Blue Book Flash Card

61. A diesel engine consumed 945 liters of fuel per day at 35°C. If the fuel was purchased at

15.6°C and 30°API at P29.00/li. Determine the cost of fuel to operate the engine per day.

A. P5,677.50

B. P4,677.50

C. P48,088.90

D. P27,127.76

62. A cylindrical tank 4 m long and 3 m diameter is used for oil storage. How many days can the

tank supply the engine having 27°API with fuel consumption of 60 kg/hr?

A. 17.53

B. 5.84

C. 12.84

D. 19.84

63. A logging firm in Isabella operates a Diesel Electric Plant to supply its electric energy

requirements. During a 2 hour period, the plant consumed 250 gallons of fuel at 80°F and

produced 2900 kW-hrs. Industrial fuel is used at 30°API and was purchased at P30/li at 60°F.

Determine the overall thermal efficiency of the plant.

A. 26.08%

B. 34.23%

C. 28.00%

D. 18.46%

64. The dry exhaust gas from the oil engine has the following gravimetric analysis:

CO2 = 21.6% O2 = 4.2% N = 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 N = 0.248

Calculate the specific gravity if the molecular weight of air is 28.97 kg/kg-mol.

A. 0.981

B. 1.244

C. 1.055

D. 0.542

65. 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 Nitrogen in lb/lb of coal.

A. 2.870

B. 7.526

C. 2.274

D. 6.233

66. A gaseous fuel mixture has a molal analysis:

H2 = 14% CH4 = 3% CO = 27% O2 = 0.6% CO2 = 4.5% N2 = 50.9%

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

A. 2.130

B. 3.230

C. 1.233

D. 1.130

67. A volumetric analysis of a gas mixture is a follows:

CO2: 12% O2: 4% N2: 80% CO: 4%

What percentage of CO2 on a mass basis?

A. 17.55% B. 15.55% C. 12.73% D. 19.73%

68. The following coal has the following ultimate analysis by weight:

C = 70.5% H2 = 4.5% O2 = 6.0% N2 = 1.0% S = 3.0% Ash = 11%

Moisture = 4%

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 air pressure if the boiler efficiency is 70% and FE = 1.10.

A. 234,019 m3 /hr

B. 215,830 m3/hr

C. 213,830 m3/hr

D. 264,830 m3/hr

69.A 23.5 kg of steam per second at 5 MPa and 400°C is produced by a steam generator. The

feedwater enters the economizer at 145°C and leaves at 205°C. The steam leaves the boiler

drum with a quality of 98%. The unit consumes 3 kg of coal per second as received having value

of 25,102 kJ/kg. What would be the overall efficiency of the unit in percent?

Steam properties:

@ 5 MPa and 400°C: h = 3195.7 kJ/kg

@ 5 MPa: hf = 1154.23 kJ/kg hfg = 1640.1 kJ/kg

@ 205°C: hf = 875.04 kJ/kg

@ At 145°C: hf = 610.63 kJ/kg

A. 65.72

B. 80.67

C. 88.28

D. 78.82

70. In a Rankine cycle steam enters the turbine at 2.5 MPa (enthalpies & entropies given) and

condenser of 50 kPa (properties given), what is the thermal efficiency of the cycle?

@ 2.5 MPa: hg = 2803.1 kJ/kg sg = 6.2575 kJ/kg-K

@ 50 kPa: sf = 1.0910 kJ/kg-K sfg = 6.5029 kJ/kg-K

hf = 340.49 kJ/kg hfg = 2305.4 kJ/kg

υf = 0.00103 m3

/kg

A. 25.55% B. 45.23% C. 34.23% D. 12.34%

71. A thermal power plant generates 5 MW and the heat generated by fuel is 13,000 kJ/s. If the

thermal efficiency is 36.15%, find the power needed for the auxiliaries.

A. 310 kW B. 300 kW C. 400 kW D. 350 kW

72. A superheat steam Rankine cycle has turbine inlet conditions of 17.5 MPa and 530°C

expands in a turbine to 0.007 MPa. The turbine and pump polytropic efficiencies are 0.85 and

0.75 respectively. Pressure losses between the pump and turbine inlet are 1.5 MPa. What

should be the pump work in kJ/kg?

