热管式真空管太阳能聚光集热系统传热特性分析  

Analysis of heat transfer characteristics for parabolic trough solar collector system with heat-pipe evacuated tube

作　　者：张维蔚[1,2] 王甲斌 田瑞 薛奇成[4] 巴旭阳 

机构地区：[1]内蒙古工业大学能源与动力工程学院,呼和浩特010051 [2]风能太阳能利用技术教育部重点实验室(内蒙古工业大学),呼和浩特010051 [3]内蒙古自治区可再生能源重点实验室,呼和浩特010051 [4]北京交通大学机械与电子控制工程学院,北京100044

出　　处：《农业工程学报》2018年第3期202-209,共8页Transactions of the Chinese Society of Agricultural Engineering

基　　金：风能太阳能利用技术教育部重点实验室开放基金资助项目(2017MS05);内蒙古自治区重大基础研究开放课题资助(2017);内蒙古自治区科技创新引导项目(2017)

摘　　要：该文设计了一套最高可提供473 K高温热水的热管式真空管太阳能聚光集热系统,为研究该系统的传热特性并为系统设计提供理论依据,建立了热管式真空管太阳能聚光集热系统传热过程的一维数学模型,计算并分析了该系统的传热性能。计算结果表明,该文设计的热管式真空管太阳能聚光集热系统的瞬时热效率均高于70%,且随太阳直射辐照强度和环境温度的升高逐渐升高,随传热流体温度和风速的升高逐渐降低。热管式真空管接收器内工质的工作温度和压力也随太阳直射辐照强度、传热流体温度、环境温度及风速的变化而变化。在该文计算条件下,热管的工作温度在327.6~503.2 K,工作压力在0.016~2.8 MPa,符合以水作为热管工质的最佳工作范围(293~523 K)。环形区域压力和渗入气体种类对集热系统传热性能也有明显影响。当环形区域压力P<10^(–3) Pa时,接收器热损失较小且随压力变化基本保持不变;当P>10^(–3) Pa时,随着环形区域压力升高,接收器热损失逐渐增大。另外,环形区域渗入气体的导热系数越大,接收器热损失越大。该研究对了解热管式真空管太阳能聚光集热系统传热特性、优化集热系统结构、指导系统设计具有一定的实用价值。Heat pipe is an efficient heat transfer component. If the heat pipe and the trough concentrator with higher concentration ratio can be effectively combined, the operating temperature of working fluid can be increased obviously, thus achieving higher system thermal efficiency. Parabolic trough solar collector system with heat-pipe evacuated tube is designed in this paper to provide enough heat input to raise the temperature of an heat transfer fluid to around 200 ℃. The system consists of parabolic trough solar concentrator, heat-pipe evacuated tube（a heat collector element） and support structure. The heat-pipe evacuated tube with material of stainless steel consists of evaporator and condenser sections, and water is used as the working liquid. The evaporator section inside a glass envelope is about 45 mm in diameter with a special coating（selective coating） on the outside surface to provide the required optical properties. The selective coating has a high absorptance for radiation in the solar energy spectrum, and has low emittance in the long wave energy spectrum to reduce thermal radiation losses. The annulus space between the evaporator section and the glass envelope is under vacuum to reduce thermal losses. The condenser section of the heat pipe is inserted into the jacketed vessel and rejects heat to the heat transfer fluid. In order to analyze thermal efficiency and provide theoretical basis for collector system design, a one-dimensional heat transfer mathematical model was established. Using this model, heat transfer characteristics of the system were calculated and analyzed. The results indicate that the transient thermal efficiency of the parabolic trough solar collector system with heat-pipe evacuated tube is higher than 70%, and increases with the increase of the ambient temperature and direct normal solar insolation, and decreases with the increase of the heat transfer fluid temperature and wind speed. Working liquid in heat pipe is at saturated state when the system is running, and the temp

关 键 词：太阳能 传热 热管式真空管 槽式聚光器 瞬时热效率 数学模型 

分 类 号：TK512[动力工程及工程热物理—热能工程]