Powerplant-reviewer-2.docx

EXAM MARCH 2017 1. Consider a 320 MW steam power plant at turbine-generator efficiency of 86% which operates on a simple ideal Rankine cycle. Steam enters the turbine at 3 Mpa and 500°C (h= 3398.3 KJ/kg) and is cooled in the condenser at a pressure of 12 Kpa and enthalpy of 2141 KJ/kg at turbine exit. Find the mass of liquid at the turbine exit in kg/hr. A. 102,064 kg/hr

B. 201,165 kg/hr

C. 223,751 kg/hr

D. 206,938 kg/hr

Ans. B 2. Consider a 160 MW steam power plant has a generator efficiency of 90% which operates on a simple ideal Rankine cycle. Steam enters the turbine at 1300 psia and 1000°F (h= 1496.6 Btu/lb) and is cooled in the condenser at a pressure of 2 psia (h= 962.8 Btu/lb at turbine exit). Find the mass of flash gas on the surface of liquid in the condenser lb/hr. A. 965,755 lb/hr

B. 956,755 lb/hr

C. 855,755 lb/hr

D. 653,409 lb/hr

Ans. B

3. Consider a coal-fired steam power plant which produces 300 MW of electric power. The power plant operates on a simple ideal Rankine cycle with turbine inlet conditions of 6 Mpa and 500°C (3422.2 KJ/kg) and a condenser pressure of 20 kpa with 83% quality at turbine exit. The coal used has a heating value (energy released when the fuel is burned) generator has an efficiency of 96%. Determine he overall plant efficiency. A. 21.61%

B. 13.61%

C. 27.61%

D. 32.61%

Ans. C 4. Consider a coal-fired steam power plant which produces 300 MW of electric power. The power plant operates on a simple ideal Rankine cycle with turbine inlet conditions of 6 Mpa and 500°C (3422.2 KJ/kg) and a condenser pressure of 20 kpa. The coal used has a heating value (energy released when the fuel is burned) of 29.300 KJ/kg. Assuming that 75% of this energy is transferred to the steam in the boiler and that the electric generator has an efficiency of 96%, determine the required rate of heat supply in tons/hr. A. 124.18 tons/hr

B. 714.18 tons/hr

C. 417.18 tons/hr

D. 147.18 tons/hr

Ans. D. 5. Consider a steam power plant which operates on a reheat Rankine cycle and has a net power output of 175 MW. Steam enter the high-pressure turbine at 1500 psia and 1200°F (h=1607.1 Btu/lb) and the low pressure turbine at 500 psia and 1100°F (1575.1 Btu/lb). Steam leaves the condenser as saturated liquid at a pressure of 3 psia. The adiabatic efficiency of the turbine is 82% and that of the pump is 95%. Determine the thermal efficiency of the plant if the enthalpy at the exit of the high pressure turbine is 1423 Btu/lb. Turbine exit quality is 82%. A. 44.66%

B. 42.66%

C. 37.66%

D. 47.65%

Ans. A. 6. Consider a steam power plant which operates on a reheat Rankine cycle and has a net power output of 175 MW. Steam enter the high-pressure turbine at 1600 psia and 1200°F (h=1607.1 Btu/lb) and the low pressure turbine at 500 psia and 1100°F (1575.1 Btu/lb). Steam leaves the condenser as saturated liquid at a pressure of 3 psia. The adiabatic efficiency of the turbine is 82% and that of the pump is 95%. Determine the mass of steam requirement, kg/s if the enthalpy at the exit of the high pressure turbine is 1423 Btu/lb. Turbine exit quality is 82%. A. 112 kg/s

B. 121 kg/s

C. 211 kg/s

D. 108 kg/s

Ans. A. 7. A Carnot refrigeration cycle has an evaporator temperature of 10°C and condenser temperature of 50°C. The volume flow of the water entering the condenser is 80 gal/min where the temperature increases from 20°C to 35°C. Find the power input to the compressor if compressor efficiency is 80% and motor efficiency is 90%, and the chilled water enters the evaporator at 34°C and leaves at 25°C. A. 123 hp

B. 162 hp

C. 73 hp

D. 65 hp

Ans. C. 8. A Carnot refrigeration cycle has an evaporator temperature of 8°C and condenser temperature of 50°C. The volume flow of the water entering the condenser is 80 gal/min where the temperature increases from 20°C to 35°C. Find the gallons per minute required of chilling water in the evaporator for a temperature decrease of 10°C and compressor efficiency is 80% and motor efficiency is 90%. A. 100.40 gpm

B. 104.40 gpm

C. 108.4 gpm

D. 112.40 gpm

Ans. B. 9.A Carnot refrigeration cycle has an evaporator temperature of 10°C and condenser temperature of 54°C. The volume flow of the water entering the condenser is 80 gal/min where the temperature enters at 20°C. The compressor efficiency is 80% and motor efficiency is 90% and the chilled water enter the evaporator at 34°C and leaves at 25°C. Find the power requirement in the compressor in KW/KW refrigeration. A. 0.155 KW/KW

B. 0.255 KW/KW

C. 0.355 KW/KW

D. 0.455 KW/KW

Ans. A. 10. A Carnot refrigeration cycle has an evaporator temperature of 10°C and condenser temperature of 48°C. The volume flow of the water entering the condenser is 80 gal/min where the temperature leaves at 35°C, and compressor efficiency is 80% and motor efficiency is 90%. Find the power requirement in the compressor in KW/Ton refrigeration. A. 0.127 KW/Ton

B. 4.447 KW/Ton

C. 0.447 KW/Ton

D. 0.627 KW/Ton

Ans. C. 11. A Carnot refrigeration cycle has an evaporator temperature of 10°C and condenser temperature of 48°C. The volume flow of the water to be cooled entering the evaporator has a rate of 120 gal/min at 33°C. The temperature differentials between evaporator and water leaving the evaporator is 6°C. The compressor has a cylinder dimensions of 10 in x 12 inches running at 400 rpm. The compressor efficiency is 80% and motor efficiency is 90%. Find the monthly bills of the system if the electric cost is P12.00 per kW-hr. A. P821,517/month

B. P822.517/month C. P823,517/month

D. P824,517/month

Ans. B. 12. A Carnot refrigeration cycle has an evaporator temperature of 10°C and condenser temperature of 48°C. The volume flow of the water to be cooled entering the evaporator has a rate of 120 gal/min at 33°C. The temperature differentials between evaporator and water leaving the evaporator is 6°C. The compressor has a cylinder dimensions of 10 in x 12 inches running at 400 rpm. The compressor efficiency is 80% and motor efficiency is 90%.Find the gallons per of the cooling requirements in the condenser for a temperature rise of 18°F. A. 4830 gpm

B. 1240 gpm

C. 230 gpm

D. 235 gpm

Ans. C. 13. Heat is supplies to an absorption refrigeration system from a geothermal well of 130°C at a rate of 106 Btu/hr. The environment is at 25°C, and the refrigerated space is maintained at 30°C. Determine the maximum rate at which this system can remove heat from the refrigerated space. A. 602,977 Btu/hr

B. 604,797 Btu/hr

C. 606,779 Btu/hr

D. 608,987 Btu/hr

Ans. A. 14. A Carnot heat plump is to be used for heating a house and maintaining it at 20°C during the winter. On the day when the average outdoor temperature remains at 2°C, the house is estimated to lose heat at a steady rate of 85,000 KJ. If the heat pump consumes 8 kW of power while operating, determine how long the heat pump run on that day. A. 4.65 min

B. 8.99 min

C. 132. 94 min

D. 10.88 min

Ans. D. 15. A Carnot heat plump is to be used for heating a house and maintaining it at 20°C during the winter. On the day when the average outdoor temperature remains at 2°C, the house is estimated to lose heat at a steady rate of 85,000 KJ/hr. If the heat pump consumes 8 kW of power while operating, determine the total heating costs, assuming an average price of P13.00 per KW-hr.

A. P472.66/hr

B. P9340.77/hr

C. 10.23/hr

D.P 19.96/hr

Ans. D. 16. A heat pump with a COP of 3.2 is used to heat a house. When running, the heat pump consumes power at the rate of 5 KW. If the temperature in the house is 7°C when the heat pump is turned on, how long will it take for the heat pump to raise the temperature of the house to 25°C? The volume of the air in the house is 700 m3. A. 13.83 min

B. 15.83 min

C. 17.83 min

D. 19.83 min

Ans. B. 17. The average atmospheric pressure in Denver (elevation = 610m) is 85 kPa. Determine the temperature at which water is uncovered pan will boil in Denver. A. 93.14°C

B. 95.14°C

C. 66.14°C

D. 71.14°C

Ans. B. 18. Water in a 5 cm deep pan is observed to boil at 98°C. At what temperature will the water in a 40 c deep pan boil? Assume both pans are full with water. A. 208.4°F

B. 218.8°F

C.228.7°F

D. 238.5°F

Ans. A. 19. Consider a Carnot cycle executed in a closed system with 0.005 kg of air. The temperature limits of the cycle are 300 and 1020K, and the minimum and maximum pressures that occur during the cycle are 20 and 1900 kPa. Assuming constant specific heats, determine the net work output per cycle. A. 5.939 KJ

B. 8.043 KJ

C. 1.912 KJ

D. 0.279 KJ

Ans. D. 20. An air-standard Carnot cycle is executed in a closed system between the temperature limits of 350 and 1250K. The pressures before and after the isothermal compression are 150 and 300 kPa, respectively. If the net work output per cycle is 0.6 KJ, determine the maximum pressure in the cycle. A. 22,659 kPa

