Experimental study on the effects of ambient pressure conditions on spray characteristics of water mist

Based on incomplete statistics, China has about 3,000 historical buildings, and most of them were built in the west plateau areas. Study on fire protection of these historical buildings with water mist has been received a considerable attention currently. The purpose of this paper is to investigate the effects of ambient pressure conditions on characteristics of water mist system, such as flow coefficient, spray cone angle and spray flux density, etc. Since these characteristics can mainly influence water mist fire suppression mechanisms and efficiencies. The experimental results show that when the ambient pressure decreases the spray droplets tend to concentrate at the edge area of the spray cone, i.e., more droplets tend to position outside of the main spray. So the spray intensity increases at the edge area and decreases at the center of the spray cone. In addition, there is no obvious effect of ambient pressure on flow coefficient and spray cone angle of the water mist nozzle.