【作者】 张雷；

【导师】 肖刚； 倪明江；

【作者基本信息】 浙江大学 ， 动力工程， 2017， 硕士

【摘要】 太阳能热发电技术包括塔式太阳能热发电系统、槽式太阳能热发电系统、碟式太阳能热发电系统和线性菲涅尔式太阳能热发电系统,其中塔式太阳能热发电系统由定日镜场、跟踪系统、吸热器、熔盐储罐、换热器以及发电系统组成。吸热器作为整个系统的核心部件,其安全性和热效率直接决定了整个塔式太阳能热发电系统的安全性和热效率。本文通过建立塔式熔盐吸热器三维模型,将吸热器实际工作中的环境作为边界条件,在分析吸热器的工作原理并利用Fluent软件模拟不同热流密度、不同熔盐流速、不同表面换热系数、不同环境温度对吸热器性能的影响。研究表明随着环境温度的升高塔式熔盐吸热器熔盐出口温度升高,热效率提高,热损失降低;随着热流密度的增高,塔式熔盐吸热器熔盐出口温度升高,热效率提高,热损失率降低,但热效率提高速度越来越慢;随着对流换热系数的增大,塔式熔盐吸热器出口温度降低,热效率降低,热损失率增大。当受热面的对流换热系数从20 W/(m2·K)增大至140 W/(m2 K)时,热损失率由8.28%上升至17.77%%,热效率由91.72%下降至82.23%,在吸热器实际运行过程中,风速对吸热器的效率有着很大的影响。塔式熔盐吸热器在复杂的天气状况下工作环境恶劣,当处于自然降温过程中往往30秒之内就下降到熔盐凝固点之下,为了防止出现管内熔盐凝固等影响吸热器安全性能的影响,本文提出了一种基于颗粒的塔式太阳能热发电的丝网保温方法及装置,具有材料成本低、系统控制简单,可以迅速实现覆盖以及掉落等优点,相对于裸露的吸热器,表面附有6mm颗粒保温层,吸热管外侧换热壁面平均温度从500℃下降到230℃的时间增加了10倍以上。进行塔式熔盐颗粒吸热器试验,试验结果表明保温颗粒温度、保温颗粒厚度、环境风速、迎风面和背风面等因素对吸热管温度影响较大。保温颗粒温度越高、保温颗粒厚度越厚、环境风速越小,保温效果越好;迎风面保温效果比背风面要差。建立三维塔式熔盐吸热器模型并与试验结果进行验证,对吸热器温度一定情况下不同颗粒温度对保温效果的影响进行探究,研究表明在吸热管壁面温度一定的前提下颗粒平均温度越高,颗粒保温效果越好。更多还原

【Abstract】 The solar power system includes tower solar thermal power generation system,parabolic through solar thermal power generation system,dish-stirling solar thermal power generation system,linear fenier-type solar thermal powe generation system.The tower solar thermal power generation system includes some main parts:heliostat field,tracking system,receiver,tank of molten salt,heat exchanger and generating system.The receiver is the key of the whole system.Its safety and thermal efficiency directly determine safety and thermal efficiency of the whole tower solar thermal power generation system.In this paper,a 3-D model of the tower solar thermal power receiver is established.Fluent——a CFD commercial software is used to simulate different heat fluxes,inlet velocity,surface coefficient of heat transfer and environmental temperature on receiver performance.The results show that the outlet temperature of the molten salt increases and the thermal efficiency increases with the increase of ambient temperature or the increase of the heat flux or the decrease of the surface coefficient of heat transfer.When the surface coefficient of heat transfer increases from 20 W/(m2·K)to 140 W/(m2·K),the heat loss rate increases from 8.28%to 17.77%,and the thermal efficiency decreases from 91.72%to 82.23%.The result shows that the wind speed has a great impact on the thermal efficiency of the receiver.The tower solar thermal power receiver works in a complex weather conditions.In a natural cooling process,the temperature of the molten salt receiver tube decreases to the point below the molten salt freezing point.In order to prevent the occurrence of molten salt solidification in the receiver tube,a new method and device for thermal insulation of tower solar thermal power generation is put forward,which has the advantages of low material cost,simple system control,rapid response,etc.Compared with the bare receiver tube,the average temperature of the receiver tube with a 6mm particle insulation layer takes 10 times time to drop from 500℃ t0 230℃The experimental results show that the factors such as the temperature of particles,the thickness of particles,the ambient wind speed,the windward surface and the leeward surface have a great influence on the temperature of the receiver tube.The higher the temperature of particles,the thicker the thickness of particles,the smaller the environmental wind speed,the better of the thermal insulation effect.The thermal insulation effect of windward surface is worse than that of leeward.A 3-D model of the tower solar thermal power receiver is established and verified with the experimental results.The influence of different particle temperature on the thermal insulation effect is investigated under the certain temperature of the receiver tube.The average temperature of the particle is higher the better of the thermal insulation effect.更多还原