B. 23,782 kPa

C. 24,965 kPa

D. 25,827 kPa

Ans. D. 21. An air-standard Carnot cycle is executed in a closed system between the temperature limits of 350 and 1250K. The pressures before and after the isothermal compression are 150 and 300 kPa, respectively. If the net work output per cycle is 0.6 KJ, determine the heat transfer to air. A. 231.94 KJ/kg

B. 248.67 KJ/kg

C. 242.94 KJ/kg

D. 257.02 KJ/kg

Ans. B. 22. It is desired to double the COP of a reversed Carnot engine for cooling from 5.0 by raising the temperature of heat addition while keeping the temperature of heat rejection constant. By what percentage must the temperature of heat addition be raised? A. 5.098%

B. 7.098%

C. 9.098%

D. 11.098%

Ans. C. 23. A small pump serving as model, when tested in the laboratory using water at 3600 rpm, delivered 3.0 cfs at a head of 125 ft. If the efficiency of this model pump is 84%. Predict the horsepower input to the prototype pump if it is to develop the same head as model pump and the model pump has a scale ratio of 1:10. Assume the efficiency of the prototype pump is 90%. A. 8304 hp

B. 6534 hp

C. 4863 hp

D. 4727 hp

Ans. D. 24. A pump will be installed below the reservoir water surface with a required net positive suction head (𝑁𝑁𝑁𝑁 ) of 50 ft. The barometric pressure is 14.3 psia, and the vapor pressure is 0.5 psia. Assume a friction losses in the intake piping are 5 ft. find the maximum allowable elevation of the pump relative to the water surface intake to avoid cavitation. A. 5,983 ft

B. 23,154 ft

C. 76,397 ft

D. 32, 083 ft

Ans. B 25. Centrifugal pump at best efficiency point (BEP). Assume the pump characteristic are head, h = 7m., flow rate, Q = 19 liters/sec, and rotative speed n = 1170 rpm. Find the specific speed in SI units. A. 0.7107

B. 0.6530

C. 0.4329

D. 0.0826

Ans. A 26. How many identical turbines, operating at 139.0 rpm and 91% efficiency (specific speed = 5.4), are needed to exploit a head of 1200 ft and a flow of 1660 ft 3 /s. A. 1 turbine

B. 2 turbines

C. 3 turbines

D. 4 turbines

Ans. C. 27. How many poles should a 60-Hz generator have, if it is connected to a turbine operating under a design head of 3000 ft with a flow of 82 cfs? Assume turbine specific speed and efficiency 3 and 84 percent respectively. Choose high speed generator. A. 14-pole Ans. A

B. 16-pole

C. 18-pole

D. 20-pole

28. A model pump delivering water at 180°F (y = 60.0 lb/ft 3 . 𝑃𝑟𝑜𝑐𝑒𝑠𝑠 = 7.54 psia) at 900 gpm and 2500 rpm begins to cavitate when the inlet pressure and velocity are 13 psia and 22 fps. Find the required NPSH of a prototype which is 4 times larger and runs at 1100 rpm. A. 63.47 ft

B. 21.39 ft

C. 382.34 ft

D. 75.33 ft

Ans. A 29. What is the powe r ratio of a pump and its 1/5 scale model if the ratio of heads is 4 to 1? A. 176.45

B. 199.98

C. 283.40

D. 207.45

Ans. B 30. A cylindrical flash tank mounted with its axis horizontal is used to separate liquid ammonia from ammonia vapor. The ammonia vapor bubbles through the liquid with 70 m3 /min leaving the disengaging surface. The disengaging rate is limited to 60 m/min and the liquid level is to operate with the liquid level one-third of the diameter from the top. Determine the diameter if the tank is 1.5 m long. A. 763.40 mm

B. 611.23 mm

C. 827.31 mm

D. 967.34 mm

Ans. C. 31. Kerosene is the fuel of a gas turbine plant: fuel – air ratio, 𝑚1 = 0.012, 𝑇3 = 972K, pressure ratio, 𝑟2 = 4.5, exhaust to atmosphere. Find the available energy in KJ per kg air flow. Assume k = 1.34 and 𝐶2 = 1.13. A. 350 kJ/kg

B. 353 kJ/kg

C. 357 kJ/kg

D. 481 kJ/kg

Ans. B. 32. An air-standard Carnot cycle is executed in a closed system between the temperature limits of 350 and 1250K. The pressures before and after the isothermal compression are 150 and 300 kPa, respectively. If the net work output per cycle is 0.6 KJ, determine the mass of air. A. 0.00135 kg

B. 0.00335 kg

C. 0.00535 kg

D. 0.00735 kg

Ans. B 33. An air-standard Carnot cycle is executed in a closed system between the temperature limits of 550 and 2000R. The pressures before and after the isothermal compression are 20 and 40 psia, respectively. If the net work output per cycle is 0.5 Btu, determine the maximum pressure in the cycle. A. 3753 psia

B. 3668 psia

C. 3693 psia

D. 1876 psia

Ans. B 34. An air-standard Carnot cycle is executed in a closed system between the temperature limits of 550 and 2000R. The pressures before and after the isothermal compression are 20 and 40 psia, respectively. If the net work output per cycle is 0.5 Btu, determine the heat transfer to air. A. 90 Btu/lb

B. 95 Btu/lb

C. 97 Btu/lb

D. 89 Btu/lb

Ans. B 35. An air-standard Carnot cycle is executed in a closed system between the temperature limits of 550 and 2000R. The pressures before and after the isothermal compression are 20 and 40 psia, respectively. If the net work output per cycle is 0.5 Btu, determine the mass of air. A. 0.07260 lb

B. 0.00726 lb

C. 0.00666 lb

D. 0.00534 lb

Ans. B 36. An ideal Otto cycle has a compression ratio of 8. At the beginning of the compression process, air is at 97 kPa and 29°C, and 760 KJ/kg of heat is transferred to air during the constant volume heat addition process. Determine the pressure and temperature at the end of heat addition process. A. 1654.48 K, 4664 kpa C. 1864.57 K, 1663 kpa

B. 1751.42 K, 4500 kpa D. 1783.27 K, 1043 kpa

Ans. B 37. A hair dryer is basically a duct in which a few layers of electric resistors are placed. A small fan pulls the air in and forces it through the resistors where it is heated. Air enters a 1200 W hair dryer at 100 kPa and 22°C and leaves at 50°C. The cross sectional area of the hair dryer at the exit is 55 cm3. Neglecting the power consumed by the fan and the heat losses through the walls of the hair dryer, determine the volume flow rate of air at the inlet. A. 0.01611 m3

B. 0.03611 m3

C. 0.05611 m3

D. 0.07611 m3

Ans. B 38. An ideal Otto cycle has a compression ratio of 8. At the beginning of the compression process, air is at 97 kPa and 29°C, and 760 KJ/kg of heat is transferred to air during the constant volume heat addition process. Determine the mean effective pressure, kPa. A. 529 kPa

B. 539 kPa

C. 549 kPa

D. 579 kPa

Ans. C 39. An air-standard Diesel cycle has a compression ratio of 15 and cut-off ratio of 2:1. At the beginning of the compression process, air is at 14.7 psia and 82°F. Accounting for the variation of the specific heats with the temperature, determine the temperature at the end of the expansion process. A. 1345.53 R

B. 1225.53 R

C. 1531.26 R

D. 1255.53 R

Ans. C 40. An air-standard Diesel cycle has a compression ratio of 18. Air is at 27°C and 0.11 Mpa at the beginning of the compression process and at 2000 K at the end of heat addition process. Determine the pressure after expansion process. A. 84.78 kpa Ans. D.

B. 386.39 kpa

C. 318.45 kpa

D. 310.39 kpa

41. An air-standard Diesel cycle has a compression ratio of 18. Air is at 27°C and 0.11 Mpa at the beginning of the compression process and at 2000 K at the end of heat addition process. Determine the heat rejection. A. 845.67 KJ/kg

B. 394.67 KJ/kg

C. 374.57 KJ/kg

D. 392.73 KJ/kg

Ans. D 42. An air-standard Diesel cycle has a compression ratio of 18. Air is at 27°C and 0.11 Mpa at the beginning of the compression process and at 2000 K at the end of heat addition process. Determine the mean effective pressure. A. 837.32 kpa

B. 857.32 kpa

C. 877.32 kpa

D. 891.50 kpa

Ans. D 43. The compression ratio of an ideal dual cycle is 14. Air is at 100 kPa and 300K at the beginning of the compression process and at 2300K at the end of heat addition process. Heat transfer takes place partly at constant volume and partly constant pressure, and it amounts to 1530 KJ/kg. Assuming variable specific heats for air, determine the fraction of heat transferred at constant volume. A. 42.63%

B. 45.85%

C. 40.31%

D. 36.83%

Ans. C 44. The compression ratio of an ideal dual cycle is 14. Air is at 100 kPa and 300K at the beginning of the compression process and at 2300K at the end of heat addition process. Heat transfer takes place partly at constant volume and partly constant pressure, and it amounts to 1530 KJ/kg. Assuming variable specific heats for air, determine the thermal efficiency. A. 62.72%

B. 68.45%

C. 60.47%

D. 65.34%

Ans. A 45. The compression ratio of an ideal dual cycle is 14. Air is at 100 kPa and 300K at the beginning of the compression process and at 2300K at the end of heat addition process. Heat transfer takes place partly at constant volume and partly constant pressure, and it amounts to 1530 KJ/kg. Assuming variable specific heats for air, determine the temperature after isentropic expansion. A. 1630 K

B. 1682 K

C. 1593 K

D. 1600 K

Ans, A 46. The compression ratio of an ideal dual cycle is 14. Air is at 100 kPa and 300K at the beginning of the compression process and at 2300K at the end of heat addition process. Heat transfer takes place partly at constant volume and partly constant pressure, and it amounts to 1530 KJ/kg. Assuming variable specific heats for air, determine the heat rejected. A. 923.56 KJ/kg Ans. C

