Numerical And Experimental Study Of Vertical Cable Fires

Cables are one of the most common combustibles in Nuclear Power Plants (NPP), so it’s necessary to study the combustion characteristics of cables. In this work, nu-merical simulation study was conducted based on algebra model, zone model and field model, and compared with experimental research.Firstly, the model, referred to as FLASH-CAT (Flame Spread over Horizontal Ca-ble Trays), was developed toestimate the heat release rate for vertical cable tray fire. The focus of this work is to investigate theapplication of an enhanced model to the sin-gle vertical cable tray fires with different cable spacing. Theexperiments on vertical cable tray fires with three typical cable spacing were conducted. The historiesof mass loss rate and flame length were recorded during the cable fire. From the experimental results, itis found that the space between cable lines intensifies the cable combustion and accelerates the flamespread. The predictions by the enhanced model show good agreements with the experimental data. Atthe same time, it is shown that the enhanced model is capable of predicting the different behaviors ofcable fires with different cable spacing by adjusting the flame spread speed only.Secondly, fire scenarios on cables related to the safe shutdown can be of crucial importance, while in general the integrity of cables is important to the safety of NPP. Therefore, fire risk analysis on cables is necessary. The surface temperature of cables is the key parameter to determine the failure time of cables. The cable is assumed to be a homogenous cylinder in fire zone model for predicting the cable surface temperature, which leads to underestimating the surface temperature of the cable. In this study, the model is improved by assuming the cable consists of two parts, which are the homoge-nous cable jacket and inner conductor respectively. By comparing the experimental results of the International Collaborative Project to Evaluate Fire Models for Nuclear Power Plant Applications (ICMFP) Benchmark Exercise #5, it is found that the accu-racy of the model is improved substantially. For power cables, the relative error of temperature rise of the improved model decreases about 7.4%～10% compared with that of the original model. For control cables, the relative error of temperature rise of the improved model decreases only about 1.8%～2.9%, which is less than that of power cables. Furthermore, the differences of surface temperature between simulation results using the improved model and the experiment data of some power cables are within an acceptable range of 20%. By incorporating the improved model, more accurate results are obtained by the zone model.Finally, this work simulated the vertical cable tray fire with 8 mm cable spacing using computational fluid dynamics (CFD) model and compared the simulated result with the experiment. it was found that there is a large difference between the simulates heat release rate curve and the experimental one, but the total experimental mass loss is close.