Download Thermofluids2 Module Exams (MECH 6033) at Cork Institute of Technology, Summer 2010 and more Exams Physics Fundamentals in PDF only on Docsity!
CORK INSTITUTE OF TECHNOLOGY
INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Semester 2 Examinations 2009/
Module Title: Thermofluids
Module Code: MECH 6033
School: Mechanical & Process Engineering
Programme Title: Bachelor of Engineering in Mechanical Engineering –Year 2 Bachelor of Engineering (Honours) in Sustainable Energy – Year 2
Programme Code: EMECH_7_Y2, ESENT_8_Y
External Examiner(s): Mr. A. Bateman, Dr. E. Ahearne Internal Examiner(s): Ms. M. Kavanagh, Mr. Michael Walsh
Instructions: Answer any 3 questions. Please tick off which questions you attempt on the front of the script.
Duration: 2 Hours
Sitting: Summer 2010
Requirements for this examination: Steam Tables, Log 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.
Q1 Internal Combustion Engine
(a) Define brake specific fuel consumption and discuss the importance of expressing the fuel consumed by an engine in this manner. (4 marks)
(b) The power developed by a petrol engine at full load is 90kW brake power and 110kW indicated power. The fuel used per minute at this load is 0.38kg. The calorific value of the fuel is 43.8MJ/kg. (i) Calculate the thermal efficiency on a brake power and an indicated power basis. (12 marks) (ii) Estimate the heat given off to the cooling water if 45% of the total energy supplied in the fuel is accounted for by friction, exhaust gases and losses to the surroundings. (7 marks)
(c) The fuel oil supplied to a boiler contains 86% carbon and 14% hydrogen by mass. Determine the stoichiometeric air to fuel ratio for complete combustion of the fuel. (10 marks)
Composition of air by mass: Oxygen 23% Nitrogen 77% Relative Atomic Mass: Oxygen(O) 16 Carbon(C) 12 Hydrogen(H) 1
Q2 Expansion and Compression of gases
1 kg air is subjected to the following cycle of events in a closed system: (i) An adiabatic compression from a pressure of 103kN/m^2 , volume 1.04m^3 and temperature 100o^ C to a volume 0.173m^3. (ii) The air is then heated at constant volume to a pressure of 3.45MN/m^2. (iii) An adiabatic expansion to its initial volume. (iv) The air is then subjected to a constant volume cooling to its initial temperature and pressure.
(a) Draw the cycle of processes on a pressure volume diagram and clearly identify each
process on the diagram. (6 marks)
(b) Determine the pressure and temperature at the four corners of the diagram.
(12 marks)
(c) Calculate the work done in compressing the air. (8 marks)
(d) Calculate the heat absorbed by the air during the constant volume heating.
(7 marks) For the air take γ = 1.4 and c (^) v = 717J/kgK.
