Flow field characteristics of dynamic radial jet reattachment nozzles
Potdar, Ashutosh Arun
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Impinging jets have many applications like heating or drying of food, paper, textiles, chemicals, and cooling of electrical equipments, turbines. For many applications, it is desirable to have small surface forces with high heat transfer. For these types of applications radial jets are often preferred over inline jets due to their ability to create smaller surface forces and greater heat transfer. Directly beneath the nozzle, however, the heat transfer is small over similar surface areas. A variant of the RJR nozzle is designed by altering the nozzle geometry and adding holes at radial locations in the nozzle diverter that have different pitch and yaw angles and is named the Dynamic Radial Jet Reattachment (DRJR) nozzle. An extensive experimental investigation is conducted to determine the effect of geometric and flow parameters on surface pressure distribution of DRJR nozzles. A Scanivalve data acquisition system is used for acquisition of surface pressures. A titanium dioxide – kerosene mixture and photographing technique is used for the surface flow visualization. It is seen that Xp/b ratio has the major effect on coefficient of pressure (Cp) and reattachment location (R/R0) while gap width and Reynolds number has negligible affects on reattachment location for the range of parameters tested. Variation in hole pitch and yaw angles have a noticeable effect in the active flow field region but negligible effect on Cp at reattachment and the reattachment location. Variation in hole diameters (d/R0) created noticeable difference for specific nozzles in active flow field region but failed to create any generalized effect. All this basic experimental results were compared and confirmed with the results obtained by flow visualization experiments and found to be in good agreement. This information on the flow field characteristics of DRJR nozzles can later be used as a platform to design effective and efficient processes depending on the application needs.