docs: def laminar_entry_Baehr_Stephan(Re=None, Pr=None, L=None, Di=None):
      r'''Calculates average internal convection Nusselt number for laminar flows
      in pipe during the thermal and velocity entry region according to [1]_ as
      shown in [2]_.
  
      .. math::
          Nu_D=\frac{\frac{3.657}{\tanh[2.264 Gz_D^{-1/3}+1.7Gz_D^{-2/3}]}
          +0.0499Gz_D\tanh(Gz_D^{-1})}{\tanh(2.432Pr^{1/6}Gz_D^{-1/6})}
  
          Gz = \frac{D}{L}Re_D Pr
  
      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
      -----
      As L gets larger, this equation becomes the constant-temperature Nusselt
      number.
  
      Examples
      --------
      >>> laminar_entry_Baehr_Stephan(Re=100000, Pr=1.1, L=5, Di=.5)
      72.65402046550976
  
      References
      ----------
      .. [1] Baehr, Hans Dieter, and Karl Stephan. Heat and Mass Transfer.
         Springer, 2013.
      .. [2] 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 (3.657/tanh(2.264*Gz**(-1/3.)+ 1.7*Gz**(-2/3.0))
              + 0.0499*Gz*tanh(1./Gz))/tanh(2.432*Pr**(1/6.0)*Gz**(-1/6.0))