30 Questions
What is the factor of evaporation for the boiler producing 1591 kg of steam per hour?
1.2
If one boiler has an efficiency of 65%, what is the efficiency of the other boiler producing 1364 kg of steam per hour?
60%
How many kilograms of steam are produced by both boilers combined per hour?
2955 kg
What is the heating surface area for boilers given in the text?
0.91 m per bo.Hp
If the heating value of coal is 7,590 kcal/kg, how many hours can the coal in the bunker run the boilers?
350.35 hrs
What is the pressure at 12000 ft altitude if air is incompressible and atmospheric air is 14.7 psia at sea level?
5.467 psia
What is the final enthalpy of the mixture when 1.5 kg of wet steam at a pressure of 73 psi and dryness 0.95 is blown into 18.5 gallons of water of 54°F?
84.80 kJ/kg
What is the final volume of the steam when wet saturated steam at 16 bar is expanded to a pressure of 0.1 bar with a dryness fraction of 0.9?
463.74 liters
If 1.5 kg of wet steam at a pressure of 5 bar and dryness 0.95 is mixed with 70 liters of water at 12°C, what is the final enthalpy of the mixture?
74.80 kJ/kg
After throttling wet saturated steam at 16 bar to a pressure of 8 bar, what is the dryness fraction of the resulting steam?
1.0498
What is the fuel consumption per BHP-hour of a Caterpillar diesel engine using fuel oil of 28 API gravity if it is rated at 650 BHP?
0.75 lb/BHP-hr
If the cost of fuel for the Caterpillar diesel engine is P 7.95 per liter, how much would it cost to run the engine for an hour at full power (650 BHP) assuming constant load?
$2787.50
What is the level capacity formula of a suspension bunker in terms of width, depth, and length?
$\frac{5}{8} wdL$
What is the density of coal mentioned in the text?
800 kg/m3
What is the drive horsepower needed for pumping 1703 L/min cold water with efficiency ep=0.75?
31.42 HP
What is the heat energy supplied per kg at constant pressure given Cp = 1.055 kJ/kg-K?
389 kJ/kg
If the brake thermal efficiency of a 1 MW diesel electric plant is 36% with a generator efficiency of 89%, what is the heat generated by fuel in kW?
3,528.64 kW
A 305 mm x 457 mm four-stroke single-acting diesel engine is rated at 150 kW at 260 rpm. What is the brake thermal efficiency given fuel consumption and heating value?
31.63%
What is the heat lost per 100 ft of insulated pipe if the temperature of the outer surface of the cork is 90°F?
847.64 Btu/hr
What is the heat generated per minute at the bearings if the journals of a shaft are 380 mm in diameter, running at 105 rpm, with a coefficient of friction of 0.02, and an average load of 200 KN?
501.375 kJ
In a reverse Carnot cycle that requires 3 Hp and extracts energy from a lake to heat a house kept at 21°F and needing 2100 Btu/min, what is the temperature of the lake?
34.25 °F
What is the pressure of an oxygen cylinder with a volume of 2.3 ft3, at 21°C, if it has a pressure of 2200 psig?
2200 psig
What is the speed (in rpm) of the journals of a shaft if they are 38 cm in diameter, have a coefficient of friction of 0.02, and generate a heat of 501.375 kJ per minute with an average load of 200 KN?
117.08 rpm
If a reverse Carnot cycle extracts energy from a lake to heat a house at 70°F requiring 2000 Btu/min, what is the temperature of the lake?
$36°F$
What is the head water elevation in the hydro-electric plant if the net head is 30 m and the head loss accounts for 5% of the gross head?
785.25 m
What is the water power of the hydro-electric plant with a flow rate of 15 m^3/s and a head loss of 10% of the gross head, given tailwater at 150 m and headwater at 200 m?
7,621.65 kW
In a 5 m x 1 m channel with a water velocity of 6 m/s, what is the annual energy produced in kilowatt-hours with a net head of 120 m and an efficiency of 80%?
247,497,582 kW-hrs
If water flows at 10 m/s in a penstock with a cross-sectional area of 1 m^2 and the turbine efficiency is 87%, what is the turbine output with a net head of 30 m?
2,501.55 kW
For a 83 MW power plant with an average load of 35,000 kW and a load factor of 65%, what is the reserve over peak?
29.15 MW
If a power plant has a use factor of 48.5% and a capacity factor of 41.9%, how many hours did it operate during the year?
7,658.23 hrs
Study Notes
Boiler Efficiency and Steam Production
- The factor of evaporation for a boiler producing 1591 kg of steam per hour can be calculated.
- A boiler with an efficiency of 65% produces 1591 kg of steam per hour, while another boiler producing 1364 kg of steam per hour has a different efficiency.
Steam Properties and Expansion
- Wet steam at a pressure of 73 psi and dryness 0.95, when mixed with 18.5 gallons of water at 54°F, results in a specific final enthalpy.
- Wet saturated steam at 16 bar, when expanded to a pressure of 0.1 bar with a dryness fraction of 0.9, has a specific final volume.
Fuel Consumption and Cost
- A Caterpillar diesel engine with a rating of 650 BHP has a fuel consumption per BHP-hour.
- The cost of running the Caterpillar diesel engine for an hour at full power is P 7.95 per liter.
Coal and Bunker Capacity
- The heating value of coal is 7,590 kcal/kg.
- The level capacity formula of a suspension bunker involves its width, depth, and length.
- The density of coal is mentioned in the text.
Thermal Efficiency and Heat Energy
- The heat energy supplied per kg at constant pressure is given by Cp = 1.055 kJ/kg-K.
- A 1 MW diesel electric plant with a brake thermal efficiency of 36% and a generator efficiency of 89% generates a specific amount of heat.
Engines and Heat Generation
- A 305 mm x 457 mm four-stroke single-acting diesel engine is rated at 150 kW at 260 rpm and has a specific brake thermal efficiency.
- The heat lost per 100 ft of insulated pipe can be calculated based on the temperature of the outer surface of the cork.
- The heat generated per minute at the bearings of a shaft can be calculated based on the journals' diameter, speed, coefficient of friction, and average load.
Refrigeration and Carnot Cycle
- In a reverse Carnot cycle that extracts energy from a lake to heat a house, the temperature of the lake can be calculated.
Pressure and Flow Rate
- The pressure of an oxygen cylinder with a volume of 2.3 ft³ at 21°C can be calculated.
- The speed of the journals of a shaft can be calculated based on their diameter, coefficient of friction, and average load.
Hydro-Electric Plant
- The head water elevation in a hydro-electric plant can be calculated based on the net head and head loss.
- The water power of a hydro-electric plant can be calculated based on the flow rate and head loss.
- The annual energy produced in a hydro-electric plant can be calculated based on the net head, efficiency, and flow rate.
Test your knowledge on calculating enthalpy of steam mixtures and superheated steam. Solve problems involving wet steam, pressure, temperature, and enthalpy to find the final enthalpy of a mixture. Ideal for students studying thermodynamics and steam properties.
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