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EMESTER 2-无代写
时间：2024-03-19
[MEC2003]
[Turn over
NEWCASTLE UNIVERSITY
________________________________
SEMESTER 2 2019/2020
________________________________
APPLICATIONS OF THERMOFLUID DYNAMICS II
Your completed work must be submitted by
9:30am (UK time), on 04/06/2020
You may submit your work at any point during the 24 hour
period of the exam.
(IMPORTANT NOTE: Time in the UK is currently GMT+1hr,
you may check what time it is in the UK at the following
link. https://www.thetimezoneconverter.com/ )
It expected that this paper will take 1.5 hours to complete.
[Note: students with SSP would be allowed to add on as normal
BUT within the 24-hour period and NOT in addition]
You are not expected to, and it is not advisable to, work on this
assessment constantly for the 24-hour period. The assessment
has been designed to be worked on for a much shorter period of
time in line with the length of a standard exam sitting.
When answering the exam, you should observe normal exam
conditions and must not communicate/collude with other
students taking the paper. The work that you submit must be
your own work.
[MEC2003]
2
Your submission may be submitted to the Turnitin similarity
checker as a check on plagiarism.
If you are unfamiliar with submitting your work to Turnitin, the
student guide is provided here:
https://www.ncl.ac.uk/ltds/assets/documents/guides/Turnitin-
How-to-submit-your-assignment.pdf
Should you encounter IT difficulties that significantly affect your
ability to complete this exam or when uploading your answer(s)
you may submit a PEC detailing these.
a) Answer all the questions. You will only need to identify the
correct choices for the multiple-choice type questions. You do
not need to submit the working for the solution to the problems.
DATA:
Material supplied:
- Heat transfer data sheet
Unless otherwise stated in the Question the following values
may be assumed:
- Air behaves as an ideal gas with constant specific heat
capacities:
cp 1005 J/(kgK) and cv 718J/(kgK) R 287J/(kgK)
- Density of liquid water 1000kg/m3
- Gravitational field strength g 9.805 N/kg
- The Stefan-Boltzmann constant = 5.67 10-8 W/m2 K4
b) It is expected that this paper will take 1.5 hours to complete.
c) Please list your choices against the question numbers
carefully in a word-processed document for submission.
[MEC2003]
3
d) A submission point has been created in the MEC2003 section
within your Blackboard course. Your submission should be a
single file uploaded through this submission point. To avoid
system overload please submit in good time within the 24 hour
period.
e) contact information for academic queries during the first hour
of the 24hour window: nilanjan.chakraborty@ncl.ac.uk. You
must use your Newcastle email address when contacting the
above. The queries will be answered by email to the whole
cohort.
f) contact information for technical queries. Please note: this is
still being confirmed and will be communicated to Schools.
This coversheet will need to be updated to include this prior
to release.
[MEC2003]
4
Q1(a) A plane surface is provided with an array of straight
rectangular fins of length and thickness 25 mm and 1.5 mm
respectively. The fins are spaced on a 3.5 mm pitch. The
fins are made of a material with a thermal conductivity of
100 W/m K, and the heat transfer coefficient at all exposed
surfaces is 300 W/m2K. The fin base temperature is 95oC
and the ambient fluid is at 25oC.
(i) Find the correct range for the overall surface efficiency
of the array
(a) 30%-40%
(b) 50%-60%
(c) 80%-90%
(d) None of the above
(4 marks)
(ii) Find the correct range for the heat transferred to the
fluid per square metre of primary surface.
(a) 10-15 kW/m2
(b) 17-22 kW/m2
(c) 5-7 kW/m2
(d) None of the above
(2 marks)
Q1(b) (i) Is a proposed heat pump for domestic space heating
possible:
- using an ambient heat source at 10C,
- with a pump motor power input of W = 200W, and
- delivering Qd = 1kW at a space temperature of 20C?
Please identify the correct statement.
