3-1C W hat is the difference between saturated liquid and compressed liquid? 3-2C What is the difference between saturated vapor and superheated vapor? 3-3C Is there any difference between the intensive properties of saturated vapor at a given temperature and the vapor of a saturated mixture at the same temperature?

3-4C If the pressure of a substance is increased during a boiling process, will the temperature also increase or will it remain constant? Why? 3-5C Why are the temperature and pressure dependent properties in the saturated mixture region? 3-6C What is the difference between the critical point and the triple point? 3-7C Is it possible to have water vapor at 10C? 3-8C A househusband is cooking beef stew for his family in a pan that is (a) uncovered, (b) covered with a light lid, and (c) covered with a heavy lid. For which case will the cooking time be the shortest? Why? 3-9C How does the boiling process at supercritical pressures differ from the boiling process at subcritical pressures?

3-11C It is well known that warm air in a cooler environment rises. Now consider a warm mixture of air and gasoline on top of an open gasoline can. Do you think this gas mixture will rise in a cooler environment? 3-12C Does the amount of heat absorbed as 1 kg of saturated liquid water boils at 100C have to be equal to the amount of heat released as 1 kg of saturated water vapor condenses at 100C? 3-13C Does the reference point selected for the properties of a substance have any effect on thermodynamic analysis? Why? 3-14C What is the physical significance of hfgl Can it be obtained from a knowledge of hf and hgl How? 3-15C Does h, change with pressure? How? 3-16C Is it true that it takes more energy to vaporize 1 kg of saturated liquid water at 100C than it would at 120C? 3-17C What is quality? Does it have any meaning in the superheated vapor region? 3-18C Which process requires more energy: completely vaporizing 1 kg of saturated liquid water at 1 atm pressure or completely vaporizing 1 kg of saturated liquid water at 8 atm pressure?

3-30 A piston-cylinder device contains 0.85 kg of refrigerant-134a at 10C. The piston that is free to move has a mass of 12 kg and a diameter of 25 cm. The local atmospheric pressure is 88 kPa. Now, heat is transferred to refrigerant-134a until the temperature is 15C. Determine (a) the final pressure, (b) the change in the volume of the cylinder, and ( c ) the change in the enthalpy of the refrigerant-134a. 153 CHAPTER 3 FIGURE P 3 -3 0 3-36 Refrigerant-134a at 200 kPa and 25C flows through a refrigeration line. Determine its specific volume. 3-37E A spring-loaded piston-cylinder device is initially filled with 0.2 lbm of an R-134a liquid-vapor mixture whose temperature is 30F and whose quality is 80 percent. The spring constant in the spring force relation F = kx is 37 lbf/in, and the piston diameter is 12 in. The R-134a undergoes a process that increases its volume by 40 percent. Calculate the final temperature and enthalpy of the R-134a. Answers: 81.5F, 120 B tu/lbm 3-31E R-134a. whose specific volume is 0.4618 ft3/lbm, flows through a tube at 120 psia. What is the temperature in the tube? 3-32 One kilogram of water fills a 150-L rigid container at an initial pressure of 2 MPa.

3-33 10-kg of R-134a fill a 1.348-m3 rigid container at an initial temperature of 40C. The container is then heated until the pressure is 200 kPa. Determine the final temperature and the initial pressure. Answer: 66.3C, 5 1 .2 5 kPa 3-34E 2-lbm of water at 500 psia intially fill the 1.5-ft3 left chamber of a partitioned system. The right chamber's volume is also 1.5 ft3, and it is initially evacuated. The partition is now ruptured, and heat is transferred to the water until its temperature is 300F. Determine the final pressure of water, in psia, and the total internal energy, in Btu, at the final state

3-38E One pound-mass of water fills a 2.4264-ft3 weighted piston-cylinder device at a temperature of 600F. The pistoncylinder device is now cooled until its temperature is 200F. Determine the final pressure of water, in psia, and the volume, in ft3. Answers: 2 5 0 psia, 0 .0 1 6 6 3 ft3 3-39 Ten kilograms of R-134a till a 1.595-m3 weighted piston-cylinder device at a temperature of -26.4C. The container is now heated until the temperature is 100C. Determine the final volume of the R-134a.

3 _ 4 3 100-kg of R-134a at 200 kPa are contained in a piston-cylinder device whose volume is 12.322 m3. The piston is now moved until the volume is one-half its original size. This is done such that the pressure of the R -134a does not change. Determine the final temperature and the change in the total internal energy of the R-134a. 344 Water initially at 300 kPa and 250C is contained in a piston-cylinder device fitted with stops. The water is allowed to cool at constant pressure until it exists as a saturated vapor and the piston rests on the stops. Then the water continues to cool until the pressure is 100 kPa. On the T-v diagrams sketch, with respect to the saturation lines, the process curves passing through both the initial, intermediate, and final states of the water. Label the T, P and w values for end states on the process curves. Find the overall change in internal energy between the initial and final states per unit mass of water.

