docs: def Elamvaluthi_Srinivas(m, x, D, rhol, rhog, Cpl, kl, mug, mu_b, mu_w=None):
      r'''Calculates the two-phase non-boiling heat transfer coefficient of a 
      liquid and gas flowing inside a tube of any inclination, as in [1]_ and 
      reviewed in [2]_.
  
      .. math::
          \frac{h_{TP} D}{k_L} = 0.5\left(\frac{\mu_G}{\mu_L}\right)^{0.25} 
          Re_M^{0.7} Pr^{1/3}_L (\mu_b/\mu_w)^{0.14}
          
          Re_M = \frac{D V_L \rho_L}{\mu_L} + \frac{D V_g \rho_g}{\mu_g}
          
      Parameters
      ----------
      m : float
          Mass flow rate [kg/s]
      x : float
          Quality at the specific tube interval [-]
      D : float
          Diameter of the tube [m]
      rhol : float
          Density of the liquid [kg/m^3]
      rhog : float
          Density of the gas [kg/m^3]
      Cpl : float
          Constant-pressure heat capacity of liquid [J/kg/K]
      kl : float
          Thermal conductivity of liquid [W/m/K]
      mug : float
          Viscosity of gas [Pa*s]
      mu_b : float
          Viscosity of liquid at bulk conditions (average of inlet/outlet 
          temperature) [Pa*s]
      mu_w : float, optional
          Viscosity of liquid at wall temperature [Pa*s]
  
      Returns
      -------
      h : float
          Heat transfer coefficient [W/m^2/K]
  
      Notes
      -----
      If the viscosity at the wall temperature is not given, the liquid viscosity
      correction is not applied.
      
      Developed for vertical flow, and flow patters of bubbly and slug.
      Gas/liquid superficial velocity ratios from 0.3 to 4.6, liquid mass fluxes 
      from 200 to 1600 kg/m^2/s, and the fluids tested were air-water and 
      air-aqueous glycerine solutions. The tube inner diameter was 1 cm, and the
      L/D ratio was 86.
      
      Examples
      --------
      >>> Elamvaluthi_Srinivas(m=1, x=.9, D=.3, rhol=1000, rhog=2.5, Cpl=2300, 
      ... kl=.6, mug=1E-5, mu_b=1E-3, mu_w=1.2E-3)
      3901.2134471578584
      
      References
      ----------
      .. [1] Elamvaluthi, G., and N. S. Srinivas. "Two-Phase Heat Transfer in Two
         Component Vertical Flows." International Journal of Multiphase Flow 10, 
         no. 2 (April 1, 1984): 237-42. doi:10.1016/0301-9322(84)90021-1.
      .. [2] Dongwoo Kim, Venkata K. Ryali, Afshin J. Ghajar, Ronald L. 
         Dougherty. "Comparison of 20 Two-Phase Heat Transfer Correlations with 
         Seven Sets of Experimental Data, Including Flow Pattern and Tube 
         Inclination Effects." Heat Transfer Engineering 20, no. 1 (February 1, 
         1999): 15-40. doi:10.1080/014576399271691.
      '''
      Vg = m*x/(rhog*pi/4*D**2)
      Vl = m*(1-x)/(rhol*pi/4*D**2)
  
      Prl = Prandtl(Cp=Cpl, mu=mu_b, k=kl)
      ReM = D*Vl*rhol/mu_b + D*Vg*rhog/mug
      Nu_TP = 0.5*(mug/mu_b)**0.25*ReM**0.7*Prl**(1/3.)
      if mu_w:
          Nu_TP *= (mu_b/mu_w)**0.14
      return Nu_TP*kl/D