Study on the efficiency of mechanical smoke exhaust in a large space fire in summer

The present paper aims to introduce the authors' investigation and research on the mechanical smoke exhaust efficiency in the large space fire in summer. In the testing process, we measured fire power and smoke temperature in such cases. When analyzing the smoke temperature distribution in such cases, we discovered that the smoke exhaust height in such fires changes steadily with the different strengths of the fire power under the mechanical smoke exhaust control. The smoke producing rates were thus calculated by using Heskestad plume correlation. Compared with the mechanical smoke exhaust rates, we have thus deduced the efficiency of the mechanical smoke exhaust in such summer fires. Results of our research have thus indicated that when the fire power wasn't high enough, the supplied air outside the space of the fire was easily mixed with the produced smoke due to the temperature difference between the inside and the outside of the space, which may greatly reduce or limit the mechanical smoke exhaust efficiency. According to our experiments, the mechanical smoke exhaust efficiency in a large space fire from 300 kW to 1 MW in summer was about 30% under 6 ACH prescribed by code. Increasing the fire power proved to be able to weaken the mixture of the supplied air with the produced smoke to a certain extent, the effect of the improved efficiency didn't seem obvious.