# Chapter 9 : Computers and their application¶

### example 9.1 page number 384¶

In [1]:
import math
D = 38.*10**-3;    #in m
U = 1.   #in m/s
density = 998.   #in kg/cubic m
viscosity = 8.*10**-4   #in Pa-s
DC = 1.   #in m
N = 10.
e = 4.*10**-6;   #in m

Re = (density*U*D)/viscosity;
print  "Reynolds number = %f"%(Re)

f = (4*math.log10((e/D)/3.7+(6.81/Re)**0.9))**-2;
print "friction factor = %f"%(f);

L = 3.14*DC*N;

delta_Pstr = (2*f*U*density*L)/D;
print "pressure drop through straight pipe = %f Pa"%(delta_Pstr)

S = 1+3.54*(D/DC);
print "correction factor = %f"%(S)

delta_P = S*delta_Pstr
print "pressure drop of coil = %f Pa"%(delta_P)

Reynolds number = 47405.000000
friction factor = 0.005330
pressure drop through straight pipe = 8791.184173 Pa
correction factor = 1.134520
pressure drop of coil = 9973.774268 Pa


### example 9.2 page number 384¶

In [2]:
import math
U = 0.5   #in m/s
N = 19.;
DT = 0.026   #in m
L = 2.7   #in m
DS = 0.2   #in m
e = 0.0002   #in m
density = 836.  #in kg/cu m
viscosity = 0.00032   #in Pa s
Pr = 6.5;
Prw = 7.6;

HYDIA = (DS**2-N*DT**2)/(DS+N*DT);
Re = HYDIA*U*density/viscosity;
print  "Reynolds number = %f"%(Re)

f = (4*math.log10((e/HYDIA)/3.7+(6.81/Re)**0.9))**-2;
print "friction factor = %f"%(f);

L = 3.14*DT*N;

delta_Pstr = (2*f*U*density*L)/HYDIA;
print "pressure drop through straight pipe = %f Pa"%(delta_Pstr)

S = (Prw/Pr)**0.33;
print "correction factor = %f"%(S)

delta_P = S*delta_Pstr
print "pressure drop of coil = %f Pa"%(delta_P)

Reynolds number = 51113.148415
friction factor = 0.008158
pressure drop through straight pipe = 270.362537 Pa
correction factor = 1.052948
pressure drop of coil = 284.677794 Pa


### example 9.3 page number 385¶

In [3]:
import math
MH = 10.   #in kg/s
MC = 12.5  #in kg/s
CPH = 4.2   #in kJ/kg
CPC = 4.2   #in kJ/kg
THI = 353.   #in K
THO = 333.   #in K
TCI = 300.   #in K
U = 1.8    #in kW/sq m K

Q = MH*CPH*(THI-THO);
print "heat load = %f J"%(Q)

TCO = Q/(MC*CPC)+TCI;
print "cold fluid outlet temperature = %f K"%(TCO)

DT1 = THI-TCO;
DT2 = THO-TCO;

LMTD = (DT1-DT2)/math.log(DT1/DT2);

A = Q/(U*LMTD);
print "for co current flow area = %f sq m"%(A);

DT1 = THI-TCO;
DT2 = THO-TCI;

LMTD = (DT1-DT2)/math.log(DT1/DT2);

A = Q/(U*LMTD);
print "for counter current flow area = %f sq m"%(A);

heat load = 840.000000 J
cold fluid outlet temperature = 316.000000 K
for co current flow area = 18.146440 sq m
for counter current flow area = 13.347874 sq m

In [ ]: