Answer to Question #150532 in Electrical Engineering for warda

Question #150532
1kg of air enclosed in a rigid container is initially at 4.8 bar and 150 °C. The container is heated until the temperature is 200 °C. Calculate the pressure of the air finally and the heat supplied during the process
1
Expert's answer
2020-12-22T05:04:34-0500

Given data

Mass of air = 1 kg

Initial temperature T1 = 150 + 273 = 423 K

Initial pressure P1 = 4.8 bar

Final temperature T2 = 200 + 273 = 473 K

The container is rigid (volume is constant)

From the ideal gas equation

P1V1T1=P2V2T2\frac{P1V1}{T1} = \frac{P2V2}{T2}

P2=P1×T2T1P2 = P1\times \frac{T2}{T1}

=4.8barx(473423)= 4.8 bar x (\frac{473}{423})

= 5.37 bar

For isochoric process

Entropy change S=Cvln(T2T1)S = Cv ln(\frac{T2}{T1})

=0.718kJ/kgK×ln(473423)= 0.718 kJ/kgK \times ln (\frac{473}{423})

= 0.08 kJ/kgK

Average temperature T = (473+423)2=448K\frac{(473 + 423)}{2} = 448 K

Heat supplied = T×ST \times S

=448Kx0.08kJ/kgK=35.9kJ/kg= 448 K x 0.08 kJ/kgK = 35.9 kJ/kg



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