A. 17.34 B. 27.32 C. 25.32 D. 47.33

73. In an open feedwater heater for a steam plant, saturated steam at 7 bar is mixed with

subcooled liquid at 7 bar and 25°C. Just enough steam is supplied to ensure that the mixed

steam leaving the heater will be saturated liquid at 7 bar when heater efficiency is 95%.

Calculate the mass flow rate of the subcooled liquid if steam flow rate is 0.865 kg/s.

Steam properties:

@ 7 bar, saturated vapor: hg = 2763.5 kJ/kg

@ 7 bar and 25°C: hf = 105.5 kJ/kg

@ 7 bar, saturated liquid: hf = 697.22 kJ/kg

A. 2.725 kg/s B. 3.356 kg/s C. 2.869 kg/s

D. 3.948 kg/s

74. A steam condenser receives 10 kg/s of steam with an enthalpy of 2770 kJ/kg. Steam

condenses and leaves with an enthalpy of 160 kJ/kg. Cooling water passes through the

condenser with temperature increases from 13°C to 24°C. Calculate the water flow rate in kg/s.

A. 583 B. 567 C. 523 D. 528

75. Steam expands adiabatically in a turbine from 2000 kPa, 400°C to 400 kPa, 250°C. What is

the effectiveness of the process in percent assuming an atmospheric pressure of 18°C? Neglect

changes in kinetic and potential energy.

Steam properties:

@ 2000 kPa and 400°C: h = 3247.6 kJ/kg s = 7.1271kJ/kg-K

@ 400 kPa and 250°C: h = 2964.2 kJ/kg s = 7.3789 kJ/kg-K

A. 82 B. 84 C. 79.60 D. 79.46

76. A heat exchanger was installed purposely to cool 0.50 kg of gas per second. Molecular

weight is 32 and k = 1.32. The gas is cooled from 150°C to 80°C. Water is available at the rate of

0.30 kg/s and at a temperature of 15°C. Calculate the exit temperature of the water in °C.

A. 44.86 B. 42.86 C. 46.45 D. 40.34

77. A 350 mm x 450 mm steam engine running at 280 rpm has a clearance steam condition of 2

MPa and 230°C and exits at 0.1 MPa. The steam consumption is 2000 kg/hr and mechanical

efficiency is 85%. If indicated mean effective pressure is 600 kPa, determine brake thermal

efficiency.

@ 2 MPa and 230°C: h1 = 2849.6 kJ/kg s1 = 6.4423 kJ/kg-K

@ 0.1 MPa: sf = 1.3026 kJ/kg-K hf = 417.46kJ/kg sfg = 6.0568 kJ/kg-K

hfg = 2258 kJ/kg hf2 = 417.46 kJ/kg

A. 23.34% B. 15.25% C. 14.16% D. 27.34%

78. A steam turbine receives 5,000 kg/hr of steam at 5 MPa and 400°C and velocity of 30 m/s. It

leaves the turbine at 0.006 MPa and 85% quality and velocity of 15 m/s. Radiation loss is 10,000

kJ/hr. Find the kW developed.

@5 MPa and 400°C: h1 = 3195.7 kJ/kg s1 = 6.6459 kJ/kg-K

@ 0.006 Mpa: hf = 151.53 kJ/kg hfg = 2415.9 kJ/kg

A. 1273.29 B. 2173.29 C. 1373.60 D. 7231.29

79. A steam turbine with 85% stage efficiency receives steam at 7 MPa and 550°C and exhausts

at 20 kPa. Determine the turbine work.

@ 7 MPa and 550°C: h1 = 3530.9 kJ/kg s1 = 6.9486 kJ/kg-K

@ 20 kPa (0.020 MPa): sf = 0.8320 kJ/kg-K hf = 251.40 kJ/kg

sfg = 7.0766 kJ/kg-K hfg = 2358.3 kJ/kg

A. 1,117 kJ/kg B. 1,132 kJ/kg

C. 1,123.34 kJ/kg D. 1,054.95 kJ/kg

80. A steam turbine with 80% stage efficiency receives steam at 7 MPa and 550°C and exhausts

at 20 kPa. Determine the quality at exhaust.

@ 7 MPa and 550°C: h1 = 3530.9 kJ/kg s1 = 6.9486 kJ/kg-K

@ 20 kPa (0.020 MPa): sf = 0.8320 kJ/kg-K hf = 251.40 kJ/kg

sfg = 7.0766 kJ/kg-K hfg = 2358.3 kJ/kg

A. 96.96% B. 76.34% C. 82.34% D. 91.69%