title: Lockhart–Martinelli parameter
text: # Lockhart–Martinelli parameter
  
  The Lockhart–Martinelli parameter ($\chi$) is a dimensionless number used in internal two-phase flow calculations. It expresses the liquid fraction of a flowing fluid. Its main application is in two-phase pressure drop and boiling/condensing heat transfer calculations.
  
  It is defined as:
  
      $\chi ={\frac {m_{\ell }}{m_{g}}}{\sqrt {\frac {\rho _{g}}{\rho _{\ell }}}},$
  
  where
  
  * $m_{\ell }$ is the liquid phase mass flowrate;
  * $m_{g}$ is the gas phase mass flowrate;
  * $\rho _{g}$ is the gas density;
  * $\rho _{\ell }$ is the liquid density.
  