(8 points) air is used as the working fluid in a simple ideal brayton cycle that has a pressure ratio of 12, a compressor inlet temperature of 300 k, and a turbine inlet temperature of 1000 k. determine the required mass flow rate of air for a net power output of 70 mw, assuming both the compressor and the turbine have an isentropic efficiency of (a) 100 percent and (b) 85 percent. answers: (a) 352 kg/s, (b) 1037 kg/s

a )

b)  

Explanation:

given data:

pressure ration rp = 12

inlet temperature = 300 K

TURBINE inlet temperature  = 1000 K

AT the end of isentropic process (compression) temperature is

AT the end of isentropic process (expansion) temperature is

isentropic work is given as

w = 1.005(610.18 - 300)

w = 311.73 kJ/kg

w(turbine) = 1.005( 1000 - 491.66)

w(turbine) = 510.88 kJ/kg

a) mass flow rate for isentropic process is given as

b) actual mass flow rate uis given as

and 1and 1

more than, less

less than, more