【作者】 李霞；

【导师】 肖益民； 郭新想；

【作者基本信息】 重庆大学 ， 工程硕士（建筑与土木工程领域）（专业学位）， 2017， 硕士

【摘要】 太阳能跨季节地下蓄热系统是太阳能利用领域新的研究方向,它是通过将非供暖季的太阳能蓄存于地下来实现冬季供暖,这对于平衡太阳能供给和热负荷需求在时间上的差异具有重要意义,然而,这一技术在国内的研究和应用很少,本课题对该系统在我国北方采暖区的应用做了初步研究。太阳能跨季节地下蓄热系统由集热系统、地下蓄热系统、供热房间、辅助供热系统及水泵等部分构成。不考虑辅助供热,地下蓄热系统的最佳容量取决于随太阳能集热器的集热量、所需的负荷及经济性因素,因此太阳能集热器面积与蓄热体积的匹配是影响系统经济性和太阳能保证率的关键条件。但本文的研究重点不在如何准确确定集热器面积和蓄热体积上,而是分析地下蓄热水箱在不做保温层时的蓄热取热特性。文中以太原地区一农村住宅建筑为例,利用FLUENT软件建立了地下蓄热水箱及周围土壤的三维数值计算模型,用Dest软件分析了其采暖负荷需求,将采暖负荷逐时变化情况作为蓄热水箱取热端的数据基础,将逐时太阳辐射强度变化情况作为蓄热水箱集热端的数据基础,利用FLUENT中的用户自定义函数(UDF),将这些数据分别转化为蓄热水箱取热端和集热端的动态边界条件,从而实现太阳能跨季节地下蓄热系统的模拟。为了解地下蓄热水箱在没有保温层的条件下,水箱及周围土壤连续多年的蓄热取热情况,同时又能避开数值计算周期过长的弊端,本文利用相似原理,对蓄热体建立相似模型以缩短数值计算时间。文章主要针对圆柱形地下蓄热水箱进行研究,比较了圆柱形水箱在不同高径比、不同土壤类型、不同埋地深度及不同集热器面积的条件下,水箱及周围土壤的温度分布,主要关注冬季供暖过程中水箱及周围土壤的取热情况。文中定义了太阳能保证率、土壤蓄热贡献率来表征蓄热水箱水和土壤的蓄热取热特性。模拟结果表明,经过6次蓄热取热过程后,土壤的蓄热贡献率达72.67%,随着系统运行年限增加,土壤蓄热贡献率平均每年增加3%;高径比为2的地下蓄热水箱太阳能保证率最高;粘土更适合作为地下蓄热水箱周围的蓄热介质;集热器面积是影响地下蓄热水箱蓄热放热特性的重要因素,随集热器面积增大,太阳能保证率也增大,但增大的程度有所减小;此外,埋地深度为8m的地下蓄热水箱对应的太阳能保证率高于埋地深度为4m时的太阳能保证率。更多还原

【Abstract】 The solar heating system with underground seasonal storage is a new work in solar energy utilization research.By storing solar energy in non heating season and extracting it for indoor heating in heating season,the system can balance the differences between solar energy supply and heat load demand in time.However,the solar heating system with underground seasonal storage has been little studied and applied in China,this research has tried to present a preliminary study on the application of the system in the heating climate zone of northern China.The solar heating system with underground seasonal storage consists of collector,underground water tank,heating room,auxiliary heating system and water pump and other components.Neglecting the auxiliary heating,the optimal capacity of underground water tank depends on the amount of heat collected by the solar collector,the required load and economic factors.Therefore,the matching of the solar collector area size with the water tank volume is the key factor which affects the solar fraction and system economy.On the basis of reasonably determining the area of collector and the volume of water tank,this paper will be mainly focus on the analysis of the heat storage characteristics of the water tank without insulation layer.Taking a rural residential building in Taiyuan area as an example in this paper,the three-dimensional numerical model of underground heat storage tank and surrounding soil was established by FLUENT software.Besides,the heating load demand was analyzed by the Dest software.Using the user-defined function in FLUENT,the heating load data and the solar radiation intensity are transformed into the dynamic boundary conditions of the water tank and the collector inlet.In order to know the heat storage characteristics of the underground water tank and the surrounding soil for many years,at the same time for the sake of reducing the calculation time,small scaled models based on similarity theory are established.In this paper,the temperature distribution of the tank and the surrounding soil under the conditions of different height-diameter ratio,different soil types,different burial depth and different collector area are compared.Besides,the solar fraction and contribution rate of soil thermal storage are defined to characterize the heat storage and heat extraction.The simulation results show that the underground heat storage tank with the height to diameter ratio of 2: 1 is the best,and the clay is more suitable as the heat storage medium around the underground heat storage tank,and the area size of the collector is an important factor which affects heat storage and heat extraction.Furthermore,the solar fraction for storage tank with 8 meter’s burial depth is relatively higher comparing with the 4 meter’s one.更多还原