B. 947.47 KJ/kg

C. 955.70 KJ/kg

D. 965.45 KJ/kg

47. An ideal Ericsson engine using helium as the working fluid operates between temperature limits of 560 and 3000R and pressure limits of 30 and 210 psia. Assuming a mass flow rate of 9 lb/s, determine the heat transfer rate in the regenerator. A. 26,304 Btu/s

B. 25,345 Btu/s

C. 27,436 Btu/s

D. 27,421 Btu/s

Ans. D 48. An ideal Ericsson engine using helium as the working fluid operates between temperature limits of 580 and 3000R and pressure limits of 30 and 210 psia. Assuming a mass flow rate of 9 lb/s, determine the power delivered. A. 5,048 hp

B. 4,652 hp

C. 4,125 hp

D. 4,973 hp

Ans. C 49. Consider an ideal Ericsson cycle with air as the working fluid executed in a steady-flow system. Air is at 27°C and 115 kPa at the beginning of the isothermal compression process during which 150 KJ/kg of heat is rejected. Heat transfer to air occurs at 1300K. Determine the maximum pressure of the cycle. A. 717.48 kpa

B. 737.48 kpa

C. 757.48 kpa

D. 777.48 kpa

Ans. B 50. Consider an ideal Ericsson cycle with air as the working fluid executed in a steady-flow system. Air is at 27°C and 115 kPa at the beginning of the isothermal compression process during which 160 KJ/kg of heat is rejected. Heat transfer to air occurs at 1300K. Determine the net work. A. 543.45 KJ/kg

B. 521.23 KJ/kg

C. 485.72 KJ/kg

D. 533.33 KJ/kg

Ans. D 51. An ideal Stirling engine using helium as the working fluid operates between temperature limits of 300 and 2120 K and pressure limits of 100 kPa and 1.90 Mpa. Assuming the mass if the helium used in the cycle is 1.5 kg, determine the amount of heat transfer in the regenerator. A. 6,293.04 KJ

B. 8,482.46 KJ

C. 8,597.43 KJ

D. 8,653.45 KJ

Ans. C 52. An ideal Stirling engine using helium as the working fluid operates between temperature limits of 300 and 2120 K and pressure limits of 100 kPa and 1.90 Mpa. Assuming the mass if the helium used in the cycle is 1.5 kg, determine the work output. A. 5,612.22 KJ

B. 5,694.52 KJ

C. 5,654.56 KJ

D. 5,763.45 KJ

Ans. A 53. In a pitot tube the pressure of air at the orifice is 14 psia and the temperature is 80°F. The flow coefficient is 0.95 and the throat diameter of the orifice is 1 inch and the absolute pressure in the reservoir is greater than 1.89 times the exhaust pressure. Find the mass flow in lb/sec. A. 0.238 lb/s

B. 0.483 lb/s

C. 0.592 lb/s

D. 0.954 lb/s

Ans. A 54. In a pitot tube the pressure of air at the orifice is 14 psia and the temperature is 80°F. The flow coefficient is 0.95 and the throat diameter of the orifice is 1 inch and the absolute pressure in the reservoir is greater than 1.89 times the exhaust pressure. The diameter ratio is 2. Find the velocity approach factor. A. 1.084

B. 0.753

C. 0.0845

D. 0.968

Ans. D 55. In a pitot tube the pressure of air at the orifice is 14 psia and the temperature is 80°F. The discharge coefficient is 0.93 and the throat diameter of the orifice is 1 inch and the absolute pressure in the reservoir is greater than 1.89 times the exhaust pressure. The diameter ratio is 2. Find the flow coefficient. A. 0.83

B. 0.68

C. 0.96

D. 1.23

Ans. C 56. A pipe discharges water at 1000 gal per minute having a diameter of 2 inches. The pipe connects 300 ft reservoir to supply water for irrigation. Find the friction factor using Harris equation. A. 0.00736

B. 0.00973

C. 0.00294

D. 0.00631

Ans. D 57. A pipe discharges water at 1000 gal per minute having a diameter of 2 inches. The pipe connects 300 ft reservoir to supply water for irrigation. Find the friction factor using Weymouth equation. A. 0.00637

B. 0.07534

C. 0.01823

D. 0.00298

Ans. A 58. A pipe discharges water at 1000 gal per minute having a diameter of 2 inches. The pipe connects 300 ft reservoir to supply water for irrigation. Find the friction factor using Unwin equation. A. 0.07344

B. 0.00666

C. 0.09745

D. 0.00784

Ans. D 59. An air compressor has an absolute temperature of air delivered of 2000°R and absolute temperature of air supplied at 500°R. If the indicated volumetric efficiency is 86%, find the actual volumetric efficiency. A. 38.45%

B. 45.23%

C. 56.45%

D. 40.47%

Ans. D 60. In a centrifugal fan the most apparent pressure difference is 2.3 inches of water gage for forward curved with tip speed of 4000 fpm. To maintain a static pressure of 1 inch of water gage, at standard air density of 0.075 lb/ft 3 , find the tip speed for forward curved.

A. 2540 fpm

B. 2640 fpm

C. 2740 fpm

D. 2840 fpm

Ans. B 61. In a centrifugal fan the most apparent pressure difference is 1.3 inches of water gage for radial bladed with tip speed of 4000 fpm. To maintain a static pressure of 1 inch of water gage, at standard air density of 0.075 lb/ft 3 , find the tip speed for radial bladed. A. 3200 fpm

B. 3400 fpm

C. 3500 fpm

D. 3700 fpm

Ans. C 62. In a centrifugal fan the most apparent pressure difference is 0.75 inches of water gage for backward curved with tip speed of 4000 fpm. To maintain a static pressure of 1 inch of water gage, at standard air density of 0.075 lb/ft 3 , find the tip speed for backward curved. A. 4592 fpm

B. 4620 fpm

C. 4753 fpm

D. 4863 fpm

Ans. B 63. The compressor performance is operated at a rotor speed of 9200 rpm, and the pressure ratio of 3.5. The inlet total pressure is 2000 lb/ft 3 (abs) and the inlet total temperature is 40°F. If the wheel tip diameter is 2 ft and the inner diameter at entrance to the first stage is 1.3 ft. Find the sonic weight flow, lb/sec. A.86.16 lb/sec

B. 75.23 lb/sec

C. 98.34 lb/sec

D. 863.45 lb/sec

Ans. A 64. The compressor performance is operated at a rotor speed of 9200 rpm, and the pressure ratio of 3.5. The inlet total pressure is 2000 lb/ft 3 (abs) and the inlet total temperature is 40°F. If the wheel tip diameter is 2 ft and the inner diameter at entrance to the first stage is 1.3 ft. Find the weight flow, lb/sec, if the isentropic efficiency is 86% (compressor entering annulus = 0.55) A. 27.39 lb/s

B. 47.39 lb/s

C. 67.39 lb/s

D. 89.34 lb/s

Ans. B 65. At 1 atm pressure and 80°F the molar volume of any perfect gas is 394.5 ft 3 . Find the molar volume at 100°F and 30 in Hg. A. 374.56 ft 3

B. 381.40 ft 3

C. 408.02 ft 3

D. 399.92 ft 3

Ans. C 66. The following coal has the following ultimate analysis by weight: C = 70.5% S = 3.0%

H2 = 4.5% Ash = 11%

O2 = 6.0% Moisture = 4%

N2 = 1.0% C1 = 0.80

Find the heating value of solid fuel using Vondracek formula. A. 130 Btu/lb Ans. B

B. 133 Btu/lb

C. 136 Btu/lb

D. 139 Btu/lb

67. In an Orsat analysis the %CO2 of the product of combustion is 20%. If the percent excess air is 30%, find the maximum percentage of CO2 attainable. A. 23.45 %

B. 29.30%

C. 32.34%

D. 34.94%

Ans. D 68. A composite wall is made up of an external thickness of brickwork 110 mm thick inside which is a layer of fiberglass 75 mm thick. The fiberglass is faced internally by an insulating board 25 mm thick. The coefficients of thermal conductivity for the three are as follows: Brickwork Fiberglass Insulating board

1.5 W/m-K 0.04 W/m-K 0.06 W/m-K

The surface transfer coefficient of the inside wall is 3.1 W/m2 − K . Take the internal ambient air temperature as 50°F and the external temperature is 80.6°F. Determine the heat transfer coefficient of free convection in air for surface facing up. A. 0.763 Btu/hr − ft 2 − F

B. 0.293 Btu/hr − ft 2 − F

C. 1.963 Btu/hr − ft 2 − F

D. 0.894 Btu/hr − ft 2 − F

Ans. D 69. A composite wall is made up of an external thickness of brickwork 110 mm thick inside which is a layer of fiberglass 75 mm thick. The fiberglass is faced internally by an insulating board 25 mm thick. The coefficients of thermal conductivity for the three are as follows: Brickwork Fiberglass Insulating board

1.5 W/m-K 0.04 W/m-K 0.06 W/m-K

The surface transfer coefficient of the inside wall is 3.1 W/m2 − K . Take the internal ambient air temperature as 60°F and the external temperature is 127°F. Determine the heat transfer coefficient of free convection in air for surface facing down. A. 0.462 Btu/hr − ft 2 − F

B. 0.572 Btu/hr − ft 2 − F

C. 0.653 Btu/hr − ft 2 − F

D. 0.751 Btu/hr − ft 2 − F

Ans. B. 70. A composite wall is made up of an external thickness of brickwork 110 mm thick inside which is a layer of fiberglass 75 mm thick. The fiberglass is faced internally by an insulating board 25 mm thick. The coefficients of thermal conductivity for the three are as follows: Brickwork Fiberglass Insulating board

1.5 W/m-K 0.04 W/m-K 0.06 W/m-K

Take the internal water temperature is 80°F. Determine the heat transfer coefficient of free convection in liquid for a temperature difference of 110°F.

