Bangladesh University of Engineering and Technology · Overall Heat Transfer Coefficient, U =...
Transcript of Bangladesh University of Engineering and Technology · Overall Heat Transfer Coefficient, U =...
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Bangladesh University of Engineering and
Technology
Course Number: Group Number:
Course Title:
Experiment Number:
Name of the Experiment(s):
Date of Performance:
Date of Submission:
Submitted By
Name:
Student ID:
Department:
Section:
ME 306
Heat Transfer Sessional
Evaluation Sheet
Experiment No Lab Report (10) Viva (10) Assessment (10) Total
1 2 3 4
Total
1
EXPERIMENT NO: 1(a)
Determination of Thermal Conductivity of a Metal by Steady State Method
Objectives:
a)
b)
c)
Apparatus: (Please mention the details of each apparatus used for this experiment)
Schematic Diagram:
2
DATA AND CALCULATION SHEET
Test Date :
Thermocouple Used :
Room Temperature (oC) :
Water Inlet Temperature (oC) :
Water Outlet temperature (oC) :
Weight of Container + Water (kg) :
Weight of Water Collected (kg) :
Time of Collection (sec) :
Mass flow rate of Water (kg/sec) :
Table-1: Steady-State Temperature Distribution in the Specimen.
Obs. Section Distance x(m) Dimensionless
Distance x/L
Temperatures
Experimental
(Thermocouple Readings),
Te (oC)
Theoretical, Tt
(oC)
1
1
2
3
4
5
2
1
2
3
4
5
3
Table-2: Calculation of Thermal Conductivity.
Obs.
Mass flow
rate of water,
mw (kg/sec)
Temperature
rise of water,
Δtw (K)
Heat carried
away by
water, (W)
Cross-sectional
area of
specimen (m2)
dT/dx from
plot of Te vs.
x (K/m)
Thermal conductivity
of specimen, k
(W/mK)
1
2
Please bring normal mm graph papers for this experiment.
Sample Calculation
4
5
Results
Discussion
6
EXPERIMENT NO: 1(b)
Determination of Thermal Conductivity of Fluid
Objectives:
Apparatus: (Please mention the details of each apparatus used for this experiment)
Schematic Diagram:
7
DATA AND CALCULATION SHEET
Nominal Resistance of Heating Element 55
Nominal Radial clearance between Plug and Jacket, r 0.34 mm
Effective Area of conducting path through fluid
Fluid
Plug Surface Temperature, t1
Jacket surface temperature, t2
Heater Voltage, V
Calculation
Element Heat Input, R
VQ
c
2
Temperature Difference, t = t1 – t2
Incidental Heat Transfer at t, Qi =
Heat Transfer by conduction through the Oil, Qc = Qe - Qi
Thermal Conductivity of Oil sample, tA
rQK
c
oil
Results
Discussion
8
Assessment
9
1
Experiment 2
Determination of Radiation Heat Transfer
Objectives:
Apparatus (with specifications where necessary):
2
Schematic Diagram of Experimental Setup (Name the missing components below the figure):
E
D
B
A
C
F
3
Results:
Thermocouple type:
Thermocouple material:
Thermocouple temperature range, (oC):
Room temperature, T∞ (oC) =
Barometric Pressure, ha (mmHg) =
Diameter of solid element, D (m) =
Area of solid element surface, A (m2) =
Measured Data:
Number of
observations
Voltage, V
in volts
Current, I
in amps
U-tube
manometer
reading in
mmHg
Element
temperature
Th in oC
Vessel temperature
Tc in oC
1
2
3
4
5
6
7
8
Calculated Result:
Number of
observations
Supplied
heat Qs
in W
Element
temperature
Th in K
Vessel
temperature
Tc in K
Temperature
difference
Th – Tc in K
Absolute
pressure
H in
mmHg
𝐻14
Radiation
heat loss
QR in W
Convection
heat loss
QC in W
1
2
3
4
5
4
6
7
8
Sample Calculation:
5
Graphical Representations:
a) Variation of (Th -Tc) with 𝐻1
4 .
b) Variation of Radiation Heat transfer with (Th - Tc)
6
Discussions: Discussion must contain appropriate explanation of the following facts.
a) Nature of curves of (Th -Tc) with 𝐻1
4 and QR vs (Th - Tc)
b) Variation of radiation heat transfer with convective heat transfer
c) Limitations of the experimental setup, if there are any (Try to observe and think critically,
you would definitely find out that).
