1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
|
printf("\t example 12.5 \n");
printf("\t approximate values are mentioned in the book \n");
T1=130; // inlet hot fluid,F
T2=125; // outlet hot fluid,F
T3=100; // after subcooling
t1=80; // inlet cold fluid,F
t3=100; // outlet cold fluid,F
W=21000; // lb/hr
w=167000; // lb/hr
printf("\t 1.for heat balance \n");
printf("\t for pentane \n");
c=0.57; // Btu/(lb)(F)
qs=((W)*(c)*(T2-T3)); // Btu/hr
printf("\t total heat required for subcooling of pentane is : %.0e Btu/hr \n",qs);
HT1=315; // enthalpy at T1, Btu/lb
HT2=170; // enthalpy at T2, Btu/lb
qc=(W*(HT1-HT2)); // for condensation
printf("\t total heat required for condensing of pentane is : %.2e Btu/hr \n",qc);
Q=qs+qc;
printf("\t total heat required for pentane is : %.2e Btu/hr \n",Q);
printf("\t for water \n");
c=1; // Btu/(lb)*(F)
Q=((w)*(c)*(t3-t1)); // Btu/hr
printf("\t total heat required for water is : %.2e Btu/hr \n",Q);
deltw=18.2;
printf("\t deltw is : %.1f F \n",deltw);
t2=t3-deltw;
printf("\t t2 is : %.1f F \n",t2)
printf("\t for condensing \n");
delt1=T2-t2; //F
delt2=T1-t3; // F
printf("\t delt1 is : %.0f F \n",delt1);
printf("\t delt2 is : %.0f F \n",delt2);
LMTDc=((delt2-delt1)/((2.3)*(log10(delt2/delt1))));
printf("\t LMTD is :%.1f F \n",LMTDc);
w1=(qc/LMTDc);
printf("\t w1 is : %.2e lb/hr \n",w1);
printf("\t subcooling \n");
delt3=T3-t1; //F
delt4=T2-t2; // F
printf("\t delt1 is : %.0f F \n",delt3);
printf("\t delt2 is : %.0f F \n",delt4);
LMTDs=((delt4-delt3)/((2.3)*(log10(delt4/delt3))));
printf("\t LMTD is :%.1f F \n",LMTDs);
w2=(qs/LMTDs);
printf("\t w1 is : %.2e lb/hr \n",w2);
delt=(Q/(w1+w2));
printf("\t delt is : % .1f F \n",delt);
Tc=((T1)+(T2))/(2); // caloric temperature of hot fluid,F
printf("\t caloric temperature of hot fluid is : %.1f F \n",Tc);
tc=((t1)+(t3))/(2); // caloric temperature of cold fluid,F
printf("\t caloric temperature of cold fluid is : %.0f F \n",tc);
printf("\t hot fluid:shell side,pentane \n");
C1=0.198; // for 0.3Ds
Ds=25; // in
L=16; // ft
N=370
a=(C1*Ds^2);
printf("\t a is : %.0f in^2 \n",a);
N1=((N*a*4)/(3.14*Ds^2));
printf("\t number of submerged tubes are : %.0f \n",N1);
Nt=N-N1;
printf("\t number of tubes for condensation are : %.0f \n",Nt);
Af=(N1/N);
printf("\t flooded surface : %.2f \n",Af);
printf("\t for condensaton \n");
G1=(W/(L*Nt^(2/3))); // from eq.12.43
printf("\t G1 is : %.1f lb/(hr)*(lin ft) \n",G1);
printf("\t cold fluid:inner tube side,water \n");
n=4; // number of passes
L=16; //ft
at1=0.302; // flow area, in^2
at=((Nt*at1)/(144*n)); // total area,ft^2,from eq.7.48
printf("\t flow area is : %.3f ft^2 \n",at);
Gt=(w/(at)); // mass velocity,lb/(hr)*(ft^2)
