【摘要】：當(dāng)今世界,能源短缺和環(huán)境污染已成為制約全球可持續(xù)發(fā)展的重要問(wèn)題之一。以可再生地?zé)嵩礊槟茉吹牡卦礋岜眉夹g(shù),受到了國(guó)內(nèi)外政府、高校和研究機(jī)構(gòu)的高度關(guān)注,并且展開(kāi)了大量的理論研究和實(shí)際工程的應(yīng)用。地埋管換熱器設(shè)計(jì)不僅是地源熱泵研究的重點(diǎn),也是地源熱泵空調(diào)系統(tǒng)的應(yīng)用基礎(chǔ)和理論核心。如何在狹窄的鉆孔內(nèi)減少熱短路的影響并且提高換熱器的性能,研究抑制熱短路的措施就顯得尤為重要。本文從換熱器傳熱模型和管內(nèi)循環(huán)流體的湍流模型兩個(gè)方面對(duì)地埋管傳熱模型進(jìn)行介紹,為研究地埋管換熱器做了理論準(zhǔn)備。介紹了數(shù)值模擬相關(guān)CFD軟件,利用Gambit軟件建立地埋管換熱器三維模型,用Fluent進(jìn)行數(shù)值仿真模擬。通過(guò)對(duì)影響地埋管換熱器熱短路現(xiàn)象的三個(gè)因素:循環(huán)流體的速度、埋管深度和運(yùn)行時(shí)間分別進(jìn)行模擬,通過(guò)對(duì)比循環(huán)流體出口水溫、不同深處的換熱器溫度分布云圖和近出口溫差以及單位井深換熱量對(duì)熱短路現(xiàn)象進(jìn)行分析和研究。得出如下結(jié)論:管內(nèi)流速推薦值為0.6 m/s,埋管深度在80 m最佳,采取縮短機(jī)組連續(xù)運(yùn)行的時(shí)間或者間歇運(yùn)行的策略更加合理。在研究不同因素對(duì)換熱器的影響時(shí),發(fā)現(xiàn)兩支管間必然發(fā)生熱短路現(xiàn)象,而且越靠近地表現(xiàn)象越嚴(yán)重。本文研究了抑制地埋管熱短路現(xiàn)象的兩種措施,即在垂直于兩支管間中心線處添加一定深度和厚度的隔熱板或在回水管敷設(shè)不同深度和厚度的保溫材料。通過(guò)比較添加不同深度隔熱板、不同深度保溫層和不同保溫層厚度三種情況,對(duì)熱短路現(xiàn)象進(jìn)行定性研究,并通過(guò)對(duì)出水溫度和單位井深換熱量對(duì)換熱器熱短路現(xiàn)象和換熱器性能進(jìn)行定量分析。當(dāng)未添加任何抑制措施即換熱器正常換熱時(shí),循環(huán)流體出水溫度為304.44 K,單位井深換熱量為56.1 W/m:當(dāng)采取添加隔熱板抑制措施時(shí),最佳工況點(diǎn)隔熱板深度為40 m時(shí),出口溫度最低為304.35 K,單位井深換熱量最高為57.5 W/m;當(dāng)采取敷設(shè)一定深度和厚度保溫層時(shí),最佳工況點(diǎn)為敷設(shè)10m深保溫層厚度為4 mm,出口溫度最低為304.16 K,單位井深換熱量為60.5 W/m。通過(guò)比較單位井深換熱量,在兩支管間添加隔熱板單位井深換熱量最高可以提高為2.5%,在回水管敷設(shè)保溫層最高可以提升7.8%。通過(guò)對(duì)地埋管換熱器熱短路現(xiàn)象的研究,并提出了兩種抑制措施,為提高換熱器性能提供理論支撐,希望為地源源熱泵的技術(shù)推廣起到積極的作用,使該技術(shù)更加節(jié)能環(huán)保。
[Abstract]:In today's world, energy shortage and environmental pollution have become one of the most important problems restricting global sustainable development. Ground-source heat pump (GSHP) technology, which uses renewable geothermal source as energy source, has been highly concerned by governments, universities and research institutions at home and abroad, and a large number of theoretical research and practical engineering applications have been carried out. The design of ground heat exchanger is not only the focus of ground source heat pump research, but also the application basis and theoretical core of ground source heat pump air conditioning system. How to reduce the influence of hot short circuit and improve the performance of heat exchanger in narrow borehole is very important. In this paper, the heat transfer model of underground tube is introduced from two aspects: heat transfer model of heat exchanger and turbulence model of circulating fluid in tube. This paper introduces the related CFD software of numerical simulation. The 3D model of underground tube heat exchanger is established by Gambit software, and the numerical simulation is carried out by Fluent. Through the simulation of three factors that affect the hot short circuit phenomenon of the ground buried tube heat exchanger: the velocity of the circulating fluid, the depth of the buried pipe and the running time, the water temperature at the outlet of the circulating fluid is compared. The thermal short-circuit phenomenon is analyzed and studied in different depths of heat exchanger temperature distribution cloud map and near outlet temperature difference as well as heat transfer in unit well depth. The conclusions are as follows: the recommended value of flow velocity in the tube is 0.6 m / s and the depth of buried pipe is 80 m. It is more reasonable to adopt the strategy of shortening the continuous operation time or intermittent operation of the unit. When studying the influence of different factors on the heat exchanger, it is found that the phenomenon of thermal short circuit between the two branch tubes is inevitable, and the phenomenon is more serious with the closer to the surface. In this paper, two kinds of measures to restrain the phenomenon of thermal short circuit of buried pipe are studied, that is, adding heat insulation plate with certain depth and thickness perpendicular to the center line between two pipes or laying insulation material of different depth and thickness in backwater pipe. The phenomenon of thermal short circuit is studied qualitatively by comparing the three conditions of adding different depth insulation plate, different depth insulation layer and different insulation layer thickness. The thermal short-circuit phenomenon and heat exchanger performance of heat exchanger were analyzed quantitatively by water temperature and heat transfer per well depth. Without adding any inhibition measures, that is, the heat transfer of the heat exchanger, the outlet temperature of the circulating fluid is 304.44 K, the heat transfer of the unit well depth is 56.1 W / m: when the heat insulation board is added, the heat transfer rate is 56.1 W / m. When the depth of the insulation plate is 40 m, the lowest exit temperature is 304.35 K, and the maximum heat transfer per well depth is 57.5 W / m; When a certain depth and thickness insulation layer is laid, the optimum operating point is that the thickness of 10 m deep insulation layer is 4 mm, the lowest exit temperature is 304.16 K, and the heat transfer of unit well depth is 60.5 W / m. By comparing the heat transfer of unit well depth, the maximum heat transfer of unit well depth can be increased to 2.5 by adding heat insulation board between two pipes, and the maximum value of heat transfer can be increased to 7.8 by laying insulation layer in backwater pipe. Through the study of heat short circuit phenomenon of ground heat exchanger, two kinds of restraining measures are put forward to provide theoretical support for improving heat exchanger performance. It is hoped that it will play an active role in popularizing the technology of ground source heat pump and make the technology more energy saving and environmental protection.
【學(xué)位授予單位】：南京師范大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：TU83

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本文編號(hào)：2419912