热力学问题，紧急！！！

来源：百度知道 编辑：UC知道 时间：2024/05/26 17:39:27
The compressor compresses the methane gas from 50kPa and 250 deg C to 300kPa. The compressor can be assumed to be adiabatic, the exit temperature of the methane is measured and found to be 580 deg C, and the mass flow rate of the methane is 150kg/hour. What is the isentropic efficiency of this compressor? (do not assume a constant of average specific heat for the methane over this temperature range.However,you can assume that the specific heat ratio for methane remains constant and at its room temperature value over this temperature range)

assuming ideal behaviour, use the isentropic relationship.
The final temperature for insentropic relationship is found to be
(273+250)(300/50)^(0.31/1.31)=799K=526 deg C.

the isentropic efficiency cannot be calculated with given information.
To obtain the enthalpy change for the isentropic and real process, an integration of Cv dT is required while the form of Cv is not given.

If on the other hand, Cv can be assumed to be constant, efficiency=(526-250)/(580-250)=0.84
The true efficiency should not be far off. That is all I can do.

一台压缩机压缩的甲烷气体从50kPa和250度C至300kPa 。压缩机如果假定为绝热，出口温度的甲烷是衡量和发现， 580度C ，以及对质量流量的甲烷是150kg/hour 。什么是熵效率，压缩机？ （不承担恒定的平均比热的甲烷超过此温度下range.However ，您可以承担的具体热比为甲烷保持不变，并在室温价值超过这一温度范围内）