Blue Book Flash Card

81. An 18,000 kW geothermal plant has a generator efficiency of 90% and 80% respectively. If 

the quality after throttling is 20% and each well discharges 400,000 kg/hr, determine the 

number of wells required to produce if the change of enthalpy at entrance and exit of turbine is 

500 kJ/kg.

A. 4 wells B. 2 wells C. 6 wells D. 8 wells

82. A liquid dominated geothermal plant with a single flash separator receives water at 204°C.

The separator pressure is 1.04 MPa. A direct contact condenser operates at 0.034 MPa. The

turbine has a polytropic efficiency of 0.75. For cycle output of 60 MW, what is the mass flow

rate of the well water in kg/s?

@ 204°C: hf = 870.51 kJ/kg

@ 1.04 MPa: hf = 770.38 kJ/kg hfg = 2009.2 kJ/kg hg = 2779.6 kJ/kg

sg = 6.5729 kJ/kg-K

@ 0.034 MPa: hf = 301.40 kJ/kg hfg = 2328.8 kJ/kg sf = 0.09793 kJ/kg-K

sfg = 6.7463 kJ/kg-K

A. 2,933 B. 2,100 C. 1,860 D. 2,444

83. An engine-generator rated 9000 kVA at 80% power factor, 3 phase, 4160 V has an efficiency

of 90%. If the overall plant efficiency is 28%, what is the heat generated by the fuel?

A. 18,800 kW B. 28,800 kW C. 7,500 kW

D. 25,714 kW

84. The indicated thermal efficiency of a two stroke diesel engine is 60%. If friction power is

15% of heat generated, determine the brake thermal efficiency of the engine.

A. 43% B. 45% C. 36% D. 37%

85. A 305 mm x 457 mm four stroke single acting diesel engine is rated at 150 kW at 260 rpm. 

Fuel consumption at rated load is 0.56 kg/kW-hr with a heating value of 43,912 kJ/kg. Calculate 

the break thermal efficiency.

A. 10.53% B. 27.45% C. 14.64% D. 18.23%

87. A diesel electric power plant supplies energy for Meralco. During a 24-hour period, the plant

consumed 240 gallons of fuel at 28°C and produced 3930 kW-hr. Industrial fuel used is 28°API

and was purchased at P30 per liter at 15.6°C. What is the cost of fuel to produce one kW-hr?

A. P6.87 B. P1.10 C. P41.07 D. P5.00

86. A waste heat recovery boiler produces 4.8 MPa (dry saturated) steam from 104°C

feedwater. The boiler receives energy from 7 kg/s of 954°C dry air. After passing through a

waste heat boiler, the temperature of the air has been reduced to 343°C. How much steam in

kg is produced per second? Note: @ 4.80 MPa dry saturated, h = 2796 kJ/kg.

A. 1.30 B. 0.92 C. 1.81 D. 3.43

88. In a gas unit, air enters the combustion chamber at 550 kPa, 227°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 in percent?

A. 70.38% B. 79.38% C. 75.38% D. 82.38%

90. In Francis turbine, the pressure gage leading to the turbine casing reads 380 kPa. The

velocity of water entering the turbine is 8 m/s. If net head of the turbine is 45 m, find the

distance from the center of the spiral casing to the tailrace.

A. 3.0 m B. 3.5 m C. 4.0 m D. 4.5

91. A turbine has a mechanical efficiency of 93%, volumetric efficiency of 95% and total

efficiency of 82%. If the effective head is 40 m, find the total head.

A. 48.72 m B. 40.72 m C. 36.22 m D. 34.72 m

92. A Pelton type turbine has 25 m head friction loss of 4.5 m. The coefficient of friction head

loss (Morse) is 0.00093 and penstock length of 80 m. What is the penstock diameter?

A. 1,355.73 mm

B. 3476.12 mm

C. 6771.23 mm

D. 1686.73 mm

93. In a 9,000 kW hydro-electric plant, the overall efficiency is 88% and the actual power

received by the costumer is 110,000 kW-hrs for that day. What is the secondary power that this

plant could deliver during the entire day?

A. 58,960 kW-hrs B. 80,080 kW-hrs C. 65,960 kW-hrs D. 70,960 kW-hrs

94. A Pelton type turbine was installed 30 m below the head gate of the penstock. The head

loss due to friction is 12 percent of the given elevation. The length of the penstock is 100 m and

the coefficient of friction is 0.00093. Determine the power output in kW. (Use Morse equation).

A. 22,273 B. 23,234 C. 32,345 D. 34,452

95. 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 of 304.8 m downstream, the pressure is 516.9 kPa. What is

the friction factor?

A. 0.134 B. 0.0050 C. 0.0307 D. 0.641

96. A hydro-electric plant having 30 sq. km reservoir area and 100 m head is used to generate

power. The energy utilized by the consumers whose load is connected to the power plant

during a five-hour period is 13.5x106

kWh. The overall generation efficiency is 75%. Find the fall

in the height of water in the reservoir after the 5-hour period.

A. 5.13 m B. 1.32 m C. 3.21 m D. 2.20 m

97. The gas density of chimney is 0.75 kg /m3

and air density of 1.15 kg /m3

. Find the driving

pressure if the height of the chimney is 63.71 m.

A. 0.15 kPa B. 0.25 kPa C. 0.35 kPa

D. 0.45 kPa

98. The actual velocity of gas entering in a chimney is 8 m/s. The gas temperature is 25°C with a

gas constant of 0.287 kJ/kg-K. Determine the gas pressure for a mass of a gas is 50,000 kg/hr

and chimney diameter of 1.39 m.

A. 95 kPa B. 98 kPa C. 101 kPa D. 92 kPa

99. A steam generator with economizer and air heater has an overall draft loss of 25.78 cm of

water. If the stack gases are at 177°C and if the atmosphere is at 101.3 kPa and 26°C, what

theoretical height of stack in meters is needed when no draft fan is used? Assume that the gas

constant for the flue gases is the same as that for air.

A. 611.10 B. 631.10 C. 651.10 D. 671.10

100. A foundation measures 12 ft x 14 ft x 16 ft. Find the number of sacks of cement needed for

a 1:2:4 mixture.

A. 302 B. 404 C. 356 D. 598

89. The specific speed of turbine is 85 rpm and running at 450 rpm. If the head is 20 m and

generator efficiency is 90%, what is the maximum power delivered by the generator?

A. 450.51 kW B. 354.52 kW C. 650.53 kW

D. 835.57 kW