Chapter 8 : Air compressors

Example 8.1 pg : 15

In [1]:
# Variables
P1 = 100.;
T1 = 300.;
P2 = 650.;
n = 1.25;
r = 0.05;

# Calculations
Ev = 1-(r*(((P2/P1)**(1./n))-1));

# Results
print 'Volumetric Efficiency =  %2.2f Percent'%(Ev*100);

Volumetric Efficiency =  82.65 Percent

Example 8.2 pg : 15

In [2]:
# Variables
D = 0.24;
LN = 5./6;
P1 = 100.;
P2 = 1000.;
n = 1.35;

# Calculations
A = (22./7)*(1./4)*D*D;
IP = (n/(n-1))*(P1*A*LN)*(((P2/P1)**((n-1)/n))-1);

# Results
print 'Indicated Power =  %2.2f kW'%(IP);

Indicated Power =  11.88 kW

Example 8.3 pg : 15

In [4]:
# Variables
N = 300.;
D = 0.2;
L = 0.24;
P1 = 1.01325;
P2 = 8*1.01325;
n = 1.35;
Et = 0.96;
Em = 0.85;
Vs = (22./7)*(1./4)*D*D*L;

# Calculations and Results
IP = (n/(n-1))*(P1*Vs)*(N/60)*(((P2/P1)**((n-1)/n))-1);
print 'Indicated Power =  %2.1f kW'%(IP*100);


BP = IP/(Et*Em);
print 'Brake Power =  %2.2f kW'%(BP*100);

Indicated Power =  10.5 kW
Brake Power =  12.91 kW

Example 8.4 pg : 16

In [6]:
# Variables
n = 1.35;
P1 = 1.013;
V1 = 1./60;
P2 = 7;
Et = 0.85;
Em = 0.9;

# Calculations and Results
IP = (n/(n-1))*(P1*100*V1)*(((P2/P1)**((n-1)/n))-1);
print 'Indicated Power =  %2.1f kW'%(IP);


BP = IP/(Et*Em);
print 'Brake Power =  %2.2f kW'%(BP);

Indicated Power =  4.2 kW
Brake Power =  5.54 kW

Example 8.5 pg : 16

In [7]:
# Variables
n = 1.2;
P1 = 1;
P2 = 6;
Vs = 1.5/60;

# Calculations and Results
IP = (n/(n-1))*(P1*100*Vs)*(((P2/P1)**((n-1)/n))-1);
print 'Indicated Power =  %2.1f kW'%(IP);

MP = 6.55;
Em = IP/MP;
print 'Mechanical Efficiency =  %2.1f Percent'%(Em*100);

Indicated Power =  5.2 kW
Mechanical Efficiency =  79.7 Percent

Example 8.6 pg : 17

In [8]:
# Variables
N = 300.;
V14 = 14/(2*N);
Vs = 0.023/(1.05-0.22);
n = 1.3;
P1 = 1.013;
P2 = 7.;
IP = (n/(n-1))*(P1*100*V14)*(((P2/P1)**((n-1)/n))-1)*(2*N/60);
print 'Indicated Power =  %2.1f kW'%(IP);


T1 = 288;
T2 = T1*((P2/P1)**((n-1)/n));
print 'Delivery Temperature =  %2.0f K'%(T2);


print 'Swept Volume =  %2.4f m**3'%(Vs);

Indicated Power =  57.6 kW
Delivery Temperature =  450 K
Swept Volume =  0.0277 m**3

Example 8.7 pg : 18

In [9]:
# Variables
P1 = 1.;
P2 = 10.;
Vs = 0.015;
FAD = 3.;
Vc = Vs*0.06;
n = 1.3;
T1 = 20.+273;

# Calculations and Results
IP = (n/(n-1))*(P1*100*3)*(((P2/P1)**((n-1)/n))-1);
print 'Indicated Power =  %2.1f kW'%(IP/60);


V4 = Vc*((P2/P1)**(1./n));
V1 = Vs+Vc;
V14 = 0.0107;
RS = 3/V14;
print 'Rotation Speed =  %2.0f RPM'%(RS);

Tf = 288;
Pf = 101.325;
Vf = (P1*100*(FAD)*Tf)/(T1*Pf);
print 'Vf =  %2.4f m**3/min'%(Vf);


Mcd = V1/(V14);
print 'Mcd =  %2.1f '%(Mcd);

Indicated Power =  15.2 kW
Rotation Speed =  280 RPM
Vf =  2.9102 m**3/min
Mcd =  1.5

