an insulated rigid tank contains 5 kg of air at 15 oc and 100 kpa. an electric resistance heater inside the tank is now turned on and kept on until the air temperature rises to 40 oc. determine the entropy change of the air during this process.

Respuesta :

Answer is Δs=0.3kJ/K

Since, the tank is insulated rigid tank, The process is constant volume process,

Air as perfect gas

Obtain the properties from the table. Consider th state 1. P=100kPa, T, = 15°C

s=6.830kJ/kg-K

v=0.827 m³/kg

Constant volume process,

Consider the state 2. T = 40°C, v, v = 0.827 m²/kg

5,6.890 kJ/kg-K

Calculate the change in entropy,

Δs=m(s, -s) =5(6.890-6.830)

Δs=0.3kJ/K

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