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CORK INSTITUTE OF TECHNOLOGY
INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Autumn Examinations 2011/
Module Title: Thermofluids 1
Module Code: MECH
School: Mechanical, Electrical & Process Engineering
Programme Title: BEng in Biomedical Engineering Year 1 BEng in Building Services Engineering Year 1 BEng (Hons) in Building Energy Systems Year 1 BEng (Hons) in Sustainable Energy Year 1 BEng in Mechanical Engineering Year 1
Programme Code: EBIME_7_Y EBSEN_7_Y EBENS_8_Y ESENT_8_Y EMECH_7_
External Examiner(s): Mr C. Leddy, Dr B. Costelloe, Mr G. Clerkin, Dr L. McNamara, Mr P. Kenny, Mr C. Buckley, Mr M. McKeon, Dr E. Ahearne Internal Examiner(s): Sally Bryan, Dr Aoife Burke, Maria Kavanagh
Instructions: Answer any 4 questions.
Duration: 2 hours
Sitting: Autumn 2012
Requirements for this examination: Log Tables, 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. Pressure (a) State the meaning of: Gauge pressure Negative gauge pressure Absolute pressure (6 Marks)
(b) A storage tank 2.2m wide has two compartments separated by a vertical partition across the full width. One side contains water to a depth of 0.8m and the other side contains oil to a depth of 3.6m. Find the resultant horizontal force on the partition. ρoil = 860kg/m3 and the ρwater = 1000kg/m3 (9 Marks)
(c) A U-tube mercury manometer is connected to two points on a piping system carrying water. Calculate the difference in pressure between point A and B in the system if: X = 0.45m, Y = 0.55m, Z = 0.7m, ρA = 1000kg/m3, ρm = 13600kg/m
(10 Marks)
Q3 Gases (a) A quantity of ideal gas is maintained at constant temperature. Its volume is 356cm^3 at 73.4kPa. If the pressure is increased to 95.6kPa, what is the final volume? (5 Marks)
(b) A sample of ideal gas occupies a volume of 2.4L at 75^0 C. If the temperature is increased to 1200 C at constant pressure, what is the new volume? (5 Marks)
(c) A sample of ideal gas occupies a volume of 72.4ml at 875kPa and at a temperature of 120^0 C. What is its new temperature after it has expanded to 128ml at 721kPa? (5 Marks)
(d) Air in a cylindrical tank of 2.4m diameter and 3m length is at a pressure of 165kN/m^2 and temperature of 20OC. The pressure is increased 250kN/m^2 and temperature increased to 100^0 C. Calculate change in mass (gas constant is 287(J/kgK). (10 Marks)
Q4 Steam (a) Define the terms: Enthalpy Latent heat of fusion Heat of vaporisation (6 Marks)
(b) Calculate the heat required to convert 11kg of ice at -10°C to water at 60°C. The specific heat capacity of ice is 2.1 kJ/kgK; Specific heat of liquid water = 4.2 kJ/kgK and its latent heat is 335kJ/kg. (9 Marks)
(c) A boiler operates at 7 bar pressure and produces steam with a quality of 98%. Water enters the boiler at 21°C -calculate the specific enthalpy of the water entering the boiler -calculate the specific enthalpy of the steam exiting the boiler -calculate the enthalpy of 8kg of steam exiting the boiler -calculate the enthalpy added to 8kg of water between the inlet and exit of the boiler (10 Marks)
Q5 Quantity of Heat (a) Define the term “ absolute temperature scale ”. (4 Marks)
(b) Illustrate and explain the operation of a Constant Volume Gas Thermometer. (5 Marks)
(c) How long in minutes would it take for 1 litre of water to boil from room temperature (16^0 C) in a kettle rated at 2.4kW. Specific heat capacity of water = 4200J/kgK. (6 Marks)
(d) A rectangular glass block has a length of 80mm, width 40mm, and depth 15mm at a temperature of 35^0 C. When heated to 90^0 C the length increases by 0.54mm ◦ what is the coefficient of linear expansion ◦ what is the increase in surface area ◦ what is the increase in volume (10 Marks)