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Conclusions: Conclusions must account the following facts
a) Calculated value of emissivity and radiation heat transfer coefficient found from the
experiment.
b) Mentioning the discrepancies of experimental values and actual values from
literature(just mention them, no explanation is required)
8
Class Assessment:
1
Experiment No. 3
Study of Boiling Heat Transfer
Objectives:
1)
2)
3)
4)
5)
Apparatus: (Please mention the details of each apparatus used for this experiment)
Experimental Set Up:
Fig. A Schematic of the Setup for Boiling Study
2
Data Table:
Sample Calculation:
1. Heat supplied, Qs(W)
Qs = VI (1)
Where, V is the voltage in volts in volts and I is the current flowing through element in amps. Here
we neglect the power losses in lead wires.
2. Heat flux, q(W/m2)
The effective heat transfer area of the element, A is 1.3 x10-3m2. Heat flux is calculated dividing
Eq. (1) by A as given follows:
q = Qs/A (2)
Data at pressure P
= ............Pa
Number of Observations
1 2 3 4 5 6 7 8 9
To b
e M
easu
red
Voltage,
V(volt)
Current, I
(amp)
Element Temp.
Tw(oC)
Liquid Temp.
Ts(oC)
Water Inlet
Temp. Twi(oC)
Water Inlet
Temp. Two(oC)
Water Flow
Rate, m/t (kg/s)
To b
e C
alc
ula
ted
Qs (W)
q (W/m2)
TsatoC
h (W/m2K)
Qc(W)
TmoC
U(W/m2K)
3
3. Wall superheat, TsatoC
Wall superheat (sometimes called excess temperature) is defined as follows
Tsat = Tw –Ts (3)
Where Tw is the surface temperature of the element and Ts is the saturation temperature of the
liquid.
4. Boiling Heat Transfer Coefficient, h (W/m2K)
Boiling heat transfer coefficient, h can be calculated using Ep. (4)
h = q/Tsat (4)
5. Overall Heat Transfer Coefficient, U (W/m2K)
Heat transfer during condensation can be calculated using the following relation:
Qc = UAcTm (5)
Where Ac = 0.032 m2 is the condenser area exposed to cooling water and Tm is the logarithmic
mean temperature difference (LMTD). Qc and Tm can be calculated using the following relations:
T = (Two – Twi) (6)
Qc = .
m CpT (7)
Tm = ( i – o)/ln( i/ o) (8)
i = Twi - Ts (9)
o = Two - Ts (10)
4
Cp is the specific heat of cooling water (= 4.18 kJ/KgK) and .
m the mass flow rate of water.
Results:
Boiling heat transfer co-efficient, h =
Overall Heat Transfer Coefficient, U =
Discussion:
(Briefly explain the boiling curve obtained in the experiment and compare with one mentioned in
any heat transfer books. Comment on critical heat flux and boiling heat transfer co-efficient.)
5
Assessment:
6
1
EXPERIMENT 4
Study of Forced Convection Heat Transfer Over a Flat Plate
Objectives:
a)
b)
c)
Apparatus: (Please mention the details of each apparatus used for this experiment)
Schematic Diagram:
2
Forced Convection over a Flat Plate
Material of the plate is copper
Length of copper plate, L = ………m
Width of the copper plate, W = ……...m
Thermocouple used:
Type:_______, Material: _________________________, Range: ______________________
Room temperature, T∞ = …….. °C
Density of air at room temperature, ρair = …….. kg/m3
Density of water at room temperature, ρwater = …….. kg/m3
Emissivity of copper plate, ε = 0.78
Table 1: Collection of experimental data for different observations.
No.
of
Obs.
Power
Input,
Qin
(W)
Thermocouple reading (°C)
Inlet
Air Temp,
T∞
(°C)
Manometer
deflection of
water,
hwater
(m)
No.1
Ts1
No.2
Ts2
No.3
Ts3
No.4
Ts4
No.5
Ts5
x1 (m)
----------
x2 (m)
----------
x3 (m)
----------
x4 (m)
--------
--
x5 (m)
--------
--
1
2
3
3
Calculation Sheet
Table 2: Thermo-physical Properties of air at different film temperature.
Properties
of air
Observation No.1 Observation No.2 Observation No.3
Film temperature,
Tf = ……..........K
Film temperature,
Tf = ……..........K
Film temperature,
Tf = ……..........K
k (W/mK)
ρ (kg/m3)
μ (kg/m.s)
Pr
Calculated Result
Table 3: Calculated parameters and convection heat transfer coefficient.
Obse
rvat
ion
No.
Power
Input
Qs
(W)
Air
Velocity
V
(m/s)
Governing Parameters
Heat Transfer Coefficient, hc (W/m2K)
Empirical Correlation Thermal Balance
ReL xcr/L Pr Isothermal Isoflux Experimental
1
2
3
Please bring normal mm graph papers for this experiment.
4
Sample Calculation
5
Results
6
Assessment
7
Discussion