contestada

Oxygen at 50 lbf/in.2, 200 F is in a piston/cylinder arrangement with a volume of 4 ft3. It is now compressed in a polytropic process with exponent, n = 1.2, to a final temperature of 400 F. Calculate the heat transfer for the process.

Respuesta :

Answer:

The value of heat transfer during the process Q = - 29.49 KJ

Explanation:

Given data

[tex]P_{1}[/tex] = 50 [tex]\frac{lbf}{in^{2} }[/tex] = 344.7 k pa

[tex]V_{1} = 4 ft^{3}[/tex] = 0.113 [tex]m^{3}[/tex]

[tex]T_{1} = 200[/tex] F = 366.4 K

[tex]T_{2} = 400 F[/tex] = 477.6 K

Poly tropic index n = 1.2

gas constant for oxygen = 0.26 [tex]\frac{KJ}{kg K}[/tex]

From ideal gas equation

[tex]P_{1}[/tex] [tex]V_{1}[/tex] = m R [tex]T_{1}[/tex]

Put all the values in above equation we get

⇒ 344.7 × 0.113 = m × 0.26 × 366.4

⇒ m = 0.408 kg

Heat transfer in poly tropic process is given by

Q = [tex]\frac{\gamma - n}{( \gamma - 1)( n - 1)} [ {m R (T_{1} - T_{2} ) ][/tex]

Put all the values in above formula we get

Q = [tex]\frac{1.4 - 1.2}{( 1.4 - 1)( 1.2 - 1)} [ {m R (T_{1} - T_{2} ) ][/tex]

⇒ Q = 2.5 × 0.408 × 0.26 × ( 366.4 - 477.6 )

⇒ Q = - 29.49 KJ

This is the value of heat transfer during the process & negative sign shows that  heat is lost during the process.