4.103 Steady-state operating data are provided for a compressor and heat exchanger in Fig. P4.103. The power input to the compressor is 50 kW. As shown in the figure, nitrogen (N2) flows through the compressor and heat exchanger with a mass flow rate of 0.25 kg/s. The nitrogen is modeled as an ideal gas. A separate cooling stream of helium, modeled as an ideal gas with k 5 1.67, also flows through the heat exchanger. Stray heat transfer and kinetic and potential energy effects are negligible. Determine the mass flow rate of the helium, in kg/s.
p1 = 4 MPa
T1 = 600°C
1
Turbine
Power out
Steam generator
4
p2 = 0.2 bar, saturated 2
vapor
Condenser
Cooling
water in at T5 = 15°C 5
6 Cooling
Power in = 50 kW
Compressor
1
T5 = 175°C 5
2
Helium
4 T4 = 25°C
T3 = 350 K
Pump
3
Power
water out at
T6 = 35°C
N2
p1 = 100 kPa
T1 = 280 K
m· 1 = 0.25 kg/s
Heat exchanger
Fig. P4.103
Fig. P4.102
in = 4 kJ/kg
