Comprehensive evaluation of spray arrangement strategies for spray-local exhaust ventilation

Abstract

A well-designed spray system, which is located near the source of high-temperature smoke, can improve the capture efficiency of traditional local exhaust ventilation (LEV). However, there is currently no comprehensive evaluation index that clearly reflects the performance of spray-local exhaust ventilation (SLEV), making it challenging to optimize the spray arrangement. The two-phase flow fields in the SLEV and LEV were compared to evaluate the impact of spray on smoke control. The effects of spray arrangement parameters, such as spray position, spacing, initial droplet size, and angle, on the performance of the SLEV system were further evaluated using current evaluation indicators. Based on this, we developed a comprehensive evaluation model for SLEV using the AHP-entropy combination weighting method. The results revealed that the decrease in smoke control with an increase in rolling speed is primarily caused by a reduction in spray control in the central region of the smoke. When the spray flow rate is 0.0028 kg/s and the velocity is 30 m/s, the primary factor that improves ventilation performance is the downward drag force exerted by the spray on smoke, rather than the cooling effect. The comprehensive model was developed using weights of 0.45, 0.34, and 0.21 for the three evaluation indicators: capture efficiency, high-quality concentration field ratio, and spatial droplet size. The model showed good reliability based on the results of the smoke concentration analysis. The results of this study are expected to guide the design, implementation, and evaluation of SLEV systems.