Investigation into the effect of nozzle shape on the nozzle discharge coefficient and heat and mass transfer characteristics of impinging air jets

High velocity impinging air jets are commonly used for heating, cooling and drying, etc. because of the high heat and mass transfer coefficients which are developed in the impingement region. In order to provide data for the designers of industrial equipment, a variety of slot nozzles were tested to determine the effect on heat transfer of both nozzle shape and slot width. A large multi-nozzle rig was also used to measure average heat and mass transfer characteristics under arrays of both slot nozzles and circular holes. As a necessary preliminary to the heat transfer investigation, the discharge coefficients of the nozzles were measured. Then, the experimental results are compared with the simplified flow model. A good agreement was found between the theoretical and experimental results. From the tests, it was also found that the heat transfer results from differently shaped nozzles could be satisfactorily correlated provided that the effective slot width or hole diameter was used to characterize the nozzle shapes.