A. 0.593 Btu/hr − ft 2 − F

B. 0.632 Btu/hr − ft 2 − F

C. 0.873 Btu/hr − ft 2 − F

D. 0.293 Btu/hr − ft 2 − F

Ans. B 71. An insulated air pipe located where the ambient temperature is 32°C, has an inside diameter of 50 mm with 10mm thick wall. The outside diameter of the corrugated asbestos insulation is 125 mm and the surface coefficient of still air, h0 = 12 W/m2 − K. Inside the smooth plane pipe is atmospheric air with speed of 13 ft/sec. Thermal conductivity of pipe and asbestos insulation are 45 and 0.12 W/m-K respectively. Determine the inner surface film coefficient. A. 3.66 Btu/hr − ft 2 − F

B. 7.39 Btu/hr − ft 2 − F

C. 973 Btu/hr − ft 2 − F

D. 0.284 Btu/hr − ft 2 − F

Ans. A 72. An insulated air pipe located where the ambient temperature is 32°C, has an inside diameter of 50 mm with 10mm thick wall. The outside diameter of the corrugated asbestos insulation is 125 mm and the surface coefficient of still air, h0 = 12 W/m2 − K. Inside the smooth plane pipe is atmospheric air with speed of 40 ft/sec. Thermal conductivity of pipe and asbestos insulation are 45 and 0.12 W/m-K respectively. Determine the inner surface film coefficient. A. 2.91 Btu/hr − ft 2 − F C. 6.91 Btu/hr − ft 2 − F

B. 4.91 Btu/hr − ft 2 − F D. 8.91 Btu/hr − ft 2 − F

Ans. D 73. An insulation is to be applied to a building wall. The annual charge for this insulation is $0.006 per sqft for 1 in of thickness; k = 0.025 Btu/hr-ft-F; an average temperature difference of 25F will exist across insulation and the boundary thermal resistances for 6000 hours during the year. Total boundary thermal resistances are 0.78 h𝑟 − ft 2 − F/Btu and the value of the heat saved is $1.10 per million Btu. Estimate the economic thickness of the insulating material. A. 2.64 in

B. 5.24 in

C. 4.02 in

D. 19.23 in

Ans. A 74. Find the weight rate of isentropic flow of air (SG = 1.4) through an orifice with a diameter of 0.25 in if the initial velocity of the air is negligible; the initial pressure is 90 psia: the intial temperature is 100F, and the final pressure is 60 psia. A. 0.0182 lb/s

B. 0.0563 lb/s

C. 0.0951 lb/s

D. 0.9723 lb/s

Ans. C 75. Find the weight rate of isentropic flow of air (SG = 1.4) through an orifice with a diameter of 0.25 in if the initial velocity of the air is negligible; the initial pressure is 90 psia: the intial temperature is 100F, and the final pressure is 14.7 psia. A. 0.07364 lb/s

B. 0.0394 lb/s

C. 0.0992 lb/s

D. 0.1735 lb/s

Ans. C 76. A 2,000 kW diesel engine has a mechanical efficiency of 80%. If the engine uses oil with 45 Say bolts seconds find the Centistokes. A. 12.34

B. 5.9

C. 273.45

D. 0.283

C. 273.4

D. 21.23

Ans. B 77. Find the Centistokes of 75 Say bolts seconds. A. 13.9

B. 6.34

Ans. A 78. Find the Centistokes of 145 Say bolts seconds of a 300 kW diesel engine. A. 13.34

B. 25.67

C. 30.97

D. 37.33

Ans. C 79. Find the heat loss due to moisture if there are 0.035 lb H2 O per lb as-fired fuel if fuel temperature is 80°F and exit temperature is 500°F. A. 12.34 Btu/lb

B. 29.45 Btu/lb

C. 38.45 Btu/lb

D. 42.32 Btu/lb

Ans. D 80. Find the heat loss due to moisture if there are 0.025 lb H2 O per lb as-fired fuel if fuel temperature is 86°F and exit temperature is 700°F. A. 19.34 Btu/lb

B. 28.24 Btu/lb

C. 33.25 Btu/lb

D. 42.39 Btu/lb

Ans. C 81. Find the pressure drop (turn loss) in inches of water in a boiler pipe having a mass-velocity of 10,000 lb/h𝑟 − ft 2 of water and constant K = 1.5 for turn loss. The stack diameter is 5 ft. A. 0.000182 in water

B. 0.000384 in water

C. 0.000461 in water

D. 0.000745 in water

Ans. C 82. Find the Hard-grove grindability index of a pulverized coal having a weight of 12 grams of the sample passes through a 200-mesh sieve. A. 66.34

B. 73.49

C. 83.38

D. 96.16

Ans. D 83. Find the Hard-grove grindability index of a pulverized coal having a weight of 10 grams of the sample passes through a 200-mesh sieve. A. 82.3

B. 76.5

C. 62.1

D. 53.4

Ans. A 84. Find the critical pressure of wet steam passing through a nozzle having an initial pressure of 70 psia. A. 38.20 psia

B. 42.56 psia

C. 58.34 psia

D. 68.35 psia

Ans. A 85. In a steam turbine, find the critical speed of shaft carrying bucket with a deflection of 0.012 inch. A. 1623.46 rpm

B. 1716.19 rpm

C. 1862.34 rpm

D. 1973.56 rpm

Ans. B 86. In a steam turbine, find the critical speed of shaft carrying bucket with a deflection of 0.022 inch. A. 1,172.34 rpm

B. 1,267.50 rpm

C. 1,394.56 rpm

D. 1,492.34 rpm

Ans. B 87. Find the maximum capability of the turbine having a mass of steam rate of 5 kg/s and enthalpy of 500 KJ/kg. A. 3,125 kW

B. 3,325 kW

C. 3,525 kW

D. 3,725 kW

Ans. A 88. Assume a turbine with nominal rating of 75500 kW, 1800 rpm with the most efficient load at 80% of rating, 80% power factor on the generator. Find the generator efficiency at rated load. A. 63.45%

B. 76.39%

C. 82.34%

D. 95.56%

Ans. D 89. Assume a turbine with nominal rating of 75500 kW, 3600 rpm with the most efficient load at 80% of rating, 80% power factor on the generator. Find the generator efficiency at rated load. A. 63.49%

B. 78.34%

C. 82.34%

D. 94.72%

Ans. D 90. Assume a turbine with nominal rating of 75500 kW, 3600 rpm with the most efficient load at 80% of rating, 80% power factor on the generator. Find the loss in percent of nominal rating. A. 1.46%

B. 3.23 %

C. 5.34 %

D. 0.375%

Ans. A 91. Assume a turbine with nominal rating of 75500 kW, 3600 rpm with the most efficient load at 80% of rating, 80% power factor on the generator. Find the loss in kW of nominal rating A. 83.45 kW

B. 109.50 kW

C. 129.34 kW

D. 156.34 kW

Ans. B 92. A boiler feed pump has a pressure drop of 20 psig and pump efficiency of 80%. Find the temperature rise in °F due to pump losses. A. 0.2345 °F

B. 0.4923 °F

C. 0.8325 °F

D. 4.344 °F

Ans. C 93. Determine the space required by a condenser to maintain an exhaust pressure of 1.5 in Hg abs, when receiving 235,000 lb of exhaust steam per hour at an enthalpy of 1009.7 Btu per lb, with 65F circulating water, and 85% clean tubes. The condenser is to use 7/8 in OD No. 18 BWG tubes having an effective length of 24 ft arranged for two-pass circulating water flow. Velocity of water in tubes must not exceed 7 ft per second. A. 32 ft

B. 72 ft

C. 84 ft

D. 88 ft

Ans. C 94. Find the capacity pump in ft 3 /hr to remove air from surface condenser condensing 250,000 lb of steam per hr. Temperature of atmosphere, 65F; barometer, 29.6 in; temperature of condensate, 87F. A. 43,245 ft 3 /hr

B. 57,345 ft 3 /hr

C. 63,456 ft 3 /hr

D. 74,800 ft 3 /hr

Ans. D 95. Find the wind load in lb/ft 2 to be set aside for cooling tower needed to cool the condenser of a 300 ton refrigeration system if the wind speed is 120 mph. A. 43. 20 lb/ft 2

B. 34.57 lb/ft 2

C. 52.35 lb/ft 2

D. 94.63 lb/ft 2

Ans. A 96. Methyl alcohol (CH3 OH) is burned with 25% excess air. Find the percent volume of unburned oxygen will there be in the product if the combination is complete? A. 1.59%

B. 3.59%

C. 5.59%

D. 7.59%

Ans. B 97. Three tons of meat (beef) enter a freezing room each 24 hrs and 3 tons of meat are moved in the same period. The incoming meat is at 60F, and the all-frozen meat is removed at 0F. Compute the refrigerant load. A. 87.45 tons of refrigeration

C. 93.40 tons of refrigeration

B. 66.80 tons of refrigeration

D. 76.25 tons of refrigeration

Ans. B 98. Find the freezing time of the cake with thickness of 6 inches at a brine temperature of 26F. A. 6 hrs

B. 45 hrs

C. 42 hrs

D. 23 hrs

Ans. C 99. Find the equivalent capacity (diameter) to a 1 1⁄4 in, 1 1⁄2 in and 2 in pipe. A. 1 1⁄2 in

