One of the important property of the free jet is that it carries with it momentum flow rate which on hitting the liquid is converted into force and penetrates into the liquid. Momentum flow rate within the jet is conserved. This is an important property of the jet since it depends only on the upstream variables like pressure, number and diameter of the nozzle. It does not depend on the downstream conditions. For details see the references given at the end of this lecture

Behaviour of jets produced by multi-nozzles depends on number of nozzles and inclination angle  of  each nozzle with the axis of the lance. Number of nozzles in converter steelmaking varies with the converter capacity but in general lay between 3 to 6. The inclination angle of each nozzle for a three hole, is and for five holes is 15 to with the axis of the lance.

(1)

Multi hole nozzles are compared with a single. The relationship between diameter of a single nozzle and the corresponding multi nozzles for the same flow rate of gas can be obtained from the area consideration in equation1

From equation 1 it follows that                                                                                                 

(3)

where  is the diameter of a single nozzle and  is the diameter of each nozzle in a multi-nozzle and N is the number of nozzles.