Example 8.8 pg : 19

In [10]:
# Variables
P1 = 1.;
P2 = 10.;
Vs = 0.014;
n = 1.3;
V1 = 3.;
FAD = 3.;

# Calculations and Results
W = (n/(n-1))*(P1*100*V1/60)*(((P2/P1)**((n-1)/n))-1);
print 'Power required =  %2.1f kW'%(W);


RPM = FAD/Vs;
print 'Rotational Speed =  %2.0f rpm'%(RPM);

Power required =  15.2 kW
Rotational Speed =  214 rpm

Example 8.9 pg : 19

In [12]:
# Variables
Vs = 5.665/600;
Vc = 0.04*Vs;
V3 = Vc;
n = 1.3;
P3 = 5.6;
P2 = 0.97;
V4 = V3*((P3/P2)**(1./n));
V1 = Vs+Vc;
Vd = V1-V4;
T1 = 300;
Tf = 288;
P1 = 0.96;
Pf = 1.01325;

# Calculations and Results
Vf = (Tf*P1*Vd)/(Pf*T1);
Mcd = V1/(Vd);
print 'Vf =  %.1e m**3/cycle'%(Vf);

print 'Mc/Md =  %2.2f '%(Mcd);


N = 600;
W = (n/(n-1))*(P1*100*Vd)*(((P3/P1)**((n-1)/n))-1);
IP = W*N/60;
print 'Indicated Power =  %2.2f kW'%(IP);

Vf =  7.6e-03 m**3/cycle
Mc/Md =  1.17 
Indicated Power =  17.48 kW

Example 8.10 pg: 20

In [13]:
# Variables
IP = 15.;
n = 1.2;
P1 = 100.;
P2 = 700.;

# Calculations
x = ((P2/P1)**((n-1)/n))-1;
V1N = (IP*(n-1)*60)/(n*P1*x*2);
LN = 150/2;
D2 = V1N*4/((22./7)*LN);
D = D2**0.5;
L = D*1.5;

# Results
print 'D =  %2.0f mm'%(D*1000);
print 'L =  %2.0f mm'%(L*1000);

D =  182 mm
L =  273 mm

Example 8.11 pg : 21

In [14]:
# Variables
P1 = 1.;
P2 = 16.;
n = 1.3;
LN = 100.;
N = 350.;
IP = 30.;
Ev = 0.95;

# Calculations
L = LN/N;
x = (((P2/P1)**((n-1)/n))-1);
V14 = (IP*(n-1)*60)/(n*P1*100*x*N);
Vs = V14/Ev;
D2 = Vs*4/((22./7)*L);
D = D2**0.5;

# Results
print 'D =  %2.0f mm'%(D*1000);
print 'L =  %2.0f mm'%(L*1000);

D =  249 mm
L =  286 mm

Example 8.12 pg : 22

In [15]:
import math 

# Variables
D = 0.2;
L = 0.3;
Vs = (22./7)*(1./4)*D*D*L;
Vc = 0.04*Vs;

V3 = Vc;
P2 = 9;
P1 = 1;
n = 1.3;
V4 = V3*((P2/P1)**(1./n));

# Calculations and Results
V1 = Vs+Vc;
W = (n/(n-1))*(P1*100)*(V1-V4)*(((P2/P1)**((n-1)/n))-1);
R = 0.287;
T1 = 15+273;
Md = (P1*(V1-V4)*100)/(R*T1);
Wpkg = W/Md;
print 'Word done per kg: %3.2f kJ/kg of air'%(Wpkg);


T2 = T1*((P2/P1)**((n-1)/n));
G = 1.4;
Q = ((G-n)/(G-1))*((R*(T1-T2))/(n-1));
print 'Heat Transfereed: %3.2f kJ/kg'%(Q);


Pm = W/Vs;
print 'Mean Effective Pressure: %3.2f kPa'%(Pm);


Mac = V1/(V1-V4);
print 'Mass of air compressed to delivered: %3.2f '%(Mac);


Tf = T1;
Pf = 101.325;
Vf = (P1*100*(V1-V4)*Tf)/(Pf*T1);
RPM = 500;
Vf = Vf*RPM;
print 'FAD at standand condition: %3.2f m**3/min'%(Vf);


IP = (W*RPM)/60;
Etrans = 0.92;
Emech = 0.85;
Emotor = 0.75;
MP = IP/(Etrans*Emech*Emotor);
print 'Motor Power: %3.2f kW'%(MP);


