(华南理工大学)作业-答案-10车辆(给学生3-4章).doc

Solutions Chapter 3 Dec. 1 Problem 3-46，3-48，3-61，3-73，3-84 (p156) 3-46 Determine the boiling temperature in Denver. Analysis The boiling temperature changes with the pressure. The atmospheric pressure in Denver is 83.4kPa. Properties The saturation temperature of water at 75 and 100kPa are 91.76 and 99.61 (C, respectively (Table A-5). Solution By linear interpolation, the boiling temperature at an atmospheric pressure 83.4kPa is 3-48 A cooking pan whose inner diameter is 20cm is covered with a 4kg lid. The local atmospheric pressure is 101kPa. Determine the boiling temperature of water in pan. Analysis The weight of the lid causes an additional pressure on the gas in pan. PA = PatmA+F Properties The saturation temperature of water at 100 and 125kPa are 99.61 and 105.97 (C, respectively (Table A-5). Solution By linear interpolation, the boiling temperature at an atmospheric pressure 102.25kPa is 3-61 The properties of compressed liquid water at a specified state are to be determined using the compressed liquid tables, and also by using the saturated liquid approximation, and the results are to be compared. Analysis Compressed liquid can be approximated as saturated liquid at the given temperature. Then from Table A-4, T = 100°C ( From compressed liquid table (Table A-7), The percent errors involved in the saturated liquid approximation are 3-73 A balloon is filled with helium gas. The mole number and the mass of helium in the balloon are to be determined. Assumptions At specified conditions, helium behaves as an ideal gas. Properties The universal gas constant is Ru = 8.314 kPa.m3/kmol.K. The molar mass of helium is 4.0 kg/kmol (Table A-1). Analysis The volume of the sphere is Assuming ideal gas behavior, the mole numbers of He is determined from Then the mass of He can be determined from 3-84 The specific volume of steam is to be determined using the ideal gas relation, the compressibility chart, and the steam tables. The errors