Off[General::spell1,General::spell,Solve::svars];
SetDirectory["FileName"/.NotebookInformation[EvaluationNotebook[]]/.FrontEnd`FileName[d_List,nam_,___]:>ToFileName[d]];

tepl=Table[i,{i,-20,25,5}];
n=Length[%];
pel35={15,15,16,17,17,18,19,21,21,22};
pel50={19.5,20,20.5,21,21,22,23,24,24.5,26};
pel60={24.5,25,26,26,26.5,27,28,29,29.5,31};
ptop35={27,32,41,48,51.5,65,77,89,96,101};
ptop50={28,33,42,48,51,62,73,82.5,89.5,101};
ptop60={30,35,43,49.5,52.5,63,72,80,87,97};
m=1000(20./138);
radekEl35[i_]:={tepl[[i]],35.,pel35[[i]]};
radekEl50[i_]:={tepl[[i]],50.,pel50[[i]]};
radekEl60[i_]:={tepl[[i]],60.,pel60[[i]]};
radekTop35[i_]:={tepl[[i]],35.,ptop35[[i]]};
radekTop50[i_]:={tepl[[i]],50.,ptop50[[i]]};
radekTop60[i_]:={tepl[[i]],60.,ptop60[[i]]};
dataEl=Flatten[Table[{radekEl35[i],radekEl50[i],radekEl60[i]},{i,n}],1];
dataTop=Flatten[Table[{radekTop35[i],radekTop50[i],radekTop60[i]},{i,n}],1];
Pel[Tvzduch_,Tvoda_]=m*Interpolation[dataEl,InterpolationOrder->{3,2}][Tvzduch,Tvoda];
Ptop[Tvzduch_,Tvoda_]=m*Interpolation[dataTop,InterpolationOrder->{3,2}][Tvzduch,Tvoda];
eps[Tvzduch_,Tvoda_]=((Ptop[Tvzduch,Tvoda])/(Pel[Tvzduch,Tvoda]));

ts=0.008;
ps={{GrayLevel[0]},{Thickness[ts],RGBColor[0,0,1]},{Thickness[ts],RGBColor[0.5,0.5,0]},{Thickness[ts],RGBColor[1,0,0]}}
Plot[{0,Ptop[Tvzduch,35],Ptop[Tvzduch,50],Ptop[Tvzduch,60]},{Tvzduch,-20,25},AxesLabel->{"Tv[°C]","Ptop[W]"},PlotStyle->ps]
Plot[{0,Pel[Tvzduch,35],Pel[Tvzduch,50],Pel[Tvzduch,60]},{Tvzduch,-20,25},AxesLabel->{"Tv[°C]","Pel[W]"},PlotStyle->ps]
Plot[{0,eps[Tvzduch,35],eps[Tvzduch,50],eps[Tvzduch,60]},{Tvzduch,-20,25},AxesLabel->{"Tv[°C]","ϵ[1]"},PlotStyle->ps]

Put[{{Pel[Tvzduch,Tvoda],Ptop[Tvzduch,Tvoda],eps[Tvzduch,Tvoda]},{"Pel","Ptop","eps"}},"struct"]