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sample-midterm - RYERSON UNIVERSITY Department of...

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Unformatted text preview: RYERSON UNIVERSITY Department of Mechanical and Industrial Engineering APPLIED THERMODYNAMICS - MEC514 MIDTERM TEST DATE: 30 October 2009 SECTIONS: 011-051 TIME: 1 hour & 30 minutes EXAMINER: Prof. R.S. Budny ASSOCIATE: Prof. J. Dimitriu INSTRUCTIONS: 1. OPEN BOOK TEST. Suggested aids for your own personal use are: course textbook; class notes + assignments & solutions (as sold at Alicos); non-communicating electronic calculator; drawing instruments (i.e., “rolling” ruler, set squares, protractor, pens and pencils). 2. Prohibited items include: cell-phones (text and/or video display), pagers and other wireless devices, Palm-pilots, laptop computers, radios/video/music players etc.. These must be switched off and left at the front of the test room. 3. Leave all bags and brief cases at the front of the test room. Traveling back and forth to bags and brief cases while the test is in progress is NOT permitted. 4. Candidates may not borrow or lend any materials while the test is in progress. 5. Answer all three (3) questions. Marks are as indicated. Total marks equal 24. 6. Answer questions in the space provided. You may use the back of the page if required. 7. Candidates must layout their work clearly and legibly at all times; otherwise, marks may be lost. Illegible answers will not be graded. 8. Full marks will be awarded for correct answers using the correct method. Marks will be deducted for incorrect units. 9. Use engineering judgment when answering questions. If you feel that there is a genuine error or omission in any question then make an assumption and draw this to the attention of the examiner right on the test paper and continue with the solution. 10. DO NOT detach any sheets from the test paper. Seat# Student Name (Please Print) Section Number Circle one of 011, 021, 031, 041, 051 Student Number Question Mark 1. 2. 3. Total MEC514.F09 - 2 of 7 - Midterm Test QUESTION 1 [Total Marks = 9]. A steam power cycle with two feedwater heaters is shown below. The enthalpy values for each point 1-12 are supplied in the table below and must be used to answer each question. The extraction steam mass fractions are shown as (y1) for the first heater and (y2) for the second heater. Note that the flow splits at point 2 into mass fractions (y1) and (1-y1). Assume saturated liquid at points 6*, 8*, and 11*. The steam cycle pressures are also included to provide a general idea of system pressures. Include the effects of pump work even though it may appear to be small. In parts (b) to (d) below, kJ/kg means kJ per kg of main steam flow (i.e., m1 ). Determine the following: ˙ (a) The steam mass fractions, y1 and y2 [2 Marks], (b) The total heat supplied in the steam generator (in kJ/kg) [1 Mark], (c) The work output (in kJ/kg) for each turbine section [3 Marks], (d) The work input (in kJ/kg) for each pump [2 Marks], and, (e) The cycle thermodynamic efficiency [1 Mark]. Steam Generator Enthalpy & Pressure Data 3, (1-y1) Reheater (* = saturated liquid state) Point h (kJ/kg) (1-y1) p (bar) 1 T1 T2 Closed heater (y1) Open heater 9 P 10 4 (y2) 8* P Pump 2 11* Trap Condenser 7 Pump 1 12, (y1) 6* 2477.1 20 3247.6 20 4 2706.7 2 5 5, (1-y1-y2) (1-y1) 2 90 3 T3 2742.1 2 1 2147.3 0.04 6* 121.5 0.04 7 121.7 2 8* 504.7 2 9 512.1 90 10 908.8 90 11* 908.8 20 12 908.8 2 MEC514.F09 QUESTION 1 (extra space). - 3 of 7 - Midterm Test MEC514.F09 - 4 of 7 - Midterm Test QUESTION 2 [Total Marks = 8]. The steam plant shown below operates as an ideal cycle with isentropic turbine (i.e., s1 = s2 = s3) and isentropic pump (i.e., s4 = s5) processes. Superheated steam enters turbine T1 at 100 bar. At point 2 a small quantity of dry saturated steam at 9 bar is extracted for feedwater heating and the rest of the steam expands through turbine T2 and exits as wet steam at 0.08 bar. Saturated liquid at 0.08 bar leaves the condenser at point 4*. The water is pressurized in the pump to 100 bar, passes through the closed feedwater heater and then enters the steam generator. At point 7* saturated liquid at 9 bar leaves the heater, passes through a steam trap and is then returned to the condenser at 0.08 bar. Determine the enthalpies h1 to h8 using the steam tables but reading data to the nearest row is not acceptable – you must use proper interpolation when required. Steam Generator 1 T1 Generator T2 3 2 6 Closed Heater Condenser 5 P 4* Pump 7* 8 Trap (a) Find enthalpy h1, (in kJ/kg). [1 Mark] (b) Find enthalpy h2, (in kJ/kg). [1 Mark] (c) Find enthalpy h3, (in kJ/kg). [1 Mark] MEC514.F09 - 5 of 7 - QUESTION 2 (continued). (d) Find enthalpy h4, (in kJ/kg). [1 Mark] (e) Find enthalpy h5, (in kJ/kg). [1 Mark] (f) Find enthalpy h6, (in kJ/kg) assuming an infinitely large heater. [1 Mark] (g) Find enthalpy h7, (in kJ/kg). [1 Mark] (h) Find enthalpy h8, (in kJ/kg). [1 Mark] Midterm Test MEC514.F09 - 6 of 7 - Midterm Test QUESTION 3 [Total Marks = 7]. An ideal regenerative gas turbine has a compressor with a pressure ratio of 6 as shown in the diagram below. Air enters the compressor at 101 kPa (absolute), 300 K. The combustor exit temperature is 1200 K and the regenerator effectiveness is 75%. The expansion is in two turbine stages where all of the power developed by the first stage is used to drive the compressor. The second stage is a free-power turbine which drives the generator. Regenerator 7 101 kPa 1200 K Combustor 2 3 Compressor 1 4 Turbine 1 Air 101 kPa 300 K 5 6 Free-power Turbine 2 Generator Assuming a cold air-standard cycle (constants k = 1.4, R = 0.287 kJ/kg·K, cp = 1.005 kJ/kg·K): (a) Determine temperature T2 (in Kelvin) [1 Mark], (b) Determine temperature T5 (in Kelvin) [1 Mark], (c) Determine pressure p5 (in kPa) [1 Mark], MEC514.F09 - 7 of 7 - Midterm Test Question 3 (continued). (d) Determine temperature T6 (in Kelvin) [1 Mark], (e) Determine temperature T3 (in Kelvin) [1 Mark], (f) Determine temperature T7 (in Kelvin) [1 Mark], and, (g) Determine the thermodynamic efficiency of the cycle (in percent) [1 Mark]. ...
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