MAC = Md*RPM;
print 'Mass of air compressed: %3.2f kg/min'%(MAC);


ACC = MAC*Mac;
print 'Air compressed in cylinder: %3.2f kg/min'%(ACC);


print 'End Temperature: %3.2f K'%(T2);

Word done per kg: 236.54 kJ/kg of air
Heat Transfereed: -45.49 kJ/kg
Mean Effective Pressure: 235.57 kPa
Mass of air compressed to delivered: 1.26 
FAD at standand condition: 3.83 m**3/min
Motor Power: 31.56 kW
Mass of air compressed: 4.70 kg/min
Air compressed in cylinder: 5.93 kg/min
End Temperature: 478.19 K

Example 8.13 pg : 24

In [16]:
# Variables
Vs = 0.015;
Vc = 0.06*Vs;
V3 = Vc;
n = 1.3;
P2 = 10.;
P1 = 1.;
N = 280.;

# Calculations and Results
V4 = V3*((P2/P1)**(1./n));
print 'V4: %3.4f m**3/cycle'%(V4);

print 'V3: %3.4f m**3/cycle'%(V3);


V1 = Vs+Vc;
print 'V1: %3.4f m**3/cycle'%(V1);


V14 = V1-V4;      #Suction Volume
V2 = V1*((P1/P2)**(1./n));
IP = (n/(n-1))*(P1*100*(V14))*(((P2/P1)**((n-1)/n))-1)*(N/60);
print 'IP: %3.0f kW'%(IP);

V4: 0.0053 m**3/cycle
V3: 0.0009 m**3/cycle
V1: 0.0159 m**3/cycle
IP:  15 kW

Example 8.14 pg : 25

In [20]:
# Variables
P2 = 6;
P1 = 0.96;
n = 1.3;
CV = 0.04;

# Calculations and Results
Ev = (1-(CV*(((P2/P1)**(1./n))-1)))*100;
print 'Clearance Volumetric Efficiency: %3.1f Percent'%(Ev);


D = 0.09;
L = 0.1;
Vs = (22./7)*(1./4)*(D*D*L);
Vc = 0.04*Vs;
V4 = Vc*((P2/P1)**(1./n));
V1 = Vc+Vs;
EDV = V1-V4;
print 'Effective Displacement Volume: %.3e m**3'%(EDV);


T1 = 313;
Tf = 293;
Pf = 1;
Vf = ((P1*(EDV)*Tf))/(T1*Pf);
N = 410;
FAD = Vf*N*2*60;
print 'Free air delivered: %3.2f m**3'%(FAD);


W = (n/(n-1))*(P1*100*(V1-V4))*(((P2/P1)**((n-1)/n))-1);
IP = W*2*N/60;
print 'Indicated Power: %3.2f kW'%(IP);

Clearance Volumetric Efficiency: 87.6 Percent
Effective Displacement Volume: 5.576e-04 m**3
Free air delivered: 24.66 m**3
Indicated Power: 1.67 kW

Example 8.15 pg : 26

In [21]:
import math 

# Variables
P1 = 1.;
P2 = 5.;
T1 = 27.+273;
m = 1.;
R = 0.287;

# Calculations and Results
W1 = m*R*T1*(math.log(P2/P1));
print 'Work in isothermal process: %3.1f kJ'%(W1);


G = 1.4;
W2 = (G/(G-1))*(m*R*T1)*(((P2/P1)**((G-1)/G))-1);
print 'Work in isentropic process: %3.0f kJ'%(W2);


n = 1.25;
W3 = (n/(n-1))*(m*R*T1)*(((P2/P1)**((n-1)/n))-1);
print 'Work in polytropic process: %3.1f kJ'%(W3);

Work in isothermal process: 138.6 kJ
Work in isentropic process: 176 kJ
Work in polytropic process: 163.5 kJ

Example 8.16 pg : 27

In [22]:
import math 

# Variables
IP = 41.;
P1 = 1.;
T1 = 17.+273;
P2 = 7.;
N = 100.;
n = 1.2;

# Calculations
L = 150/(2*N);
V1 = (22./7)*(1./4)*(L);        #Along with D**2
W = (n/(n-1))*(P1*100*V1)*(((P2/P1)**((n-1)/n))-1);
D2 = (IP*60)/(W*2*N);
D = math.sqrt(D2);

