Thermodynamics

cen84959_ch03.qxd 4/1/05 12:31 PM Page 1573–51 A rigid tank with a volume of 2.5 m 3 contains 15 kgof saturated liquid–vapor mixture of water at 75°C. Now thewater is slowly heated. Determine the temperature at whichthe liquid in the tank is completely vaporized. Also, show theprocess on a T-v diagram with respect to saturation lines.Answer: 187.0°C3–52 A rigid vessel contains 2 kg of refrigerant-134a at 800kPa and 120°C. Determine the volume of the vessel and thetotal internal energy. Answers: 0.0753 m 3 , 655.7 kJ3–53E A 5-ft 3 rigid tank contains 5 lbm of water at 20 psia.Determine (a) the temperature, (b) the total enthalpy, and (c)the mass of each phase of water.3–54 A 0.5-m 3 vessel contains 10 kg of refrigerant-134a at20°C. Determine (a) the pressure, (b) the total internalenergy, and (c) the volume occupied by the liquid phase.Answers: (a) 132.82 kPa, (b) 904.2 kJ, (c) 0.00489 m 33–55 A piston–cylinder device contains 0.1 m 3 of liquidwater and 0.9 m 3 of water vapor in equilibriumat 800 kPa. Heat is transferred at constant pressure untilthe temperature reaches 350°C.(a) What is the initial temperature of the water?(b) Determine the total mass of the water.(c)(d)Calculate the final volume.Show the process on a P-v diagram with respect tosaturation lines.H 2 OP = 800 kPaFIGURE P3–553–56 Reconsider Prob. 3–55. Using EES (or other)software, investigate the effect of pressure on thetotal mass of water in the tank. Let the pressure vary from 0.1MPa to 1 MPa. Plot the total mass of water against pressure,and discuss the results. Also, show the process in Prob. 3–55on a P-v diagram using the property plot feature of EES.3–57E Superheated water vapor at 180 psia and 500°F isallowed to cool at constant volume until the temperaturedrops to 250°F. At the final state, determine (a) the pressure,(b) the quality, and (c) the enthalpy. Also, show the processon a T-v diagram with respect to saturation lines. Answers:(a) 29.84 psia, (b) 0.219, (c) 426.0 Btu/lbmChapter 3 | 1573–58E Reconsider Prob. 3–57E. Using EES (or other)software, investigate the effect of initial pressureon the quality of water at the final state. Let the pressurevary from 100 psi to 300 psi. Plot the quality against initialpressure, and discuss the results. Also, show the process inProb. 3–57E on a T-v diagram using the property plot featureof EES.3–59 A piston–cylinder device initially contains 50 L ofliquid water at 40°C and 200 kPa. Heat is transferred to thewater at constant pressure until the entire liquid is vaporized.(a) What is the mass of the water?(b) What is the final temperature?(c) Determine the total enthalpy change.(d) Show the process on a T-v diagram with respect tosaturation lines.Answers: (a) 49.61 kg, (b) 120.21°C, (c) 125,943 kJ3–60 A 0.3-m 3 rigid vessel initially contains saturated liquid–vapor mixture of water at 150°C. The water is now heateduntil it reaches the critical state. Determine the mass of theliquid water and the volume occupied by the liquid at the initialstate. Answers: 96.10 kg, 0.105 m 33–61 Determine the specific volume, internal energy, andenthalpy of compressed liquid water at 100°C and 15MPa using the saturated liquid approximation. Compare thesevalues to the ones obtained from the compressed liquidtables.3–62 Reconsider Prob. 3–61. Using EES (or other)software, determine the indicated properties ofcompressed liquid, and compare them to those obtained usingthe saturated liquid approximation.3–63E A 15-ft 3 rigid tank contains a saturated mixture ofrefrigerant-134a at 50 psia. If the saturated liquid occupies 20percent of the volume, determine the quality and the totalmass of the refrigerant in the tank.3–64 A piston–cylinder device contains 0.8 kg of steam at300°C and 1 MPa. Steam is cooled at constant pressure untilone-half of the mass condenses.(a) Show the process on a T-v diagram.(b) Find the final temperature.(c) Determine the volume change.3–65 A rigid tank contains water vapor at 250°C and anunknown pressure. When the tank is cooled to 150°C, thevapor starts condensing. Estimate the initial pressure in thetank. Answer: 0.60 MPa3–66 Water is boiled in a pan covered with a poorly fitting lidat a specified location. Heat is supplied to the pan by a 2-kWresistance heater. The amount of water in the pan is observed todecrease by 1.19 kg in 30 minutes. If it is estimated that 75percent of electricity consumed by the heater is transferred tothe water as heat, determine the local atmospheric pressure inthat location. Answer: 85.4 kPa