docs: def McNelly(rhol, rhog, kl, Cpl, Hvap, sigma, P, Te=None, q=None):
      r'''Calculates heat transfer coefficient for a evaporator operating
      in the nucleate boiling regime according to [2]_ as presented in [1]_.
  
      Either heat flux or excess temperature is required.
  
      With `Te` specified:
      
      .. math::
          h = \left(0.225\left(\frac{\Delta T_e C_{p,l}}{H_{vap}}\right)^{0.69}
          \left(\frac{P k_L}{\sigma}\right)^{0.31}
          \left(\frac{\rho_L}{\rho_V}-1\right)^{0.33}\right)^{1/0.31}
  
      With `q` specified:
      
      .. math::
          h = 0.225\left(\frac{q C_{p,l}}{H_{vap}}\right)^{0.69} \left(\frac{P 
          k_L}{\sigma}\right)^{0.31}\left(\frac{\rho_L}{\rho_V}-1\right)^{0.33}
  
      Parameters
      ----------
      rhol : float
          Density of the liquid [kg/m^3]
      rhog : float
          Density of the produced gas [kg/m^3]
      kl : float
          Thermal conductivity of liquid [W/m/K]
      Cpl : float
          Heat capacity of liquid [J/kg/K]
      Hvap : float
          Heat of vaporization of the fluid at P, [J/kg]
      sigma : float
          Surface tension of liquid [N/m]
      P : float
          Saturation pressure of fluid, [Pa]
      Te : float, optional
          Excess wall temperature, [K]
      q : float, optional
          Heat flux, [W/m^2]
      
      Returns
      -------
      h : float
          Heat transfer coefficient [W/m^2/K]
  
      Notes
      -----
      Further examples for this function are desired.
  
      Examples
      --------
      Water boiling, with excess temperature of 4.3 K.
  
      >>> McNelly(Te=4.3, P=101325, Cpl=4180., kl=0.688, sigma=0.0588,
      ... Hvap=2.25E6, rhol=958., rhog=0.597)
      533.8056972951352
  
      References
      ----------
      .. [1] Cao, Eduardo. Heat Transfer in Process Engineering.
         McGraw Hill Professional, 2009.
      .. [2] McNelly M. J.: "A correlation of the rates of heat transfer to n
         ucleate boiling liquids," J. Imp Coll. Chem Eng Soc 7:18, 1953.
      '''
      if Te:
          return (0.225*(Te*Cpl/Hvap)**0.69*(P*kl/sigma)**0.31*(rhol/rhog-1.)**0.33
              )**(1./0.31)
      elif q:
          return 0.225*(q*Cpl/Hvap)**0.69*(P*kl/sigma)**0.31*(rhol/rhog-1.)**0.33
      else:
          raise Exception('Either q or Te is needed for this correlation')