density

Plot[351/T,{T,273,1000},PlotRange->{{273,1000},{0.1,1.5}},AxesOrigin->{0,0},Frame->True,ImageSize->800,FrameLabel->{Style["T (K)",FontSize->25,Bold],Style["Density (kg/(m^3))",FontSize->25,Bold]},BaseStyle->{FontSize->20,FontFamily->"Calibri"}]

Viscoisty

Plot[0.42*10^(-6)*T^(2/3.),{T,273,1000},PlotRange->{{273,1000},{0,1*10^(-4)}},AxesOrigin->{0,0},Frame->True,ImageSize->800,FrameLabel->{Style["T (K)",FontSize->25,Bold],Style["Viscosity (pa s)",FontSize->25,Bold]},BaseStyle->{FontSize->20,FontFamily->"Calibri"}]

Specific capacity

Plot[(0.99+1.22*10^(-4)*T-5.68*10^(3)*(T^(-2)))*1000,{T,273,1000},PlotRange->{{273,1000},{800,1.2*10^(3)}},AxesOrigin->{0,0},Frame->True,ImageSize->800,FrameLabel->{Style["T (K)",FontSize->25,Bold],Style["Specific capacity (J (kg^(-1)) (K^(-1)))",FontSize->25,Bold]},BaseStyle->{FontSize->20,FontFamily->"Calibri"}]

Thermal conductivity

Plot[5.66*10^(-5)*T+1.1*10^(-2),{T,273,1000},PlotRange->{{273,1000},{0,0.1*10^(0)}},AxesOrigin->{0,0},Frame->True,ImageSize->800,FrameLabel->{Style["T (K)",FontSize->25,Bold],Style["Thermal conductivity (W (m^(-1)) (K^(-1))) ",FontSize->25,Bold]},BaseStyle->{FontSize->20,FontFamily->"Calibri"}]

Nus=(7-10*elfa+5*elfa^2)*(1+0.7*REs^0.2*Pr^(1/3.))+(1.33-2.4*elfa+1.2*elfa^2)*REs^0.7*Pr^(1/3.)

elfa=0.98

Nus

REs=0.6/1000.*2650*U/(0.42*10^(-6)*T^(2/3.))

Pr=(0.99+1.22*10^(-4)*T-5.68*10^(3)*(T^(-2)))*1000*(0.42*10^(-6)*T)/(5.66*10^(-5)*T+1.1*10^(-2))

Nus

h=(5.66*10^(-5)*T+1.1*10^(-2))*Nus/(0.6/1000)

Nusc=(7-10*elfa+5*elfa^2)*(1+0.7*REsc^0.2*Prc^(1/3.))+(1.33-2.4*elfa+1.2*elfa^2)*REsc^0.7*Prc^(1/3.)

Prc=1006.4*1.8*10^(-5)/0.024

REsc=0.6/1000.*2650*U/(1.8*10^(-5))

hc=0.024*Nusc/(0.6/1000)

Plot3D[{h,hc},{T,273,1000},{U,5,0},ImageSize->800,BaseStyle->{FontSize->25,FontFamily->"Times"},PlotStyle->{{Red,Opacity[0.6]},{Blue,Opacity[0.6]}},PlotLegends->Placed[{"Air properties depend on T","Air properties constant "},After],PlotRange->{0,150000},AxesLabel->{"T(K)","(Subscript[U, gs])(m/s)","(Subscript[h, gs])((Wm^(-2))(s^(-1)))"},BoxRatios->{1,1,1},Mesh->30,PlotPoints->100,FaceGrids->{{0,1,0},{1,0,0},{0,0,-1}},Ticks->{Automatic,{0,1,2,3,4,5},Automatic}]

Plot3D[{h,hc},{T,273,1000},{U,5,0},ImageSize->800,BaseStyle->{FontSize->25,FontFamily->"Times"},PlotStyle->{{Red,Opacity[1]},{Blue,Opacity[1]}},PlotLegends->Placed[{"Air properties depend on T","Air properties constant "},After],PlotRange->{0,150000},AxesLabel->{"T(K)","(Subscript[U, gs])(m/s)","(Subscript[h, gs])((Wm^(-2))(s^(-1)))"},BoxRatios->{1,1,1},Mesh->30,PlotPoints->100,FaceGrids->{{0,1,0},{1,0,0},{0,0,-1}},Ticks->{Automatic,{0,1,2,3,4,5},Automatic}]

Plot3D[{h,hc},{U,0,5},{T,273,1000},ImageSize->800,BaseStyle->{FontSize->25,FontFamily->"Times"},PlotRange->{0,60000},AxesLabel->{"U(m/s)","T(K)","h"},BoxRatios->{1,1,0.7},Mesh->50,MaxRecursion->0,ColorFunction->"Rainbow",PlotPoints->100,PlotLegends->{Placed[{"Air properties constant ","Air properties depend on T"},Above],BarLegend[Automatic,LegendMarkerSize->{20,200}]}]