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//(10.4) Air enters the compressor of an ideal Brayton refrigeration cycle at 1 bar, 270K, with a volumetric flow rate of 1.4 m3/s. If the compressor pressure ratio is 3 and the turbine inlet temperature is 300K, determine (a) the net power input, in kW, (b) the refrigeration capacity, in kW, (c) the coefficient of performance
//solution
//variable initialization
p1 = 1 //in bar
T1 = 270 //in kelvin
AV = 1.4 //in m^3/s
r = 3 //compressor pressure ratio
T3 = 300 //turbine inlet temperature in kelvin
//analysis
//From Table A-22,
h1 = 270.11 //in kj/kg
pr1 = .9590
pr2 = r*pr1
//interpolating in Table A-22,
h2s = 370.1 //in kj/kg
//From Table A-22,
h3 = 300.19 //in kj/kg
pr3 = 1.3860
pr4 = pr3/r
//Interpolating in Table A-22, we obtain
h4s = 219 //in kj/kg
//part(a)
R = 8.314 //universal gas constant, in SI units
M = 28.97 //molar mass of air in grams
mdot = (AV*p1)/((R/M)*T1)*10^2 //mass flow rate in kg/s
Wcycledot = mdot*((h2s-h1)-(h3-h4s))
printf('the net power input in kw is: %f',Wcycledot)
//part(b)
Qindot = mdot*(h1-h4s) //refrigeration capacity in kw
printf('\nthe refregeration capacity in kw is: %f',Qindot)
//part(c)
beta = Qindot/Wcycledot //coefficient of performance
printf('\nthe coefficient of performance is: %f',beta)
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