B. 2 1⁄2 in

C. 3 1⁄2 in

D. 4 1⁄2 in

Ans. B 100. Find the pressure loss of air flowing through a smooth sheet metal ducts measured in inches of water, for 70F air, and for a length of duct 100 ft if duct dimension is 6 in x 8 in at 1500 ft/min. A. 0.195 in water

B. 0.395 in water

C. 0.595 in water

D. 0.795 in water

Ans. C 101. Find the pressure loss of air flowing through a smooth sheet round metal ducts measured in inches of water, for 70F air, and for a length of duct 100 ft if duct dimension is 8 inches in diameter at 1600 ft/min. A. 0.845 in water

B. 0.246 in water

C. 0.463 in water

D. 0.580 in water

Ans. D 102. A house-healing boiler burns coal of 12,000 Btu per lb with 60% efficiency. With the generating set thermal efficiency of 15%, the coal required at 60% efficiency. Find the coal required in pounds to produce 1 kw-hr for electrical heating. A. 1.23 lbs

B. 3.16 lbs

C. 5.30 lbs

D. 7.39 lbs

Ans. B 103. Find the rate of heat flow into a room at 2 pm in July for a an outdoor design temperature at 105F and indoor condition of 78F for a 4 in stone concrete roof covered with an average depth of 4 in cinder concrete on which is placed a 3/8 in thick felt roof with a ¼ in pitch and slag surface exposed to sun. Daily range temperature of 30F, that is, outdoor temperature 75F at 4 or 5 am. A. 12 Btu/hr − ft 2

B. 15 Btu/hr − ft 2

C. 18 Btu/hr − ft 2

D. 32 Btu/hr − ft 2

Ans. B 104. A diesel engine consumed 945 liters of fuel per day at 35°C. IF the fuel was purchased at 15.5°C and 30°API at P29.00/li determine the cost of fuel to operate the engine per day. If suction pressure of engine is 15 psig, find the supercharging pressure requires the full power output of the engine to drive the supercharger. A. 92.5 psig

B. 97.5 psig

C. 93.5 psig

D. 95.5 psig

Ans. B 105. A 305 mm x 457 mm four stroke single acting diesel engine is rated at 150 KW at 260 rpm. Fuel has a heating value of 43,912 KJ/kg. Calculate the typical volume of fuel for diesel engine daily.

A. 323 gallons

B. 302 gallons

C. 314 gallons

D. 353 gallons

Ans. C 106. A 12 cylinder, 305 mm x 457 mm four stroke engine acting diesel engine is rated at 1,250 KW at 460 rpm. Fuel has a heating value of 43,912 KJ/kg. Calculate the typical volume of fuel for diesel engine daily. A. 2,112 gallons

B. 2,212 gallons

C. 2,312 gallons

D. 2,412 gallons

Ans. B 107. Find the tractive effort of 2-cylinder simple locomotive required to run an indicated 100 hp steam engine at 40 mph. A. 873.45 lbs

B. 903.34 lbs

C. 953.43 lbs

D. 937.50 lbs

Ans. D 108. Find the density ratio of air at an altitude 25,000 ft where an airplane is flying. A. 0.2375

B. 0.4375

C.0.6375

D. 0.8375

Ans. B 109. Find the power required for a 500 hp airplane flying at an altitude 20,000 ft. A. 228,125 hp

B. 234,577 hp

C. 202,345 hp

D. 982 hp

Ans. A 110. Find the power required for a 500 hp airplane flying straight horizontally at an altitude 29,000 ft. A. 309.15 hp

B. 319.15 hp

C. 329.15 hp

D. 339.15

Ans. A 111. Find the minimum or stalling speed of an airplane where the wing loading is 15 lb/ft 3 and K= 17. A. 39.30 miles/hr

B. 42.24 miles/hr

C. 59.34 miles/hr

D. 65.84 miles/hr

Ans. D 112. Find the minimum or stalling speed of an airplane where the wing loading is 50 lb/ft 2 and K= 12. A. 58.39 mph

B. 63.45 mph

C. 73.46 mph

D. 84.85 mph

Ans. D 113. Find the limit load factors for level and three-point landing of an airplane if wing loading is 50. A. 2.45

B. 5.34

C. 7.62

D. 9.65

Ans. D 114. Air is discharged from a convergent-divergent nozzle at Mach number of 1,732. The exit pressure is 15 psia, and the temperature is 150°F. For isentropic expansion and a negligible inlet velocity. Calculate the Mach angle in degrees. A. 31.26 deg

B. 35.26 deg

C. 43.26 deg

D. 93.26 deg

Ans. B 115. Find the diameter of the propeller in feet if the power needed to drive a ship is 6,000 hp and propeller speed of 100 rpm. A. 17.97 ft

B. 27.35 ft

C. 32.35 ft

D. 46.77 ft

Ans. A 116. A power system has an original power factor of 0.7. If the system power factor angle is moved to 30 degrees, find the percent loss reduction. A. 23.23%

B. 34.66%

C. 43.24%

D. 59.34%

Ans. B 117. Referring to 1937 and 1938 prices in dollars, find the expenses needed to construct for single circuit H-frame if the voltage line is 138 kV. A. $53.45/mile-year

B. $64.67/mile-year C. $74.53/mile-year

D.$2834.56/mile-year

Ans. B 118. Referring to 1937 and 1938 prices in dollars, find the expenses needed to construct for single circuit single pole if the voltage line is 238 kV. A. $103.45/mile-year

B. $206.54/mile-year C. $384.56/mile-year D. $455.34/mile-year

Ans. B 119. Convert 15.21 curies in disintegrations/sec. A. 3.23 x 1011 disintegrations/sec

C. 4.23 x 1011 disintegrations/sec

B. 5.63 x 1011 disintegrations/sec

D. 6.34 x 1011 disintegrations/sec

Ans. B 120. Two kilograms of gas is confined in a 1 m3 tank at 214 kpa and 88°C. What type of gas is in the tank? A. Ethylene

B. Methane

C. Ethane

D. Ethene

Ans. A 121. Find the enthalpy of Carbon dioxide if its internal energy is 230 KJ/kg. A. 236.24 KJ/kg

B. 256.24 KJ/kg

C. 276.24 KJ/kg

D. 296.24 KJ/kg

Ans. D 122. Compute the mass of a 2 m3 Cyanogen at 320 kpa and 40°C. A. 10.53 kg

B. 12.79 kg

C. 14.66 kg

D. 16.33 kg

Ans. B 123. Compute the air flow in ft 3 /min of mechanical ventilation required to exhaust an accumulation of refrigerant due to leaks of the system capable of revolving air from the machinery room for a mass of 6 lbs of refrigerant. A. 183 ft 3 /min

B. 245 ft 3 /min

C. 384 ft 3 /min

D. 492 ft 3 /min

Ans. B 124. Compute the free-aperture cross section in m2 for the ventilation of a machinery room if the mass of refrigerant is 7 kg. A. 0.192 m2

B. 0.293 m2

C. 0.365 m2

D. 0.492 m2

Ans. C. 125. A 27.53° x 37.37° pressure vessel contains ammonia with f = 0.0521. Compute the minimum required discharge capacity of the relief device in kg/hr. A. 113.45 kh/hr

B. 124.50 kh/hr

C. 138.45 kh/hr

D. 142.41 kh/hr

Ans. B 126. Compute the maximum length of the discharge pipe installed on the outlet of a pressurerelief device in feet for internal pipe diameter of 0.5 inch and rated discharge capacity is 9 lb/min of air. The rated pressure of relief valve is 16 psig. A. 0.226 ft

B. 0.483 ft

C. 0.603 ft

D. 0.834 ft

Ans. A 127. What is the hydraulic gradient of a 15 inches inside diameter pipe when 3300 gal/min of water flow with f = 0.0171. A. 0.00283

B. 0.004613

C. 0.006534

D. 0.008634

Ans. B 128. Fins the loss of head in the pipe entrance if speed of flow is 13 m/s A. 8.62 m

B. 4.31 m

C. 6.34 m

D. 863 m

Ans. B 129. Wet material, containing 250% moisture (dry basis) is to be dried at the rate of 1.8kg/s in a continuous dryer to give a product containing 18% moisture (wet basis). Find the moisture removed, kg/hr.

A. 3945 kg/hr

B. 2734 kg/hr

C. 4,222 kg/hr

D. 5634 kg/hr

Ans. C 130. Find the depth in furiong of the ocean (SG = 1.02) if the pressure at the sea bed is 2,232.56 kpag. A. 1.11

B. 2.45

C. 3.50

D. 4.53

Ans. A 131. Find the heat needed to raise the temperature of water from 30°C to 120°C at 70% quality. A. 1384 KJ/kg

B. 1593 KJ/kg

C. 1723 KJ/kg

D. 1920 KJ/kg

Ans. D 132. Am air compressor 300 mm x 450 mm, twin cylinder at 450 rpm has delivers a power of 40 kw at 4% clearance. If clearance will increase to 8%, what is new power? A. 32.34 KW

B. 40 hp

C. 42.34 KW

D. 53.62 hp

Ans. D 133. A certain gas at 101.325 Kpa and 10°C whose volume is 2.83 m3 are compressed into a storage vessel of 0.31m3 capacity. Before admission, the storage vessel contained the gas at a pressure and temperature of 137.8 Kpa and 26 °C, after admission the pressure has increased to 1171.8 Kpa. What should be the final temperature of the gas in the vessel in Kelvin? A. 183.45

B. 265.56

C. 314.20

D. 482.45

Ans. C 134. A 4 m3 /hr pump delivers water to a pressure tank. At the start, the gage reads 138 Kpa until it reads 276 Kpa and then the pump was shut off. The volume of the tank is 180 liters. At 276 Kpa the water occupied 2/3 of the tank volume. Determine the volume of water that can be taken out until gage reads 138 Kpa. A. 26.45 liters

