Carnot cycle thermodynamics problems?

[haley5p]

Thermodynamics tutorials Carnot cycle

 

q1 A domestic fridge uses refrigerant R 134 as the working fluid and operates on a standard idealised Carnot type cycle

 

A) Draw the typical flow diagram for the refrigerator and sketch the temperature-entropy diagram for the process.

B) Explain how the refrigerator works with reference to the diagrams produced for part 1 .

C) State the Clausius version of the second law of thermodynamics and explain why the refrigerator you have described meets the requirements of Clausius’s Statement.

2)

The ice box for the fridge must be kept at a constant temperature of -14 ^○C to prevent bacterial growth in the food stored there. For a refrigerant flow 1.5 kg/s calculate:

D) The heat removed from the ice box.

1. The coefficient of performance of the cycle and comment on your answer.

1. In practice ideal Carnot cycles are not suitable to model real refrigeration cycles. Explain why this is so.

3)A heat pump is used to heat a domestic house to give a room temperature of 25°C by pumping low grade heat from the atmospheric air 5 °C.

 

 

“The heat pump described above obeys the second law of thermodynamics as stated by Clausius”:

a)Is this statement correct and if the pump obeys the second law give a clear explanation of why it obeys said law.

b)Sketch the typical flow diagram for the heat pump

c)Use your diagram to explain how the heat pump works.

4)The heat pump operates on freon 134a and follows a standard Carnot cycle. The condenser delivering heat to the room is supplied with saturated vapour at 30 ^○C that is condensed to give saturated liquid also at 30°C.

 

Assuming the air temperature is an average 15 °C for a refrigerant flow of 0.02kg/s, calculate:

a)The heat delivered to the room

b)The heat transferred from the air

c)The work done by the compressor

d)The coefficient of performance of the cycle and comment on your answer

e)If the air temperature drops by 5 degrees in a bad winter will the coefficient of performance of the cycle increase or decrease comment on your answer.

 

 

[CaptainPanic]

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Moderator Note

haley5p,

 

Please note that this is obviously homework. You will not get any answers, unless you show what you have so far done to solve these problems. Posting only the questions is not sufficient. You are obviously doing some engineering course, not a management course, so asking other people to do your work is not going to teach you the necessary skills to pass the class.

 

Everybody,

Please do not answer any questions until our OP has shown any efforts into solving these problems.