Thermodynamics

cen84959_ch03.qxd 4/1/05 12:31 PM Page 161it flows in the pipe so that the temperature of CO 2 drops to450 K at the exit of the pipe, determine (b) the volume flowrate at the exit of the pipe.3–111 A piston–cylinder device initially contains 0.2 kg ofsteam at 200 kPa and 300°C. Now, the steam is cooled atconstant pressure until it is at 150°C. Determine the volumechange of the cylinder during this process using the compressibilityfactor and compare the result to the actual value.Steam0.2 kg200 kPa300°CFIGURE P3–1113–112 Combustion in a diesel engine may be modeled as aconstant-pressure heat addition process with air in the cylinderbefore and after combustion. Consider a diesel engine withcylinder conditions of 950 K and 75 cm 3 before combustion,and 150 cm 3 after it. The engine operates with an air–fuel ratioof 22 kg air/kg fuel (the mass of the air divided by the mass ofthe fuel). Determine the temperature after the combustionprocess.QChapter 3 | 161(b) On the T-v diagram sketch the constant specific volumeprocess through the state T 120°C, v 0.7163 m 3 /kgfrom P 1 100 kPa to P 2 300 kPa. For this data set placethe temperature values at states 1 and 2 on its axis. Place thevalue of the specific volume on its axis.3–114 The gage pressure of an automobile tire is measuredto be 200 kPa before a trip and 220 kPa after the trip at alocation where the atmospheric pressure is 90 kPa. Assumingthe volume of the tire remains constant at 0.035 m 3 , determinethe percent increase in the absolute temperature of theair in the tire.3–115 Although balloons have been around since 1783 whenthe first balloon took to the skies in France, a real breakthroughin ballooning occurred in 1960 with the design of the modernhot-air balloon fueled by inexpensive propane and constructedof lightweight nylon fabric. Over the years, ballooning hasbecome a sport and a hobby for many people around the world.Unlike balloons filled with the light helium gas, hot-air balloonsare open to the atmosphere. Therefore, the pressure in the balloonis always the same as the local atmospheric pressure, andthe balloon is never in danger of exploding.Hot-air balloons range from about 15 to 25 m in diameter.The air in the balloon cavity is heated by a propane burnerlocated at the top of the passenger cage. The flames from theburner that shoot into the balloon heat the air in the ballooncavity, raising the air temperature at the top of the balloonfrom 65°C to over 120°C. The air temperature is maintainedat the desired levels by periodically firing the propane burner.Combustionchamber950 K75 cm 3FIGURE P3–1123–113 On the property diagrams indicated below, sketch(not to scale) with respect to the saturated liquid and saturatedvapor lines and label the following processes and statesfor steam. Use arrows to indicate the direction of the process,and label the initial and final states:(a) On the P-v diagram sketch the constant temperatureprocess through the state P 300 kPa, v 0.525 m 3 /kg aspressure changes from P 1 200 kPa to P 2 400 kPa.Place the value of the temperature on the process curve on theP-v diagram.FIGURE P3–115© Vol. 1/PhotoDisc