矩形渡槽冬季输水水温预测研究
发布时间：2018-09-01 16:41
【摘要】：我国水资源在地域上分配不均匀,为了使水资源得到优化配置,国家已兴建了一批长距离引水工程,而渡槽是一种常见的输水结构。由于用水需求,渡槽有时候需要冬季输水。西北地区冬季气温偏低,日温差和年温差较大,采用渡槽输水时水易结冰,使整个输水过程受阻,对保证输水和结构安全有不利的影响。寒冷地区输水水温对于结构的冻胀破坏和安全运行起到了至关重要的作用,而现在关于低温工况下渡槽中水体的热量损失与水温变幅的研究甚少。本文以引大入秦工程庄浪河渡槽为例,研究渡槽在冬季低温工况下输水时的水温变化及水的散热,并进行表面保温计算,研究成果可为类同的工程提供参考。本文使用流固耦合原理,应用ANSYS/FLOTEAN CFD计算软件建立了渡槽的空间模型,计算出渡槽的温度场分布、流速分布以及流体通过渡槽的热通量。根据稳态传热过程进行理论分析,并引用导热微分方程和牛顿冷却公式进行计算,采用模型和理论计算相结合的方式,计算出水温的变化和热量损失。通过对于不同工况下流体的计算,结果表明:渡槽水体的热量损失及温降的主要影响因素有渡槽的长度、流体的入口速度、大气温度、以及有无保温措施。水温降低主要是由于流体温度与外界大气温度不一致,产生温差导致的。流体与冷空气进行进行对流换热,并且通过渡槽进行热传导,流体与冷空气的温差越大,散热速率更快,热量损失更多,水温降低幅度更大。随着渡槽长度增加,水的热量损失与温度降低越多,水的散热速率与温降速率却逐渐变小。外界环境温度相同的情况下,水的入口流速越小,在同一长度处滞留的的时间越多,热量损失相应的增多。在所研究的几种工况下,水温最低降至0.561℃,接近于冰点0℃。因此应该对渡槽采取相应的保温措施来防止水温降低幅度过大。对比分析了在槽身外表面附有聚氨酯泡沫塑料和聚苯乙烯泡沫塑料两种材料的保温板分别以2cm、5cm、7cm的厚度进行保温时的热通量。通过简单的对比,表明:同种材质的保温板保温效果随其厚度的增加而增大,保温板越厚,热通量越小,保温效果就越好;相同厚度的保温板,聚氨酯保温板的保温效果优于聚苯乙烯保温板。进而选出最优的保温措施。考虑到经济性,庄浪河渡槽应使用5cm厚度的聚氨酯保温板。渡槽附有保温层可有效阻止水体与冷空气的热交换和对流换热,流体热量损失和水温降低幅度明显小。
[Abstract]:In order to optimize the allocation of water resources, a number of long-distance water diversion projects have been built in China, and aqueduct is a common water conveyance structure. Because of water demand, aqueducts sometimes need to carry water in winter. The winter temperature in Northwest China is low, the daily temperature difference and annual temperature difference are big, the water is easy to freeze when using aqueduct to carry water, so the whole water conveyance process is blocked, which has adverse effect on ensuring the water conveyance and structural safety. The water temperature in cold regions plays an important role in the frost heaving damage and safe operation of the structure, but there is little research on the heat loss and water temperature variation in the aqueduct under low temperature conditions. This paper takes Zhuanglong River aqueduct as an example to study the variation of water temperature and the heat dissipation of the aqueduct under the condition of low temperature in winter, and to calculate the surface heat preservation. The research results can provide reference for similar projects. Using the principle of fluid-solid coupling, the spatial model of aqueduct is established by using ANSYS/FLOTEAN CFD software. The distribution of temperature field, velocity distribution and heat flux of fluid passing through the aqueduct are calculated. According to the steady-state heat transfer process, the heat conduction differential equation and Newtonian cooling formula are used to calculate the change of water temperature and heat loss. The results show that the main factors affecting the heat loss and temperature drop of the aqueduct are the length of the aqueduct, the inlet velocity of the fluid, the atmospheric temperature and the insulation measures. The decrease of water temperature is mainly due to the temperature difference between fluid temperature and ambient temperature. The temperature difference between the fluid and the cold air is larger, the heat dissipation rate is faster, the heat loss is more, and the temperature of water is decreased more greatly through the aqueduct heat transfer and convection heat transfer between the fluid and the cold air, and through the aqueduct, the temperature difference between the fluid and the cold air is larger. With the length of aqueduct increasing, the heat loss and temperature of water decrease more, but the heat dissipation rate and temperature drop rate of water become smaller. Under the same ambient temperature, the smaller the inlet velocity of water is, the longer the water stays at the same length, and the more the loss of heat is. Under several conditions studied, the lowest water temperature is 0.561 鈩，
本文编号：2217770
[Abstract]:In order to optimize the allocation of water resources, a number of long-distance water diversion projects have been built in China, and aqueduct is a common water conveyance structure. Because of water demand, aqueducts sometimes need to carry water in winter. The winter temperature in Northwest China is low, the daily temperature difference and annual temperature difference are big, the water is easy to freeze when using aqueduct to carry water, so the whole water conveyance process is blocked, which has adverse effect on ensuring the water conveyance and structural safety. The water temperature in cold regions plays an important role in the frost heaving damage and safe operation of the structure, but there is little research on the heat loss and water temperature variation in the aqueduct under low temperature conditions. This paper takes Zhuanglong River aqueduct as an example to study the variation of water temperature and the heat dissipation of the aqueduct under the condition of low temperature in winter, and to calculate the surface heat preservation. The research results can provide reference for similar projects. Using the principle of fluid-solid coupling, the spatial model of aqueduct is established by using ANSYS/FLOTEAN CFD software. The distribution of temperature field, velocity distribution and heat flux of fluid passing through the aqueduct are calculated. According to the steady-state heat transfer process, the heat conduction differential equation and Newtonian cooling formula are used to calculate the change of water temperature and heat loss. The results show that the main factors affecting the heat loss and temperature drop of the aqueduct are the length of the aqueduct, the inlet velocity of the fluid, the atmospheric temperature and the insulation measures. The decrease of water temperature is mainly due to the temperature difference between fluid temperature and ambient temperature. The temperature difference between the fluid and the cold air is larger, the heat dissipation rate is faster, the heat loss is more, and the temperature of water is decreased more greatly through the aqueduct heat transfer and convection heat transfer between the fluid and the cold air, and through the aqueduct, the temperature difference between the fluid and the cold air is larger. With the length of aqueduct increasing, the heat loss and temperature of water decrease more, but the heat dissipation rate and temperature drop rate of water become smaller. Under the same ambient temperature, the smaller the inlet velocity of water is, the longer the water stays at the same length, and the more the loss of heat is. Under several conditions studied, the lowest water temperature is 0.561 鈩，
本文编号：2217770
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