Simulation Program
outtextxy(200,30,"ALL THE DIMENSIONS ARE IN MM");
long float NT,L,Dr,Di,Lf,Tf,NF,AF=3264464.3,l_eff,A,Aw,Pi=3.141592,wf ,a,AT,di,Lc=300,SD ;
cout<<"\n\n\nEnter total no of tubes\n";
cin>>NT;
cout<<"\nEnter length of tube\n";
cin>>L;
cout<<"\nEnter outer dia of tube\n";
cin>>Dr;
cout<<"\nInternal dia of tube\n";
cin>>Di;
cout<<"\nInternal dia of tube with turbulator (Hydraulic Diameter)\n";
cin>>di;
cout<<"\nEnter the length of fin\n";
cin>>Lf;
cout<<"\nEnter the thickness of fin\n";
cin>>Tf;
cout<<"\nEnter the width of fin\n";
cin>>wf;
cin>>NF;
l_eff=290-(Tf*NF);
cout<<"\n\nSurface area of the tube between the fins\t";
Aw=NF*Pi*Dr*l_eff ; cout<<"Aw="<<Aw;
A=AF+Aw;
cout<<"\n\nThe total external area of the tube without fins\t";
AT=NT*Lc*Pi*Dr;
cout<<"AT="<<AT;
long float AFR,Ma,Vmax,P_air=1.145,Gw , Ge ; cout<<"\n\nEnter the velocity of air (m/s)\n";
cin>>Vmax;
cout<<"\n\nFrontal area of the radiator through the air passes\t";
AFR= (290*Lf)-(Lf*Tf*NF) ; cout<<"AFR="<<AFR;
Ma=Vmax*P_air*AFR*pow(10,-6);
cout<<"\n\nMass flow rate of air(Ma)="<< Ma;
long float Ga=0.00001895,Re_air,Nu,z,fct,Ef,ha,ha1 , Pr=0.7268,s=1.4,h=3.75,p1=14,p2=12.82, kf=237;
cout<<"\n\nThe corresponding reynold no\t";
Re_air=Vmax* Dr*pow(10,-3)* P_air/Ga;
cout<<"Re_air="<<Re_air;
cout<<"\n\n\nPress any key to continue...";
getch();
cout<<"\n\nThe air side heat transfer coefficient is obtained using the"
<<"\nESDU CORRELATION for high fin staggered array heat exchanger";
Nu=0.242* pow(Re_air,0.688)*pow((s/h),0.297)*pow((p1/p2),-0.91)*pow(Pr,(0.333));
cout<<"Nu="<<Nu;
cout<<"\n\n Air side heat transfer coefficient\t";
long float ka=0.02625,V_coolant,ha_r;
ha=ka*Nu/Dr*pow(10,(3));
cout<<"ha="<<ha;
z= Dr*pow(10,(-3))/2*((14/Dr)-1)*(1+0.35*log(14/Dr));
fct=pow((2*ha/(wf*kf) *z),(0.5));
Ef=(tanh(fct))/(fct);
cout<<"\n\nEfficiency of the fins:\t"<<"Ef="<<Ef;
cout<<"\n\nThe effective air-side heat transfer coefficient"
<<"\n based on total surface area is given by\t";
ha1=(Ef*AF*pow(10,-6)*Aw/A)*ha;
cout<<"ha1="<<ha1;
cout<<"\n\n\nPress any key to continue...";
getch();
cout<<"\n\nThe air side heat transfer coefficient referred to "<<"\nthe external surface to the tube without fins:";
ha_r=ha1*(A/AT);
cout<<"ha_r="<< ha1*(A/AT);
long float p_coolant=1070
,G_coolant=0.00156025,Re_coolant,h_coolant,k_coolant=0.4685,Nu_coolant, A_tube_internal,M_coolant,Pr1= 29.13,a1,a2,a3,a4;
cout<<"\n\nWater side heat transfer coefficient:\n";
cout<<"\n\nEnter velocity of coolant:\n";
cin>>V_coolant;
cout<<"\nReynolds no:\t";
Re_coolant=V_coolant*di*pow(10,-3)* p_coolant/G_coolant;
cout<<"\n\n\nPress any key to continue...";
getch();
cout<<"\n\nMass flow rate of coolant (M_coolant)\t";
A_tube_internal= Pi/4*di*di*pow(10,-6);
cout<<" A_tube_internal="<<A_tube_internal;
M_coolant =NT* V_coolant*p_coolant*A_tube_internal;
cout<<"M_coolant="<<M_coolant;
long float RF=0.000175 ,T_coolant_in=92.0,T_coolant_out=30.0,k_tube=237;
cout<<"\n\nOverall heat transfer coefficient ";
cout<<"\n\nAssumption: "
<<"\n\nThe thermal assumption at junction of fins & tubes are neglected "
<<"\nHence, the value of Ur ,related to the external surface of the tube without fins, i.e. to dia. Dr";
long float sd,Ur,T_air_out,T_air_in=27,C_min,C_max,e,Q,R,DTm, NTU_air,Cp_coolant=3383,Cp_air=1007,exp=2.718281828,x1,y1;
sd=RF+ 1/ha_r+(Dr/(2000*k_tube))*log(Dr/di)+1/h_coolant;
Ur=1/sd;
cout<<"\n\n\nPress any key to continue...";
getch();
T_coolant_out= (T_coolant_in)- (Q/C_max);
cout<<"\n\nOutlet temp. of coolant="<<T_coolant_out;
T_air_out=(Q/C_min)+T_air_in;
cout<<"\n\nOutlet temp. of Air="<<T_air_out;
getch();
closegraph();
}
ADVANCEMENT:
Improvement is an endless phenomenon. The same is true for different outcomes of different manufacturing concerns, which required continuous improvement to withstand the global competition in the market .
Thatswhy the aim which we have taken as our responsibility is not fulfilled completely.
What we have done is just an initialization and there is a lot to still now.
On the basis of the theory we have explained more mathematical models can be developed that can be solved by computer and more information can be added about the reasons of reduction in efficiency.
In the current advancement the composite aluminium foil used for radiators is a core of Al-Mn alloy sandwiched by Al-Si brazing material, made through hot rolling composite technology. This product is mainly used on fins of automobile heat exchanger, requiring not only an excellent surface quality, accurate dimension and flat contour, but also uniform structure, good forming performance, and in particular the uniformity of the covering layers and brazing features.
Brazed composite aluminium foils are a type of new aluminium alloy of high performance among the top brands of aluminium process products, characterized by its high technical content and value added. Such sandwich structure of composite aluminium foils, possessing properties of light weight, corrosion resistance, good brazing features and reliability has been widely applied in automobile heat exchangers, such as automobile water tanks, condensers of automobile air conditioners, and evaporators.
We can improve design of tubes in the following manner as shown below:
Internally and externally finned tubes (Enhancement)
Internally and externally finned tubes (Enhancement)
Conclusion
After passing so many hurdles finally we achieve our target to
minimize the design time of cooling system by preparing a simulation model in form of a mathematical model. That can be solved by using a digital computer.
The computer program that is attached in the “project”
could give results or effects of change in different parameters and thus helps in design.
We also got success to explain the causes of downfall of effectiveness of radiator (heat exchanger).
Thus we have constructed a platform (simulation program) to further proceed for betterment in form of efficient design cheaply in least possible time and improved effectiveness.