School of Engineering and Applied Science
ME3080 – Engineering Design and the Environment
Final Year Examination
CLOSED BOOK
Date:
Time:
Duration:
May 2019
XXX
2 hours
Instructions to Candidates
1.
2.
3.
4.
Answer any THREE questions
There are FIVE questions on the paper
All questions carry equal marks
Use of calculators is allowed. Students should bring their own calculator
which must be from the Casio FX-83, Casio FX-85, HP10s or HP10s+ series. No
other type of calculator is allowed.
Materials provided
1. Answer booklets
2. Appendix: ME3080 Data and formulae (separate from paper)
This exam paper must not be removed from the exam room
This examination is subject to the Examination Regulations for Candidates
THIS PAGE IS LEFT INTENTIONALLY BLANK
Page 1
This examination is subject to the Examination Regulations for Candidates
Question 1
(a) Does the atmosphere make earth colder or warmer? Based on the Energy balance
calculations, estimate the Greenhouse effect on earth.
[20 marks]
(b) Explain how the Greenhouse effect work
[7 marks]
(c) Although Venus is closer to the sun, its temperature is much lower than the earths. Explain
why.
[6 marks]
Note: Earth’s albedo= 0.3, measured average temperature= 18 oC, Stephan Boltzmann constant =
σ = 5.67 x 10-8 W m-2 K-4 , Energy flux arriving to the earth= S=1360 W/m2
Question 2
Recently you have completed a feasibility study on ‘Responses to Climate Change’ in the context of
your Group Project.
(a) Justify your overall choice of approach – i.e. mitigation, adaptation, greenhouse gas
removal, or solar radiation management – explaining why it was preferred over the other
options.
[15 marks]
(b) Summarise the main recommendations of your study.
[18 marks]
Page 2
This examination is subject to the Examination Regulations for Candidates
Question 3
(a) In terms, of the approach effectiveness, cost, and public acceptance, compare the Carbon
Dioxide removal, and the Solar Radiation Management approaches.
[6 marks]
(b) An array of DAC units consists of 2000 units each containing 20 fans. Each fan is 1 m in
diameter, moving air at 10 m/s velocity:
I. What is the volume of air moved per second and per year?
[5 marks]
II. It is planned to use this technology to reduce the level of carbon dioxide in the atmosphere
from 400 ppm (0.04% by volume) down to 300 ppm. The DAC units reduce the
concentration entering by half. How long will this take? Assume that there are no other
processes going on to remove or emit CO2.
[9 marks]
III. How many of these arrays will be needed to achieve the target reduction in 80 years?
[8 marks]
IV. Based on them, discuss suggestions to make this technology more realistic?
[5 marks]
Note: Atmosphere volume= 4.2 1018 m3
Page 3
This examination is subject to the Examination Regulations for Candidates
Question 4
(a) It is proposed to use artillery to deliver SO2 to the stratosphere (18 km height). Shells will be
fired vertically at an initial velocity of 750 m/s. Once they reach their maximum altitude, they
will release their payload of SO2, then fall to the ground.
Calculate the maximum altitude reached by the shells, showing whether the aim of the project
has been met
[15 marks]
The following data are provided with regard to each shell:
Mass with payload:
2500 kg
Diameter:
0.5 m
Drag coefficient:
0.5
Assume air to be of constant density =0.8 kg/m3.
(b) Choose any three of the following:
i.
ii.
iii.
iv.
Third generation biofuel
Anaerobic Digestion
Problem shifting
Functional Unit
In the context of Engineering Design and the Natural Environment, what do you understand by the
term? Write a concise paragraph explaining the meaning in each case, including chemical
equations where appropriate.
[6 marks each]
Page 4
This examination is subject to the Examination Regulations for Candidates
Question 5
(a) In terms of water quality, cost, and practicality, compare the pressure-driven, and the thermaldriven desalination technologies. Give examples where each technology can be used efficiently.
[6 marks]
(b) A reverse osmosis plant (Figure Q5) is configured to treat water from the Pacific Ocean. A
schematic of the plant with some parameters is shown below. The pump used has 80% efficiency,
and operates at a pressure equivalent to twice the osmotic pressure of the concentrated seawater.
I. Explain the meaning of each of the desalination measures (the recovery ration, the rejection
fraction, and the energy consumption).
[3 marks each]
II. Work out the value of each of the measures (recovery ration, the rejection fraction, and the
specific energy consumption) of the system in kWh/m3 and the recovery ratio.
[15 marks]
III. What do you suggested to reduce the system specific energy consumption
[3 marks]hgfhgh
Valve
RO module
Pump
Concentrated
Seawater
𝑚𝑐 =400 kg/s
Seawater
𝑚𝑠 = 800 𝑘𝑔/𝑠
𝑋𝑠 = 0.035
Purified water
𝑋𝑝 = 0.0005
Figure. Q5: Reverse Osmosis Configuration
Note: Osmotic pressure K = 7.9 x 104 kPa
END OF PAPER
Page 5
This examination is subject to the Examination Regulations for Candidates