First heat-up of 1D multi-layer walls and 2D geometries consisting of refractory concrete
First heat-up of 1D multi-layer walls and 2D geometries consisting of refractory concrete
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DOI：
10.1016/j.ijthermalsci.2016.11.021
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发表时间：
2017-06
影响因子：
4.5
通讯作者：
Karl-Georg Fey;I. Riehl;R. Wulf;U. Gross
中科院分区：
文献类型：
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作者：
Karl-Georg Fey;I. Riehl;R. Wulf;U. Gross
窑炉通常内衬低渗透性耐火混凝土。在炉膛的第一次加热过程中，初湿的耐火混凝土内部的高蒸汽压力会导致混凝土结构的爆炸破坏。本文通过模拟和大规模实验研究了复杂几何形状的首次加热过程。本文是在前人关于一维单层壁面首次升温的研究基础上进行的。对一维三层壁面的首次升温过程进行了模拟，结果表明壁面内存在多个干燥锋。即使墙壁只从一侧加热，两个干燥锋也会出现在两个表面，在墙壁内部越来越深。另外四个干燥锋面在两个边界表面形成，向相反方向移动。模拟结果表明，尽管第一层混凝土层位于第一层混凝土层的前面，但第一层混凝土层的干燥速度比第一层混凝土层还要快。此外，模拟预测在很长一段时间内，壁面未受热表面的温度略低于100°C。该模型得到了大规模实验的验证，证实了两个观测结果。此外，还借助二维模型研究了两种更复杂的几何形状。其中一个几何形状，一个角落，需要更多的时间来干燥过程中，一个（多层）墙或暴露的边缘。这主要是由于热量缓慢地传递到角落的核心。第二种二维几何形状，即（暴露的）边缘，在所有被研究的几何形状中显示出最高的压力最大值，这是由于快速的热量传递到几何形状的暴露针头造成的。对于两种二维几何形状，计算了优化的（压力驱动的）加热曲线。这些曲线在不超过给定压力限制的情况下影响尽可能快的加热过程。这两种几何形状的曲线彼此之间以及对等厚度的单层壁计算的曲线都有很大的不同。
Furnaces are frequently lined with low permeability refractory concrete. During the first heat-up process of a relined furnace, high vapour pressures inside the initially wet refractory concrete can result in an explosive destruction of the concrete structure. In this article, the first heat-up process of complex geometries is investigated by modeling and further by a large-scale experiment. The article bases on a previous one, concerning the first heat-up of a one-dimensional single layer wall.The simulation of the first heat-up process of a one-dimensional three-layer wall shows the occurrence of several drying fronts inside the wall. Even if the wall is heated only from one side, two drying fronts appear at both surfaces, moving deeper and deeper inside the wall. Four further drying fronts are arising at the two boundary surfaces, moving in contrawise directions. The simulation shows that the first boundary surface is drying even faster than the first concrete layer, although this layer is arranged in front of that boundary surface. Further the simulation predicts a constant temperature slightly below 100° C at the wall's unheated surface over a large period of time. The model is validated by a large scale experiment which confirms both observations. Further, two more complex geometries are investigated by the aid of a two-dimensional model. One of these geometries, a corner, needs much more time for drying compared with the drying process of a (multilayer-) wall or an exposed edge. This is mainly caused by the slow heat transfer into the corner's core. The second two-dimensional geometry, the (exposed) edge shows the highest pressure maximum of all investigated geometries, caused by the fast heat transfer into the geometry's exposed needle.For both two-dimensional geometries, optimized (pressure-driven) heat-up curves are calculated. These curves are effecting the fastest possible heat-up process without exceeding a given pressure limit. The curves of both geometires are differing significantly from each other and from those ones calculated for a single-layer wall of equal thickness.