课程名称︰热力学 课程性质︰必修 课程教师︰陈瑶明 开课学院：工学院 开课系所︰机械系 考试日期（年月日）︰2011/11/03 考试时限（分钟）：110分钟 是否需发放奖励金：是 （如未明确表示，则不予发放） 试题 : 1.(40%) Please answer the following questions. (a) The concept of a continuum was used to describe the limit of macroscopic thermodynamic analysis. Describe "continuum" in your own words. (b) What is the zeroth law of thermodynamics? Why is the zeroth law important in thermometry? (c) What is the principle of corresponding states? (d) What are the mechanisms of heat transfer? (e) What is throttling process? Would you expect the temperature of air to drop as it undergoes a steady flow throttling process? Explain. 2.(20%) A piston-cylinder device initially contains air at 150 kPa and 27℃. At this state, the piston is resting on a pair of stops, and the enclosed volume is 400 L. The mass of the piston is such that a 350 kPa pressure is required to move it. The air is now heated until its volume has doubled. Determine (a) the final temperature (b) the work done by the air, and (c) the total heat transferred to the air (the gas constant for air: R = 0.287 kJ/kg‧K ) 3.(20%) An adiabatic gas turbine expands air at 1300 kPa and 500℃ to 100 kPa and 127℃. Air enters the turbine through a 0.2 m^2 opening with an average velocity of 40 m/s, and exhausts through a 1 m^2 opening. Determine (a) the mass flow rate of air through the turbine and (b) the power produced by the turbine. 4.(20%) An air-conditioning system is to be filled from a rigid container that initially contains 5 kg of liquid R-134a at 24℃. The valve connecting this container to the air-conditioning system is now opened until the mass in the container is 0.25 kg, at which time the valve is closed. During this time, only liquid R-134a flows from the container. Presuming that the process is isothermal while the valve is open, determine the final quality of the R-134a in the container and the total heat transfer. --

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