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clc;
clear;
//Example 5.3
me_dot=5500 ; //[kg/h]
me_dot1=me_dot/3600 //[kg/s]
Di=0.037 ; //I.D of inner pipe in [m]
Ai=(%pi/4)*Di^2 //[sq m]
G=me_dot1/Ai //[kg/sq m.s]
mu=3.4*10^-3 ; //[Pa.s] or [kg/(m.s)]
Nre=Di*G/mu //Reynolds number
Cp=2.68 ; //[kJ/kg.K]
Cp1=Cp*10^3 //[J/kgK]
k=0.248 ; //[W/m.K]
Npr=Cp1*mu/k //Prandtl number
//Nre is greater than 10,000,Use Dittus-Boelter eqn:
Nnu=0.023*(Nre^0.8)*(Npr^0.3) //Nusselt number
hi=k*Nnu/Di //[W/sq m.K]
T2=358 //[K]
T1=341 //[K]
Cp2=1.80 //[kJ/kg.K]
t2=335 //[K]
t1=303 //[K]
mt_dot=me_dot*Cp*(T2-T1)/(Cp2*(t2-t1)) //[kg/h]
mt_dot=mt_dot/3600 //[kg/s]
D1=0.043 //[m]
D2=0.064 //Inside dia of outer pipe
De=(D2^2-D1^2)/D1 //Equivalent diameter [m]
Aa=%pi/4*(D2^2-D1^2) //[sq m]
Ga=mt_dot/Aa //kg/(sq m.s)
mu2=4.4*10^-4 // Viscosity of toluene Pa.s
k2=0.146 //For toluene [W/m.K]
Cp2=1.8*10^3 //J/kg.K
Nre=De*Ga/mu2 //Reynolds number
Npr=Cp2*mu2/k2 //Prandtl number
Nnu=0.023*Nre^0.8*Npr^0.4 //Nusselt number
ho=k2*Nnu/De //W/(sq m.K)
Dw=(D1-Di)/log(D1/Di) //[m]
x=0.003 //Wall thickness in [m]
Uo=1/(1/ho+(1/hi)*(D1/Di)+(x*D1/(46.52*Dw))) //[W/sq m.K]
dT1=38 //[K]
dT2=23 //[K]
dTlm=(dT1-dT2)/log(dT1/dT2) //[K]
Q=me_dot1*Cp*(T2-T1) //[kJ/s]
Q=Q*1000 //[J/s]
L=Q/(Uo*%pi*D1*dTlm) //[m]
printf("\nTotal lenggth of double pipe heat exchanger is %f m",L)
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