docs: def laminar_entry_thermal_Hausen(Re=None, Pr=None, L=None, Di=None):
      r'''Calculates average internal convection Nusselt number for laminar flows
      in pipe during the thermal entry region according to [1]_ as shown in
      [2]_ and cited by [3]_.
  
      .. math::
          Nu_D=3.66+\frac{0.0668\frac{D}{L}Re_{D}Pr}{1+0.04{(\frac{D}{L}
          Re_{D}Pr)}^{2/3}}
  
      Parameters
      ----------
      Re : float
          Reynolds number, [-]
      Pr : float
          Prandtl number, [-]
      L : float
          Length of pipe [m]
      Di : float
          Diameter of pipe [m]
  
      Returns
      -------
      Nu : float
          Nusselt number, [-]
  
      Notes
      -----
      If Pr >> 1, (5 is a common requirement) this equation also applies to flows
      with developing velocity profile.
      As L gets larger, this equation  becomes the constant-temperature Nusselt
      number.
  
      Examples
      --------
      >>> laminar_entry_thermal_Hausen(Re=100000, Pr=1.1, L=5, Di=.5)
      39.01352358988535
  
      References
      ----------
      .. [1] Hausen, H. Darstellung des Warmeuberganges in Rohren durch
         verallgeminerte Potenzbeziehungen, Z. Ver deutsch. Ing Beih.
         Verfahrenstech., 4, 91-98, 1943
      .. [2] W. M. Kays. 1953. Numerical Solutions for Laminar Flow Heat Transfer
         in Circular Tubes.
      .. [3] Bergman, Theodore L., Adrienne S. Lavine, Frank P. Incropera, and
         David P. DeWitt. Introduction to Heat Transfer. 6E.
         Hoboken, NJ: Wiley, 2011.
      '''
      Gz = Di/L*Re*Pr
      return 3.66 + (0.0668*Gz)/(1+0.04*(Gz)**(2/3.))