1. A piston-cylinder device contains 3 kg of air at 300 kPa and 25°C. During a quasi-equilibrium isothermal expansion process, 20 kJ of boundary work is done by the system, and 8 kJ of paddle-wheel work is done on the system. What is the heat transfer during this process?
2. Steel balls at 150°C with a specific heat of 0.50 kJ/kg.°C are quenched in an oil bath to an average temperature of 70°C at a rate of 15 balls per minute. If the average mass of steel balls is 1.2 kg, what is the rate of heat transfer from the balls to the oil?
3. Steam is accelerated by a nozzle steadily from a low velocity to a velocity of 220 m/s at a rate of 1.2 kg/s. If the steam at the nozzle exit is at 300°C and 2 MPa, what is the exit area of the nozzle?