【作者】 王凯；

【导师】 杨昆；

【作者基本信息】 华中科技大学 ， 动力工程， 2019， 硕士

【摘要】 随着煤炭石油等非可再生能源的逐渐枯竭,人类所面临的能源危机越来越严重,可在生能源的利用是解决能源及环境危机的一种关键手段,而太阳能又是一种重要的可再生能源。利用太阳能发电既能节约资源又不会破坏环境。其中塔式太阳能发电技术是一种很有前途的太阳能发电方式,容积式太阳能吸热器是其重要部件。在学者对于单层以及双层太阳能吸热器研究的基础上,本文中提出了有多层结构并且填充多孔介质的容积式太阳能吸热器。并研究了相应的传热传质特性,分别用Darcy-Forchheimer方程和局部非热平衡模型描述了多孔介质内的流体流动和传热。采用Rosseland近似来描述容积式太阳能吸热器内的辐射换热。利用解析法求解吸热器内部空气的温度分布,空气的压降以及多孔骨架的温度分布,同时也定义了吸热器的效率。讨论了相关参数对多层吸热器内部传热特性以及性能的影响,其中主要参数包括填充的多孔介质的孔隙率、孔径以及吸热器第一层的厚度。设计了多种不同孔隙率以及孔径分布的多层太阳能吸热器模型,其中包括孔隙率递增或递减,孔径递增或递减,以及孔隙率或孔径先增加后减少的设计模型。分别研究了多层吸热器第一层的厚度比对吸热器内部空气温度和多孔骨架温度的影响。同时对比了不同模型对应的多孔骨架入口处温度和热效率,最后分析了不同模型内部压降的分布。结果表明,多层吸热器第一层的参数对吸热器整体性能有着重要的影响。对比不同的模型发现,当孔隙率先减小后增大时,多层吸热器具有最佳的性能。采用遗传算法对三层吸热器进行多目标优化,优化的目标函数是吸热器的热效率和压降,这两个是评价吸热器性能的重要指标。结果表明,当第一层及第三层的孔隙率和孔径高于中间层的孔隙率和孔径时,吸热器的性能可以达到最优,同时在吸热器各层的厚度方面,采用逐渐增厚的设计有利于吸热器的性能提高。将入射辐射设置为周期变化,在非稳态的条件下,分析入射辐射的变化对入口处骨架温度及出口处空气温度的影响。同时,研究了不同时刻单层吸热器内部的温度分布。更多还原

【Abstract】 With the gradual depletion of non-renewable energy such as coal and oil.The energy crisis facing mankind is becoming more and more serious.The use of renewable energy is a key means of addressing energy and environmental crises,and solar is an important renewable energy.Using solar energy to generate electricity can save resources without destroying the environment.Tower Solar Power Generation is a promising way to generate electricity from solar energy,in which porous volumetric solar receiver is a key component.On the basis of previous scholars’ research on single-layer and double-layer porous volumetric solar receiver According to the current research works,the porous volumetric solar receiver is made of singlelayer porous medium.However,the volumetric solar receiver made of multi-layer porous media is presented in this work.And the corresponding thermal performance are studied,the fluid flow and heat transfer inside the porous medium are described by the Darcy-Forchheimer equation and the local thermal non-equilibrium model,respectively.The Rosseland approximation is adopted to describe the radiation within the volumetric solar receiver.Analytical solutions for the air temperature,pressure distribution along the receiver and solid phase temperature are derived.The receiver efficiency is also obtained.The influence of pertinent parameters,including the porosity and pore diameter of the porous media are discussed.In addition,the effects of different porous design on the performance of the volumetric solar receiver are investigated.A multi-layer volumetric solar receiver model with different porosity and pore diameter distributions was designed,including increasing or decreasing porosity,increasing or decreasing pore diameter,and a design model in which the porosity or pore diameter first increased and then decreased.The effects of the thickness of the first layer of the receiver on the internal air temperature of the heat receiver and the temperature of the porous skeleton were investigated.At the same time,the temperature of the inlet of the porous skeleton of different models and the thermal efficiency of the receiver were compared.Finally,the distribution of pressure drop inside different models was analyzed.The results show that the parameters of the first layer of the multi-layer volumetric solar receiver have an important impact on the overall performance of the receiver.Comparing the different models,it is found that the multi-layer volumetric solar receiver has the best performance when the porosity first decreases and then increases.The multi-objective optimization is adopted to optimize the three-layer porous volumetric solar receiver system.The optimized objective function is the thermal efficiency and pressure drop of the receiver.These two are important indicators for evaluating the performance of the receiver.The results show that the porosity distribution of the first layer and the third layer are obviously higher than that of the second layer,and the pore diameter distribution of the first layer and the third layer are also higher than that of the second layer.The first layer is the thinnest layer of the receiver,and the third layer is the thickest layer of the receiver.According to this rule,the best three-layer porous volumetric solar receiver can be designed.Finally,the incident radiation is designed to change periodically.Under the condition of unsteady state,the analytical solution of the internal porous skeleton temperature and air temperature of the single-layer solar receiver is obtained,and the effects of the incident radiation on skeleton temperature at the inlet and the air temperature at the outlet are analyzed.The temperature distribution in the single-layer solar receiver at different time was studied.更多还原