發(fā)布時間：2018-11-23 08:52

【摘要】：太陽能中溫集熱系統(tǒng)應(yīng)用于工業(yè)加熱、驅(qū)動制冷空調(diào)和中溫?zé)岚l(fā)電等領(lǐng)域的需求巨大,替代傳統(tǒng)化石燃料燃燒具有顯著的節(jié)能環(huán)保優(yōu)勢。目前常規(guī)的太陽能中溫集熱器吸收涂層的高溫耐久性差、聚光引起集熱管局部受熱而易發(fā)生彎曲變形損壞,導(dǎo)致制造和維護(hù)成本高,成為其應(yīng)用的主要障礙。本文提出并研究一種聚光型納米流體直接吸收太陽能集熱器(NDASC),采用透明無涂層集熱管,通過在集熱流體(導(dǎo)熱油)中添加吸熱納米顆粒,使其具有很強(qiáng)的太陽輻射吸收特性,用于太陽能中溫集熱。在對導(dǎo)熱油/CuO納米流體的光譜吸收特性研究基礎(chǔ)上,探討集熱管內(nèi)納米流體直接吸收及熱量傳遞機(jī)理,研究非均勻聚光工況下NDASC集熱管內(nèi)流體的溫度分布與集熱特性,主要工作如下：(1)配制了四種不同質(zhì)量分?jǐn)?shù)的導(dǎo)熱油/CuO納米流體,理論分析結(jié)合實(shí)驗(yàn)測試,研究了納米流體的全光譜輻射吸收特性,以及粘度、熱導(dǎo)率等基礎(chǔ)熱物性；并根據(jù)太陽輻射的能量分布,計(jì)算得出了納米流體全光譜的平均吸收系數(shù)。(2)在對聚光器的光學(xué)特性、納米流體吸熱-傳熱過程機(jī)理分析基礎(chǔ)上,建立了槽式聚光型NDASC的集熱數(shù)學(xué)模型,并利用CFD軟件對NDASC在非均勻聚光工況下的管內(nèi)流體溫度分布和集熱性能進(jìn)行了模擬,分析了添加納米顆粒質(zhì)量分?jǐn)?shù)、太陽輻射強(qiáng)度、環(huán)境溫度、集熱流體入口溫度等因素對集熱特性的影響規(guī)律,得到了典型工況下的最佳質(zhì)量分?jǐn)?shù)。并且,對采用相同聚光器的NDASC和傳統(tǒng)間接吸收太陽能集熱器(IASC)進(jìn)行了性能對比。結(jié)果表明：NDASC的管內(nèi)納米流體溫度分布更加均勻,集熱管壁面溫差明顯降低；并且在一定集熱溫度范圍內(nèi),NDASC的集熱效率要高于IASC。(4)搭建了槽式聚光型NDASC與IASC中溫集熱工況下的對比實(shí)驗(yàn)系統(tǒng),進(jìn)行典型工況下的實(shí)驗(yàn)測試。實(shí)驗(yàn)結(jié)果表明:NDASC的最大瞬時集熱效率達(dá)62%,集熱效率隨集熱溫度升高而降低；在124.2℃集熱溫度范圍內(nèi),效率高于IASC,驗(yàn)證了NDASC中溫集熱的可行性。(5)對復(fù)合拋物面聚光器(CPC)進(jìn)行了光學(xué)特性分析,計(jì)算得到了集熱管表面的輻射熱流分布。在此基礎(chǔ)上,模擬分析了CPC聚光型NDASC的內(nèi)部溫度分布特性和集熱性能。結(jié)果表明,集熱效率在入口溫度低于106.7℃時優(yōu)于傳統(tǒng)IASC。
[Abstract]:The application of solar energy medium-temperature system in industrial heating, driving refrigeration, air conditioning and medium-temperature thermal power generation has a huge demand, replacing the traditional fossil fuel combustion has a significant advantage in energy saving and environmental protection. At present, the high temperature durability of the conventional solar collector absorbs the coating at high temperature, and the concentrated light causes local heating of the collector pipe, which is prone to bending deformation and damage, which leads to high manufacturing and maintenance costs, and becomes the main obstacle to its application. In this paper, we present and study the direct absorption of solar energy collector (NDASC), by adding endothermic nanoparticles into the collector fluid (heat conduction oil) by using transparent and uncoated collector tubes. It has strong absorption characteristics of solar radiation, and is used for solar energy moderate temperature heat collection. Based on the study of the spectral absorption characteristics of the thermal conductivity oil / CuO nanofluids, the mechanism of direct absorption and heat transfer of the nano-fluids in the collector tube is discussed, and the temperature distribution and the heat collecting characteristics of the fluid in the NDASC collector tube under the condition of non-uniform concentrating light are studied. The main works are as follows: (1) four kinds of thermal conductive oil / CuO nanofluids with different mass fraction were prepared. Theoretical analysis and experimental tests were used to study the absorption characteristics of full-spectrum radiation, viscosity, thermal conductivity and other basic thermal properties of nano-fluids. According to the energy distribution of solar radiation, the average absorption coefficient of the whole spectrum of nano-fluid is calculated. (2) based on the analysis of the optical properties of the condenser and the mechanism of endotherm-heat transfer process of nano-fluid, In this paper, the mathematical model of collecting heat of trough type NDASC is established, and the temperature distribution and heat collecting performance of NDASC are simulated by CFD software. The mass fraction of nano-particles and the intensity of solar radiation are analyzed. The influence of environmental temperature and inlet temperature of heat collecting fluid on the characteristics of heat collection is studied. The optimum mass fraction under typical working conditions is obtained. The performance of NDASC with the same concentrator is compared with that of the traditional indirect absorption solar collector (IASC). The results show that the temperature distribution of nanofluids in NDASC tubes is more uniform, and the temperature difference on the wall of collector tubes is obviously reduced. And in a certain temperature range, the heat collection efficiency of NDASC is higher than that of IASC. (4). A comparative experimental system of trough type NDASC and IASC is set up, and the experimental tests are carried out under typical conditions. The experimental results show that the maximum instantaneous heat collection efficiency of NDASC is 62%, and the heat collection efficiency decreases with the increase of collecting temperature. At the temperature range of 124.2 鈩，

本文編號：2350968