A stationary, un-insulated piston-cylinder device contains 5 kg. of Refrigerant-134a at 800 kPa and 60oC. The R-134a is now cooled at constant pressure until exists as a liquid at 20oC. Determine the heat transfer. Sketch the process on a Tv diagram showing the saturation lines. (Answer: -1088.6 kJ)
The radiator of a residential steam heating system has a volume of 20 L and is filled with steam at 300 kPa and 250oC. At the start of this process, both the inlet and exit valves are fully closed. Determine the amount of heat transfer from the H2O to the room around the radiator when the steam pressure has dropped to 100 kPa. What is the final temperature of the water ? Sketch the process on a Pv diagram showing the saturation lines. (Answers: - 33.4 kJ, 99.63oC)
A well-insulated rigid tank contains 5 kg. of saturated liquid-vapor mixture of water at 100 kPa. Initially, three-quarters of the mass is in the liquid phase. An electric heater is placed in the tank and connected to a 110 Volt source and draws 8 Amps of current. Determine how long it will take to vaporize all the liquid in the tank. Sketch the process on a Tv diagram showing the saturation lines. HINT: We = VIDt ; 1 kJ/s = 1000 Volt*Amps (Answer: 153.2 minutes)
A mass of 12 kg. of saturated vapor Refrigerant-134a is contained in a piston-cylinder device at 200 kPa. Now 250 kJ of heat is transferred to the refrigerant at constant pressure while, in addition, a 110 Volt source supplies current to an electric heater in the cylinder for 6 minutes. Determine the current supplied, if the final temperature is 70oC. Sketch the process on a Tv diagram showing the saturation lines. (Answer: 15.723 Amps)