(a) Clausius inequality gives a value in the range of (0.5
to 0.60) W/K and it is possible.
(b) Clausius inequality gives a value in the range of (-0.6
to -0.50) W/K and it is possible.
[MEC2003]
5
(c) Clausius inequality gives a value in the range of (-0.2
to -0.40) W/K and it is possible.
(d) Clausius inequality gives a value in the range of (0.5
to 0.60) W/K and it is not possible.
(4 marks)
(ii) With the same ambient source and extraction rate, and
with the same motor, it is proposed to split the 1kW
delivered heat equally between space heating at the
same temperature of 20C and water heating at 40C.
Identify the correct statement.
(a) Clausius inequality gives a value in the range of (-0.6
to -0.55) W/K and it is possible.
(b) Clausius inequality gives a value in the range of (-0.6
to -0.55) W/K and it is not possible.
(c) Clausius inequality gives a value in the range of (-0.5
to -0.40) W/K and it is possible.
(d) Clausius inequality gives a value in the range of (0.4
to 0.50) W/K and it is not possible.
(3 marks)
Q1(c) Modifications to a chemical process will require 120,000
kg/h of toluene to be heated from 15oC to a temperature of
at least 55oC. A steam-heated shell-and-tube exchanger is
available. It has 100 steel tubes arranged in a single pass.
The tube dimensions are: outside diameter 17 mm, inside
diameter 15 mm, length 5.5 m. Saturated steam at 3 bar is
used on the shell side.
Take the shell side heat transfer coefficient ho = 8000 W/m2
K. Take the fouling factor to be 0.001 m2.K /W on both sides
of the tube.
Physical properties of toluene at the mean temperature of
(15 + 55)/2 = 35oC are: density = 870 kg/m3, specific heat
[MEC2003]
6
= 1.8 kJ/kg K, viscosity = 280 × 10−6 N.s/m2, thermal
conductivity = 0.15 W/m.K.
Take the thermal conductivity of steel as 50 W/m.K.
(i) Estimate the correct range within which the mean velocity
within the tube lies:
(a) 2.0 m/s – 3.0 m/s
(b) 3.5 m/s – 4.0 m/s
(c) 1.0 m/s – 1.5 m/s
(d) None of the above
(2 marks)
(ii) Estimate the correct range of the Reynolds number for
the tube flow and nature of the flow:
(a) 2000-3000, laminar flow
(b) 50000-80000, turbulent flow
(c) 15000-20000, turbulent flow
(d) 100000-200000, turbulent flow
(2 marks)
(iii) Estimate the correct range of the overall heat transfer
coefficient for the internal surface:
(a) 400W/m2.K-500 W/m2.K
(b) 550 W/m2.K-600 W/m2.K
(c) 3000 W/ m2.K-3500 W/m2.K
(d) None of the above
(3 marks)
(iv) Estimate the correct range of the log mean temperature
difference:
(a) 70oC-80oC
(b) 90oC-100oC
(c) 110oC-120oC
(d) 130oC-140oC
[MEC2003]
7
(3 marks)
(v) Is the heat exchanger suitable for duty?
(a) Yes
(b) No
(2 marks)
Q2. A cylindrical vessel of diameter 2.0 m contains molten metal
whose surface temperature is 1600 K; the height of the vessel
above the level of the liquid metal is 1.0 m and the vessel is in
large surroundings at a mean temperature of 300 K. The
cylindrical sides of the vessel are insulated. The emissivity of
the liquid metal surface is 0.3. Assume steady state conditions.
Fig. Q2
Let us consider the molten metal surface as surface 1. The
opening is taken to be surface 2. The curved cylindrical surface
is taken to be surface 3.
