Thermodynamics

0°C and 333.7 kJ/kg, respectively, and the density of water is1 kg/L.4–129 Reconsider Prob. 4–128. Using EES (or other)software, investigate the effect of the initialtemperature of the ice on the final mass required. Let the icetemperature vary from –20 to 0°C. Plot the mass of iceagainst the initial temperature of ice, and discuss the results.4–130 In order to cool 1 ton of water at 20°C in an insulatedtank, a person pours 80 kg of ice at 5°C into thewater. Determine the final equilibrium temperature in thetank. The melting temperature and the heat of fusion of ice atatmospheric pressure are 0°C and 333.7 kJ/kg, respectively.Answer: 12.4°C4–131 An insulated piston–cylinder device initially contains0.01 m 3 of saturated liquid–vapor mixture with a quality of0.2 at 120°C. Now some ice at 0°C is added to the cylinder. Ifthe cylinder contains saturated liquid at 120°C when thermalequilibrium is established, determine the amount of ice added.The melting temperature and the heat of fusion of ice atatmospheric pressure are 0°C and 333.7 kJ/kg, respectively.4–132 The early steam engines were driven by the atmosphericpressure acting on the piston fitted into a cylinderfilled with saturated steam. A vacuum was created in thecylinder by cooling the cylinder externally with cold water,and thus condensing the steam.Consider a piston–cylinder device with a piston surfacearea of 0.1 m 2 initially filled with 0.05 m 3 of saturated watervapor at the atmospheric pressure of 100 kPa. Now coldwater is poured outside the cylinder, and the steam insidestarts condensing as a result of heat transfer to the coolingwater outside. If the piston is stuck at its initial position,determine the friction force acting on the piston and theamount of heat transfer when the temperature inside thecylinder drops to 30°C.Coldwater0.05 m 3100 kPaSteamFIGURE P4–1324–133 Water is boiled at sea level in a coffee makerequipped with an immersion-type electric heating element. Thecoffee maker contains 1 L of water when full. Once boilingstarts, it is observed that half of the water in the coffee makerChapter 4 | 213evaporates in 25 min. Determine the power rating of the electricheating element immersed in water. Also, determine howlong it will take for this heater to raise the temperature of 1 Lof cold water from 18°C to the boiling temperature.CoffeemakerH 2 O400 kPa1 atm1 LFIGURE P4–1334–134 Two rigid tanks are connected by a valve. Tank Acontains 0.2 m 3 of water at 400 kPa and 80 percent quality.Tank B contains 0.5 m 3 of water at 200 kPa and 250°C. Thevalve is now opened, and the two tanks eventually come tothe same state. Determine the pressure and the amount ofheat transfer when the system reaches thermal equilibriumwith the surroundings at 25°C. Answers: 3.17 kPa, 2170 kJQABFIGURE P4–134H 2 O200 kPa4–135 Reconsider Prob. 4–134. Using EES (or other)software, investigate the effect of the environmenttemperature on the final pressure and the heat transfer.Let the environment temperature vary from 0 to 50°C.Plot the final results against the environment temperature,and discuss the results.4–136 A rigid tank containing 0.4 m 3 of air at 400 kPa and30°C is connected by a valve to a piston–cylinder device withzero clearance. The mass of the piston is such that a pressureof 200 kPa is required to raise the piston. The valve is nowopened slightly, and air is allowed to flow into the cylinderuntil the pressure in the tank drops to 200 kPa. During thisprocess, heat is exchanged with the surroundings such that