本文選題：閃蒸干燥　切入點：氣固兩相流　出處：《華南理工大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：旋流閃蒸干燥機是集打散、干燥、收集于一體的氣流干燥設(shè)備,但其能耗問題一直沒有得到很好的解決,因此開展基于數(shù)值模擬和實驗的閃蒸干燥流場、物料干燥特性的研究,對閃蒸干燥工藝優(yōu)化、節(jié)能降耗及設(shè)備改進將具有一定的參考價值。本文成功設(shè)計出旋流閃蒸干燥機實驗平臺,并以之為研究對象。一方面,建立閃蒸干燥數(shù)學(xué)模型,并借助Fluent軟件對其進行氣固兩相流數(shù)值模擬;另一方面,利用旋流閃蒸干燥機實驗平臺,研究了不同熱風(fēng)進口速度、熱風(fēng)溫度、葉片轉(zhuǎn)速等諸多工況下,熱風(fēng)溫度分布、物料出口含水量等方面的變化規(guī)律,深入探究了干燥區(qū)域傳熱傳質(zhì)機理。得到如下研究成果和結(jié)論:(1)在數(shù)值模擬方面,連續(xù)相壓降主要分布在旋流外筒段、環(huán)形縫隙段以及干燥筒體段,其中環(huán)形縫隙單位長度壓降損失最大,達到了3.61Pa/mm;通過對顆粒相軌跡線進行穩(wěn)態(tài)數(shù)值模擬分析,得出顆粒停留時間=0.29s;提出采用Multicomponent方式對離散相進行非穩(wěn)態(tài)DPM模擬,得到了顆粒干燥特性曲線。通過改變不同操作參數(shù),深入分析了旋流閃蒸干燥過程。(2)在實驗研究方面,將實驗結(jié)果與模擬結(jié)果進行對比分析,發(fā)現(xiàn)熱量散失、物料組分的混合形式以及打散裝置是二者存在一定差別的主要原因,具體結(jié)果和差別如下:1)在熱風(fēng)溫度隨筒體高度變化曲線中,模擬值較實驗值存在一定差別,T=400K工況,風(fēng)溫最大差別發(fā)生在h=440mm處,溫度相差11.3K;2)物料出口含水量隨熱風(fēng)溫度的升高減小較為明顯,T=340K時,物料出口干基含水量的模擬值為8.3%,而實驗值為5.4%;3)在物料出口含水量隨速度變化曲線中,均存在含水量拐點,在T=400K工況下,(v=22m/s,X=2.88%)為實驗值拐點;4)葉片轉(zhuǎn)速相對其他因素,對物料出口含水量影響較小。(3)經(jīng)過模擬和實驗對比,模擬結(jié)果和實驗結(jié)果趨勢性符合較好,但具體數(shù)值上有一定偏差,因此本文建立的理論模型可以作為一種研究閃蒸干燥過程特性的輔助手段之一。
[Abstract]:The swirl flash dryer is a kind of airflow drying equipment which integrates dispersion, drying and collection, but its energy consumption has not been solved very well. Therefore, the flow field and material drying characteristics of flash drying based on numerical simulation and experiment are studied. It will have some reference value for optimizing the flash drying process, saving energy and reducing consumption and improving the equipment. In this paper, the experimental platform of swirl flash dryer is designed successfully, and taking it as the research object. On the one hand, the mathematical model of flash drying is established. The numerical simulation of gas-solid two-phase flow is carried out with the help of Fluent software. On the other hand, the distribution of hot air temperature under different conditions, such as inlet velocity, hot air temperature, blade speed and so on, is studied by using the experimental platform of swirl flash dryer. The mechanism of heat and mass transfer in drying region is studied in detail. The results and conclusions are as follows: in numerical simulation, the pressure drop of continuous phase mainly distributes in the outer cylinder of swirl flow. The pressure drop per unit length of the annular slot is the largest, which reaches 3.61 Pa / mm.Through the steady state numerical simulation of the trajectory of the particle phase, the pressure drop of the annular slot and the drying cylinder is analyzed. The particle residence time (RTD) is 0.29 s, and the unsteady DPM simulation of discrete phase by Multicomponent is proposed, and the drying characteristic curve of particle is obtained. By changing different operating parameters, the drying process of swirl flash drying is deeply analyzed. By comparing the experimental results with the simulation results, it is found that the heat loss, the mixing form of the material components and the dispersing device are the main reasons for the difference between the two. The specific results and differences are as follows: (1) in the curve of the variation of hot air temperature with the height of the cylinder, there is a certain difference between the simulated value and the experimental value, and the maximum difference of the wind temperature occurs at 440 mm, When the water content at outlet of material decreases obviously with the increase of hot air temperature, the simulated value of moisture content in dry base of material outlet is 8.3, while the experimental value is 5.4%) there are inflection points of water content in the curve of changing water content of material outlet with velocity. Under the operating condition of TX 400K, the speed of the blade is less affected by the rotating speed of the blade than other factors, and the simulation results are in good agreement with the experimental results, but there is a certain deviation in the specific value, compared with the experimental results, after the simulation and the experiment, the simulation results are in good agreement with the experimental results, which is the inflection point of the experimental value. (4) the speed of the blade has a small effect on the water content of the material outlet. Therefore, the theoretical model established in this paper can be used as an auxiliary means to study the characteristics of flash drying process.
【學(xué)位授予單位】：華南理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TQ051.892

【引證文獻】

相關(guān)碩士學(xué)位論文 前1條

1 劉敏;重力熱管傳熱極限影響因素的研究[D];華南理工大學(xué);2016年

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本文編號：1573392