Mechanical Engineering Quiz

Steam enters a throttling calorimeter at a pressure of 1.03 MPA. The calorimeter downstream pressure and temperature are 0.1 MPA and 125 . °C What is the percent moisture of the steam supplied? Use the steam properties in kJ/kg: At 1.03 MPA hfg = 2010.7,hg = 2779.25 at 0.1 MPA and 125 ,°Ch=2726.6

• 7.23 ％

• 5.12 ％

• 2.01 ％

• 2.62 ％

The drinking water in a food store in Cebu is made by cooling a tap water in a refrigerated water fountain from 22 to 8 at a flow rate of °C°C 8 kg/hr. If the COP of this refrigerator is 3.1, what is the required power input to this refrigerator?

• 42 W

• 24 W

• 35 W

• 57 W

The heat capacity of an object is:

• The amount of heat energy that raises its temperature by 1°C

• The amount of heat energy that changes its state without changing its temperature

• The amount of heat energy per kilogram that raises its temperature by 1°C

• The ratio of its specific heat to that water

The work done in a turbine is _____ since it is done by the fluid.

• Positive

• Zero

• Negative

• None of these

A fuel has the following volumetric analysis: CH_4 = 68%, C_2 H_6 = 32％ Assume complete combustion with 15％ excess air at 101.325 KPA, 21°C wet bulb and 27°C dry bulb. What is the partial pressure of water vapor in kpa?

• 17.54 kPa

• 11.15 kPa

• 13.21 kPa

• 15.95 kPa

What is the specific gravity of an oil which has a Baume reading of 28°?

• 0.966

• 0.886

• 0.800

• 0.586

The unit of radioactivity is...

• Electron volt

• Curie

• Electron ampere

• MV

Which of the following valves is the one designed to allow a fluid to pass through in one direction?

• Globe valve

• Float valve

• Gate valve

• Check valve

The second law of thermodynamics says that whenever energy is exchanged or converted from one form to another, the potential for energy to do work will be _____.

• Decreased

• Zero

• Increased

• Stagnant

A steam generator on a test generates 885, 000 lb of steam in a 4-hr period. The average steam pressure is 400 psia, the average steam temperature is 700°F, and the average temperature of the feedwater supplied to the boiler is 280°F. If the boiler efficiency for the period is 82.5％ and the coal has a heating value of 13, 850 BTU/lb in actual firing, find the average amount of coal burned in short tons per hour.

• 10.75 short tons per hour

• 8.230 short tons per hour

• 5.345 short tons per hour

• 15.34 short tons per hour