B. 34.59 liters

C. 42.34 liters

D. 59.46 liters

Ans. B 135. Atmospheric pressure boils at 212°F. At the vacuum pressure at 24 in Hg, the temperature is 142°F. Find the boiling temperature when the pressure is increased by 40 psia from atmospheric. A. 173.45°F

B. 274.41°F

C. 382.34°F

D. 449.42°F

Ans. D 136. The dry exhaust gas from oil engine has the following gravimetric analysis: CO2 = 21.6%

O2 = 4.2%

N2 = 74.2%

Specific heats at constant pressure for each component of the exhaust gas in Kcal/kg °C are: CO2 = 0.203

O2 = 0.219

N2 = 0.248

Calculate the specific gravity if the molecular weight of air is 28 kg/kg-mol A. 1.091

B. 2.345

C. 3.456

D. 3.672

Ans. A 137. A bituminous coal has the following composition: C = 71.5%

H = 5.0%

O = 7.0%

N = 1.3%

S= 3%

Ash 7.6%

W= 3.4%

Determine the theoretical weight of Oxygen in lb/lb of coal. A. 1.2934 lb/lb

B. 2.2736 lb/lb

C. 3.0485 lb/lb

D. 4.8364 lb/lb

Ans. B 138. A gaseous fuel mixture has a molal analysis: H2 = 14% O2 = 0.6%

CH4 = 3% 𝐶O2 = 4.5%

CO = 27% N2 = 50.9%

Determine the air-fuel ratio for complete combustion on molal basis. A. 0.3453

B. 1.233

C. 2.083

D. 3.072

Ans. B 139. The following coal has the following ultimate analysis by weight: C = 70.5% S = 3.0%

H2 = 4.5% Ash = 11%

O2 = 6.0% Moisture = 4%

N2 = 1.0%

A stocker fired boiler of 195,000 kg/hr steaming capacity uses this coal as fuel. Calculate volume of air in m3 /hr with air at 60°F and 14.7 psia pressure if boiler efficiency is 70% and FE = 1.10. Use 30% excess air. A. 263,945 m3 /hr

B. 263,456 m3 /hr

C. 234, 019 m3 /hr

D. 231,203 m3 /hr

Ans. C 140. Fuel oil, C12 H26, is burned in air at atmospheric pressure. The Orsat analysis of the products of combustion yields: CO2 = 12.6%, O2 = 3.5%, CO = 0.2%, N2 = 83.5%. Find the percent theoretical air required. A. 103.78%

B. 110.78%

C. 123.78%

D. 132.78%

Ans. B 141. A C14 H26 is burned with the following percentage in the product of combustion. N2 = 83%

CO2 = 12%

CO = 1%

O2 = 4%

Find the excess air. A. 11.96%

B. 13.96%

C. 15.96%

D. 17.96%

Ans. C 142. Fuel is burned with 30% excess air is represented with 30% CH4 and 70% C14 H27. Find the partial pressure of H2 O. A. 10.32 kpa

B. 12.32 kpa

C. 14.32 kpa

D. 16.32 kpa

Ans. A 143. A coal fired power plant has a n overall plant efficiency of 28%. Coal with a heating value of 12,000 Btu per lb costs of P 1.50 per lb. What is fuel cost of producing one kw-hr. A. P 1.02 per kw-hr

B. P 1.32 per kw-hr C. P 1.52 per kw-hr

D. 1.72 per kw-hr

Ans. C 144. In a gas turbine unit, air enters the combustion chamber at 550 kpa, 277°C and 43 m/s. The products of combustion leave the combustor at 511 kpa, 1004°C and 180 m/s. Liquid fuel enters with a heating value of 43,000 KJ/kg. For fuel-air ratio of 0.0229, what is the combustor efficiency of the unit in percent? A. 53%

B. 64%

C. 84%

D. 75%

Ans. D 145. A Palton type turbine was installed 30 m below the head gate of the penstock. The head loss due to friction 12 percent of the given elevation. The length of penstock is 100 m and coefficient of friction is 0.00093. Determine the power output in KW. A. 34,150 KW

B. 34,250 KW

C. 34,450 KW

D. 34,450 KW

Ans. D 146. Water flows steadily with a velocity of 3.05 m/s in a horizontal pipe having a diameter of 25.24 cm. At one section of the pipe, the temperature and pressure of the water are 21°C and 689.3 Kpa, respectively. At a distance at 304.8 m downstream, the pressure is 516.9 Kpa. What is the friction factor? A. 0.0007

B. 0.0107

C. 0.0307

D. 0.0507

Ans. C 147. A concrete foundation has a base dimension of 14 ft x 16 ft. It needs 598 sacks of cement for 1:2:4 mixtures. Find the foundation height. A. 10 ft

B. 12 ft

C. 14 ft

D. 16 ft

Ans. B 148. A submersible, multi-stage, centrifugal deep well pump 260 gpm capacity is installed in a well 27 feet below the static water level and running at 3000 rpm. Drawdown when pumping at

rated capacity is 10 feet. The pump delivers the water into a 25,000 gallons capacity overhead storage tank. Total discharge head developed by pump, including friction piping is 243 feet. Calculate the diameter of the impeller of this pump in inches if each impeller diameter developed a head of 38 ft. A. 1.7001

B. 2.7001

C. 3.7001

D. 4.7001

Ans. C 149. A fan draws 1.42 m3 per second of air at a static pressure of 2.54 cm of water through a duct 300 mm diameter and discharges it through a duct of 275 mm diameter. Determine the static fan efficiency if total fan mechanical is 75% and air is measured at 25°C and 750 mm Hg. A. 46%

B. 54%

C. 63%

D. 73%

Ans. B 150. A water cooler uses 50 lb/hr of melting ice to cool running water from 80°F to 42°F. BBased on the inside coil area, U1 = 110 Btu/hr-ft 2 -F. Find the gpm of water cooled. A. 0.1834 GPM

B. 0.3790 GPM

C. 0.5934 GPM

D. 0.7831 GPM

Ans. B 151. The charge in a Diesel engine consists of 18.34 grams off fuel, with lower heating value of 42,571 KJ/kg, and 409 grams of fuel and products of combustion. At the beginning of compression, t1 = 60°C, Let r1 = 14. For constant c0 = 1.11 KJ/kg-C what should be cut-off ratio in the corresponding ideal cycle? A. 1.034

B. 2.045

C. 3.001

D. 4.384

Ans. C 152. An auditorium seating 1500 people is to be maintained at 80°F dry bulb and 65°F wet bulb temperature when outdoor air is at 91°F dry bulb and 75°F wet bulb. Solar heat load is 110,000 Btu/hr and supply air is at 60°F, determine the amount of supply air. A. 86,458 lb/hr

B. 88,048 lb/hr

C. 92,238 lb/hr

D. 93,230 lb/hr

Ans. D 153. At 35% solution leaves the absorber and 30% solution enter the absorber. The heat removed from the absorber by cooling water is 547.6 Btu and ammonia is superheated by 10°. Find the pound per pound of ammonia gas from the evaporating coils. A. 10.384 lb

B. 12.890 lb

C. 14.056 lb

D. 15.374 lb

Ans. B 154. Assume 8 ft 3 of air at 100 psi, 100°F are compressed isothermally to a volume of 2 ft 3 . For each of end states of the process, find the bulk modulus. A. 493.45 and 97.45 psi B. 399.80 and 99.75 psi

C. 375.34 and 92.34 psi D. 385.50 and 94.32 psi

Ans. B 155. Predict the pressure of nitrogen gas at T = 200°K and v = 0.00385 m3 /kg and b = 0.00141 m3 /kg; a = 0.178 m2 kpa/kg 2 . Use van der waals equation. A. 12,130.98 kpa

B. 12,330.98 kpa

C. 12,530.98 kpa

D. 12,730.98

Ans. B 156. A 50 kg block of iron casting at 500 K is thrown into a large lake that is at a temperature of 285°K. The iron block eventually reaches thermal equilibrium with the lake water. Assuming average specific heat of 0.45 KJ/kg-K for the iron, determine the entropy generated during this process. A. -12.65 KJ/K

B. -14.65 KJ/K

C. 16.65 KJ/K

D. -18.65 KJ/K

Ans. A 157. A 4 liter (2-liter per revolution at standard pressure and temperature) spark ignition engine has a compression ratio of 8 and 2200 KJ/kg heat addition by fluid combustion. Considering a cold air-standard Otto cycle model, how much power will the engine produce when operating at 2500 rpm? A. 973.45 hp

B. 863 hp

C. 453 hp

D. 167 hp

Ans. D 158. An ammonia ice plant operates between a condenser temperature of 35°C and evaporator of -15°C. It produces 10 metric tons of ice per day from water at 30°C to ice at -5°C. Assuming simple saturation cycle, determine the horsepower of the motor if the adiabatic efficiency of the compressor n𝑒 = 0.85 and mechanical efficiency n𝑚 = 0.95. The specific heat of ice is 2.094 kJ/kg °C and the latent heat is 335 kJ/kg. From the table for ammonia the following enthalpies are: condenser entrance = 1703 kJ/kg, exit 356.1 kJ/kg; compressor entrance = 1443.9 kJ/kg, exit = 1703 kJ/kg. A. 10 hp

B. 13 hp

C. 17 hp

D. 22 hp

Ans. D 159. A twin cylinder ammonia compressor with volume displacement of 14,726 cm3 operates at 300 rpm. Condenser and evaporator pressure are 1200 kPa and 227 kPa respectively. Specific volume of refrigerant at the entrance of compressor is 528.26 L//kg. Compression process is polytrophic with n= 1.20 and clearance factor of compressor is 2 percent. Determine horsepower required. A. 45.34 hp

