An ideal gas within a piston-cylinder assembly undergoes a Carnot refrigeration cycle. The isothermal compression occurs at 325 K from 2 bar to 4 bar. The isothermal expansion occurs at 250 K. Determine:

a. the coefficient of performance
b. the heat transfer to the gas during the isothermal expansion, in kj per kmol of gas
c. the magintude of the net work input, in kj per kmol of gas.

Respuesta :

Answer:

a) [tex]\mu=3.3[/tex]

b)  [tex]Q=1440.7KJ/Kmol[/tex]

c)  [tex]W=1872.9KJ/Kmol[/tex]

Explanation:

From the question we are told that:

Initial Temperature [tex]T_1=325k[/tex]

initial Pressure [tex]P_1=2 bar[/tex]

Final Pressure [tex]P_2=4 bar[/tex]

iso-thermal expansion [tex]T_2=250k[/tex]

a)

Generally the equation for Coefficient of performance is mathematically given by

[tex]\mu=\frac{T_2}{T_1-T_2}[/tex]

[tex]\mu=\frac{250}{325-250}[/tex]

[tex]\mu=3.3[/tex]

b)

Generally the equation for Heat Expansion is mathematically given by

[tex]Q=RT_2 In(\frac{P_2}{P_1})[/tex]

Where

R=Gas constant

[tex]R=8.314462618[/tex]

Therefore

[tex]Q=8.314462618*250 In(\frac{4}{2})[/tex]

[tex]Q=1440.7KJ/Kmol[/tex]

c)

Generally the equation for work input is mathematically given by

[tex]W=RT_1 In(\frac{P_2}{P_1})[/tex]

[tex]W=8.314462618*250 In(\frac{4}{2})[/tex]

[tex]W=1872.9KJ/Kmol[/tex]

The coefficient of performance is 3.33, the heat transfer in the isothermal expansion is 1440.71kJ/K.mol and the work input is calculated as 1872.92kJ/K.mol

Given Data:

  • T1 = 325K
  • P1 = 2 bar
  • P2 = 4 bar
  • T2 = 250K

Isothermal expansion occurs at 250K.

a) The coefficient of performance

This is calculated as

COP =[tex]\frac{T_2}{T_1-T_2}=\frac{250}{325-250} =3.33[/tex]

b) Heat Transfer in isothermal expansion

[tex]Q = RT_2In(\frac{p_2}{p_1})[/tex]

Therefore; In isothermal process du = 0

R = 8.314 AkJ/K.mol

Q = 8.314 * 250 In(4/2)

Q = 1440.71kJ/K.mol

c) Work Input

W[tex]_i_n[/tex]=[tex]RT_1In(\frac{p_2}{p_1})\\W_i_n=8.314*325In(4/2)\\W_i_n=1872.92kJ/K.mol[/tex]

The work input is 1872.92kJ/K.mol

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