Quiet@Remove["Global`*"];
$HistoryLength=2;
SetDirectory[NotebookDirectory[]];

vykon=((5000.*4186*85)/(3600*8));
Print["vykon= ",(vykon/1000)," kW"]

T1=5;
T2=90;
Tpara=150;
Δ1=Tpara-T1;
Δ2=Tpara-T2;
kS=kSpom/.Solve[vykon==kSpom*((Δ1-Δ2)/(Log[((Δ1)/(Δ2))]))][[1]];
Print["kS= ",kS," \!\(\*FractionBox[\(\(W\)\(\\ \)\), \(K\)]\)"]

mm=0.001;
Dout=7mm;
dStena=1mm;
Dchar=Dout-2*dStena;
(*Tdef=((100+100+5+90)/4.);*)
Tdef=70;
ν=0.4*(10^(-6));
nTrubek=100;
prurez=((Pi*(Dchar^2))/4);
Vsteckou=(5000./(3600*8*1000));
rychlost=(Vsteckou/(prurez*nTrubek));
Rey=((rychlost*Dchar)/ν);
Print["Rey= ",Rey," -"]

Nu=3.66;
λ=0.65;
α=((Nu*λ)/Dchar);
Print["α= ",α," W.(m^(-2)).(K^(-1))"];
k=α;
S=(kS/k);
Solve[nTrubek*Pi*Dchar*delka==S]

Quiet@Remove["Global`*"];
(*tepelna pohoda*)
αin=5;
αext=15;
cm=0.01;
dCihla=30cm;
dIz=15cm;
Din=10;
λCihla=0.8;
λIzolace=0.04;
objem=(4/3)*Pi*((((Din/2)))^3);
RthCihla=(2/(4*Pi*λCihla))*((1/Din)-(1/(Din+2*dCihla)));
RthIzolace=(2/(4*Pi*λIzolace))*((1/(Din+2*dCihla))-(1/(Din+2*dCihla+2*dIz)));
RthKonvekceIn=(1./(αin*4*Pi*((((Din/2)))^2)));
RthKonvekceVenku=(1./(αext*4*Pi*(((((Din+2*dCihla+2*dIz)/2)))^2)));

(1/RthIzolace)*{RthCihla,RthIzolace,RthKonvekceIn,RthKonvekceVenku}

Texterni=-10;
Tin=25;
casVymenyVzduchu=3*3600;
cp=1010.;
roVzduch=(349/(Tin+273));
RthStenaExterier=RthKonvekceVenku+RthIzolace+RthCihla;
rce={PztratyVedeni==((TinStena-Texterni)/RthStenaExterier),
Pvetrani==((roVzduch*cp*objem*(Tin-Texterni))/casVymenyVzduchu)
}