發(fā)布時間：2019-03-08 18:57

【摘要】：隨著國家能源結(jié)構(gòu)調(diào)整步伐的推進(jìn),太陽能熱發(fā)電由于其在節(jié)能減排、提升經(jīng)濟(jì)效益上巨大的潛力,已經(jīng)被提上中國清潔能源重點發(fā)展的“日程”。從審批通過太陽能熱發(fā)電項目到電價政策出臺,可以預(yù)見,在未來的幾年內(nèi),我國太陽能熱發(fā)電產(chǎn)業(yè)將會出現(xiàn)“百家爭鳴”式的發(fā)展。目前太陽能熱發(fā)電主要以槽式為主,塔式太陽能熱發(fā)電系統(tǒng)中又主要以熔鹽為導(dǎo)熱介質(zhì)為主,對于以水/水蒸氣為傳熱介質(zhì)的吸熱器,汽液兩相分配的復(fù)雜性始終是阻礙其發(fā)展的一大障礙;同時,太陽能熱發(fā)電的不連續(xù)性及熱流密度分配不均等問題,也使得氣液兩相流分配不均更加嚴(yán)重。本文針對一種新型兩段式塔式太陽能熱發(fā)電的吸熱器進(jìn)行幾何設(shè)計,建立了高斯熱流密度分布條件下吸熱器輻射和對流換熱以及流動模型,確定了吸熱器I和吸熱器II受熱面蛇形管管道布置方式和幾何尺寸,獲得了吸熱器內(nèi)部不同位置受熱面的熱流密度分布情況;結(jié)合氣液兩相傳熱和流動特點確定了吸熱器典型管道內(nèi)部工質(zhì)溫度、干度、壓降和沿管道流程的壁溫分布規(guī)律;整理出兩段式太陽能腔式吸熱器幾何結(jié)構(gòu)的系統(tǒng)化設(shè)計流程。對吸熱器進(jìn)行熱力性能分析結(jié)果表明:兩段式腔式吸熱器能夠有效減少預(yù)熱蒸發(fā)吸熱器的幾何尺寸,提高平均輻射熱負(fù)荷的同時降低吸熱器的平均溫度,有效提高吸熱器的熱效率;多管程蛇形管道布置可使出口參數(shù)分布更加均勻,避免受熱嚴(yán)重不均等安全問題。為進(jìn)一步改善聯(lián)箱內(nèi)部的水工質(zhì)在加熱過程中的兩相流動特性,基于專利提出的笛形管均流器對聯(lián)箱內(nèi)兩相流均勻分配的作用,本文采用CFD數(shù)值模擬,對加裝笛形管前后聯(lián)箱內(nèi)汽液兩相流的體積分?jǐn)?shù)、速度場及分支管出口兩相流的流量分配特性進(jìn)行比較。結(jié)果表明:在兩相流吸熱器聯(lián)箱中加裝合適的笛形管均流器能對聯(lián)箱內(nèi)的汽液兩相流進(jìn)行再分配,明顯改善聯(lián)箱內(nèi)部汽液分層現(xiàn)象和兩相流分配不均勻問題。對太陽能熱發(fā)電水工質(zhì)吸熱器設(shè)計有一定的指導(dǎo)意義。
[Abstract]:With the progress of national energy structure adjustment, solar thermal power generation has been put on the agenda of China's clean energy development because of its huge potential in energy saving and emission reduction and in promoting economic benefits. From the examination and approval of solar thermal power projects to the introduction of electricity price policy, it can be predicted that in the next few years, there will be a "hundred schools of thought"-style development in China's solar thermal power generation industry. At present, solar thermal power generation mainly consists of trough type, tower type solar power generation system is mainly composed of molten salt as heat conduction medium, and water / water vapor as heat transfer medium. The complexity of vapor-liquid two-phase distribution is always a major obstacle to its development. At the same time, the discontinuity of solar thermal power generation and the uneven distribution of heat flux make the distribution of gas-liquid two-phase flow more uneven. In this paper, the geometric design of a new type of two-stage tower solar energy heat exchanger is carried out, and the radiation, convection heat transfer and flow model of the absorber under the condition of Gao Si's heat flux distribution are established. The arrangement mode and geometric size of the snakelike pipes on the endothermic I and II heating surfaces are determined, and the heat flux distribution of the heating surfaces in different positions of the endoheater is obtained. Combined with the gas-liquid two-phase heat transfer and flow characteristics, the working fluid temperature, dryness, pressure drop and wall temperature distribution along the pipeline flow are determined, and the systematic design process of the geometry structure of the two-stage solar cavity absorber is arranged. The thermal performance analysis shows that the two-stage cavity absorber can effectively reduce the geometric size of the preheated evaporator, increase the average radiative heat load, and decrease the average temperature of the absorber, and the results show that the two-stage cavity heat absorber can effectively reduce the geometric size of the preheated evaporator. The heat efficiency of the heat absorber is improved effectively; The arrangement of multi-pipe serpentine pipe can make the distribution of outlet parameters more uniform and avoid the serious unbalance of heat. In order to further improve the two-phase flow characteristics of the hydraulic fluid in the header during the heating process, based on the effect of the patented pipe equalizer on the uniform distribution of the two-phase flow in the header, the numerical simulation of the two-phase flow in the header is carried out by using the CFD numerical simulation. The volume fraction, velocity field and flow distribution characteristics of the two-phase flow at the outlet of the branch pipe were compared before and after the flutes were installed in the header. The results show that it is possible to redistribute the vapor-liquid two-phase flow in the two-phase flow heater header by adding a suitable flute-tube equalizer, which can obviously improve the phenomenon of vapor-liquid stratification and the uneven distribution of the two-phase flow in the header. It has a certain guiding significance for the design of solar thermal hydro-hydraulic absorbers.
【學(xué)位授予單位】：華北電力大學(xué)(北京)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TM615

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本文編號：2437108