| With the rapid development of new digital technologies,the number of data centers in China is growing at a high speed.At the same time,closed channel systems,with their advantages in cooling efficiency and cost,are increasingly being applied in the construction of new data centers.However,the closed channel system will turn the originally open channels between data center cabinets into narrow spaces with restricted ventilation.When the main combustibles in the data center(power and communication cables)catch fire,the accumulated hot smoke and gas in the closed channel cannot be timely discharged,which will cause a series of problems such as the temperature rise and the decrease in visibility in the data center,seriously threatening the safety of data center equipment and personnel.From the current research status at home and abroad,the research on cable fires in closed channel data centers is still in its infancy,and there is a lack of experimental data and theoretical basis on the combustion characteristics and fire hazards of commonly used cables in data centers.The impact of the closed channel system and fire source characteristics on the fire characteristics of data centers is also not clear.Therefore,researching cable fires in closed channel data centers is of great significance.This thesis focuses on cable fires in closed channel data centers.Radiant ignition experiments were conducted on four types of commonly used cables in data centers using a cone calorimeter to obtain the combustion characteristic parameters of different cables.Based on this,the fire thermal hazard and smoke toxicity of cables were quantitatively evaluated.Then,the FDS simulation software was used to establish a numerical simulation model of closed channel data centers.The simulation analysis method was used to study the fire characteristics of data centers under different closed states,fire source positions,and fire source powers.The main aspects are as follows:Firstly,using a cone calorimeter,the effects of different external radiation intensities(30,40,50,and 60 kW/m~2)on the combustion characteristics and fire hazards of different types of cables(power cables,wires,network cables,and optical fibers)in a data center were investigated.The results showed that:(1)The cable combustion process can be roughly divided into four stages:Melting and Pyrolysis Stage→Ignition Stage→Combustion Stage→Decay Stage,which basically conforms to the combustion rules of polymers;(2)Among the four cable materials,the ignition time of optical fibers is the shortest,the proportion of combustion mass loss is the largest,and the combustion is the most complete.The ignition time of network cables is the longest,and the smoke generation rate and CO concentration are the lowest.The proportion of combustion loss of power cables is the smallest,and the total heat release is the largest;(3)The curves of the unit area heat release rate and smoke generation rate of the four cables all show a form of increasing to a peak and then gradually decreasing,but the number and period of peaks in the curves have significant differences;(4)Using the Petrella evaluation system to analyze,it was found that the four cables have a medium or above fire hazard under external radiation intensity of 30kW/m2 and above,and the comprehensive thermal hazard of power cables is the greatest;(5)Network cables have the best smoke suppression effect,and the smoke release rate and CO release rate during the combustion process are far lower than those of other cables.At a high radiation intensity(60 kW/m~2),the peak concentration of CO released is only 0.0217%,and based on the FED method,it was found that the smoke toxicity did not reach a dangerous level that could cause human fatalities.Secondly,To investigate the fire characteristics of a data center under different degrees of enclosure,a physical model of the machine room in a closed channel of a company in Xuzhou was established using Pyrosim software.The temperature changes within the cold and hot aisles of the data center were analyzed for both open and closed channel configurations,and the smoke concentration patterns were studied based on these temperature changes.The findings indicate that in a closed channel system,smoke accumulates within the cold aisle during the initial stages of a fire.Some of the accumulated smoke then spreads laterally through the cabinet to the hot aisle,resulting in higher peak temperatures and smoke concentrations within the channel compared to those observed in simulations of an open channel system.Finally,the numerical simulation study was conducted on the fire characteristics of a closed channel data center under different fire source characteristics.The results showed that when the fire occurred under the raised floor,the smoke was affected by factors such as the air flow of the data center air conditioning,the raised floor,and perforated tiles,and would fill the entire room faster and decrease visibility more quickly than when the fire occurred in a cabinet.When the fire source location was fixed,an increase in the fire source power led to an increase in smoke generation rate.The closed channel system would amplify its impact,resulting in a shorter time for smoke to spread to the same area,a faster decrease in visibility,and an increase in smoke temperature.When the fire source power increased from 2 MW to 4 MW,the visibility at human eye level in the data center decreased to the critical value 5 seconds faster;the temperature inside the channel increased by about 50%;and the peak temperature of the data center ceiling increased by about 55.6%.An increase in fire source power significantly increased the danger of fire in a closed channel data center.The research results of this thesis can provide important reference basis for improving the fire prevention standards,fire risk assessment,and fire protection design of closed-circuit data centers. |
