Experimental study on the relation between internal flow and flashing spray characteristics of R134a using straight tube nozzles

Internal flow, specifically nucleation, inside the nozzle has a significant effect on external spray characteristics. The relation between the internal flow pattern and spray characteristics of R134a flashing spray was investigated by using the transparent nozzle with length of 60 mm and inner diameter of 1.4 mm. In addition, the effect of inlet pressure on the spray characteristics, such as spray cone angle, droplet velocity, and temperature, were measured by using stainless-steel tube nozzles with length of 60 mm and diameter of 1.4, 1.2, and 1.0 mm. The high flow velocity, droplet velocity, low mass flow rate and decrease of superheat caused by the evaporation inside the nozzle lead to the decrease of spray cone angle, while the evaporation inside the nozzle contributes to the formation of fine droplets. Promoting the formation of stable bubbly flow inside the nozzle could be an effective way to acquire a small cone angle and fast drop of droplet temperature.