cm=0.01;
Dchar=1cm;
v=(5/3.6);
Print["velocity= ",v," m.(s^(-1))"]
Ts=50;
Ta=20;
Tdef=0.5*(Ts+Ta);
Print["Tdef= ",Tdef," °C"]
dataPr={{20,0.713},{40,0.711}};
Pr=Fit[dataPr,{1,T},T]/.T->Tdef;
Print["Pr= ",Pr," -"]
dataKinVisc={{20,15.11*(10^(-6))},{40,16.97*(10^(-6))}};
ν=Fit[dataKinVisc,{1,T},T]/.T->Tdef;
Print["ν= ",ν," (m^2).(s^(-1))"];
Rey=((v*Dchar)/ν);
Print["Re= ",Rey," -"]
Nu=0.97*(Rey^0.42);
Print["Nu= ",Nu," -"]
dataLambda={{20,0.0257},{40,0.027}};
λ=Fit[dataLambda,{1,T},T]/.T->Tdef;
Print["λ= ",λ," W.(m^(-1)).(K^(-1))"];
α=Nu*(λ/Dchar);
Print["α= ",α," W.(m^(-2)).(K^(-1))"]
Qconvection1meter=α*π*Dchar*1*(Ts-Ta);
Print["Qconv= ",Qconvection1meter," W/m"]

σ=5.67*(10^(-8));
ϵ=0.9;
Qradiation1meter=π*Dchar*1*ϵ*σ*((((Ts+273))^4)-(((Ta+273))^4));
Print["Qrad= ",Qradiation1meter," W/m"]

Qtotal1m=Qradiation1meter+Qconvection1meter;
Print["Qtotal= ",Qtotal1m," W/m"]

(*   H2O in pipe*)
Dchar=5cm;
QV=(8/3600.);
Print["QV= ",QV," (m^3)/s"];
Scross=(((Dchar^2)*Pi)/4);
v=(QV/Scross);
Print["v= ",v," m.(s^(-1))"]
s=1;
mm=0.001;
ν=1.003*((mm^2)/s);
Rey=((v*Dchar)/ν);
Print["Re=",Rey," -"];
Pr=7.01;
Nu=0.023*(Rey^0.8)*(Pr^0.4);
Print["Nu= ",Nu," -"];
λ=0.6;
α=Nu*(λ/Dchar);
Print["α= ",α," W.(m^(-2)).(K^(-1))"]