本文選題：熱化學儲熱　切入點：水合鹽　出處：《華北電力大學(北京)》2016年碩士論文

【摘要】：跨季節(jié)儲熱技術中,水合鹽熱化學吸附具有儲熱密度高、長周期存儲無熱損、清潔環(huán)保、成本低廉等優(yōu)勢,逐漸成為國內外儲熱領域的研究熱點。本文對基于水合鹽熱化學吸附的跨季節(jié)儲熱技術的發(fā)展進行了深入調研,對比分析不同水合鹽儲熱材料的儲熱特性和反應器選型的優(yōu)劣。由于低溫運行條件下,儲熱材料MgCl_2·6H_2O表現出優(yōu)良的反應性能,結合本文數值模擬的需求,選擇以MgCl_2·6H_2O顆粒材料構成的堆積床反應器作為模擬對象。針對MgCl_2·6H_2O堆積床反應器中固體顆粒吸附劑表面發(fā)生的熱化學儲熱過程進行理論建模,建立與熱化學反應耦合的多孔介質多尺度傳輸理論模型,闡明反應器內多尺度熱質傳輸規(guī)律及與熱化學動力性能的作用機制。采用計算流體力學軟件FLUENT對于MgCl_2·6H_2O堆積床反應器中儲熱過程進行數值模擬。自定義編寫化學反應過程中的質量和能量源項,用以描述反應器內熱化學吸附／脫附過程的物質交換和能量傳輸過程。從FLUENT設置、模擬結果與實驗對照、網格獨立性檢驗等方面驗證了熱化學吸附模型的可靠性。基于本文建立的熱化學反應傳熱傳質模型,對MgCl_2·6H_2O堆積床反應器儲熱過程進行了模擬分析,得到不同時刻反應器中溫度場、組分濃度場、固體顆粒含水量場的分布規(guī)律。綜合分析了MgCl_2·6H_2O堆積床反應器儲熱過程中顆粒吸附量與水蒸氣產率的變化特性,得出傳質區(qū)的移動是與化學反應耦合的傳熱傳質過程綜合作用的結果,也是影響顆粒吸附量及水蒸氣產率的關鍵因素。通過改變運行工況包括空氣入口流速及反應床溫度,對儲熱反應器的不同運行狀態(tài)進行模擬分析。得出針對本文MgCl_2·6H_2O堆積床反應器,入口空氣流速提高0.5倍,儲熱進程縮短41%；降低0.5倍,儲熱進程延長45%。床體初溫降低20℃,脫附進程延長10%；床體初溫升高10℃,脫附進程縮短8.5%。最后,本文總結了水合鹽熱化學吸附跨季節(jié)儲熱的技術特點,并指出了該技術未來的主要研究方向。
[Abstract]:In the cross-season heat storage technology, the thermal chemisorption of hydrated salt has the advantages of high heat storage density, long period storage without heat loss, clean and environmental protection, low cost and so on, and has gradually become the research hotspot in the field of heat storage at home and abroad.In this paper, the development of cross-season heat storage technology based on hydrated salt thermal chemisorption was investigated, and the heat storage characteristics of different hydrated salt thermal storage materials and the advantages and disadvantages of reactor selection were compared and analyzed.Because of the excellent reaction performance of the thermal storage material MgCl_2 6H_2O under low temperature operation conditions, combined with the requirement of numerical simulation in this paper, the pile-up bed reactor composed of MgCl_2 6H_2O granular material was selected as the simulation object.The thermochemical heat storage process on the surface of solid particle adsorbent in MgCl_2 6H_2O packed bed reactor was modeled theoretically, and the multi-scale transport theory model of porous media coupled with thermal chemical reaction was established.The multiscale heat and mass transfer in the reactor and the mechanism of its interaction with the thermochemical dynamic properties are described.The heat storage process in MgCl_2 6H_2O packed bed reactor was numerically simulated by computational fluid dynamics software FLUENT.The mass and energy source terms in the chemical reaction process are customized to describe the material exchange and energy transfer in the thermochemical adsorption / desorption process in the reactor.The reliability of the thermochemical adsorption model was verified from the FLUENT setting, the comparison between the simulation results and the experimental results, and the grid independence test.Based on the thermal chemical reaction heat and mass transfer model established in this paper, the heat storage process of MgCl_2 6H_2O packed bed reactor was simulated and analyzed. The distribution of temperature field, component concentration field and water content field of solid particles in the reactor at different times were obtained.The variation characteristics of particle adsorption capacity and water vapor yield during heat storage in MgCl_2 6H_2O packed bed reactor are comprehensively analyzed. It is concluded that the movement of mass transfer zone is a comprehensive result of heat and mass transfer process coupled with chemical reaction.It is also a key factor to influence the adsorption capacity and water vapor yield.By changing the operating conditions, including air inlet velocity and reaction bed temperature, the different operating conditions of the heat storage reactor were simulated and analyzed.For MgCl_2 6H_2O packed bed reactor, the inlet air velocity is increased 0.5 times, the heat storage process is shortened by 41 times, and the heat storage process is prolonged by 45 times.The initial temperature of the bed decreased by 20 鈩，

本文編號：1723450