# Results
print 'D: %3.3f m'%(D);

D: 0.301 m

Example 8.17 pg : 27

In [23]:
# Variables
D = 0.15;
L = 0.2;
P1 = 1.;
T1 = 17.+273;
P2 = 7.;
N = 100.;
R = 0.287;
V1 = (22./7)*(1./4)*D*D*L;
m = (P1*100*V1)/(R*T1);
Mpm = m*N;
n = 1.25;

# Calculations and Results
IP = (n/(n-1))*(P1*100*V1)*(((P2/P1)**((n-1)/n))-1)*(N/60);
print 'Mass/min: %3.1f Mpm'%(Mpm);


print 'Indicated Power: %3.1f kW'%(IP);


T2 = T1*((P2/P1)**((n-1)/n));
print 'T2: %3.1f K'%(T2);

Mass/min: 0.4 Mpm
Indicated Power: 1.4 kW
T2: 428.0 K

Example 8.18 pg : 28

In [27]:
# Variables
D = 0.15;
N = 100.;
L = 0.2;
P1 = 1.;
T1 = 27.+273;
P2 = 6.;
n = 1.25;

Vs = (22./7)*(1./4)*D*D*L;
Vc = 0.05*Vs;
V1 = Vs+Vc;
V4 = Vc*((P2/P1)**(1./n));

# Calculations and Results
IP = (n/(n-1))*(P1*100*(V1-V4))*(((P2/P1)**((n-1)/n))-1);
IPf = IP**(N/60)
print 'IP: %3.2f kJ'%(IPf);


Pm = IP/Vs;
print 'Mean Effective Pressure: %3.2f kN/m**2'%(Pm);

IP: 0.48 kJ
Mean Effective Pressure: 181.08 kN/m**2

Example 8.19 pg : 29

In [28]:
# Variables
n = 1.2;
m = 5.;
R = 0.287;
T2 = 107.+273;
T1 = 27.+273;

# Calculations and Results
IP = (n/(n-1))*(m/60)*(R*(T2-T1));
print 'Air Power: %3.2f kW'%(IP);


BP = 14;
Em = IP*100/BP;
print 'Mechanical Efficiency: %3.0f Percent'%(Em);

Air Power: 11.48 kW
Mechanical Efficiency:  82 Percent

Example 8.20 pg : 30

In [30]:
import math 

# Variables
V1 = 50.;
P1 = 1.;
P2 = 5.5;
n = 1.3;
Em = 0.82;

# Calculations and Results
IP = (n/(n-1))*(P1*100*V1)*(((P2/P1)**((n-1)/n))-1)*(1./60);
BP = IP/Em;

print 'IP: %3.1f kW'%(IP);
print 'BP: %3.1f kW'%(BP);


IsoP = P1*100*V1*(math.log(P2/P1))*(100./60);
Eo = IsoP/BP;
print 'Isothermal Efficiecy: %3.1f Percent'%(Eo);

IP: 174.1 kW
BP: 212.3 kW
Isothermal Efficiecy: 66.9 Percent

Example 8.21 pg : 30

In [31]:
# Variables
P1 = 1.;
P2 = 5.5;
T1 = 27.+273;
Pa = 1.01325;
Ta = 17.+273;
C = 0.06;
n = 1.3;

# Calculations
Ev = ((P1*Ta)/(Pa*T1))*(1+C-(C*((P2/P1)**(1./n))));

# Results
print 'Volumetric Efficiency: %3.0f Percent'%(Ev*100);

Volumetric Efficiency:  80 Percent

Example 8.22 pg : 31

In [32]:
# Variables
V14 = 7.5;
P1 = 1.;
T1 = 27.+273;
P2 = 5.5;
n = 1.3;
C = 0.06;

# Calculations and Results
T2 = T1*((P2/P1)**((n-1)/n));
print 'T2: %3.1f K'%(T2);


Ev = 1+C-(C*((P2/P1)**((1./n))));
print 'Vol Eff: %3.1f Percent'%(Ev*100);


AP = (n/(n-1))*(P1*100*V14/60)*(((P2/P1)**((n-1)/n))-1);
print 'Air Power: %3.1f kW'%(AP);


Em = 0.9;
BP = AP/Em;
print 'BP: %3.1f kW'%(BP);


Emot = 0.96;
EMC = BP/Emot;
print 'Electric Motor Capacity: %3.1f kW'%(EMC);

T2: 444.6 K
Vol Eff: 83.7 Percent
Air Power: 26.1 kW
BP: 29.0 kW
Electric Motor Capacity: 30.2 kW

