% Natural convection from long horizontal cylinder
function [h, NuD, RaD] = HorzCylNatNuT(Ts,Tinf,D,mat)
  [RaD,Pr,kf] = Ra(Ts,Tinf,D,mat);                                  
  if max(RaD) > 1e12 warning = 'HorzCylNatNuT: RaD > 1e12' 
  end
  NuD = (0.6+0.387*RaD.^(1/6)./(1+(0.559./Pr).^(9/16)).^(8/27)).^2; 
  h   = NuD.*kf/D;                                                  
end
