% Average convection correlation for Graetz problem
function [Nu, OLev, n] = GrtzNuL(Wall,fReD,NuInf,Z)
  NuLev = LevNuL(Wall,fReD,Z);                
  OLev=(NuInf-6.54)/4.35;                     
  n=(NuInf+41.0)/13.3;                        
  Nu=(NuLev.^n+(NuInf-OLev).^n).^(1./n)+OLev; 
end
