the bubble dispersion device 15 the refrigerant expanding in the ejector motive nozzle 18 would be metastable and not in a state of thermodynamic equilibrium flow through the ejector motive nozzle 18 under those conditions would consist of an annulus of vapor surrounding a core of metastable liquid refrigerant due to minimal nucleation sites for dispersed boiling the kinetic energy of the liquid vapor mixture leaving the nozzle 18 would then be considerably less than if the fluid were in a state of thermodynamic equilibrium as a result the pressure increase between lines 27 and 21 due to the use of the ejector would be considerably less it will be understood that large unevenly dispersed bubbles contribute nothing to solving the problem of metastability the method of the invention reduces flow metastability as the pressurized liquid refrigerant flows through and partially flashes to vapor upon exiting from the ejector motive nozzle 18 this is achieved by one of the methods illustrated schematically in fig2 and 4 the bubble generator 14 15 in fig1 schematically represents any one of the fig2 to 4 embodiments in the fig2 method of achieving bubbly flow seeding in the ejector motive nozzle 18 the liquid in a saturated or subcooled state enters from a relatively large diameter section 30 corresponding to the line 13 in fig1 it then passes through a flow restrictive orifice 35 corresponding to the bubble generating device 14 in fig1 the throttling action of the orifice 31 causes the refrigerant to become a liquid vapor mixture with much lower average density than the pure liquid.