课程名称︰热力学 课程性质︰必修 课程教师︰苏金佳老师 开课学院：工学院 开课系所︰机械系 考试日期（年月日）︰99/11/11 考试时限（分钟）：open book 60 min and close book 50 min 是否需发放奖励金：Yes （如未明确表示，则不予发放） 试题 : Open book 1.A throttling calorimeter is connected to a desuperheated steam line supplying steam to the auxiliary feed pump in a steam power plant.The line presure is 2.70MPa,the calorimeter presure is 0.1MPa,and the temperature is 150℃. Determine the enthalpy and quality of the desuperheated steam.(15%) 2.An ordinary egg can be approximated as a 55 mm-diameter sphere.The egg is initially at a uniform temperature of 5℃ and is drop into boiling water at 97℃.Taking the properties of the egg to be ρ=1020 kg/m^3 and c=3.32 KJ/kg K determine how much heat is traansferred to the egg by the time the average temperature of the egg rises to 85℃.(10%) 3.A heat exchanger is to cool ethylene glycol (c=2.56 kJ/kg K) floeing at a rate of 4.0 kg/s from 70℃ to 35℃ by water (c=4.18 kJ/kg K) that enters at 25℃ and leaves at 65℃.Determine the mass flow rate of water.(10%) 4.A rigid, insulated tank that is initially evacuated is connected through a valve to a supply line that carries air at 0.20Mpa and 300℃.Now the valve is opened,and air is allowed to flow into the tank until the pressure reaches 0.20MPa,a which points the valve is closed. Determine the flow work of the air in the supply line and the final temperature of the air in the tank.(15%) Close book 5.Schematically draw the T-v diagram illustrating the three regions of state of liquid water and steam.The explain the variation of the state of the substance with temperature under constant pressure.(10%) 6.Write down the equation of energy conservation for an open system and explain the physical meaning of each term in the equation.(10%) 7.Briefly explain the following terms:(a)critical point of a pure substance, (b)latent heat (c)total energy of a closed system (d)quality of a pure substance. (5% each,20% total) 8.What is the defination of a pure substance? Can air be treated as a pure substance? Why?(10%) -- 世界上最遥远的距离不是生与死 而是考试openbook我却不知道答案在哪一页 --

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