Quiz 02 in ME 223

A piston cylinder system contains a gas which expands under a constant pressure of 1,200 lbf/ft². If the piston is displaced 12” during the process, and the piston diameter is 24”, what is the work done by the gas on the piston?

• 1,768 ft-lb
• 1,890 ft-lb
• 2,387 ft-lb
• 3,770 ft-lb

Ammonia weighing 22 kg is confined inside a cylinder equipped with a piston and has an initial pressure of 413 kPa at 38°C. If 2,900 kJ of heat is added to the ammonia until its pressure and temperature are 413 kPa and 100°C respectively. What is the amount of work done by the fluid in kJ?

• 391 kJ
• 450 kJ
• 630 kJ
• 667 kJ

An amount of 1.63 lb of gas is contained in a tank, the volume of which is 2 ft³. If the internal energy is decrease by 27.4 Btu as temperature changes from 200°F to 100°F, compute the specific heat at constant volume conditions.

• 0.1681 Btu/lb-R
• 0.1714 Btu/lb-R
• 0.618 Btu/lb-R
• 0.714 Btu/lb-R

Two lb of air at 50 psia and occupying 10 ft³ undergo a process at constant volume until the temperature has risen 500R°. Calculate the initial and final pressures and temperatures, the heat added, and the heat gain of internal energy and enthalpy.

• 50 psia; 87 psia; 675 F; 1,175 F; 171.4 Btu; 171.4 Btu; 240 Btu
• 50 psia; 78 psia; 675 F; 920 F; 171.4 Btu; 240 Btu; 411 Btu
• 50 psia; 87 psia; 675 R; 1,175 R; 171.4 Btu; 171.4 Btu; 240 Btu
• 50 psia; 78 psia; 675 R; 920 R; 171.4 Btu; 240 Btu; 411 Btu

Determine the theoretical horsepower required for the isothermal compression of 800 ft³/min of air from 14.7 psia to 120 psia.

• -102 hp
• -108 hp
• -118 hp
• -180 hp

Helium (R = 0.4968 Btu/lbₘ-R) is compressed isothermally from 14.7 psia and 68°F. The compressed ratio is 4. Calculate the work done by the gas.

• -46.7 Btu/lb
• -187 Btu/lb
• -364 Btu/lb
• -1,454 Btu/lb

Air undergoes an isentropic compression from 14.7 psia to 180.6 psia. If the initial temperature is 68°F and the final temperature is 621.5 F, calculate the work done on the gas.

• -49.78 Btu/lb
• -78.94 Btu/lb
• -84.79 Btu/lb
• -94.87 Btu/lb

Air having an initial pressure of 6,516 kPa and an initial volume of 0.113 m³ is compressed adiabatically to a final volume of 0.057 m³. Calculate the pressure at the end of compression.

• 15 MPa
• 16 MPa
• 17 MPa
• 18 Mpa

During an isentropic non-flow process with air, the pressure drops from 60 psia to 20 psia. The air has mass of 0.10 lb and the initial temperature was 280 F. Find the final temperature, °F.

• 40.86 °F
• 60.84 °F
• 80.64 °F
• 86.04 °F

Air is compressed in a cylinder during a non-flow reversible polytropic process from an initial temperature and pressure of 80°F and 15 psia to a final temperature of 285°F and 75 psia. The cylinder contains 0.01 lb of air, and the area of the piston is 0.20 ft². Find: i. The value of the polytropic exponent, n ii. The work done iii. The change of internal energy iv. The heat transferred v. The distance the piston moves during the process

• 1.25; -437 ft-lb; 0.3514 Btu; 0.2108 Btu; 0.48 ft
• 1.25; 437 ft-lb; 0.3514 Btu; -0.2108 Btu; 0.84 ft
• 1.25; -437 ft-lb; 0.3514 Btu; -0.2108 Btu; 0.48 ft
• 1.25; 437 ft-lb; -0.3514 Btu; -0.2108 Btu; 0.84 ft