Spray dispersion measurements of a sprinkler array

Abstract

A careful measurement methodology has been developed for highly resolved spray dispersion measurements. These measurements are used to establish spatial resolution requirements for evaluation of sprinkler spray patterns and to provide a comprehensive data set for computer model validation. For this study, four nozzles were arranged in a square configuration typical of fire sprinkler system installations. Volume flux of water delivered to the floor was measured 1.5m below the array at locations on a 50mm grid. The detailed measurements accurately portray the spatial variations existing in the spray and indicate that each sprinkler contributes a unique spray pattern. The total mean volume flux was 5.9mm/min, with local measurements ranging from 25% to nearly 400% of the mean value. A spatial averaging analysis suggests that at least 25 measurements should be taken across the reach (i.e. extent) of the spray to resolve gradients in the spray pattern. Fewer measurements provide limited insight beyond the overall mean flux (due to resolution errors), while more measurements become increasingly expensive and less accurate (due to repeatability errors). To quantify the significant spray pattern variations, a meticulous measurement and alignment routine is described to ensure results are sufficiently comprehensive, detailed, and accurate for use in computational model validation.