1.A piston-cylinder device contains helium gas initially at 150 kPa, 20 degrees C, and 0.5 m^3. The helium is now compressed in a polytropic process (PV^n = constant) to 400 kPa and 140 degrees C. Determine the heat loss or gain during this process.
2.A mass of 12 kg saturated refrigerant-134a vapor is contained in a piston-cylinder device at 240 kPa. Now 300 kJ of heat is transferred to the refrigerant at constant pressure while 110-V source supplies current to a resistor within the cylinder for 6 min. Determine the current supplied if the final temperature is 70 degrees C. Also, show the process on a T-v diagram with respect to the saturation lines.