hl=100;
mDen=100hl;
T1=4;
T2=80;
c=4186;
ro=1000;
msteckou =(mDen/(24.*3600));
Print ["msteckou= ",msteckou,"  kg/s"]
Q=c*msteckou*(T2-T1);
Print["Q = ", Q/1000," kW"]

Tp=105;

Δ1=Tp-T1;
Δ2=Tp-T2;

Solve[Q==kS$*((Δ1-Δ2)/(Log[((Δ1)/(Δ2))]))];
kS=1.2*Round[kS$/.%[[1]]];
Print["volime kS= ",kS," (w/K)"]

λFeCrNi=15;
Rtrubka=(1/(2*Pi*delka*λFeCrNi))*Log[(d2/d1)];
mm=0.001;
d1=10mm;
tlsteny=1mm;
d2=d1+2tlsteny;

Tdef=((T1+T2+2Tp)/4.);
Print["Tdef= ",Tdef," °C"];
dataν={{70,0.413*(10^(-6))},{80,0.365*(10^(-6))}};
ν=Fit[dataν,{1,T},T]/.T->Tdef;
Print["ν= ",ν," (m^2).(s^(-1))"];
Rey=((w*d1 )/ν);
prutok=msteckou/ro;
prurez=((π*d1^2)/4);
n=20;
w=prutok/(n*prurez);
Print["Re= ",Rey," [-]"]