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Thermodynamics: An Engineering Approach, 4/e

Yunus A. Çengel, University of Nevada, Reno
Michael A. Boles, North Carolina State University

The First Law of Thermodynamics

Multiple Choice Quiz


1	Air at 1 MPa, 27° C is contained in a piston-cylinder device that is arranged to maintain a constant pressure. How much heat is required to raise the temperature of this air to 527° C?
		A)	180 KJ/kg
		B)	370 KJ/kg
		C)	520 KJ/kg
		D)	1040 KJ/kg


2	Two kilograms of steam at 2 MPa, 250° C are contained in a rigid vessel. How much heat must be removed from this vessel to cool it to 25° C?
		A)	Q_12,in = 5030 kJ
		B)	Q_12,in = 2512 kJ
		C)	Q_12,in = -2512 kJ
		D)	Q_12,in = -5030 kJ


3	Air is compressed in an insulated piston-cylinder device. Using constant specific heats and treating the process as internally reversible, the amount of work required to compress this air from 100 kPa, 27° C to 2 MPa, 706° C is:
		A)	q_12,in = 418 kJ/kg
		B)	q_12,in = 512 kJ/kg
		C)	q_12,in = 721 kJ/kg
		D)	q_12,in = 1030 kJ/kg


4	Air enters an adiabatic, steady-flow turbine at 1 MPa, 527° C through a 1 m² duct with a velocity of 100 m/s. The air leaves the turbine at 100 kPa, 157° C. The mass flow rate of the air is:
		A)	87.4 kg/s
		B)	137.3 kg/s
		C)	327.2 kg/s
		D)	435.6 kg/s


5	Air enters an adiabatic, steady-flow turbine at 1 MPa, 527° C throuigh a 1 m² duct with a velocity of 100 m/s. The air leaves this turbine at 100kPa, 157° C. The work produced by this turbine based upon temperature variable specific heats is:
		A)	293.2 kJ/kg
		B)	360.3 kJ/kg
		C)	390.5 kJ/kg
		D)	420.6 kJ/kg


6	Steam at 4 MPa, 400° C enters a steady-flow, adiabatic turbine through a 20 cm-diameter-pipe with a velocity of 20 m/s. It leaves this turbine at 50 kPa with a quality of 80% through a 1 m-diameter pipe. What is the velocity of the steam as it leaves the turbine?
		A)	10.3 m/s
		B)	28.2 m/s
		C)	32.6 m/s
		D)	73.3 m/s


7	Saturated liquid water enters an adiatic steady-flow throttle valve at 500 kPa and leaves at 100 kPa. What is the quality of the water liquid-vapor mixture leaving this valve?
		A)	9.87%
		B)	10.6%
		C)	14.3%
		D)	21.1%


8	Air enters the afterburner nozzle of a jet fighter at 427° C with a velocity of 100 m/s. It leaves this adiabatic nozzle at 377° C. Assuming that the air specific heats do not change with temperature, the velocity at the nozzle exit is:
		A)	142 m/s
		B)	178 m/s
		C)	227 m/s
		D)	343 m/s


9	Air is compressed from 100 kPa, 300 K to 500 kPa, 500 K in an adiabatic, steady-flow compressor. Allowing for variations in the air's specific heat with temperature, the work required for this compression is:
		A)	132 kJ/kg
		B)	186 kJ/kg
		C)	203 kJ/kg
		D)	241 kJ/kg


10	An initially empty, rigid, insulated container is filled with air from a constant pressure, P_l, and temperature, T_l, supply line. When filled, the air pressure in the vessel matches that in the line. The final temperature of the air in the vessel is given by which of the following equations?
		A)	T_f = c_vT_l / c_p
		B)	T_f = c_pT_l / c_v
		C)	T_f = T_l
		D)	T_f = RT_l / c_v

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