Thermodynamics

cen84959_ch03.qxd 4/1/05 12:31 PM Page 1593–78E A rigid tank contains 20 lbm of air at 20 psia and70°F. More air is added to the tank until the pressure andtemperature rise to 35 psia and 90°F, respectively. Determinethe amount of air added to the tank. Answer: 13.73 lbm3–79 A 400-L rigid tank contains 5 kg of air at 25°C.Determine the reading on the pressure gage if the atmosphericpressure is 97 kPa.3–80 A 1-m 3 tank containing air at 25°C and 500 kPa isconnected through a valve to another tank containing 5 kg ofair at 35°C and 200 kPa. Now the valve is opened, and theentire system is allowed to reach thermal equilibrium withthe surroundings, which are at 20°C. Determine the volumeof the second tank and the final equilibrium pressure of air.Answers: 2.21 m 3 , 284.1 kPaCompressibility Factor3–81C What is the physical significance of the compressibilityfactor Z?3–82C What is the principle of corresponding states?3–83C How are the reduced pressure and reduced temperaturedefined?3–84 Determine the specific volume of superheated watervapor at 10 MPa and 400°C, using (a) the ideal-gas equation,(b) the generalized compressibility chart, and (c) the steamtables. Also determine the error involved in the first two cases.Answers: (a) 0.03106 m 3 /kg, 17.6 percent; (b) 0.02609 m 3 /kg,1.2 percent; (c) 0.02644 m 3 /kg3–85 Reconsider Prob. 3–84. Solve the problem usingthe generalized compressibility factor feature ofthe EES software. Again using EES, compare the specificvolume of water for the three cases at 10 MPa over the temperaturerange of 325 to 600°C in 25°C intervals. Plot thepercent error involved in the ideal-gas approximation againsttemperature, and discuss the results.3–86 Determine the specific volume of refrigerant-134avapor at 0.9 MPa and 70°C based on (a) the ideal-gas equation,(b) the generalized compressibility chart, and (c) datafrom tables. Also, determine the error involved in the firsttwo cases.3–87 Determine the specific volume of nitrogen gas at10 MPa and 150 K based on (a) the ideal-gas equation and(b) the generalized compressibility chart. Compare these resultswith the experimental value of 0.002388 m 3 /kg, and determinethe error involved in each case. Answers: (a) 0.004452 m 3 /kg,86.4 percent; (b) 0.002404 m 3 /kg, 0.7 percent3–88 Determine the specific volume of superheated watervapor at 3.5 MPa and 450°C based on (a) the ideal-gas equation,(b) the generalized compressibility chart, and (c) thesteam tables. Determine the error involved in the first twocases.Chapter 3 | 1593–89E Refrigerant-134a at 400 psia has a specific volumeof 0.13853 ft 3 /lbm. Determine the temperature of the refrigerantbased on (a) the ideal-gas equation, (b) the generalizedcompressibility chart, and (c) the refrigerant tables.3–90 A 0.016773-m 3 tank contains 1 kg of refrigerant-134aat 110°C. Determine the pressure of the refrigerant, using(a) the ideal-gas equation, (b) the generalized compressibilitychart, and (c) the refrigerant tables. Answers: (a) 1.861 MPa,(b) 1.583 MPa, (c) 1.6 MPa3–91 Somebody claims that oxygen gas at 160 K and3 MPa can be treated as an ideal gas with an error of lessthan 10 percent. Is this claim valid?3–92 What is the percentage of error involved in treatingcarbon dioxide at 3 MPa and 10°C as an ideal gas?Answer: 25 percent3–93 What is the percentage of error involved in treatingcarbon dioxide at 7 MPa and 380 K as an ideal gas?3–94 Carbon dioxide gas enters a pipe at 3 MPa and 500 Kat a rate of 2 kg/s. CO 2 is cooled at constant pressure as itflows in the pipe and the temperature CO 2 drops to 450 K atthe exit. Determine the volume flow rate and the density ofcarbon dioxide at the inlet and the volume flow rate at theexit of the pipe using (a) the ideal-gas equation and (b) thegeneralized compressibility chart. Also, determine (c) theerror involved in each case.3 MPa500 K2 kg/sCO 2FIGURE P3–94450 KOther Equations of State3–95C What is the physical significance of the two constantsthat appear in the van der Waals equation of state? Onwhat basis are they determined?3–96 A 3.27-m 3 tank contains 100 kg of nitrogen at 175 K.Determine the pressure in the tank, using (a) the ideal-gasequation, (b) the van der Waals equation, and (c) the Beattie-Bridgeman equation. Compare your results with the actualvalue of 1505 kPa.3–97 A 1-m 3 tank contains 2.841 kg of steam at 0.6 MPa.Determine the temperature of the steam, using (a) the idealgasequation, (b) the van der Waals equation, and (c) thesteam tables. Answers: (a) 457.6 K, (b) 465.9 K, (c) 473 K3–98 Reconsider Prob. 3–97. Solve the problem usingEES (or other) software. Again using the EES,compare the temperature of water for the three cases at constantspecific volume over the pressure range of 0.1 MPa to