An insulated air compressor is to pressurize air from 100 kPa to 700 kPa. The air enters at 15°C, and exits at 250°C.

Question

(a) Using your model of a compressor, plot the power required for this compressor for mass flow rates varying from 0.005 kg/s to 5 kg/s. (b) If the maximum power that can be supplied to the compressor via the current electrical system in use is 300 kW, determine the range of mass flow rates of compressed air that this compressor can produce.
Given: P1 = 100 kPa; T1 = 15°C; T2 = 250°C; P2 = 700 kPa;
Air (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?

Answer 1

With these assumptions, the First Law for open systems reduces to W?=m?(h1?h2)

While the temperature change is a little large, the error introduced by using constant specific heats taken at a temperature of 300 K will still be small, so we will use a constant specific heat approach, with cp = 1.005 kJ/kg-K: W?=m?(h1?h2)=m?cp(T1?T2)

(a) For the range of mass flow rates:



(b) If |W?max|=300 kW, then the maximum mass flow rate possible is m?max = 1.27 kg/s

The range of possible flow rates to be produced is 0 ? ????? ? 1.27 kg/s .