纳米流体对太阳辐射的吸收特性及集热适用性研究

发布时间：2018-05-28 04:33

本文选题：纳米流体 + 直接吸收　；参考：《东南大学》2016年硕士论文

【摘要】：由于纳米颗粒的存在,纳米流体表现出不同于基液的辐射吸收特性和热传输性能,成为一种新型高效的太阳能辐射吸收材料。本研究提出并探讨了一种采用无吸收涂层集热管,以导热油为基液的纳米流体直接作为吸热和载热工质的太阳能集热系统。首先,采用分光光度计测试了添加不同纳米颗粒和质量分数的导热油基液纳米流体的光谱透射率和消光系数,进而研究了质量分数和颗粒种类对纳米流体全光谱辐射吸收特性的影响。结合积分球部件,测试得到了不同质量分数的导热油/CuO纳米流体的吸光系数,分析了纳米颗粒的散射作用对流体吸收特性的影响。结果表明：与基液相比,纳米流体对太阳辐射的强化吸收效果显著,纳米颗粒的质量分数越大,其吸光效果越好。其次,建立了纳米流体直接吸收集热(NDASC)与采用吸收涂层集热管的传统间接吸收集热(IASC)的传热数学模型,通过数值模拟对这两种集热方式在不同工况下的集热性能进行了对比分析,并结合集热实验测试,得到了该新型NDASC的适宜集热温度范围。结果表明：NDASC在不同太阳辐照强度、环境温度等运行工况下,分别对应存在一个集热效率高于相同结构的IASC的最大工作温度,即效率转折温度；聚光比和太阳辐照强度越高,效率转折温度越大,即NDASC适宜的工作温度越高。再次,研究了热管式与U型管式两种结构的NDASC的集热性能。分别建立了二者的传热数学模型,利用CFD模拟比较了不同集热器结构、太阳辐照强度对NDASC内流体温度分布特性的影响。结果表明：与IASC相比,相同结构尺寸的NDASC具有更高的管内中心主流温度和集热效率；随着太阳辐照强度和管径的增大,热管式NDASC和U型管式NDASC的集热效率升高。并且,搭建了热管式NDASC太阳能集热实验系统并与热管式IASC装置进行对比测试。实验结果表明：与热管式IASC相比,热管式NDASC的集热效率提高了20.4%。最后,以U型管式NDASC作为热泵蒸发器,提出了一种基于NDASC的太阳能热泵系统。建立了热泵系统的动态数学模型,模拟分析了该热泵系统在循环加热水过程中各参数的变化规律,并与基于IASC的太阳能热泵系统进行对比。结果表明：基于NDASC的太阳能热泵系统的平均COP比基于IASC的太阳能热泵系统提高了18.3%。
[Abstract]:Due to the existence of nano-particles, nano-fluids exhibit different radiation absorption characteristics and heat transfer properties than the base solution, so they become a new and efficient solar radiation absorption material. In this paper, a solar energy collector system is proposed, in which the unabsorbed coating collector tube is used, and the thermal conductivity oil is used as the base liquid to directly serve as the endothermic and heat-carrying heat collecting system. First of all, the spectral transmittance and extinction coefficient of thermal conductive oil-based fluids with different nanoparticles and mass fraction were measured by spectrophotometer. Furthermore, the effects of mass fraction and particle type on the full spectral radiation absorption characteristics of nanofluids were studied. The absorptivity of heat conduction oil / CuO nanofluids with different mass fraction was obtained by combining the integral sphere component. The influence of scattering action of nanoparticles on the absorption characteristics of the fluid was analyzed. The results show that compared with the base solution, the enhanced absorption of solar radiation by nano-fluid is remarkable, and the higher the mass fraction of nanoparticles, the better the absorptivity of solar radiation. Secondly, the mathematical models of heat transfer between NDASC-NDASC-NDASC) and traditional indirect absorption collector (IASC-AC) with absorbing coating are established. Through numerical simulation, the performance of these two methods in different working conditions is compared and analyzed, and the suitable temperature range of the new NDASC is obtained by combining with the experimental test. The results show that under different operating conditions such as solar radiation intensity and ambient temperature, the maximum working temperature of IASC with higher collector efficiency than that of the same structure is corresponding to the maximum operating temperature, I. e., the transition temperature of efficiency, the higher the concentration ratio and the intensity of solar irradiation. The higher the transition temperature of efficiency is, the higher the working temperature of NDASC is. Thirdly, the heat collecting performance of NDASC with two types of heat pipe and U-tube is studied. The mathematical models of heat transfer were established, and the effects of different collector structures and solar radiation intensity on the temperature distribution of fluid in NDASC were simulated by CFD. The results show that NDASC with the same structure has higher central temperature and heat collection efficiency than IASC, and with the increase of solar radiation intensity and tube diameter, the heat collection efficiency of heat-pipe NDASC and U-tube NDASC increases. In addition, the heat pipe NDASC solar energy collecting experiment system is built and compared with the heat pipe IASC device. The experimental results show that the heat collection efficiency of heat pipe NDASC is increased by 20.4than that of heat pipe IASC. Finally, a solar energy heat pump system based on NDASC is proposed using U tube NDASC as heat pump evaporator. The dynamic mathematical model of the heat pump system is established, and the variation law of the parameters of the heat pump system in the process of circulating heating water is simulated and analyzed, and compared with the solar energy heat pump system based on IASC. The results show that the average COP of solar heat pump system based on NDASC is 18. 3% higher than that of solar heat pump system based on IASC.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TU83;TU18

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