docs: def Boyko_Kruzhilin(m, rhog, rhol, kl, mul, Cpl, D, x):
      r'''Calculates heat transfer coefficient for condensation
      of a pure chemical inside a vertical tube or tube bundle, as presented in
      [2]_ according to [1]_.
  
      .. math::
          h_f = h_{LO}\left[1 + x\left(\frac{\rho_L}{\rho_G} - 1\right)\right]^{0.5}
  
          h_{LO} = 0.021 \frac{k_L}{L} Re_{LO}^{0.8} Pr^{0.43}
  
      Parameters
      ----------
      m : float
          Mass flow rate [kg/s]
      rhog : float
          Density of the gas [kg/m^3]
      rhol : float
          Density of the liquid [kg/m^3]
      kl : float
          Thermal conductivity of liquid [W/m/K]
      mul : float
          Viscosity of liquid [Pa*s]
      Cpl : float
          Constant-pressure heat capacity of liquid [J/kg/K]
      D : float
          Diameter of the tubing [m]
      x : float
          Quality at the specific interval [-]
  
      Returns
      -------
      h : float
          Heat transfer coefficient [W/m^2/K]
  
      Notes
      -----
      To calculate overall heat transfer coefficient during condensation,
      simply average values at x = 1 and x = 0.
  
      Examples
      --------
      Page 589 in [2]_, matches exactly.
  
      >>> Boyko_Kruzhilin(m=500*pi/4*.03**2, rhog=6.36, rhol=582.9, kl=0.098,
      ... mul=159E-6, Cpl=2520., D=0.03, x=0.85)
      10598.657227479956
  
      References
      ----------
      .. [1] Boyko, L. D., and G. N. Kruzhilin. "Heat Transfer and Hydraulic
         Resistance during Condensation of Steam in a Horizontal Tube and in a
         Bundle of Tubes." International Journal of Heat and Mass Transfer 10,
         no. 3 (March 1, 1967): 361-73. doi:10.1016/0017-9310(67)90152-4.
      .. [2] Hewitt, G. L. Shires T. Reg Bott G. F., George L. Shires, and
         T. R. Bott. Process Heat Transfer. 1E. Boca Raton: CRC Press, 1994.
      '''
      Vlo = m/rhol/(pi/4.*D**2)
      Relo = rhol*Vlo*D/mul
      Prl = mul*Cpl/kl
      hlo = 0.021*kl/D*Relo**0.8*Prl**0.43
      return hlo*(1. + x*(rhol/rhog - 1.))**0.5