代做MAE 115 APPLIED ENGINEERING THERMODYNAMICS Hw#6调试R语言程序
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MAE 115
1. It is proposed to use water instead of refrigerant R-134a as the working fluid in air-conditioning applications where the minimum temperature never falls below the freezing point. Would you support this proposal? Explain.
2. A refrigerator uses refrigerant R-134a as the working fluid and operates on an ideal vapor-compression refrigeration cycle between 0.12 and 0.7 MPa. The mass flow rate of the refrigerant is 0.05 kg/s. Show the cycle on a T-s diagram with respect to saturation lines. Determine:
a. The rate of heat removal from the refrigerated space
b. The power input to the compressor
c. The rate of heat rejection to the environment
d. The coefficient of performance
3. Consider a refrigeration system using refrigerant R-134a as the working fluid. If this refrigerator is to operate in an environment at 30oC, what is the minimum pressure to which the refrigerant should be compressed? Why?
4. Refrigerant R-134a enters the confenser of a residential heat pump at 800 kPa and 55oC at a rate of 0.018 kg/s and leaves at 750 kPa subcooled by 3oC. The refrigerant enters the compressor at 200 kPa superheated by 4oC. Determine:
a. The isentropic efficiency of the compressor
b. The rate of heat supplied to the heated room
c. The COP of the heat pump
d. The COP of the heat pump if replaced with an ideal vapor-compression system operating between 200 and 800 kPa.
e. The rate of heat supplied to the room for the ideal vapor-compression system operating between 200 and 800 kPa.
5. A regenerative gas refrigeration system using air as the working fluid has a
pressure ratio of 5. Air enters the compressor at 0oC. The high pressure air is cooled to 35oC by rejecting heat to the surroundings. The refrigerant leaves the turbine at -80oC and then it absorbs heat from the refrigerated space before entering the regenerator. The mass flow rate of the air is 0.4 kg/s. Assuming isentropic efficiencies of 80% for the compressor and 85% for the turbine and using constant specific heats at room temperature, determine:
a. The effectiveness of the regenerator
b. The rate of heat removal from the refrigerated space
c. The COP of the cycle
d. The refrigeration load and the COP if this system operated on the simple gas refrigeration cycle. Use the same compressor inlet temperature as given, the same turbine inlet temperature as calculated, and the same compressor and turbine efficiencies.