Example 8.23 pg : 31

In [34]:
import math 

# Variables
V1 = 5.;
P1 = 1.;
P2 = 5.;
n = 1.25;
Em = 0.9;

# Calculations and Results
IP = (n/(n-1))*(P1*100*V1/60)*(((P2/P1)**((n-1)/n))-1);
SP = IP/Em;
print 'Shaft Power: %3.1f kW'%(SP);


IsoP = P1*100*V1*(math.log(P2/P1))*(1./60);
Eo = IsoP/SP;
print 'Overall Efficiency: %3.0f Percent'%(Eo*100);

Shaft Power: 17.6 kW
Overall Efficiency:  76 Percent

Example 8.24 pg : 32

In [35]:
import math 

# Variables
V1 = 25.;
P1 = 1.;
P2 = 7.;
N = 460.;
Em = 0.8;
Ev = 0.76;
Ei = 0.81;

# Calculations
IsoP = P1*100*V1*(math.log(P2/P1));
IndP = IsoP/Ei;
Vs = V1/Ev;
Pm = IndP/Vs;
BP = IndP/(3600*Em);

# Results
print 'Mean Effective Pressure: %3.2f bar'%(Pm/100);
print 'BP: %3.2f kW'%(BP);

Mean Effective Pressure: 1.83 bar
BP: 2.09 kW

Example 8.25 pg : 33

In [36]:
# Variables
Va = 3.;
Pa = 1.;
Ta = 17.+273;
P2 = 8.2;
N = 300.;
n = 1.35
LD = 1.2;
Em = 0.9;
C = 0.05;

# Calculations and Results
P1 = Pa-0.05;
T1 = Ta+10;
V14 = (Pa*Va*T1)/(P1*Ta);

IP = (n/(n-1))*(P1*100*V14/60)*(((P2/P1)**((n-1)/n))-1);
BP = IP/Em;
print 'BP: %3.1f kW'%(BP);


Ev = 1+C-(C*((P2/P1)**(1./n)));
print 'Volumetric Efficiency: %3.1f Percent'%(Ev*100);


Vs = (22./7)*(1./4)*LD;
VsMin = Vs*2*N;
D3 = V14/(VsMin*Ev);
D = D3**(1./3);
print 'Cylinder Diameter: %3.0f mm'%(D*1000);

BP: 16.6 kW
Volumetric Efficiency: 80.3 Percent
Cylinder Diameter: 193 mm

Example 8.26 pg : 34

In [37]:
import math 

# Variables
V1 = 1.;
P1 = 1.013;
T1 = 15.+273;
P2 = 7.;
R = 0.287;
n = 1.35;

# Calculations and Results
m = (P1*100*V1)/(R*T1);
print 'Mass of air per minute: %3.1f kg'%(m);


T2 = T1*(((P2/P1)**((n-1)/n)));
print 'T2: %3.1f K'%(T2);


IP = (n/(n-1))*(P1*100*V1/60)*(((P2/P1)**((n-1)/n))-1);
print 'IP: %3.1f kW'%(IP);


IsoP = P1*100*V1*(1./60)*math.log(P2/P1);
Ei = IsoP/IP;
print 'Isothermal Efficiency: %3.0f Percent'%(Ei*100);

Mass of air per minute: 1.2 kg
T2: 475.4 K
IP: 4.2 kW
Isothermal Efficiency:  77 Percent

Example 8.27 pg : 36

In [38]:
import math 

# Variables
P1 = 1.013;
T1 = 15.+273;
P2 = 7.;
FAD = 0.3;
G = 1.4;

# Calculations and Results
IP = (G/(G-1))*(P1*100*FAD/60)*(((P2/P1)**((G-1)/G))-1);
print 'For Isentropic process ';
print 'IP: %3.1f kW'%(IP);


T2 = T1*((P2/P1)**((G-1)/G));
print 'T2: %3.0f K'%(T2);


print 'For Reversible Isothermal process ';
IP = P1*100*FAD*(1./60)*(math.log(P2/P1));
print 'IP: %3.3f kW'%(IP);


T2 = T1;
print 'T2: %3.0f K'%(T2);


print 'For Polytropic process ';
n = 1.25
IP = (n/(n-1))*(P1*100*FAD/60)*(((P2/P1)**((n-1)/n))-1);
print 'IP: %3.3f kW'%(IP);


T2 = T1*((P2/P1)**((n-1)/n));
print 'T2: %3.2f K'%(T2);

