Problem_Solving_04

20問 • 1年前

問題一覧

Calculate the calorific value of coal which has the following analysis: Carbon 81 %, Hydrogen 5 %, Hydrogen 5 %, Oxygen 5.6 %, Sulfur 1 % and the remainder is ash content.

A. 33,688.35 kJ/kg

The percent rating of water tube boiler is 200 %, factor of evaporation is 1.10, and heating surface is 400 ft². Compute the rate of evaporation in kg/hr.

B. 1138

A 373 kW ( 500 Hp ) internal combustion engine has a brake mean effective pressure of 551.5 kPa at full load. What is the friction power if mechanical efficiency is 85 %.

D. 88.23 Hp

A four cylinder, 4 stroke cycle, 20 cm × 25 cm × 550 rpm diesel engine has a mean effective pressure of 150 psi. Calculate the brake power in kW if engine efficiency is 88 %.

A. 131 kW

The brake thermal efficiency of a 1 MW diesel electric plant is 36 %. Find the heat generated by fuel in kW if the generator efficiency is 89 %.

A. 3,121.10 kW

What is the mechanical efficiency of a 0.5 MW diesel engine if the friction power is 70 kW.

C. 87.72 %

Gas is expanded in an engine cylinder following the law PV^n = C where the value of n is 1.3. The initial pressure is 2550 kPa and the final pressure is 210 kPa. If the volume at the end of expansion is 0.75 m³, calculate the volume at the beginning of expansion.

B. 0.1099 m³

Consider 1 kg of air at 32°C that explained by a reversible polytropic process with n = 1.25 until the pressure is halved. If the specific heat at constant volume for air is 0.7186 kJ/kg.K, then determine the heat transfer.

D. 17.02 kJ heat added

If the specific enthalpy of wet saturated steam at a pressure of 11 bar is 2681 kJ/kg, find its dryness fraction. At 11 bar, hf = 781 kJ/kg & hfg = 2000 kJ/kg.

C. 0.95

If the temperature of an air parcel is -20.5°C, and its density is 0.690 kg/m³, then calculate the pressure of the air parcel.

C. 50 kPa

A tank contains 80 ft³ of air at a pressure of 350 psig. If the air is cooled until its pressure and temperature decrease to 200 psig and 70°F respectively, what is the decrease in internal energy?

B. -5507

The stroke of a gas engine which works on the constant volume cycle is 450 mm. The pressure at the beginning of the compression is 1.01 bar and at the end of compression it is 1.1 bar. Assuming compression follows the law PV^1.36 = C, calculate the clearance between the piston and cylinder cover at the end of compression in mm of length.

C. 93.26 mm

Calculate the minimum volume of day tank of 28° API fuel having a fuel consumption of 1 kg/s.

B. 97.41 m³

A steam turbine has an entrance enthalpy of 3000 kJ/kg and an exit enthalpy of 2000 kJ/kg. What is the stage efficiency if the actual enthalpy after isentropic expansion is 2,200 kJ/kg?

D. 80 %

A steam engine delivers 1000 kg/hr steam. The enthalpies at entrance and exit of the engine are 3000 kJ/kg and 400 kJ/kg respectively. Calculate the brake power of the engine if the brake thermal efficiency is 20 %.

A. 144.44 kW

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 2.75 kg of coal per second as received having a heating value of 25,102 kJ/kg. What would be the overall efficiency of the unit in percent? Steam properties: At 5 Mpa and 400°C: • h = 3195.7 kJ/kg At 5 Mpa: • hf = 1154.23 kJ/kg • hfg = 1640.1 kJ/kg At 205°C : • hf = 875.04 kJ/kg At 145°C : • hf = 610.63 kJ/kg

C. 88

The condenser of a reheat power plant rejects heat at the rate of 600 kW. The mass flow rate of cooling tower is 5 kg/s and the inlet cooling water temperature is 35°C. What is the exit temperature of condenser cooling tower?

B. 63.66°C

The heating surface area of a fire tube boiler is 400 m². What is the equivalent rated boiler horsepower?

A. 363.64 Hp

Calculate the pipe diameter if water flows at the rate of 10 kg/s and the velocity of flow is 10 m/s.

C. 35.68 mm

If the compression ratio and the cut off ratio of a Diesel engine are 15 and 3 respectively, what is the expansion ratio?

B. 5

Machine Design ( 1st Set )

Jacky Shane Luyas Buhia · 20問 · 2年前

Machine Design ( 1st Set )