Lockhart–Martinelli parameter

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The Lockhart–Martinelli parameter (\chi) is a dimensionless number used in internal two-phase flow calculations.[1] 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}},


  • m_\ell is the liquid phase mass flowrate;
  • m_g is the gas phase mass flowrate;

See also[edit]


  1. ^ Lockhart, R.W., Martinelli, R.C.; Chem. Eng. Prog., Vol. 45. 1949, pp. 39–48