[MEC2003]
8
(i) Identify the correct set of view factors (identify the choice
that is the closest to your answer)
(a) F11 = 0.0; F12 = 0.38; F13 = 0.62; F21 = 0.38;
F22 = 0.0; F23 = 0.62; F31 = 0.31; F32 = 0.31; F33 = 0.38
(b) F11 = 0.0; F12 = 0.18; F13 = 0.82; F21 = 0.18;
F22 = 0.0; F23 = 0.82; F31 = 0.41; F32 = 0.41; F33 = 0.18
(c) F11 = 0.0; F12 = 0.75; F13 = 0.25; F21 = 0.75;
F22 = 0.0; F23 = 0.25; F31 = 0.13; F32 = 0.13; F33 = 0.74
(d) F11 = 0.0; F12 = 0.5; F13 = 0.5; F21 = 0.5;
F22 = 0.0; F23 = 0.5; F31 = 0.5; F32 = 0.5; F33 = 0.0
(6 marks)
(ii) Identify the correct [M][J] = [S] matrix (identify the choice
that is the closest to your answer):
(a) [
3.33 −0.887 −1.4467
−0.887 3.33 −1.4467
−0.31 −0.31 0.62
] [
J1
J2
J3
] = [
371589.1
459.27
0
]
(b) [
3.33 −0.887 −1.4467
0.0 1.0 0.0
−0.31 −0.31 0.62
] [
J1
J2
J3
] = [
371589.1
459.27
0
]
(c) [
1.0 0.0 0.0
−0.887 3.33 −1.4467
−0.31 −0.31 0.62
] [
J1
J2
J3
] = [
459.27
371589.1
0
]
(d) None of the above
(10 marks)
[MEC2003]
9
(iii) Estimate the correct range of radiation heat transfer from
the molten surface:
(a) 140 kW/m2 -150 kW/m2
(b) 90 kW/m2 - 100 kW/m2
(c) 280 kW - 350 kW
(d) 420 kW - 450 kW
(4 marks)
(iv) Estimate the correct range of average temperature of the
vessel wall above the metal surface.
(a) 500oC – 700oC
(b) 800 K – 1100 K
(c) 1200oC – 1500oC
(d) None of the above
(5 marks)
END OF PAPER
[Turn over
NEWCASTLE UNIVERSITY
________________________________
SEMESTER 2 2019/2020
________________________________
APPLICATIONS OF THERMOFLUID DYNAMICS II
Your completed work must be submitted by
9:30am (UK time), on 04/06/2020
You may submit your work at any point during the 24 hour
period of the exam.
(IMPORTANT NOTE: Time in the UK is currently GMT+1hr,
you may check what time it is in the UK at the following
link. https://www.thetimezoneconverter.com/ )
It expected that this paper will take 1.5 hours to complete.
[Note: students with SSP would be allowed to add on as normal
BUT within the 24-hour period and NOT in addition]
You are not expected to, and it is not advisable to, work on this
assessment constantly for the 24-hour period. The assessment
has been designed to be worked on for a much shorter period of
time in line with the length of a standard exam sitting.
When answering the exam, you should observe normal exam
conditions and must not communicate/collude with other
students taking the paper. The work that you submit must be
your own work.
[MEC2003]
2
Your submission may be submitted to the Turnitin similarity
checker as a check on plagiarism.
If you are unfamiliar with submitting your work to Turnitin, the
student guide is provided here:
https://www.ncl.ac.uk/ltds/assets/documents/guides/Turnitin-
How-to-submit-your-assignment.pdf
Should you encounter IT difficulties that significantly affect your
ability to complete this exam or when uploading your answer(s)
you may submit a PEC detailing these.
a) Answer all the questions. You will only need to identify the
correct choices for the multiple-choice type questions. You do
not need to submit the working for the solution to the problems.
DATA:
Material supplied:
- Heat transfer data sheet
Unless otherwise stated in the Question the following values
may be assumed:
- Air behaves as an ideal gas with constant specific heat
capacities:
cp 1005 J/(kgK) and cv 718J/(kgK) R 287J/(kgK)
- Density of liquid water 1000kg/m3
- Gravitational field strength g 9.805 N/kg
- The Stefan-Boltzmann constant = 5.67 10-8 W/m2 K4
b) It is expected that this paper will take 1.5 hours to complete.
c) Please list your choices against the question numbers
carefully in a word-processed document for submission.
