Air is compressed in an isentropic process from an initial pressure and temperature of P1 = 90 kPa and T1=22°C to a final pressure of P2=900 kPa. Determine: a)- The final temperature of the air. b)-The work done per kg of air during the process.

Respuesta :

Answer:

a) [tex]T_2=569.35 K[/tex]

b)Work done per kg of air=196.84 KJ/Kg

Explanation:

Given: [tex]\gamma =1.4[/tex] for air.

[tex]P_1=90 KPa ,T_=22^\circ C,P_2=900 KPa[/tex]

We know that  

[tex]\dfrac{T_2}{T_1}=\left (\frac{P_2}{P_1}\right )^{\dfrac{{\gamma-1}}{\gamma}}[/tex]

So  [tex]\dfrac{T_2}{295}=\left (\frac{900}{90}\right )^{\dfrac{{1.4-1}}{1.4}}[/tex]

[tex]T_2=569.35 K[/tex]

(a) [tex]T_2=569.35 K[/tex]

(b)Work for adiabatic process

  W=[tex]\frac{P_1V_1-P_2V_2}{\gamma -1}[/tex]

We know that PV=mRT for ideal gas.

 W=[tex]mR\frac{T_1-T_2}{\gamma -1}[/tex]

Now by putting values

work per kg of air=[tex]0.287\times \frac{295-569.35}{1.4 -1}[/tex]

Work w=-196.84 KJ/Kg    (Negative sign indicate work given to input.)

So work done per kg of air=196.84 KJ/Kg

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