UFMFW8302 Faculty of Environment and Technology

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You win a prize in the lottery and you are offered to take Prize A: a £40,000 lump sum or Prize B: £15,000 a year for 3 years. The current rate of inflation (discount rate) is 4%. State, with evidence, which prize you would prefer to have.

Question A2 [10 marks]

After making a cup of tea you leave it to cool. As it decreases in temperature the entropy of the tea also decreases. With supporting evidence, state if this example is a violation of the second law of thermodynamics.

Question A3 [50 marks]

A 160 MW steam power plant operates on a Rankine cycle, the condenser and boiler pressure are 40 kPa and 1.5 MPa respectively. The maximum temperature of steam that can enter the turbine is 400 °C.

a) Determine the thermal efficiency of the plant, including the pump work.

The turbine is replaced with a model that operates with a higher inlet temperature and the steam at the exit is dry, but not superheated. All other parts of the power station remain constant.

b) Determine the thermal efficiency of the power plant with the new turbine.

c) Compare the thermal efficiency of the two plants and comment, with reference to a Carnot cycle, why the thermal efficiency has changed.

Question A4 [30 Marks]

According to the governments statistical release of green-house emissions for 2017, 27% of the UK’s carbon dioxide came from transportation. The biggest contributor was road transportation.

Discuss, from a holistic point of view, how the carbon dioxide emissions from road transportation could be reduced over the next 10 years.

a) Preliminary calculations: Calculate the geometric characteristics of the cross-section needed to carry out your analyses. Explain why these characteristics are important here. (Hint: these quantities are key to the following analysis, take time to check them)

b) Preliminary analysis: These sketches do not need to be exact (in fact it’s impossible at this stage). They just need to be representative to help guide your analysis. But include reference points as necessary.

i. Draw a sketch of the elastic curve (or beam deflection)

ii. Draw a sketch of the bending moment diagram.

c) Calculate the values of the moment point force and UDL. (Hint: relate strain to stress, and stress to bending moment)

d) Identify the position of maximum bending stress and calculate its value. Hence, write out the stress state at this position.

e) Calculate the factor of safety for plastic failure (or identify that the beam is not safe). You must decide on which failure criterion to use, with justification.