[MEC2003]
3
d) A submission point has been created in the MEC2003 section
within your Blackboard course. Your submission should be a
single file uploaded through this submission point. To avoid
system overload please submit in good time within the 24 hour
period.
e) contact information for academic queries during the first hour
of the 24hour window: nilanjan.chakraborty@ncl.ac.uk. You
must use your Newcastle email address when contacting the
above. The queries will be answered by email to the whole
cohort.
f) contact information for technical queries. Please note: this is
still being confirmed and will be communicated to Schools.
This coversheet will need to be updated to include this prior
to release.
[MEC2003]
4
Q1(a) A plane surface is provided with an array of straight
rectangular fins of length and thickness 25 mm and 1.5 mm
respectively. The fins are spaced on a 3.5 mm pitch. The
fins are made of a material with a thermal conductivity of
100 W/m K, and the heat transfer coefficient at all exposed
surfaces is 300 W/m2K. The fin base temperature is 95oC
and the ambient fluid is at 25oC.
(i) Find the correct range for the overall surface efficiency
of the array
(a) 30%-40%
(b) 50%-60%
(c) 80%-90%
(d) None of the above
(4 marks)
(ii) Find the correct range for the heat transferred to the
fluid per square metre of primary surface.
(a) 10-15 kW/m2
(b) 17-22 kW/m2
(c) 5-7 kW/m2
(d) None of the above
(2 marks)
Q1(b) (i) Is a proposed heat pump for domestic space heating
possible:
- using an ambient heat source at 10C,
- with a pump motor power input of W = 200W, and
- delivering Qd = 1kW at a space temperature of 20C?
Please identify the correct statement.
(a) Clausius inequality gives a value in the range of (0.5
to 0.60) W/K and it is possible.
(b) Clausius inequality gives a value in the range of (-0.6
to -0.50) W/K and it is possible.
[MEC2003]
5
(c) Clausius inequality gives a value in the range of (-0.2
to -0.40) W/K and it is possible.
(d) Clausius inequality gives a value in the range of (0.5
to 0.60) W/K and it is not possible.
(4 marks)
(ii) With the same ambient source and extraction rate, and
with the same motor, it is proposed to split the 1kW
delivered heat equally between space heating at the
same temperature of 20C and water heating at 40C.
Identify the correct statement.
(a) Clausius inequality gives a value in the range of (-0.6
to -0.55) W/K and it is possible.
(b) Clausius inequality gives a value in the range of (-0.6
to -0.55) W/K and it is not possible.
(c) Clausius inequality gives a value in the range of (-0.5
to -0.40) W/K and it is possible.
(d) Clausius inequality gives a value in the range of (0.4
to 0.50) W/K and it is not possible.
(3 marks)
Q1(c) Modifications to a chemical process will require 120,000
kg/h of toluene to be heated from 15oC to a temperature of
at least 55oC. A steam-heated shell-and-tube exchanger is
available. It has 100 steel tubes arranged in a single pass.
The tube dimensions are: outside diameter 17 mm, inside
diameter 15 mm, length 5.5 m. Saturated steam at 3 bar is
used on the shell side.
Take the shell side heat transfer coefficient ho = 8000 W/m2
K. Take the fouling factor to be 0.001 m2.K /W on both sides
of the tube.
Physical properties of toluene at the mean temperature of
(15 + 55)/2 = 35oC are: density = 870 kg/m3, specific heat
[MEC2003]
6
= 1.8 kJ/kg K, viscosity = 280 × 10−6 N.s/m2, thermal
conductivity = 0.15 W/m.K.
Take the thermal conductivity of steel as 50 W/m.K.