44 3-45E The atmospheric pressure at a location is usually specified at standard conditions, but it changes with the weather conditions. As the weather forecasters frequently state, the atmospheric pressure drops during stormy weather and it rises during clear and sunny days. If the pressure difference between the two extreme conditions is given to be 0.2 in of mercury, determine how much the boiling temperatures of water will vary as the weather changes from one extreme to the other. 3-46 A person cooks a meal in a 30-cm-diameter pot that is covered with a well-fitting lid and lets the food cool to the room temperature of 20C. The total mass of the food and the pot is 8 kg. Now the person tries to open the pan by lifting the lid up. Assuming no air has leaked into the pan during cooling, determine if the lid will open or the pan will move up together with the lid. 3-47 Water is boiled at 1 atm pressure in a 25-cm-internaldiameter stainless steel pan on an electric range. If it is observed that the water level in the pan drops by 10 cm in 45 min, determine the rate of heat transfer to the pan.

3-48 Repeat Prob. 3-47 for a location at 2000-m elevation where the standard atmospheric pressure is 79.5 kPa. 3-49 Saturated steam coming off the turbine of a steam power plant at 40C condenses on the outside of a 3-cmouter-diameter, 35-m-long tube at a rate of 130 kg/h. Determine the rate of heat transfer from the steam to the cooling water flowing through the pipe. 3-50 Water in a 5-cm-deep pan is observed to boil at 98C. At what temperature will the water in a 40-cm-deep pan boil? Assume both pans are full of water. 3-51 Water is being heated in a vertical piston-cylinder device. The piston has a mass of 20 kg and a cross-sectional area of 100 cm2. If the local atmospheric pressure is 100 kPa, determine the temperature at which the water starts boiling. 3-52 A rigid tank with a volume of 1.8 m3 contains 15 kg of saturated liquid-vapor mixture of water at 90C. Now the water is slowly heated. Determine the temperature at which the liquid in the tank is completely vaporized. Also, show the process on a T-v diagram with respect to saturation lines.

3-54 Reconsider Prob. 3-53. Using EES (or other) software, investigate the effect of pressure on the total mass of water in the tank. Let the pressure vary from 0.1 MPa to 1 MPa. Plot the total mass of water against pressure, and discuss the results. Also, show the process in Prob. 3-53 on a P-v diagram using the property plot feature of EES. 3-55E Superheated water vapor at 180 psia and 500F is allowed to cool at constant volume until the temperature drops to 250F. At the final state, determine (a) the pressure, (b) the quality, and (c ) the enthalpy. Also, show the process on a T-v diagram with respect to saturation lines. Answers: (a) 2 9 .8 4 psia, (b) 0 .2 1 9 , (c) 4 2 6 .0 B tu/lbm 3-56E r g | Reconsider Prob. 3-55E. Using EES (or other) L'SsSI software, investigate the effect of initial pressure on the quality of water at the final state. Let the pressure vary from 100 psi to 300 psi. Plot the quality against initial pressure, and discuss the results. Also, show the process in Prob. 3-55E on a T-v diagram using the property plot feature of EES.

3-57 Determine the specific volume, internal energy, and enthalpy of compressed liquid water at 80C and 20 MPa using the saturated liquid approximation. Compare these values to the ones obtained from the compressed liquid tables. 3-58 Reconsider Prob. 3-57. Using EES (or other) software, determine the indicated properties of compressed liquid, and compare them to those obtained using the saturated liquid approximation. 3-59 A piston-cylinder device contains 0.8 kg of steam at 300C and 1 MPa. Steam is cooled at constant pressure until one-half of the mass condenses. (a) Show the process on a T-v diagram. (b) Find the final temperature. (c) Determine the volume change.

3-60 A rigid tank contains water vapor at 250C and an unknown pressure. When the tank is cooled to 124C, the vapor starts condensing. Estimate the initial pressure in the tank. Answer: 0 .3 0 MPa 3-61 A piston-cylinder device initially contains 1.4-kg saturated liquid water at 200C. Now heat is transferred to the water until the volume quadruples and the cylinder contains saturated vapor only. Determine (a) the volume of the tank, (b) the final temperature and pressure, and (c) the internal energy change of the water. FIGURE P 3 -6 1 3-62E How much error would one expect in determining the specific enthalpy by applying the incompressible-liquid approximation to water at 1500 psia and 400F? 3-63 How much error would result in calculating the specific volume and enthalpy of water at 20 MPa and 140C by using the incompressible-liquid approximation? 3-64 100 grams of R-134a initially fill a weighted pistoncylinder device at 60 kPa and 20C. The device is then heated until the temperature is 100C. Determine the change in the device's volume as a result of the heating. Answer: 0 .0 1 6 8 m3 FIGURE P 3 -6 4

3-65 A rigid vessel contains 2 kg of refrigerant-134a at 800 kPa and 120C. Determine the volume of the vessel and the total internal energy. Answers: 0 .0 7 5 3 m3, 6 5 5 .7 kJ 3-66 A 0.5-m3 vessel contains 10 kg of refrigerant-134a at 20C. Determine (a) the pressure, (b) the total internal energy, and (c) the volume occupied by the liquid phase