Effect of nozzle geometry on the efficiency of compressed air nozzles

Papers presented to the 11th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 20-23 July 2015.This paper evaluates the performance of different nozzle geometries which are all used in industrial blowing applications. Five different geometries were selected: a converging nozzle, a stepped nozzle, a straight pipe, a converging-diverging nozzle and an energy-efficient nozzle. The flow field of the various nozzles was calculated using CFD simulations. The compressible RANS equations were solved using the SST k-omega turbulence model. Different properties, like the total impact force, the impact pressure and the entrainment rate were obtained from the simulations to compare the nozzles with each other. For each of these properties, the most efficient nozzle was the one for which the mass flow rate of compressed air was the lowest. All nozzles showed comparable mass flow rates for the same impact force and the difference was in the order of 5% better than a straight pipe geometry. Only the energy saving nozzle used around 10% less mass flow and is the best solution to reduce compressed air consumption without losing performance.The authors gratefully acknowledge the funding of this study by the Agency for Innovation by Science and Technology (IWT) through the TETRA project nr. 130223.am201