B. 64.34 hp

C. 80.02 hp

D. 183.45 hp

Ans. C 160. Saturated vapor ammonia at -16°C (ℎ7 = 1442.60 kJ/kg) leaves the evaporator and enters the compressor at -6°C (ℎ1 = 1465 kJ/kg). The refrigerant leaves the condenser as saturated liquid at 40°C (h4 = 390.6 kJ/kg) and enter the expansion valve at 35°C (ℎ5 = 366.1 kJ/kg). Heat rejected from the condenser amount to 50 kW. The work to compressor is 208 kJ/kg, while the

heat loss from the compressor is 33 kJ/kg. If 95 kJ/kg of heat are lost in the piping between the compressor discharge and condenser inlet, determine the refrigerating capacity of the system. A. 7.34 TR

B. 19.34 TR

C. 13.33 TR

D. 28.56 TR

Ans. C 161. A 2200-kg automobile traveling at 90 km/h (25 m/s) hits the rear of a stationary, 1000-kg automobile. After the collision, the large automobile slows to 50 km/h (13.89 m/s), and the smaller vehicle has a speed of 88 km/h (24.44 m/s). What has been the increase in internal energy, taking both vehicles as the system? A. 176.26 kJ

B. 176.62 kJ

C. 186.62 kJ

D. 196.26 kJ

Ans. B 162. A bell jar 100 mm in diameter sits on a flat plate and is evacuated until a vacuum of 720 mmHg exists. The local barometer reads 760 mmHg. Estimate the force required to lift the jar off the plate. Neglect the weight of the jar. A. 754.45 N

B. 754.54 N

C. 744.60 N

D. 766.40 N

Ans. A 163. A paddle wheel and an electronic heater supply energy to a system. If the torque is 20 N.m, the rotational speed is 400 rpm, the voltage is 20 V, and the amperage is 10 A, the work rate is nearest. A. -1038 W

B. 1038 W

C. -1040 W

D. 1040 W

Ans. A 164. A 200-mm-diameter piston is lowered by increasing the pressure from 100 to 800 kPa such that the P.V relationship is 𝑃𝑉 2 = const. If V1 = 0.1 m3, the work done on the system is nearest. A. 18.3 kJ

B. -16.3 kJ

C. 163 kJ

D. -18.3 kJ

Ans. D 165. Air flows through the supersonic nozzle. The inlet conditions are 400 m/s, 7 kPa, and 420°C with 200 mm inlet diameter. The nozzle exit diameter is adjusted such that the existing velocity is 700 m/s. Calculate the exit diameter. Assume and adiabatic quasi-equilibrium flow. A. 212.3 mm

B. 212. 1 mm

C. 212.4 mm

D. 212.2 mm

Ans. C 166. Methane is heated at constant pressure from 0 to 300°C. How much heat is needed? A. 614.45 kJ/kg Ans. D

B. 614.54 kJ/kg

C. 641.45 kJ/kg

D. 641.54 kJ/kg

167. Nitrogen enters a diffuser at 200 m/s with a pressure of 80 kPa and a temperature of 20°C. It leaves with a velocity of 15 m/s at an atmospheric pressure of 95 kPa. If the inlet diameter is 100 mm, the exit temperature is nearest: A. 0

B. -0.9°C

C. 11°C

D. 0.9°C

Ans. B 168. Two Carnot engines operate in series between two reservoirs maintained at 327 and 27°C, respectively. The energy rejected by the first engine is input into the second engine. If the first engine’s efficiency is 20 percent greater than the second engine’s efficiency, calculate the intermediate temperature. A. 135.6°C

B. 36.5°C

C. 136.5°C

D. 35.6°C

Ans. A 169. Calculate the total entropy change if 10 kg of ice at 0°C are mixed in an insulated container with 20 kg of water at 20°C. Heat of melting for ice is 340 kJ/kg. A. 0.124 kJ/K

B. 0.189 kJ/K

C. 0.318 kJ/K

D. 0.214 kJ/K

Ans. D 170. A 5-kg block of copper at 100°C is submerged in 10 kg of water at 10°C, and after a period of time, equilibrium is established. If the container is insulated, calculate the entropy change of the universe. A. 0.82 kJ/K

B. 0.082 kJ/K

C. 0.161 kJ/K

D. 0.16 kJ/K

Ans. B 171. An automobile that has a gas mileage of 13 km/L is traveling at 100 km/h. At this speed essentially all the power 12 𝑉 2 𝐴𝐶𝐷 determine the thermal efficiency of the engine at this speed using projected area A = 3 m2 , drag coefficient CD = 0.28, and heating value of gasoline 9000 kJ/kg. Gasoline has a density of 740 kg/m3 . A. 0.195

B. 0.29

C. 0.58

D. 0.519

Ans.D 172. Butane is burned with dry air at an air-fuel ratio of 20. Calculate the percent excess air, the volume percentage of CO2 in the products, and the dew-point temperature of the products. A. 29°C

B. 38°C

C. 49°C

D. 57°C

Ans. C 173. An engine operates with air on the cycle with two constant volume processes isentropic processes during the compression and expansion. If the compression ratio is 12, the minimum pressure is 200 kPa, and the maximum pressure is 10 MPa, determine the Mean Effective Pressure, assuming constant specific heats. A. 1324 kPa

B. 1629 kPa

C. 1386 kPa

D. 1824 kPa

Ans. D 174. A tubular solid-oxide fuel cell with an outlet diameter of 2.2 cm and a length of 150 cm is operating at a current density of 202.6 mA/cm2. Determine the heat generation rate in W/m3 if the voltage of the fuel cell is 1 V. Assume that the thickness of the electrodes and electrolyte membrane are small compared to the overall diameter of the fuel cell. A. 3.68 x 105 W/m3

B. 3.68 x 104 W/m3 C. 6.8 x 103 W/m3

D. 6.8 x 104 W/m3

Ans. A 175. An impulse turbine is to be used to develop at a site where water discharge is ft 3 /s and effective head is 980 ft. Find the theoretical estimate of the jet diameter for a single jet. A. 2.56 in

B. 3.86 in

C. 3.16 in

D. 2.84 in

Ans. D 176. 1250 cm3/s of water is to be pumped through a steel pipe, 25 mm diameter and 30 m long, to a tank 12 m higher than its reservoir. Calculate the approximate power required assuming 60% pump efficiency? Viscosity of water = 1.30 mN s/m2 . Density of water = 1000 kg/m3 and roughness of steel is 0.045 mm. A. 156 W

B. 458 W

C. 645 W

D. 318 W

Ans. B 177. A steel ball (SG = 7.85) having a diameter of 100 mm is dropped into the ocean (SG = 1.03). What is the terminal velocity assuming a drag coefficient of 0.2? A. 5.56 m/s

B. 7.54 m/s

C. 6.58 m/s

D. 8.68 m/s

Ans. C 178. A small boat is moving in shallow still water where the depth is 1.5 m; its bow makes an angle of 65° with the line of motion. Compute the speed of the boat. A. 2.13 m/s

B. 5.34 m/s

C. 5.23 m/s

D. 4.43 m/s

Ans. D 179. A jet plane flies at an altitude of 5000 feet where atmospheric temperature is 40°F. An observer on the ground notes that he hears the sound of the plane exactly 3 seconds after the plane has passed directly overhead. Assuming that velocity of sound remains constant at its value corresponding to 40°F. Estimate the speed of the jet plane in ft/s. A. 1290 fps

B. 1360 fps

C. 1270 fps

D. 1460 fps

Ans. D 180. An Otto cycle is proposed to have a compression ratio of 10 while operating with a low temperature of 227°C and a low pressure of 200 kPa. If the work output is to be 1000 kJ/kg, calculate the maximum possible thermal efficiency. A. 50.7%

B. 60.2%

C. 56.8%

D. 63.7%

Ans. B 181. A Carnot piston engine operates with air between 20 and 600°C with a low pressure kPa. If it is to deliver 800 kJ/kg of work, calculate mean effective pressure. A. 243 kPa

B. 295 kpA

C. 334 kPa

D. 112 kPa

Ans. A 182. The internal energy of carbon dioxide having an enthalpy of 400 KJ/kg is? A. 311 kJ/kg

B. 291 kJ/kg

C. 343 kJ/kg

D. 334 kJ/kg

Ans. A 183. A Diesel Cycle has an intake condition of 100 KPa and 30°C and maximum temperature of 1200°C. What is the cycle efficiency if compression ratio is 10:1? A. 53.78%

B. 59.78%

C. 43.8%

D. 58.9%

C. 2.03 m3

D. 1.83 m3

Ans. A 184. How much water comes out in 1 hour? A. 2.19 m3

B. 1.99 m3

Ans. D 185. A 20 kg of Cetane is burned with 25% excess air. Find the mass of air needed. A. 368.2 kg

B. 392.5 kg

C. 389.4 kg

D. 372.1 kg

Ans. D 186. A 3 MW Diesel Power generating unit has a generator efficiency of 85%. Determine the volume flow rate in lps, of cooling water required for the engine at 18°C temperature rise. A. 38.95 lps

B. 29.63 lps

C. 41.42 lps

D. 48.91 lps

Ans. C 187. A soap bubble of a 15 cm radius is formed by blowing through a 2.3-cm diameter wire loop. Assume that all the soap film goes into making the bubble. The surface tension of the film is 0.02 N/m, find the total work required to make the bubble. A. 0.04436 J