For Isentropic process 
IP: 1.3 kW
T2: 500 K
For Reversible Isothermal process 
IP: 0.979 kW
T2: 288 K
For Polytropic process 
IP: 1.195 kW
T2: 423.93 K

Example 8.28 pg : 37

In [40]:
import math 

# Variables
V1 = 94.;
P1 = 1.;
T1 = 25.+273;
P2 = 9.;

# Calculations and Results
print 'For isothermal process ';
T2 = T1;
print 'T2: %3.0f K'%(T2);


P = P1*100*V1*math.log(P2/P1);
print 'Power required: %3.0f kW'%(P/60);


Q = P;
print 'Heat Rejected: %3.0f KW'%(Q/60);


print ' For adiabatic process ';
G = 1.4;
T2 = T1*((P2/P1)**((G-1)/G));
print 'T2: %3.0f K'%(T2);


P = (G/(G-1))*(P1*100*V1/60)*(((P2/P1)**((G-1)/G))-1);
print 'Power required: %3.0f kW'%(P);


Q = 0;
print 'Heat Rejected: %3.0f kW'%(Q);


print ' For adiabatic process ';
n = 1.25;
T2 = T1*((P2/P1)**((n-1)/n));
print 'T2: %3.0f K'%(T2);


P = (n/(n-1))*(P1*100*V1/60)*(((P2/P1)**((n-1)/n))-1);
print 'Power required: %3.0f kW'%(P);


R = 0.287;
Cp = 1.005;

m = (P1*100*V1)/(R*T1);
H = m*(1./60)*Cp*(T2-T1);
Q = H-P;
print 'Heat Rejected: %3.0f kW'%(Q);

# note: rounding off error.

For isothermal process 
T2: 298 K
Power required: 344 kW
Heat Rejected: 344 KW
 For adiabatic process 
T2: 558 K
Power required: 479 kW
Heat Rejected:   0 kW
 For adiabatic process 
T2: 462 K
Power required: 432 kW
Heat Rejected: -130 kW

Example 8.29 pg : 39

In [41]:
import math 

# Variables
P1 = 1.;
P2 = 12.;
n = 1.3;
N = 350.;
L = 180./(2*N);
IP = 30.;
Ev = 0.92;

# Calculations
W = (n/(n-1))*(P1*100)*(((P2/P1)**((n-1)/n))-1);   #with (V1-V4)
V14 = (IP*60)/(N*W);
Vs = V14/Ev;
D2 = Vs*4/((22./7)*L);
D = math.sqrt(D2);

# Results
print 'D: %3.3f m'%(D);
print 'L: %3.3f m'%(L);

D: 0.287 m
L: 0.257 m

Example 8.30 pg : 40

In [42]:
import math 

# Variables
m = 1.;
P1 = 1.;
P2 = 5.;
T1 = 27.+273;
n = 1.25;
R = 0.287;

# Calculations and Results
W = m*R*T1*math.log(P2/P1);
print 'Work Done for Isothermal Process: %3.2f kJ/kg '%(W);


G = 1.4;
W = (G/(G-1))*(m*R*T1)*(((P2/P1)**((G-1)/G))-1);
print 'Work Done for Isentropic Process: %3.2f kJ/kg '%(W);


W = (n/(n-1))*(m*R*T1)*(((P2/P1)**((n-1)/n))-1);
print 'Work Done for Polytropic Process: %3.2f kJ/kg '%(W);

Work Done for Isothermal Process: 138.57 kJ/kg 
Work Done for Isentropic Process: 175.93 kJ/kg 
Work Done for Polytropic Process: 163.47 kJ/kg

Example 8.31 pg : 41

In [43]:
# Variables
D = 0.15;
L = 0.3;
P1 = 1.;
T1 = 27.+273;
P2 = 8.;
N = 120.;
G = 1.4;
R = 0.287;
Vs = (22./7)*(1./4)*D*D*L;

# Calculations and Results
m = (P1*100*Vs)/(R*T1);
print 'Mass of air compressed per cycle: %3.4f kJ/cycle '%(m);


W = (G/(G-1))*(P1*100*Vs)*(((P2/P1)**((G-1)/G))-1);
print 'Work required per cycle: %3.3f kJ/cycle '%(W);


P = (W*N)/60;
print 'Power required to drive compressor: %3.2f kJ/cycle '%(P);

Mass of air compressed per cycle: 0.0062 kJ/cycle 
Work required per cycle: 1.506 kJ/cycle 
Power required to drive compressor: 3.01 kJ/cycle