【作者】 赵宏明；

【导师】 吴智敏； 王松根；

【作者基本信息】 大连理工大学 ， 结构工程， 2010， 博士

【摘要】 高速公路、城市高架桥、机场跑道、人行道及隧道口等重要场所及路段做好除冰雪的工作对保障道路畅通及人们出行安全具有非常重要的实际意义。本文介绍并比较了各种路面融雪化冰方式,选取混凝土板内埋设碳纤维发热线通电升温的方式融雪化冰。该融雪化冰方式避免了融雪剂对混凝土路面结构和环境产生的负面影响,而且碳纤维发热线比传统金属发热线材电热性能更好,成本更低。本文通过理论分析和试验研究,开展了如下研究工作：1.由基本传热学理论,得出布置发热线混凝土板的融雪化冰过程为在边界条件存在传导、对流和辐射换热情况下,且包括冰雪融化时的相变问题在内的有内热源物体的非线性瞬态传热问题。对系统融雪化冰过程中涉及到的重要参数做了详细介绍说明。由有限元温度场计算分析得出发热线间距小于100mm的混凝土板表面温差小于2℃,满足融雪化冰板面温度均匀性要求,且发热线的保护层厚度在20-60mm间变动对混凝土板表面温度场分布影响较小。2.室内试验研究首先对比了不同类型的碳纤维发热线,选取硅胶外被的碳纤维发热线作为埋设于混凝土板内融雪化冰的发热线缆。不同间距发热线的混凝土板温升试验显示发热线间距为100mm的混凝土板可以满足-25℃的化雪要求,即板面温度均匀性要求和在给定时间内板面平均温度达到0℃以上的化雪温度要求。3.混凝土小板试件在空气温度为-25℃时的升温试验结果显示不同功率下的升温幅度为10℃～30℃,功率与温度增量的拟合结果基本成线性。混凝土板的升降温全过程曲线显示加热过程中冰柜内空气温度变化不大,这证明了冰柜内模拟混凝土板融雪化冰试验方法的合理性。混凝土小板融雪化冰试验研究给出了不同空气温度、不同冰层厚度,化冰时间不超过3小时情况下所需要的最小功率值。板面融雪及化冰的对比试验显示融雪较快,因此路面清除积雪的工作应在雪变成冰之前进行。另外还对影响板升温的其他因素：有无预热、有无隔热层及缠绕发热线的钢筋进行了试验研究。4.室外试验研究首先介绍了布置发热线混凝土桥面板及路面板的制作方法。大板的温升试验研究了布置三种不同发热线间距的混凝土板板面温度的均匀性及风力等级对温升的影响。分析比较了路面板桥面板的温升过程。大板室外的融雪化冰试验在不同天气条件下进行,混凝土大板化雪试验的输入功率范围在300-1000W／m2,积雪融化时间最长不超过5.25小时。分析研究了路面融雪化冰系统控制电路的连接及工作流程,提出了由温湿度检测设备同时返回报警信号控制电源开闭的工作方式。5.发热线混凝土板融雪化冰的温度场有限元分析采用结冰的路面作为研究对象。由试错法根据温升试验的温度监测结果确定温度场有限元分析中的重要参数：混凝土导热系数,再将该导热系数运用于混凝土板的融雪化冰有限元分析计算中。与试验结果相比,数值结果较准确模拟了布置发热线的混凝土板融雪化冰的过程,证明了该计算方法的可行性。混凝土路面融雪化冰的有限元预测分析给出了不同天气条件下3-4小时内融雪化冰的输入功率和发热线布置间距。该预测分析为实际工程中混凝土板内发热线设计及输入功率的选取提供了参考和借鉴。更多还原

【Abstract】 Deicing at the important locations, such as freeway, pedestrian bridge, airfield runway, side walks, and tunnel entrance, have an important practical significance to ensure road traffic safe and unblocked. By surveying the existing deicing and anti-icing methods and comparing them, a method of deicing with carbon fiber heating wire (CFHW) buried inside concrete slabs is presented in this paper to avoid the negative effects of traditional deicing salt on the structure, function and environment. In addition, CFHW is cheaper and has better electrical-thermal property than traditional metalic heating wire. Then the work is done in this dissertation using theoretical analysis and experimental method as follows.1. By the theory of heat transfer, the process of concrete slab deicing with CFHW belongs to nonlinear transient heat transfer issue of research object with inner heat source. The boundary conditions including thermal conduction, convection, radiation and the phase transition of ice and snow are involved in this issue. The important parameters related to thermal analysis of system deicing are described in detail. The finite element analysis of temperature field shows that the temperature difference on concrete slab surface is less than 2℃when CFHW spacing is not more than 100mm, which meets the temperature uniformity requirements for deicing. The change of CFHW cover thickness in the range of 20-60mm has the less influence on temperature distribution on concrete slab surface.2. In laboratory experiments of small-scale slab, CFHW with silicon gel coat was selected to be used in concrete deicing system by evaluating different types of CFHW. The slab heating experiments of different CFHW spacings indicate 100 mm CFHW spacing can meet the deicing requirements at-25℃, i.e., the temperature distribution on the slab surface is uniform and the average temperature can rise above 0℃within a given time period.3. When air temperature is-25℃, the range of temperature increment on slab surface is 10℃-30℃under different input power. The fitting result from the real values of experiments approximates a straight line. During the heating process, the environment temperature in refrigerator was stable, which verified the rationality of the experiment method of refrigerator simulating low-temperature environment. For different air temperature and ice thickness, the minimum input power of slab for deicing in 3h was summarized. Snow melting is more quickly than ice melting under similar situation. So in practice the road deicing should be done before snow turn into ice for saving time and energy. Another influence factors on slab heating, such as pre-heating, insulating layer, reinforcing steel bar wound around CFHW, were experimental researched.4. In field experiments, the production process of concrete slabs simulating pavement and bridge deck installed with CFHW is introduced. For these concrete slabs with three types of CFHW spacing, temperature uniformity of slab surface and the influence of wind force scale on slab heating were researched. The heating experiments of pavement and bridge deck model were analyzed and compared. The range of input power is 300-1000W/m2 for deicing experiments and deicing time is not more than 5.25h under different weather condition. The control circuit connection and working flow chart for control circuit of deicing system were studied and an operation mode of controlling switch by returning alarm signal obtained from temperature and humidity sensors was proposed. The analysis about net participants’cost and operation cost of concrete slab deicing with CFHW shows that this method has advantages of not only eco-friendly but also cost-effective.5. The ice pavement is determined as study object in finite element analysis of temperature field of concrete slab deicing with CFHW. According to experimental results of slab heating, a trial-error approach is proposed to determine the important parameter in finite element analysis of temperature field:thermal conductivity of concrete, and then it is applied in finite element analysis of concrete slab deicing. Compared with experimental results, the calculated ones show good agreement for the heating process of concrete slab deicing, which verified the validity of analytical method. Prediction results of concrete pavement deicing with CFHW in 3-4 hours by finite element analysis list the input power and CFHW spacing under different weather situation, which provides some references for designing CFHW spacing and selecting input power in the real projects of concrete slab deicing with CFHW.更多还原