Purpose/Aim
Once the shaft cable catches fire, the burning rate is generally about three times that of the horizontal cable, and the "chimney effect" will make the fire burn fiercely and spread quickly. Temperature overheat is often one of the causes of fire. In order to reveal the mechanism of overheating and improve the isolation ability of high-rise buildings against electrical fire, simulation analysis of electromagnetic-fluid-temperature field is carried out in this paper.
Experimental/Modeling methods
Firstly, the electromagnetic field control equation is deduced through Maxwell equations, and the flow field-temperature field control equation is deduced through three-dimensional fluid steady-state flow equation and heat transfer equation. Then, a three-dimensional simulation model is established according to the actual size of cable shaft and cable. Next, the joule heat in the current field is taken as the heat source of the heat field, the effect of temperature in the heat field on conductor conductivity is considered to realize the bidirectional coupling between the current field and the heat field. The bidirectional coupling of heat field and flow field drives the heat circulation through the heat flow of air in the cable shaft, and the change of gas pressure will affect the heat capacity of air. Finally, the influence factors of temperature rise in the temperature field are analyzed by changing the ac current in the cable, the coefficient of thermal conductivity and constant pressure heat capacity of the middle sealing layer, and the mechanism of temperature overheating is studied.
Results/discussion
Based on the multi-physical field calculation model of electrical fire prevention and plugging of high-rise buildings, the spatial and temporal temperature distribution and fluid velocity distribution of cable body and air in the cable shaft are obtained. The temperature in the shaft presents uneven distribution state, and the temperature in the upper part of the shaft is higher, and the influence rule of changing parameters on the temperature field is also obtained.
Conclusions
This study is helpful to further analyze the cause of cable shaft fire, and provide reference for cable selection, material selection of blocking layer in the middle of cable shaft and optimization of cable shaft.
 

cable shaft,high-rise buildings,simulation,multi ⁃ physics coupling