【摘要】：隨著工業(yè)的飛速發(fā)展和人類生活水平的提高,能源需求量一直處于上升趨勢。由于不合理的開采和利用,能源短缺問題已在全球范圍內(nèi)出現(xiàn),但能源浪費現(xiàn)象依然十分嚴(yán)重,因此采用合理有效的方法提高能源利用率顯得尤為重要。儲能技術(shù)可以將太陽能、工業(yè)余熱等以熱能的形式儲存起來,緩解能源供給與使用之間存在的空間和時間差問題,成為提高能源利用率的有效手段。儲能技術(shù)的研究主要包括對儲熱材料和儲熱裝置結(jié)構(gòu)的研究。由于大部分的儲熱材料熱導(dǎo)率不高,使得儲熱裝置整體傳熱效率較低,因此尋求合適的強化傳熱手段以提高系統(tǒng)充放熱效率很重要。本文選取中高溫儲熱材料中常見的NaNO3-46KNO3、LiNO3、己二酸作為相變儲熱材料,組建相應(yīng)的蓄熱裝置結(jié)構(gòu),研究裝置的傳熱特性和強化傳熱效果。為提高系統(tǒng)整體傳熱效率,針對裝置中煙氣熱導(dǎo)率較低的問題,分別設(shè)計了盤管式和波紋管式兩種蓄熱裝置。盤管結(jié)構(gòu)能在較小的尺寸范圍內(nèi)延長煙氣的行駛路徑,增加接觸時間,提高傳熱速率;波紋管結(jié)構(gòu)能增大換熱接觸面積、增強流體擾動以強化傳熱,且相變材料的體積填充比大,材料利用率高。建立了盤管式余熱回收蓄熱裝置結(jié)構(gòu)模型,根據(jù)理論計算經(jīng)驗公式,初步確定了結(jié)構(gòu)單元特征和尺寸,簡化模型后進行三維建模,利用Fluent軟件對蓄熱裝置的放熱過程進行數(shù)值模擬研究,模擬換熱過程中蓄熱裝置內(nèi)的溫度場分布、液相率分布,各監(jiān)測點監(jiān)測面的溫度變化等,分析了不同導(dǎo)熱油入口流速、蓄熱裝置初始溫度和自然對流對系統(tǒng)充放熱性能的影響,得出最佳的工況條件。計算了相變材料選用NaNO3-46KNO3和LiNO3時的裝置蓄熱量分別為0.481MWh和0.508MWh。根據(jù)結(jié)構(gòu)中相關(guān)部件的合理化分析,對蓄熱裝置中各單元結(jié)構(gòu)和尺寸進行優(yōu)化,為盤管式蓄熱裝置的實際應(yīng)用提供參考。建立了波紋管式蓄熱裝置的單管二維數(shù)學(xué)模型,與相應(yīng)尺寸光管單元模型的充放熱過程進行對比分析,比較波紋管的強化傳熱效果。并在25mm管徑條件下,模擬了充放熱過程中儲熱單元溫度場分布、相界面移動規(guī)律、監(jiān)測點溫度變化趨勢和相變材料蓄熱量等,分析了不同波節(jié)間距和波節(jié)高度對蓄熱單元充放熱性能的影響,得到最佳波節(jié)高度和波節(jié)間距尺寸參數(shù)。經(jīng)過計算得到在最佳結(jié)構(gòu)參數(shù)下的波紋管蓄熱裝置整體蓄熱量為66978kJ,為波紋管式余熱回收蓄熱裝置在工程實際中的應(yīng)用提供一定的參考價值。
[Abstract]:With the rapid development of industry and the improvement of human living standards, energy demand has been on the rise. Because of unreasonable exploitation and utilization, the problem of energy shortage has appeared all over the world, but the phenomenon of energy waste is still very serious, so it is very important to adopt reasonable and effective methods to improve energy efficiency. Energy storage technology can store solar energy and industrial waste heat in the form of heat energy, alleviate the space and time difference between energy supply and use, and become an effective means to improve energy efficiency. The research of energy storage technology mainly includes the research of heat storage material and heat storage device structure. Due to the low thermal conductivity of most heat storage materials, the overall heat transfer efficiency of the heat storage device is low, so it is very important to find suitable means to enhance the heat transfer efficiency of the system. In this paper, NaNO3-46KNO3,LiNO3, adipic acid, which is common in medium and high temperature heat storage materials, is selected as phase change storage material, and the corresponding heat storage device structure is constructed to study the heat transfer characteristics and enhanced heat transfer effect of the device. In order to improve the overall heat transfer efficiency of the system, two kinds of heat storage devices, coil type and corrugated tube type, were designed to solve the problem of low thermal conductivity of flue gas in the device. The coil structure can prolong the running path of flue gas, increase the contact time and increase the heat transfer rate in the small size range, and the corrugated tube structure can increase the heat transfer contact area and enhance the fluid disturbance to enhance the heat transfer. The volume filling ratio of phase change material is large and the material utilization ratio is high. The structure model of coil type waste heat recovery and storage device is established. According to the empirical formula of theoretical calculation, the characteristics and dimensions of the structure unit are preliminarily determined, and the three-dimensional modeling is carried out after simplifying the model. The heat release process of heat storage device is simulated by Fluent software. The temperature field distribution, liquid phase rate distribution and temperature change of monitoring surface in the heat storage device during heat transfer process are simulated, and the inlet velocity of different heat conduction oil is analyzed. The effects of the initial temperature and natural convection of the heat storage device on the system's heat filling and releasing performance are discussed. The optimal operating conditions are obtained. The heat storage of the device with NaNO3-46KNO3 and LiNO3 is calculated as 0.481MWh and 0.508MWh. respectively. According to the reasonable analysis of the relative parts in the structure, the structure and size of each unit in the heat storage device are optimized, which provides a reference for the practical application of the coil type heat storage device. The two-dimension mathematical model of the corrugated tube type heat storage device is established. The heat transfer enhancement effect of the corrugated tube is compared with that of the corresponding size light tube unit model. Under the condition of 25mm pipe diameter, the temperature field distribution of heat storage unit, the law of phase interface movement, the temperature change trend of monitoring point and the heat storage of phase change material during heat filling and exothermic process are simulated. The effects of different pitch spacing and pitch height on the heat storage unit are analyzed and the optimum parameters of pitch height and pitch size are obtained. The overall heat storage capacity of the corrugated tube heat storage device under the optimum structural parameters is 66978kJ, which provides a certain reference value for the application of the corrugated tube heat recovery device in engineering practice.
【學(xué)位授予單位】：武漢理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TB34;TK115

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