1-3 Multiple Choice: choose all that apply.

If none of the choices can be expressed with confidence, indicate that this is unanswerable.

1. (2pts) Fill in the table to indicate whether the following statements are True  (T) or False (F), or Neither (N) if their validity cannot be determined given the information.

A.  An ideal gas experiencing a constant temperature process in which the pressure increases must experience an increase in specific entropy.

B.  An ideal gas experiencing a constant temperature process in which the pressure increases, must experience an increase in specific internal energy.

C.  The most efficient gas power cycle will convert all of the heat addition to work.

D.  Increasing the compression ratio of an ideal Diesel cycle will result in an increase in the cycle

efficiency

2. (2pts) A mass of saturated liquid ammonia undergoes a constant temperature process that results in an increase in pressure, what will the phase be at the end of the process?

(a)  compressed liquid

(d) saturated vapor

(b) saturated liquid

(e) superheated vapor

(c) liquid-vapor mixture

(f) unanswerable

3. (2pts) Which of the following best represent the specific volume of Refrigerant R134a at 12 bar and 8°C (to 3 significant digits)?

(a)  0.000893 m3/kg

(d) 0.00117 m3/kg

(b) 0.000788 m3/kg

(e) unanswerable

(c) 0.00100 m3/kg

(f) none of these are within 5%

4-7 Short Work Problem (show all work to receive credit)

4. (4 pts) A heat engine receives heat from a source at 1500K and rejects waste heat to a sink at 350K.

Determine the maximum theoretical cycle efficiency

5. (3 pts) A liquid vapor mixture of water is at 200 bar with a quality of 30%

Determine the specific volume of the mixture.

6. (4 pts) Air (R=0.287kJ/kgK) steadily flows through a pipe with a cross sectional area of

500 cm2 .

The air is at 25°C and at 1 bar and has an average velocity of 35 m/s.

What is the mass flow rate of the air entering the pipe?

7. (3 pts) Air (R=0.287kJ/kgK) steadily enters an adiabatic nozzle at 30 m/s and exits at 140 m/s. Determine the air’s change in specific enthalpy (kJ/kg) as it passes through the nozzle.

8-13 Work Problems (show all work to receive credit)

8. (3 pts) An adiabatic compressor steadily takes in Air (R=0.287kJ/kgK) at 300K and 1 bar. The air leaves the compressor at 8 bar. The mass flow rate is 5 kg/s. Using constant specific heats, determine:

The theoretical minimum power required to operate the compressor in kW.

9. (3 pts) A 6 kg mass of air (R=0.287 kJ/kgK) is contained in an adiabatic piston-cylinder. The air is initially at 1700 K and 58 bar.

The air experiences a sudden expansion with a drop in temperature and pressure to 800 K and 2.3 bar.

Using the ideal gas tables for air: (Do not assume constant specific heats) Find the entropy production of this process (kJ/K).

10.(4 pts) In a closed adiabatic piston cylinder device, air (R=0.287 kJ/kgK) experiences a polytropic compression for which PV1.3=constant.

The air is initially at 0.8 bar and 400˚C and occupies a volume of 1.7 m3 .

The final volume of the air is 0.15 m3 .

What is the work done by the air in kJ?

11.(3pts) A refrigeration cycle cools a refrigerated space that is maintained at 1˚C.       The cycle uses R134a which enters the compressor at a mass flow rate of 3.8 kg/s.

The compressor has an isentropic efficiency of 75%.

The system operates between 1.0 bar and 3.2 bar.

a. Sketch and label the system

b. Sketch and label the T-s plot

c. Determine the rate of heat removal from the refrigerated space (KW). (do not evaluate the entire system- only evaluate as indicated above)

12.(3 pts) Air is used in a Brayton cycle.

Air (R=0.287kJ/kgK) steadily enters the compressor at 8.0 kg/s at 250K and at 0.8 bar. Air enters the turbine at 1800K and at 15 bar.

The turbine and compressor are isentropic.

A regenerator with an effectiveness of 0.85 is used to increase cycle performance.

a. Sketch and label the system

b. Sketch and label the T-s plot

c. Use the cold air standard analysis to determine the rate of heat addition (kW). (do not evaluate the entire system- only evaluate as indicated above)