Abstract
The Radial Jet Reattachment (RJR) nozzle was developed over the past decade as a modification of the In-Line Jet (ILJ) nozzle in order to enhance the heat and mass transfer characteristics of the ILJ nozzle. This research compares the heat transfer characteristics of turbulent, submerged ILJ and RJR nozzles under constant fluid flow power and under matched peak pressure exerted on the impingement surface. Air was used as the working fluid. The RJR nozzles with exit angles of O[] and +45[] were found to enhance the heat transfer considerably, while the-10[] exit angle heat transfer was almost the same as the ILJ nozzle. The local surface pressure exerted by the O[] RJR nozzle under same flow power condition was an order of magnitude lower than the ILJ nozzle. A new two-dimensional reattachment nozzle, entitled 'Slot Jet Reattachment' (SJR) nozzle was designed and built with four exit angles of-10[], O[], +20[] and +45. This nozzle is a modification of the slot jet nozzle commonly used in industries, based on the RJR concept. The local heat transfer and surface pressure distributions were measured under various Reynolds numbers, nozzle to surface spacings, exit openings, and exit angles. The SJR was found to provide good heat transfer, while providing an effective control over the local and net surface pressures. A correlation has been developed for the maximum local Nusselt number along the minor axis, as a function of Reynolds number and exit opening. A comparison of the heat transfer characteristics of the slot jet and the SJR nozzles under constant fluid flow power showed that the +45[]+20[]and 0[] exit angle SJR nozzles performed better than the slot jet nozzle. The-10[] exit angle SJR nozzle heat transfer was lower than the slot jet nozzle, but resulted in a net negative force and much lower local surface pressures on the impingement surface. A comparison of the two nozzles under matching peak surface impingement pressures showed that the SJR nozzle provided superior heat transfer to the slot jet.
Narayanan, Vinod (1997). Comparison of heat transfer characteristics of axisymmetric and two dimensional reattachment jet nozzles to conventional jet impingement nozzles. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1997 -THESIS -N37.