printf("\t mass velocity is : %.1e lb/(hr)*(ft^2) \n",Gt);
V=(Gt/(3600*62.5));
printf("\t V is : %.2f fps \n",V);
mu2=1.98; // lb/(ft)*(hr)
D=0.0517; // ft
Ret=((D)*(Gt)/mu2); // reynolds number
printf("\t reynolds number is : %.2e \n",Ret);
hi=940; //Btu/(hr)*(ft^2)*(F)
printf("\t hi is : %.0f Btu/(hr)*(ft^2)*(F) \n",hi);
ID=0.62; // ft
OD=0.75; //ft
hio=((hi)*(ID/OD)); // using eq.6.5
printf("\t Correct hio to the surface at the OD is : %.0f Btu/(hr)*(ft^2)*(F) \n",hio);
ho=251; // Btu/(hr)*(ft^2)*(F), from fig 12.9
printf("\t Correct ho to the surface at the OD is : %.0f Btu/(hr)*(ft^2)*(F) \n",ho);
Uc=((hio)*(ho)/(hio+ho)); // clean overall coefficient,Btu/(hr)*(ft^2)*(F)
printf("\t clean overall coefficient is : %.0f Btu/(hr)*(ft^2)*(F) \n",Uc);
Ac=(qc/(Uc*LMTDc));
printf("\t clean surface required for dcondensation : %.0f ft^2 \n",Ac);
printf("\t subcooling \n");
ho=50; // Btu/(hr)*(ft^2)*(F)
printf("\t individual heat transfer coefficient is : %.0f Btu/(hr)*(ft^2)*(F) \n",ho);
Us=((hio)*(ho)/(hio+ho)); // clean overall coefficient,Btu/(hr)*(ft^2)*(F)
printf("\t clean overall coefficient is : %.0f Btu/(hr)*(ft^2)*(F) \n",Us);
As=(qs/(Us*LMTDs));
printf("\t clean surface required for desuperheating : %.0f ft^2 \n",As);
AC=As+Ac;
printf("\t total clean surface : %.0f ft^2 \n",AC);
UC=((Us*As)+(Uc*Ac))/(AC);
printf("\t weighted clean overall coefficient : %.0f Btu/(hr)*(ft^2)*(F) \n",UC);
A=1160; // ft^2
printf("\t total surface area is : %.0f ft^2 \n",A);
UD=((Q)/((A)*(delt)));
printf("\t actual design overall coefficient is : %.1f Btu/(hr)*(ft^2)*(F) \n",UD);
Rd=((UC-UD)/((UD)*(UC))); // (hr)*(ft^2)*(F)/Btu
printf("\t actual Rd is : %.4f (hr)*(ft^2)*(F)/Btu \n",Rd);
printf("\t pressure drop for annulus \n");
printf("\t condensation \n");
printf("\t It will be necessary to spread the batHes to a spacing of 18in.to compensate for the reduction in crossfiow area due to the flooded subcooling zone. The tube-side pressure drop will be the same as before. Assume bundle flooded to 0.3Ds.\n");
As=0.547; // ft^2
Gs=(W/(As)); // mass velocity,lb/(hr)*(ft^2)
printf("\t mass velocity is : %.1e lb/(hr)*(ft^2) \n",Gs);
De=0.0792; // fig 28
Res=((De)*(Gs)/0.0165); // reynolds number
printf("\t reynolds number is : %.2e \n",Res);
f=0.00121; // friction factor for reynolds number 193000, using fig.29
s=0.00454; // for reynolds number 193000,using fig.6
Ds=2.08; // ft
B=18
phys=1;
N=(12*L/B); // number of crosses,using eq.7.43
printf("\t number of crosses are : %.0f \n",N);
delPsc=((f*(Gs^2)*(Ds)*(N))/(5.22*(10^10)*(De)*(s)*(phys)))/(2); // using eq.12.47,psi
printf("\t delPsc is : %.1f psi \n",delPsc);
printf("\t delPss is negligible \n");
printf("\t allowable delPa is 2 psi \n");
//end
|
