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CORK INSTITUTE OF TECHNOLOGY
INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Semester 2 Examinations 2008/
Module Title: Introductory Thermofluids
Module Code: MECH 6010
School: Mechanical and Process Engineering
Programme Title: Bachelor of Engineering (Honours) in Mechanical Engineering – Year 1 Bachelor of Engineering (Honours) in Biomedical Engineering – Year 1
Programme Code: EMECH_8_Y1, EBIOM_8_Y
External Examiner(s): Mr. P. Clarke, Prof. R. Clarke
Internal Examiner(s): Mr. W. M. Corr
Instructions: Answer any Three Questions. All Questions carry equal marks.
Duration: 2 Hours
Sitting: Summer 2009
Requirements for this examination: Steam Tables
Note to Candidates: Please check the Programme Title and the Module Title to ensure that you have received the correct examination paper. If in doubt please contact an Invigilator.
Q1. An oil and gas well is closed in at the surface for observation prior to a repair re-entry. The well is vertical, 5500 m deep with surface pressure and temperature 146.5 bars and 63°C respectively. A well bore survey shows: − the top 1000 m is pure ethane, C 2 H 6. − the next 2000 m is oil with relative density 0.854. − the bottom 2500 m is saline water with density 1035 kg/m^3. (i) Calculate the density of the ethane ‘leg’ assuming constant density throughout, and treating the ethane as an ideal gas. (3 Marks) (ii) Sketch the pressure profile in the well from surface to bottom. (5 Marks) (iii) Calculate the closed-in bottom-hole-pressure (CIBHP) i.e. the reservoir pressure. (6 Marks) (iv) The well is to be rendered safe for re-entry by filling with brine to ensure a 40 bars overbalance on reservoir pressure; what density of brine is required? (4 Marks) (v) Sketch the brine profile superimposed on (ii). (2 Marks)
Q2. (a) Describe throttling of a fluid and how the fluid’s
- pressure
- temperature
- enthalpy
- dryness is affected. Illustrate your answer with reference to an aerosol spray. (6 Marks) (b) The nozzles of a steam turbine receive steam at 3 bar and 150^0 C with negligible velocity. The steam expands adiabatically through the nozzles and leaves at 1 bar with a dryness fraction of 0.96. Calculate: (i) the exit velocity (8 Marks) (ii) the total exit area for a mass flow rate of 10 kg/s. (6 Marks)
Q5. (a) State the Theorem of Parallel Axes and demonstrate it fully for a rectangular area with parallel axes through the centroid and along one edge. (6 Marks)
(b) (i) The gate of Fig 5 is pinned at O. Find the height of the free surface, h, at which the gate will start to rotate, neglecting the weight of the gate. (10 Marks) (ii) Will h increase or decrease from this value if the weight is not neglected? (4 Marks)
