An insulated compressor is used to pressurize N2 gas from 100 kPa to 1200 kPa. The nitrogen enters at 20°C, and exits at 380°C. The mass flow rate of the nitrogen is 0.25 kg/s. Determine the power required to operate the compressor.
Given: P1 = 100 kPa; T1 = 20°C; P2 = 1200 kPa; T2 = 380°C; m?= 0.25 kg/s; N2 (Take State 1 as the inlet, State 2 as the outlet.)
Assume: Q?=0 (insulated). For a compressor, assume steady-state, steady-flow, single-inlet, single-outlet flow, with ?KE = ?PE = 0
What will be an ideal response?
With these assumptions, the First Law for open systems reduces to W?=m?(h1?h2)
The temperature change is large enough to consider using variable specific heats for the analysis. However, here we will use a constant specific heat approach, but choosing the specific heat of N2 at a temperature in the middle of the temperature range – 450 K: cp = 1.049 kJ/kg-K
Solving: W?=m?(h1?h2)=m?cp(T1?T2)= -94.4 kW
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