Explain all your answers using the Problem-Solving Technique

1. A piston-cylinder device initially contains 0.07 m3 of nitrogen at 130 kPa and 120oC. The nitrogen is now expanded polytropically to a state of 100 kPa and 100oC. Determine the boundary work during this process.

2. A piston-cylinder device with a set of stops initially contains 0.3 kg of steam at 1.0 MPa and 400oC. The location of the stops corresponds to 60 percent of the initial volume. Now the steam is cooled. Determine the compression work if the final state is (a) 1.0 Mpa and 250 oC and (b) 500 kPa. (c) Also determine the temperature at the final state in part (b)

3. A frictionless piston-cylinder device initially contains 200L of saturated liquid refrigerant-134a. The piston is free to move, and its mass is such that it maintains a pressure of 900 kPa on the refrigerant. The refrigerant is now heated until its temperature rises to 70oC. Calculate the work done during this process.

4. A mass of 2.4 kg of air at 150 kPa and 12oC is contained in a gas-tight, frictionless piston-cylinder device. The air is now compressed to a final pressure of 600 kPa. During the process, heat is transferred from the air such that the temperature inside the cylinder remains constant. Calculate the work input during this process.

5. Saturate water vapor at 200oC is isothermally condensed to a saturated liquid in a piston-cylinder device. Calculate the heat transfer and the work done during this process in kJ/kg.

6. An insulated piston-cylinder device contains 5 L of saturated liquid water at a constant pressure of 175 kPa. Water is stirred by a paddle wheel while a current of 8 A flows for 45 min through a resistor placed in the water. In one-half of the liquid is evaporated during this constant-pressure process and the paddle-wheel work amounts to 400 kJ, determine the voltage of the source. Also, show the process on a P-v diagram with respect to the saturation lines.

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