In tunnel fires, a hot gas propagates beneath a ceiling called the ceiling jet. The characteristics of the ceiling jet must be understood for safety and evacuation assessment. Small-scale experiments are useful to simulate the ceiling jet flow. The tunnel models used in previous studies have different dimensions (height and width) and wall thicknesses, and the walls were made of various materials. The heat loss through the tunnel walls (ceiling and side walls) significantly affects the property of the ceiling jet flow. However, few studies have investigated the influence of the properties of the tunnel walls on heat loss. In this study, the scaling parameters of the heat loss through the tunnel walls were introduced by conducting a theoretical analysis. Furthermore, the influence of the thermal properties of the tunnel walls, i.e., the material type and thickness, on the heat loss were quantitatively evaluated before and after thermal penetration. The results showed that the heat loss through the tunnel walls was expressed as the function of the Biot number and the Fourier number. Furthermore, the combustion time that should be satisfied in the model experiments was introduced.

在隧道火灾中，热气在称为“天花板射流”的天花板下传播。为了安全和疏散评估，必须了解天花板喷射器的特性。小规模的实验对于模拟天花板射流非常有用。先前研究中使用的隧道模型具有不同的尺寸（高度和宽度）和壁厚，并且壁由各种材料制成。通过隧道壁（天花板和侧壁）的热量损失会严重影响天花板射流的特性。然而，很少有研究调查隧道壁的性质对热损失的影响。在这项研究中，通过进行理论分析，介绍了通过隧道壁的热损失的比例参数。此外，隧道壁的热特性的影响，即 在热渗透之前和之后，定量评估材料类型和厚度，热损失。结果表明，通过隧道壁的热损失表示为比奥数和傅立叶数的函数。此外，介绍了模型实验中应满足的燃烧时间。