Quantitative Evaluation of Stability of Water Flow Injected from Pipe Laminar Nozzle

Abstract

Cooling equipment of the pipe laminar type is utilized on run-out tables in hot strip mills. It is known that the stability of the water flow injected from the cooling equipment nozzles affects cooling performance. In this study, new criteria and an experimental method for quantifying water flow stability are proposed. The experimental apparatus consists of the water injection equipment, an electric circuit and a logger. The time variation of voltage represents the electric resistance of the injected water and is measured under various conditions of flow rate and nozzle diameter. A new laminar stability index, R_σ/R_AVE was proposed, in which R_σ and R_AVE mean the standard deviation and the average value of electric resistance of water flow injected from the nozzle, respectively. The proposed index qualitatively shows good agreement with the appearance of the laminar flow in the experiment. Based on the experiment, an equation of continuous laminar length is suggested.