B. 0.03698 J

C. 0.05579 J

D. 0.04524 J

Ans. D 188. An atmospheric cooling tower is to provide cooling for the jacket water of a four-stroke 300 KW diesel generator. The cooling tower efficiency is 55% at a temperature of approach of 10 deg C, if ambient air has a relative humidity of 60% ad dry bulb temperature of 31 deg C, determine the cooling water supplied to the diesel engine in liters/hour. A. 18,557.72 li/hr

B. 18,621.72 li/hr

C. 19,001.23 li/hr

D. 18,001.23 li/hr

Ans. B 189. A windmill with a 10 m radius rotor is to be installed where atmospheric pressure conditions prevail at 95 kPa and 22°C. It was observed that wind is blowing steadily at an average velocity of 20 m/s. Determine the maximum available horsepower that can be extracted from the windmill. A. 1120.84 hp

B. 1220.47 hp

C. 1350.23 hp

D. 1230.48 hp

Ans. A 190. An impulse turbine which has a diameter, D = 60 in, speed N = 350 rpm, bucket angle B = 160 degrees, coefficient of g = 0.90, and a jet diameter from nozzle of 8 inches. A. 5186 hp

B. 5088 hp

C. 5348 hp

D. 5114 hp

Ans. B 191. Air flows at rate of 2.0 kg/s through the compressor of an ideal-gas refrigeration cycle where the pressure increases to 500 kPa from 100 kPa. The maximum and minimum cycle temperatures are 300 and -20°C, respectively. Calculate the power needed to drive the compressor fluid using the ideal-gas equations. A. 139 kW

B. 127 kW

C. 141 kW

D. 109 kW

Ans. B 192. Liquid octane at 25°C fuels at jet engine. Air at 600 K enters the insulated combustion chamber and the products leave at 1000 K. The pressure is assumed constant at 1 atm. Estimate the exit velocity using theoretical air. A. 2119 m/s

B. 3170 m/s

C. 1989 m/s

D. 2120 m/s

Ans. D 193. A torque of 40 N m is needed to rotate a shaft at 40 rad/s. It is attached to a paddle wheel located in a rigid 2-m3 volume. Initially the temperature is 47°C and the pressure is 200 kPa; if the paddle wheel rotates for 10 min and 500 kJ of heat is transferred to the air in the volume, determine the entropy increase assuming constant specific heats. A. 1.89 kJ/kg

B. 1.92 kJ/kg

C. 2.81 kJ/kg

D. 3.019 kJ/kg

Ans. C 194. A steel ball of diameter 60 mm is initially in thermal equilibrium at 1030°C in a furnace. It is suddenly removed from the furnace and cooled in ambient air at 30°C, with convective heat transfer coefficient h = 20 W/m2 K. The thermo-physical properties of steel are: density p =7800 kg/m3 , conductivity k = 40 W/mK and specific heat c = 600 J/kgK. The time required in seconds to cool the steel ball in air from 1030°C to 430°C is? A. 2139 sec Ans. B

B. 2144 sec

C. 2293 sec

D. 1997 sec

195. Temperature of nitrogen in a vessel of volume 2m3 is 288 K. A U-tube manometer connected to the vessel shows a reading of 70 cm of mercury (level higher in the end open to atmosphere). The mass of nitrogen in kg in the vessel is? A. 3.6 kg

B. 4.1 kg

C 4.6 kg

D. 5.2 kg

Ans. C 196. The total emissive power of a surface is 500 w/m2 at a temperature T1 and 1200 W/m2 at a temperature T2, where the temperatures are in Kelvin. Assuming the emissivity of the surface to be constant, the ratio of the temperatures T1/T2 is? A. 0.803

B. 0.789

C. 0.779

D. 0.824

Ans. A 197. ) of its roof maintained at 800 K, while its ) is kept at 600 K. Stefan-Boltzmann constant is 5.668 x 10-5 W/m2.K4. The net radiative heat transfer (in kW) from the roof to the flow is? A. 23.9 kW B. 24.8 kW C. 25.2 kW D. 30.1 kW 198. Water flows through a tube of diameter 25 mm at an average velocity of 1.0 m/s. The properties of water are  = 1000 kg/m3,  = 7.25 x 10-1 N s/m2,  = 0.625 W/m/K, the convective heat transfer coefficient (in W/m2-K) is? A. 4896.4 W/m2-K

B. 5009.1 W/m2-K

C. 4199.2 W/m2-K

D. 4516.3 W/m2-K

Ans. D 199. An iron block of unknown mass at 85°C is dropped into an insulated tank that contains 100 L of water at 20°C. At the same time, a paddle wheel driven by a 200-W motor is activated to stir the water. It is observed that thermal equilibrium is established after 20 min with a final temperature of 24°C. Assuming the surroundings to be at 20°C, determine the energy destroyed during this process. A. 399 kJ

B. 403 kJ

C. 376 kJ

D. 387 kJ

Ans. C 200. The bucket angle B of a Felton turbine is 30°C. Pressure at the nozzle = 600 psi. Center line buckets is a 100 in diameter circle. What is the theoretical efficiency? A. 96.3%

B. 88.9%

C. 94.2%

D. 90.3%

Ans. C 201. The 54° diameter drum on a boiler is 96° long and has a 10° gauge glass at mid-drum level. Find the maximum steam generation that could be cared of a blow down of half a water gauge each 8-hr shift. Pressure, 250 psig; s1 =150 ppm; sb = 2000 ppm. A. 1281 lbs/hr Ans. B

B. 1230 lbs/hr

C 1383 lbs/hr

D. 1292 lbs/hr

202. Forty percent of the electrical input to a motor-driven pump is converted into a hydraulic jet, ½ ° in diameter, for the purpose of washing down ashes. Find the jet velocity in fps. The motor has 3-phase, 220-V. 7.5 amp rating. Power factor, 85%. A. 79.3 fps

B. 81.5 fps

C. 69.7 fps

D. 93.6 fps

Ans. B 203. A freezer is maintained at 20°F by removing heat from it at a rate of 75 Btu/min. the power input to the freezer is 0.70 hp, and the surrounding air is at 75°F. Determine the second-law efficiency of this freezer. A. 31.8%

B. 29.7%

C. 30.6%

D. 28.9%

Ans. D 204. A 50-kg iron block (c = 0.45 kJ/kg-K) and a 20-kg copper block (c = 0.40 kJ/kg-K), both initially at 80°C, are dropped into a large lake at 15°C. Thermal equilibrium is established after a while as a result of heat transfer between the blocks and the lake water. Determine the total entropy generation for this process. A. 0.69 kJ/K

B. 0.67 kJ/K

C. 1.62 kJ/K

D. 2.18 kJ/K

Ans. B 205. Carbon dioxide flows steadily through a varying-cross-sectional-area nozzle at a mass flow rate of 3 kg/s. The carbon dioxide enter a duct at a pressure of 1400 kPa and 200°C with a low velocity, and it expands in the nozzle to a pressure of 200 kPa. The nozzle is design so that the flow can be approximated as isentropic. Determine the critical pressure. A.. 767 kPa

B. 794 kPa

C. 802 kPa

D. 854 kPa

Ans. A 206. A pump at elevation 1,000 is pumping 2.0 cfs through 5,000 ft or 6-in pipe to a reservoir whose level is at elevation 1,250. What pressure will be found in the pipe at a point where the elevation is 1,100 ft above datum and the distance (measured along the pipe) from the pump is 3,200 ft? Assume f = 0.0225. A. 216 psi

B. 214 psi

C. 215 psi

D. 217 psi

Ans. A 207. Seven pounds of steam at atmospheric pressure, superheated at 242°F, is introduced simultaneously with 8 lb of ice at 26°F into a copper calorimeter which weighs 5 lb and which contains 50 lb of water at 60°F. The heats of fusion and of vaporization for water are 144 and 970 Btu per pound per °F may be taken as follows: steam 0.48; ice 0.50; and copper 0.093. Neglecting heat losses to all bodies other than the calorimeter itself is the resulting temperature of the mixture. A. 157°F Ans. B

B. 160°F

C. 258°F

D. 273°F

208. A two-pass steam surface condenser is to be designed using an overall heat transfer coefficient of 500 Btu per hour per degree F per square foot outside tube surface. The tubes are to have 7/8 inch outside diameter with walls 1/16 of an inch thick. Entering circulating water velocity is to be 6 feet per second. Steam enters the condenser at a rate of 800,000 pounds per hour at a pressure of 1 psia and an enthalpy of 1080 Btu per pound. Condensate leaves as saturated liquid at 1 psia. Circulating water enters the condenser at 85°F and leaves at 95°F. Calculate the length of condenser tubes. A. 16.5 ft

B. 21.4 ft

C. 23.2 ft

D. 19.7 ft

Ans. A 209. Repairs are to be made on a valve in a steam line. When the valve is isolated, the insulation is removed from the valve and the valve surface temperature is measured and found to be 700°F with an ambient temperature of 60°F. Thirty minutes later the valve surface temperature is again measured and found to be 500°F with ambient temperature still at 60°F.Estimate the time required for the valve surface temperature to reach 150°F, assuming that the ambient temperature remains constant. A. 0.35 hrs

B. 1.96 hrs

C. 3.42 hrs

D. 2.64 hrs

Ans. D 210. An electrical cable has an outer diameter of one inch. It is to be insulated with rubber whose conductivity is 0.1 Btu/(hr.ft.F). The insulated cable is exposed to be ambient air at 80°F with an average outer unit surface conductance of 1.2 Btu/(hr.sq.ft.°F). For a cable surface (at the interface between cable and insulation) temperature of 150°F, find the thickness of rubber insulation that will result in maximum heat transfer. A. 1 ½ in Ans. B

B. ½ in

C. 3/8 in

D. 2/16 in