本文關(guān)鍵詞： 冰漿 壓降 臨界速度 含冰率　出處：《天津商業(yè)大學(xué)》2014年碩士論文　論文類型：學(xué)位論文

【摘要】：蓄冷技術(shù)在制冷空調(diào)領(lǐng)域應(yīng)用廣泛，冰漿作為蓄冷介質(zhì)，因其顆粒較小、流動性好、融冰速度快成為國內(nèi)外學(xué)者的研究重點(diǎn)。在已有的刮片式制取冰漿裝置基礎(chǔ)上，重點(diǎn)分析了冰漿在管網(wǎng)內(nèi)的流動特性，流阻情況以及冰漿安全運(yùn)輸時(shí)的臨界速度等。 本文的研究工作主要集中在以下幾個(gè)方面： 1）冰漿物性分析：分析了冰漿中冰晶和水溶液的物性，得出冰漿密度、導(dǎo)熱系數(shù)、比熱的計(jì)算公式，分析得出冰漿的熱物性同時(shí)受冰晶顆粒和水溶液二者共同的影響。 2）冰漿管內(nèi)流動數(shù)值模擬：采用Fluent中的雙流體歐拉模型得出冰粒子在管內(nèi)的分布云圖，分析發(fā)現(xiàn)水平管道內(nèi)粒子分布從頂部到底部呈規(guī)律性變化，在相同截面處，流速越小、管徑越大，分層越明顯，造成分層的主要原因是粒子碰撞以及浮力的作用。然后通過模擬分析了冰漿在管內(nèi)流動的臨界速度以及壓降值隨各參數(shù)（冰粒子直徑、管道直徑、入口含冰率、添加劑濃度等）的變化情況。 a）冰漿在管內(nèi)安全運(yùn)輸?shù)捻敳勘Ｗ幼畲笕菁{率（冰粒子體積含冰率）為0.501，，臨界速度隨著粒子直徑、含冰率、鹽濃度、管直徑的增大而增大； b）冰漿水平管內(nèi)流動的單位壓降隨著流速、含冰率的增大而增大，隨著管直徑以及粒子直徑的增大而減小。 將上述Fluent模型計(jì)算的壓降值與Bingham模型理論值進(jìn)行比較分析，發(fā)現(xiàn)二者最大差別在15%左右，驗(yàn)證了采用Fluent模型的正確性。 3）冰漿管內(nèi)流動特性實(shí)驗(yàn)：本實(shí)驗(yàn)采用三個(gè)循環(huán)系統(tǒng)（制冷劑循環(huán)系統(tǒng)、冰漿制取系統(tǒng)以及冰漿管內(nèi)流動循環(huán)系統(tǒng)）。通過可視化玻璃管觀察冰漿在不同流速、不同含冰率下的流動狀態(tài)，發(fā)現(xiàn)冰漿在較高流速下混合均勻，在較低流速下會出現(xiàn)類似絮網(wǎng)狀結(jié)構(gòu)，產(chǎn)生的原因是由于擾動的減小會造成冰粒子的凝聚。分析實(shí)驗(yàn)數(shù)據(jù)得到：冰漿壓降隨著流速的變化在較低鹽濃度時(shí)呈階梯狀上升，較高鹽濃度時(shí)呈拋物線型上升。最后將實(shí)驗(yàn)得到的冰漿管內(nèi)流動壓降隨著含冰率的變化規(guī)律與模擬結(jié)果進(jìn)行對比，發(fā)現(xiàn)實(shí)驗(yàn)值與模擬值變化趨勢一致，而且實(shí)驗(yàn)值高于模擬值，二者最大差值發(fā)生在管直徑32mm管內(nèi)且為5%。由于在實(shí)驗(yàn)過程中，隨著體積含冰率的降低鹽濃度也會逐漸減低，兩者都會增大冰漿壓降的下降速率，所以實(shí)驗(yàn)條件下的壓降下降速率比同等條件下模擬值要大。 4）由于在初始含冰率下測得的鹽濃度會隨著冰粒子的融化而降低，根據(jù)氯堿手冊中1%-5%的氯化鈉濃度理論值擬合出該范圍內(nèi)氯化鈉密度隨濃度變化的關(guān)系式，然后得出隨著冰粒子融化處于不同含冰率下的鹽濃度計(jì)算式。
[Abstract]:Cold storage technology is widely used in the field of refrigeration and air conditioning, ice slurry as a cold storage medium, because of its small particles, good fluidity. On the basis of the existing scraper ice slurry device, the flow characteristics of ice slurry in pipe network are analyzed. Flow resistance and critical velocity of ice slurry in safe transportation. The research work of this paper mainly focuses on the following aspects: 1) physical properties of ice slurry: the physical properties of ice crystal and aqueous solution in ice slurry were analyzed, and the calculation formulas of density, heat conductivity and specific heat of ice slurry were obtained. It is concluded that the thermal properties of ice slurry are affected by both ice grain and aqueous solution. 2) numerical simulation of ice slurry flow: the two-fluid Euler model in Fluent is used to get the distribution of ice particles in the pipe. It is found that the particle distribution in the horizontal pipe changes regularly from the top to the bottom. At the same section, the smaller the velocity is, the larger the diameter of the pipe is, and the more obvious the stratification is. The main causes of stratification are particle collision and buoyancy. Then the critical velocity and pressure drop of ice slurry flow in pipe are analyzed with the parameters (ice particle diameter pipe diameter and ice content at the inlet). Change in the concentration of additives, etc. A) the maximum ice particle holding ratio (ice particle volume ice content) at the top of the ice slurry transported safely in the pipe is 0.501, and the critical velocity increases with the increase of particle diameter, ice content, salt concentration and pipe diameter. B) the unit pressure drop of ice slurry flow increases with the increase of flow velocity and ice content, and decreases with the increase of tube diameter and particle diameter. The pressure drop calculated by the above Fluent model is compared with the theoretical value of the Bingham model, and the maximum difference between them is found to be about 15%. The correctness of the Fluent model is verified. 3) experiment of flow characteristics in ice slurry pipe: this experiment adopts three circulating systems (refrigerant circulation system). The ice slurry production system and the flow circulation system in the ice slurry pipe were observed by visual glass tube. The mixture of ice slurry was found to be uniform at higher flow rate and at different velocity of flow and different ice content. At a lower velocity, a similar floc network will appear. The reason is that the decrease of disturbance will lead to the condensation of ice particles. The experimental data show that the pressure drop of ice slurry increases with the change of flow velocity in the form of ladder when the concentration of salt is lower. When the salt concentration is high, the flow pressure drop in the ice slurry pipe is increased in parabola shape. Finally, the experimental results are compared with the simulation results, and it is found that the experimental value is consistent with the simulated value. And the experimental value is higher than the simulated value, the maximum difference between the two occurs in the diameter of 32mm tube and is 5. Because in the experiment process, the salt concentration will gradually decrease with the decrease of the volume ice content. Both of them will increase the falling rate of ice slurry pressure drop, so the pressure drop rate under the experimental condition is larger than that under the same condition. 4) the salt concentration measured at the initial ice content will decrease with the melting of the ice particles. According to the theoretical value of 1 ~ 5% sodium chloride concentration in the manual of chlor-alkali, the relationship between the density of sodium chloride and the concentration of sodium chloride in this range is fitted, and the formula for calculating the salt concentration under different ice content with the melting of ice particles is obtained.
【學(xué)位授予單位】：天津商業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TB64

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