(i) Estimate the correct range within which the mean velocity
within the tube lies:
(a) 2.0 m/s – 3.0 m/s
(b) 3.5 m/s – 4.0 m/s
(c) 1.0 m/s – 1.5 m/s
(d) None of the above
(2 marks)
(ii) Estimate the correct range of the Reynolds number for
the tube flow and nature of the flow:
(a) 2000-3000, laminar flow
(b) 50000-80000, turbulent flow
(c) 15000-20000, turbulent flow
(d) 100000-200000, turbulent flow
(2 marks)
(iii) Estimate the correct range of the overall heat transfer
coefficient for the internal surface:
(a) 400W/m2.K-500 W/m2.K
(b) 550 W/m2.K-600 W/m2.K
(c) 3000 W/ m2.K-3500 W/m2.K
(d) None of the above
(3 marks)
(iv) Estimate the correct range of the log mean temperature
difference:
(a) 70oC-80oC
(b) 90oC-100oC
(c) 110oC-120oC
(d) 130oC-140oC
[MEC2003]
7
(3 marks)
(v) Is the heat exchanger suitable for duty?
(a) Yes
(b) No
(2 marks)
Q2. A cylindrical vessel of diameter 2.0 m contains molten metal
whose surface temperature is 1600 K; the height of the vessel
above the level of the liquid metal is 1.0 m and the vessel is in
large surroundings at a mean temperature of 300 K. The
cylindrical sides of the vessel are insulated. The emissivity of
the liquid metal surface is 0.3. Assume steady state conditions.
Fig. Q2
Let us consider the molten metal surface as surface 1. The
opening is taken to be surface 2. The curved cylindrical surface
is taken to be surface 3.
[MEC2003]
8
(i) Identify the correct set of view factors (identify the choice
that is the closest to your answer)
(a) F11 = 0.0; F12 = 0.38; F13 = 0.62; F21 = 0.38;
F22 = 0.0; F23 = 0.62; F31 = 0.31; F32 = 0.31; F33 = 0.38
(b) F11 = 0.0; F12 = 0.18; F13 = 0.82; F21 = 0.18;
F22 = 0.0; F23 = 0.82; F31 = 0.41; F32 = 0.41; F33 = 0.18
(c) F11 = 0.0; F12 = 0.75; F13 = 0.25; F21 = 0.75;
F22 = 0.0; F23 = 0.25; F31 = 0.13; F32 = 0.13; F33 = 0.74
(d) F11 = 0.0; F12 = 0.5; F13 = 0.5; F21 = 0.5;
F22 = 0.0; F23 = 0.5; F31 = 0.5; F32 = 0.5; F33 = 0.0
(6 marks)
(ii) Identify the correct [M][J] = [S] matrix (identify the choice
that is the closest to your answer):
(a) [
3.33 −0.887 −1.4467
−0.887 3.33 −1.4467
−0.31 −0.31 0.62
] [
J1
J2
J3
] = [
371589.1
459.27
0
]
(b) [
3.33 −0.887 −1.4467
0.0 1.0 0.0
−0.31 −0.31 0.62
] [
J1
J2
J3
] = [
371589.1
459.27
0
]
(c) [
1.0 0.0 0.0
−0.887 3.33 −1.4467
−0.31 −0.31 0.62
] [
J1
J2
J3
] = [
459.27
371589.1
0
]
(d) None of the above
(10 marks)
[MEC2003]
9
(iii) Estimate the correct range of radiation heat transfer from
the molten surface:
(a) 140 kW/m2 -150 kW/m2
(b) 90 kW/m2 - 100 kW/m2
(c) 280 kW - 350 kW
(d) 420 kW - 450 kW
(4 marks)
(iv) Estimate the correct range of average temperature of the
vessel wall above the metal surface.
(a) 500oC – 700oC
(b) 800 K – 1100 K
(c) 1200oC – 1500oC
(d) None of the above
(5 marks)
END OF PAPER
