核电厂自然通风条件下横向多层电缆火灾实验及其烟气层温度预测模型验证

Investigation of Upper smoke Layer Temperature Generated by a Three-layer Cable Tray Fire in a Natural-ventilated Compartment in Nuclear Power Plant

核电厂内电缆火灾分析是核安全分析重要内容。核电厂内横向多层电缆火灾,即多个电缆桥架在横向方向同时燃烧具有一定特殊性。本文针对核电厂内自然通风条件下的横向多层电缆燃烧热烟气层温度的预测,进行了横向三层电缆桥架电缆燃烧实验及重复实验。基于室内中心处纵向温度分布,自然通风条件下电缆燃烧形成的室内热环境可以分为三层,即上热烟气层,下冷空气层以及中间的过渡区域。根据实验数据对MQH公式应用于自然通风条件下的横向多层电缆桥架火灾热烟气层预测的可靠性进行验证。通过比较模型预测温度与实测热烟气层温度,可以看出MQH模型可以精确预测烟气层最高温度,其相对误差为1%。但是,由于该模型没有考虑烟气层的扩散时间,以及热烟气与墙壁和顶棚之间的热传递时间,其全局误差达到25.2%。

Firerisk analysis of cables in nuclear power plant is important for nuclear safety analysis.A cable fire in a multi-layer cable tray has special characteristic associated with several horizontal fire sources burning in vertical direction at the same time.To investigate the smoke layer temperature and its predicted model,fire experiments with three-layer cable tray fire were conducted in a door-open room,which was considered as a natural-ventilated compartment.A thermal couple tree was set in the middle of the room.Based on the measured vertical temperature profile,the room under fire can be divided into three layers by the smoke temperature,which were the upper hot smoke layer,the lower cool air layer,and the middle transition layer.The experimental results were used to evaluate the reliability of MQH model,which has not been evaluated by the multi-layer cable tray fire.By comparing the predicted temperature with experimental data,it shows that the MQH model accurately catch the maximum temperature of the upper smoke layer.The local error for maximum temperature of upper smoke layer is approximately 1%.The MQH model doesn’t consider the diffusion time of smoke in the confined room and the heat transfer time from smoke to the compartment walls and the compartment ceiling.Therefore,the estimated transient temperature was validated to be conservative and its global error was approximately 25.2%.