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ID: 2994032 • Letter: #

Question

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Explanation / Answer

KNOWN

T1 = 50 deg = 323 K

T2 = 400 deg = 673 K

P1 = 300 kPa

m = 0.75 kg

FIND:

P2

dU, change in internal energy

ASSUMPTIONS:

Rigid Tank

PROPERTIES:

Molecular weight of CO2 = 44.01 kg/kmol

Density at 50 deg = 1.668 kg/m^3

Density at 400 deg = 0.7949 kg/m^3

Cp at 50 deg = 0.8747 KJ/kg.K

Cp at 400 deg = 1.11385 kJ/kg.K

ANALYSIS

p is used as a for density


At Tx = 320 K

px = 1.683 kg/m^3 and Cpx = 0.872 KJ/kg.K

At Ty = 340 K

py = 1.583 and Cpy = 0.890

Now at T1 = 323 K

By linear Interpolating

(T1-Tx)/(Ty-Tx) = (p1-px)/(py-px)

p1 = 1.668

Similarly

Cp1 = 0.8747

At Tx = 660    px = 0.813 Cpx = 1.108

At Ty = 680 py = 0.789 Cpy = 1.117

At T2 = 673 K

p2 = 0.7949

Cp2 = 1.11385

Specific Volumes

v1 = 1/p1 = 0.5995 m^3/kg

v2 = 1/p2 = 1.2580 m^3/kg

P1*v1/T1 = P2*v2/T2

300*(0.5995)/323 = P2*1.2580/673

P2 = 297.88 kPa

dQ = m*(Cp2*T2