深井巷道热湿传递规律及壁面隔阻降温机理研究

Following gas, coal dust, roof, water inrush and fire accidents, heat harm becomes the sixth disaster which affects safety production of mine. The problem attributing to heat harm is gradually serious with the increasing mining depth. Aiming at the engineering characteristics of high temperature and humidity, and the current status of high input and energy consumption, we take the heat harm control as engineering background of the project, with the key scientific issues of coupled heat-mass transfer and cooling by thermal-hydraulic insulation of wet airway. Through physical simulation experiments, sample tests, theoretical analysis and numerical simulation, scientific issues are researched in this project, including: the characteristics of thermophysics and seepage of fractured rock is investigated, and the laws of equivalent thermal conductivity and non-Darcy seepage are acquired. The transport process of heat and water is studied, the coupled heat-mass transfer equation is built and laws of heat-mass transfer on the airway surface are analyzed. Mechanism of thermal-hydraulic insulation on the airway surface is researched, and heat-mass dissipation of airway is calculated. Change of airflow temperature and humidity is acquired. The foam materials with low thermal conductivity and permeability coefficient are manufactured and results of thermal-hydraulic insulation are analyzed. The heat harmful mines are provided with theoretical and technical supports of cooling technology through this project.

继瓦斯、煤尘、顶板、水灾和火灾事故后，热害已成为威胁煤矿安全生产的"第六大"灾害，且随着开采深度的不断增加有日趋严重的趋势。项目以热害治理为工程背景，针对深部热环境高温、高湿的特点，基于当前降温系统大投入、高耗能的现状，紧紧围绕围岩壁面热湿输运及阻断机理这一关键科学问题，通过物理模拟试验、试样试验、理论分析及数值模拟相结合的方法，研究裂隙岩体热物理及渗透性质，获得等效导热系数变化及非达西渗流规律；研究含湿围岩体热量与水分输运特性，建立热湿耦合传递方程并深入分析巷道壁面热湿传递规律；研究巷道壁面阻热隔湿机理和分析壁面散热与散湿量，获得巷道内风流温湿度变化规律，同时研制低导热系数和低渗透系数的泡沫材料并测试其隔热阻湿效果，为深部热害治理技术的研究及工程应用提供可靠的理论支持和科学依据。

针对深部矿井巷道内高温高湿的特点，进行了三个方面的研究：孔隙介质热物性、含湿巷道围岩传热传质规律以及隔热材料和隔热效果分析。第一根据有效导热系数的定义和热阻模拟方法，计算了干燥破碎煤体的导热系数，与实测值吻合；对于孔隙岩体，模拟了不同孔隙率条件下孔隙规则分布与随机分布两类模型的稳态热传导。结果表明等效导热系数与固体基质率之间呈双对数线性关系，拟合指数符合Archie定律；含小孔隙且未集中分布的岩体导热系数是各向同性的。第二针对深部巷道湿壁巷道与风流间非稳态传热传质问题，研究发现在瞬态传热传质试验初始阶段，巷道围岩温度迅速降低，此后降幅趋缓并逐渐稳定为定值。水分扩散半径要比热扰动半径小，湿壁巷道的出风口焓值要远远高于干燥巷道，水分传递引起的潜热在深部热环境中具有重要作用。周期性传热发现，巷道风流的温度、湿度和焓值以及围岩温度均呈现周期性变化。距离壁面越远的位置，巷道围岩温度波动幅度越小，且巷道温度波相位滞后于风流。第三研究了隔热材料的力学性质，发现抗压强度与干密度呈指数关系；水灰比对纤维最优添加量有一定影响。对低干密度泡沫混凝土，添加短纤维对抗压、抗拉强度提升明显，最高增幅分别为180%和86%；网状纤维对抗压、抗拉强度的提升优于丝状纤维；添加纤维后泡沫混凝土弹性模量和峰后残余强度分别为原来的4倍和2倍。隔热材料导热系数与干密度也呈指数关系，且随含水率增大迅速增加，增幅主要受孔隙率决定。求解了巷道隔热层瞬态传热方程，计算发现铺设隔热层后围岩原始温度受到风流扰动显著降低，通风5年时未隔热巷道传热量为铺设隔热层的1.6倍；巷道/隔热层热阻与隔热层铺设厚度呈线性变化，随着铺设厚度增加热阻迅速增加，同时换热强度不断降低。当巷道铺设双隔热层时，热阻与厚度间仍呈线性关系且与顺序无关。巷道/隔热层热阻受导热系数小的材料影响更大。隔热层厚度增加后，传热系数对传热量影响也逐渐降低。数值计算发现，一定长度的巷道壁面与风流温度沿轴向呈线性增加，但两者增加率并不相同。铺设隔热层的轴向风流温升率明显低于未铺设时；巷道风速越高、巷道尺寸越大、原始围岩温度越低、冷却半径越大，出风口风流温升越小。项目研究所获得的结论，可为高温高湿矿井采用壁面隔热阻湿技术实现热环境改善提供一定参考。