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）︰2012/01/12 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. How does the ideal Diesel cycle differ from the ideal Otto cycle? Determine the thermal efficiencies of the above mentioned cycles in terms of compression ratio, cutoff ratio and specific heat ratio. (30%) 2. Consider a steam power plant that operates on the ideal reheat cycle. The plant maintains the boiler at 7000 kPa, the reheat section at 800 kPa, and the condenser at 10 kPa. The mixture quality at the exit of both turbines is 93%. Determine the temperature at the inlet of each turbine and the cycle's efficiency. (20%) 3. Steam enters a turbine steadily at 3 MPa and 450 ℃ at a rate of 8 kg/s and exits at 0.2 MPa and 150 ℃. The steam is losing heat to the surrounding air at 100 KPa and 25 ℃ at a rate of 300 kW, and the kinetic and potential energy changes are negligible. Determine (a) the actual power output (b) the maximum power output (c) the second law efficiency (d) the exergy destroyed (e) the exergy of the steam at the inler conditions. (30%) 4. Please answer the following questions: (a) List the characteristics of a working fluid most suitable for vapor power cycles. (b) What is the differences between a refrigerator and a heat pump? Define the coefficient of performance for each of them. (c) What are the four processes that make up the Carnot cycle? (d) What is an ideal Brayton cycle? --

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