FUNDAMENTALS OF POWER PLANT ENGINEERING

FUNDAMENTALS OF POWER PLANT ENGINEERING THERMODYNAMICS 1. An air bubble rises from the bottom of a well where the temperature is 25 ºC, to the surface where the temperature is 27 ºC. Find the percent increase in the v ...

FUNDAMENTALS OF POWER PLANT ENGINEERING THERMODYNAMICS 1. An air bubble rises from the bottom of a well where the temperature is 25 ºC, to the surface where the temperature is 27 ºC. Find the percent increase in the volume of the bubble if the depth of the well is 5 m. Atmospheric pressure is 101,528 Pascals. Answer: A A. 49.3 B. 56.7 C. 41.3 D. 38.6 2. An ideal gas is 45 psig and 80 ºF is heated in a closed container to 130 ºF. What is the final pressure? Answer: B A. 54 psia B. 65 psia C. 75 psia D. 43 psia 3. A large mining company was provided with a 3000 cm3 of compressed air tank. Air pressure in the tank drops from 700 kPa to 180 kPa while the temperature remains unchanged at 28 ºC. What percentage has the mass of air in the tank been reduced? Answer: A A. 74 B. 72 C. 76 D. 78 4. How much work is necessary to compress air in an insulated cylinder from 0.20 m3 to 0.01 m3. Use T1 = 20 ºC and P2 = 100 kPa. Answer: D A. 113.4 kJ B. 121.4 kJ C. 110.1 kJ D. 115.7 kJ 5. A heat engine is operated between temperature limits of 1370 ºC and 260 ºC. Engine is supplied with 14,142kJ/kwh. Find the Carnot cycle efficiency in percent. Answer: C A. 70.10 B. 65.05 C. 67.56 D. 69.32 6. A closed vessel contains air at a pressure of 160 kN/m2 gauge and temperature of 30 ºC. The air is heated at constant volume to 60 ºC with the atmospheric pressure of 759 mm Hg. What is the final gauge pressure? Answer: B A. 174 B. 186 C. 167 D. 1727. What is the temperature in ºC of 2 liters of water at 30 ºC after 500 Calories of heat have been added? Answer: B A. 35.70 B. 30.2 C. 38 D. 39.75 8. A volume of 450 cm3 of air is measured at a pressure of 740 mm Hg absolute and a temperature of 20 ºC. What is the volume in cm3 at 760 mm Hg absolute and 0 ºC? Answer: B A. 516.12 B. 408.25 C. 620.76 D. 375.85 9. Assuming compression is according to the law PV=constant. Calculate the initial volume of gas at a pressure of 2 bar which will occupy a volume of 6 m3 when it is compressed to a pressure of 42 bar. Answer: A A. 1263 B. 1203 C. 1303 D. 1363 10. A steam condenser receives 10 kg per second of steam with an enthalpy of 2,570kJ/kg. Steam condenses into liquid and leaves with an enthalpy of 160kJ/kg. Cooling water passes through the condenser with temperature increases from 13 ºC to 24 ºC. Calculate the cooling water flowrate in kg/s. A. 533 B. 518 C. 523 D. 528 11. A steam expands adiabatically in a turbine from 2,000 kPa, 400 ºC to 400 kPa, 250 ºC. What is the effectiveness og the process in percent assuming an atmospheric temperature of 15 ºC. Neglect changes in kinetic and potential energy. Answer: C A. 82 B. 84 C. 80 D. 86 12. Steam enters the superheaters of a boiler at a pressure of 25 bar and dryness of 0.98 and leaves at the same pressure at a temperature of 370 ºC. Calculate the heat energy supplied in the suerheaters. Properties of steam: At 25 bar and 370 ºC (h= 3171.8kJ/kg) and at 25 bar and 0.98 dryness (hf =962.11kJ/kg, hfg =1841.01kJ/kg).Answer: C A. 407.46 B. 408.57 C. 405.51 D. 406.5413. The thermal efficiency of a particular engine operating on an ideal cycle is 35%. Calculate the heat supplied per 1200 watt-hr of work developed in kJ. Answer: A A. 12,343 B. 10,216 C. 14,218 D. 11,108 14. Determine the average Cp value in kJ/kg-K of a gas if 522 kJ of heat is necessary to raise the temperature from 300 K to 800 K making the pressure constant. Answer: B A. 1.440 B. 1.044 C. 1.038 D. 1.026 15. Determine the force in Newtons required to produce an acceleration of 0.30 m/s2 on a 0.05 kg mass. Answer: C A. 0.018 N B. 0.025 N C. 0.015 N D. 0.200 N 16. Ammonia weighing 22 kg is confined inside a cylinder equipped with a piston has an initial pressure of 413 kPa at 38 ºC. If 2900 kJ of heat is added to the ammonia until its pressure and temperature are 413 kPa and 100 ºC, respectively. What is the amount of work done by the fluid in kJ? Answer: A A. 667 B. 304 C. 420 D. 502 17. What is the total required heating energy in raising the temperature of a given amount of water when the energy supplied is 1000 kwh with heat losses of 25%? Answer: C A. 1000 B. 1500 C. 1333 D. 1250 18. A vessel of 0.058 m3 capacity is well insulated and is divided equally by rigid conducting diaphragm. Initially both halves contain air at pressure of 137.8 kPa and 413.4 kPa and a temperature of 27 ºC and 177 ºC respectively. What is the increase of entropy of the system in kJ/ ºC. Answer: C A. 1.002 B. 0.5080 C. 0.00173 D. 0.1080