In this study, experiments were conducted to develop a means to estimate mass flow rate of opening jet plume. From the results obtained through small and middle-scale experiments, the following findings were obtained: (1)when the opening jet plume is modeled into a vertical plume, the height Z_D at which the mass flow rate becomes equal to the opening flow rate depends only on the section height of opening jet in any geometry of the opening, (2)The nondimensional height of virtual origin of opening jet plume depends only on the nondimensional mass flow rate of opening jet, (3)The mass flow rate of the small and middle-scale experiments are well scaled by nondimensional mass flow rate of opening jet and nondimensional entrainment length. And (4)when using opening width for the representative length, the nondimensional mass flow rate μ_p is given by μ_p=0.19{(Z_e+ Z_D+Z_0/B}^<5/3> regardless of the opening shape and temperature of opening jets.
