Question

A 0.5 m^3 tank containing air at 17.5 bar and 220°C is to be exhausted to the atmosphere through a cleverly designed black-box engine. The engine is directly connected to the tank, and the air exiting from the engine is always at 1 bar and 220°C. The process will be continued until the pressure of the air in the tank is 1 bar. There is no transfer of heat between the air and walls of the tank or into or out of the engine. Air can be considered to be an ideal gas with CP = 30 J/mole·K and R = 8.314 J/mole·K. a) Develop an expression relating the temperature and pressure of the air in the tank at any time during the process. b) Compute the final temperature of the air in the tank. c) Calculate the maximum work obtained from the engine during the complete exhaustion process. Show that this process is possible. d) Assume the process was carried out isothermally and the temperature of the air throughout the system was maintained at 220°C. Compute the maximum amount of work that could be obtained. How much heat must be added to the system when the maximum work is obtained?

          A 0.5 m^3 tank containing air at 17.5 bar and 220°C is to be exhausted to the atmosphere through a cleverly designed black-box engine. The engine is directly connected to the tank, and the air exiting from the engine is always at 1 bar and 220°C. The process will be continued until the pressure of the air in the tank is 1 bar. There is no transfer of heat between the air and walls of the tank or into or out of the engine.

Air can be considered to be an ideal gas with CP = 30 J/mole·K and R = 8.314 J/mole·K.

a) Develop an expression relating the temperature and pressure of the air in the tank at any time during the process.
b) Compute the final temperature of the air in the tank.
c) Calculate the maximum work obtained from the engine during the complete exhaustion process. Show that this process is possible.
d) Assume the process was carried out isothermally and the temperature of the air throughout the system was maintained at 220°C. Compute the maximum amount of work that could be obtained. How much heat must be added to the system when the maximum work is obtained?

Added by Paula P.

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