different types of heaters or mixers as an example the nozzle designs to be described below could be used with various different types of steam injection heaters that do not include any type of modulation but rather utilize steam pressure modulation to control the amount of heating in a direct steam injection heater that does not include internal modulation the amount of steam injected into the liquid being heated is controlled by the pressure and supply of steam into an injection tube the nozzle designs of the present disclosure can be utilized as part of the injection tube to further improve the introduction of heated gas into the liquid flow throughout the present disclosure the injection of a heated gas into a flow of an unheated liquid is commonly referred to as the injection of steam however it should be understood that other types of gases could be injected into the fluid stream as an example heated ozone nitrous air or other gases could be utilized while operating within the scope of the present disclosure fig4 illustrates one possible nozzle design with the purpose of stabilizing the steam jet under conditions which may cause instability in the standard straight walled nozzle this design is characterized by two coaxial cylinders the first is a small cylinder 17 open to.