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CORK INSTITUTE OF TECHNOLOGY
INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ
Autumn Examinations 2008/
Module Title: Applied Thermodynamics
Module Code: INTR 8004
School: Mechanical and Process Engineering
Programme Title: Bachelor of Engineering (Honours) in Mechanical Engineering – Award
Programme Code: EMECH_8_Y
External Examiner(s): Prof R Clarke, Mr P Clarke Internal Examiner(s): Dr K McMullan
Instructions: Answer 3 questions. All questions carry equal marks.
Duration: 2 Hours
Sitting: Autumn 2009
Requirements for this examination: Steam tables, Log book
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. Describe the main processes available to a HVAC engineer that can be used to condition a moist air-stream. Identify each on a psychrometric sketch. (7 Marks)
Explain the difference between relative humidity and humidity ratio. (3 Marks)
Using the Psychrometric chart attached answer the following question; include the chart with your answer script.
Water from a power-plant condenser enters a forced-draft wet cooling tower at 45degC at a rate of 130kg/s, and is cooled to 30degC. Atmospheric air at 1bar, 25degC dry-bulb temperature, Relative Humidity 50% enters the tower and leaves in a saturated state at 32degC. Make-up water enters at 30degC. If fan work is neglected, determine the following:
- Volumetric flow-rate of air entering the cooling-tower (13 Marks)
- Mass flow-rate of make-up water (10 Marks)
Q2. With regard to a converging-diverging adiabatic frictionless nozzle flowing gas, describe the possible pressure distributions along the nozzle and potential shock locations depending on the pressure ratio. Use a sketch to enhance your explanation. (10 Marks)
A normal shock occurs in a flow of air where the Mach number is 1.6. The local temperature and pressure immediately upstream of the shock are 210K and 170kPa. Determine the change in the following values across the shock:
- T • P • T 0 • P (^0) (23 Marks)
- Isentropic flow for k=1.4 Normal shock for k=1.
