An assessment of nozzles for steam attemperation

• The pressure swirl nozzle is robust and produces homogeneous, steady sprays.
• Various correlations for spray characteristics are presented.
• Sprays of spring loaded nozzles are generally inhomogeneous and unsteady.
• The impaction pin nozzle must be made more robust for steam attemperation.

With state of the art optical techniques, the drop velocity, drop size distributions, spray homogeneity and spray constancy of three nozzle types have been measured. Inlet water temperature has been varied up to 85 °C. Existing correlations for the exit drop velocity, discharge rate and drop size distributions of various types of pressure swirl nozzles have been examined and adapted for the new data. The resulting expressions are believed to be applicable to this type of atomizers in a general sense. Sprays of spring loaded nozzles are usually both non-uniform and unsteady. The pressure swirl nozzle is found to be robust and at present best suited for steam attemperation. Redesigns of impaction pin nozzles are believed to have potential to prevent wetting of downstream wall area in a wider range of gas flows than with the other nozzle types.