM CAREFULLY. will be
repo
reports and you need to submit the revised rer
the lab reports are:
1. Title Page: This page shows the title of the experiment, the date performed, the date
submitted, authors and team members.
2. Abstract: A concise (normally 200 words or less) statement of the essential
contents of the report for the reader who must get your message in 60 to 90
seconds. The abstract should include a brief statement of the objective, methods
used, significant results and major conclusions.
3. Introduction The introduction presents the background of the project and
describes how the project relates to the “big picture”. It should explain fully:
Why the work is being done? (what are the learning objectives)
What has been done previously in the field both at Widener and at other
locations? What the reader (assume another engineering student) will need
to know to understand your report
4. Procedure: Describe what was done in sufficient detail that an engineer who was
no associated with the project could duplicate your work.
5. Results: An objective discussion of the principle results and observations from
any experimental work. You are to show that the conclusions are justified. This
is the most important section of the report. Discuss what you have accomplished
in a positive manner. Do not dwell on minor factors or attempt to “lay blame” for
failures.
6. Conclusions: Conclusions reached in the results are to be restated here in a more
general, less specific manner. In the Interim Report, these are honest answers to
the questions in Section 2. In the Final Report these are the principle things
learned during the project.
7. Safety Protocols: Write list of safety protocols you have undertaken in the course
of experiments.
8. List of References: Put all the references in the number format in word’s endnote.
9. Appendices (optional): This part may contain symbols listings, sample
calculations, computer program listings, communications, detailed test results
etc.
Unsteady State Heat Transfer
Objective
To perform the experiments related to unsteady state heat transfer and calculate the
differences in thermal parameters with the knowledge of heat transfer phenomena.
Apparatus
Several solids of cylindrical, spherical, or cubical shape; the solids have holes
1.
drilled to attach thermocouples.
2. Thermocouples
3. Thermocouple reader.
Background
дt pc,
k =
The temperature distribution inside a solid in which there is no internal heat
generation can be found from the Fourier field equation:
ᏧᎢ k
ᏙᎢ
……. (1)
where Cp = heat capacity or specific heat (Btu/lb°R, W/kgK)
thermal conductivity (Btu/(hr ft ‘R),
W/(m K)) T = temperature (°R, K)
t = time (sec)
p= density (lb/ft”, kg/mº)
The group k/pCp is the thermal diffusivity (a). This equation has been solved for simple
geometrical systems with appropriate boundary conditions. In one dimension the
Fourier equation is
ОТ
k д?Т
діt pc, дх*
(2)
The heat flux normal to a given cross section is given by
ОТ
дх (3)
where A = the area of the cross section (ft?, m?)
(x = the heat flux (Btu/hr, W)
…..
9x =-KA
Analogous forms exist in cylindrical and spherical coordinate systems.
If a film surrounds the external surface with a temperature drop across it, the
surface temperature, which determines the boundary condition, is given by
9x
dT
=-k =h(T.-T.)
A
dx
surface
surface
….(4)
where h = convective (plus radiation) heat transfer coefficient from surface to
surroundings
Too = (constant) surrounding temperature
To = surface temperature
The solution of the differential equations can be obtained in different ways. In order to
ease the calculations, a new dimensionless number has been introduced and known as
Biot Number (Bi) and given by
hLe
Bi=
k
…..(5)
Where Lc is the characteristics length, given by volume (V)/area (A). If Bi0.1, i.e., conductive resistance is more than convective
resistance (for mostly non-metals where the conductive resistance is the controlling
factor), the analytical solution is given by
T-T. – 45 пл.
e-(nt/2) F.
To To
L
…(9)
–
sin
n
TT
n=
The solution to this equation can also be obtained from the graphical form often
referred to as the Gurney-Lurie charts. These charts use the following terms to describe
the temperature profile.
10
T-T
Y =
To-To
…(10)
at
X = 1
2
X; … (11)
х
n=
X, … (12)
k
m=
hX) …(13)
where h = the heat transfer coefficient of
the liquid k = the thermal
conductivity of the solid
n = relative position (a value of the charts)
m = relative thermal resistance (a value on the charts)
t= time
T = local temperature at timet
T. = the initial temperature
To = Temperature of surrounding medium
X = relative time
x = length
X1 = a key dimension, such as radius, the exact definition is specified on each chart
Y = unaccomplished temperature change
k
a = thermal diffusivity
PC,
2
Cp= heat capacity
p = density
The ratio m represents the relative resistance of the outside film 1/h to the
resistance of the path of longest distance for heat flow x1/k. The differential equations
have been solved for various geometric shapes and values of m, n, X and Y. Solutions are
presented in the references.
This value can be compared to the one-dimensional graphical or analytical solution.
General Procedure
1) Before starting experiment, get familiarized with experimental set up.
2) Turn on the oven on for about 100 °C (around position “3” for the knob). Wait till it
gets desired temperature.
11
3) Make all measurements necessary to determine volume/mass of each cylinder
4) When the oven ready, put the cylinde pone at a time) for 30 mins.
5) Take out the cylinder carefully (it iſ hot, need gloves) and hang it on the stand.
6) Take the temperature reading from each hole by using the thermocouple. Take the
reading for 30 mins in the interval of 0,2,5,10,15,20 & 30 mins.
7) While taking reading, put the other cylinder inside oven for heating to save time.
Treatment of Results:
1. Get the thermodynamic properties of the materials (thermal conductivity, specific
heat etc.)
2.
For metals, assume Biot number approximations and calculated the heat transfer
coefficients for cooling medium. Cross-check the validity of Biot number
assumptions.
3. For non-metallic samples, employ Gurney-Lurie charts and calculate the thermal
parameters.
{References
1. C. O. Bennett and J. E. Myers, Momentum, Heat, and Mass Transfer, 3rd Edition, Ch. 19,
McGraw-Hill, New York, 1982.
** 2. J. R. Welty, C. E. Wicks, and R. E. Wilson, Fundamentals of Momentum, Heat, and Mass
Transfer, 3rd edition, Ch. 18, John Wiley, New York, 1984

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