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CORK INSTITUTE OF TECHNOLOGY
INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Semester 1 Examinations 2008/
Module Title: Thermofluids
Module Code: MECH
School: Mechanical & Process Engineering
Programme Title: B.Eng. in Building Services Engineering / B.Eng in Biomedical Engineering / B.Eng (Hons) in Sustainable Energy Technology
Programme Code: EBSEN_7_Y1, EBIME_7_Y1, ESENT_8-Y
External Examiner(s): Dr. P. O’Sullivan, Dr. B. Costelloe Internal Examiner(s): Maria Cullinane, Sean Williams, Maria Kavanagh, Sally Bryan
Instructions: Answer any 4 questions
Duration: 2 hours
Sitting: Winter 2009/
Requirements for this examination: Log Tables, Steam Tables
Note to Candidates: Please check the Programme Title and the Module Title to ensure that you are attempting the correct examination. If in doubt please contact an Invigilator.
Q. 1 Pressure a) Describe with the aid of a sketch the operation of a Bourdon Tube. (7 Marks)
F i g u r e
Figure Q1 - U-Tube Manometer
b) The U-Tube Manometer shown in figure Q1 is used to measure the gauge pressure of a fluid P of density ρ = 800kg/m^3. If the density of the liquid Q is 13600 kg/m^3 , what will be the gauge pressure at A if: i. h 1 = 0.5 m and D is 0.9 m above BC ii. h 1 = 0.1 m and D is 0.2 m below BC (8 Marks) c) A tank contains water to a depth of 2 m with a layer of oil 3 m deep resting on top of it. The density of the oil is 800 kg/m^3. While the tank measures 5m wide x 3 m long. Find the load on the side walls and the base of the tank. (10 Marks)
3m
3m Oil 2m H 2 0 5m
End Wall
SideWall
Q. 4 Steam a) Define the terms “Enthalphy” and “Latent heat of fusion” (4 marks) b) Calculate the heat required to convert 8kg of ice at -10OC to water at 60 OC. The specific heat capacity of ice is 2.1 kJ/kgK, its latent of fusion is 335 kJ/kg and the specific heat capacity of water is 4.2 kJ/kg OC. (6 marks) c) A packaged boiler operates at 10 bar pressure and produces 9080kg/hr of steam with a quality of 99%. Water enters the boiler at 40^0 C. Using steam tables, calculate the following: (15 marks) i. The specific enthalpy of the water entering the boiler. ii. The specific enthalpy of steam exiting the boiler. iii. The enthalpy added to 9080kg between inlet and exit. iv. The volumetric flowrate in m^3 /s of steam exiting the boiler.
Q. 5 Quantity of heat a) List 4 sources of error of mercury in glass thermometer (4 marks) b) Define each term in the equation for the rate of heat addition in a stationary system and state its SI unit (4 marks) c) Heat is supplied at a constant rate of 100 kW to a boiler for a period of 5 minutes. If the water temperature rises by 60°C find the volume of water in the boiler. State any assumptions made. (6 marks) d) A brass sphere has a diameter 50mm at 16°C. If the temperature is raised to 516 °C, find the increase i. in diameter, ii. surface area and iii. find the new volume of the sphere. (11 marks) Use α (^) brass = 2 x 10 -5^ /°C Surface area of sphere = 4πr 2 Volume of sphere = 4/3 πr 3
