东南大学学报(自然科学版)
東南大學學報(自然科學版)
동남대학학보(자연과학판)
JOURNAL OF SOUTHEAST UNIVERSITY
2014年
4期
756-763
,共8页
朱立平%秦霞%袁竹林%闫亚明%罗登山%李斌
硃立平%秦霞%袁竹林%閆亞明%囉登山%李斌
주립평%진하%원죽림%염아명%라등산%리빈
丝状颗粒%滚筒干燥器%传热传质%标准偏差
絲狀顆粒%滾筒榦燥器%傳熱傳質%標準偏差
사상과립%곤통간조기%전열전질%표준편차
filamentous particle%rotary dryer%heat and mass transfer%standard deviation
针对丝状物料在滚筒内干燥不均等问题,从干燥机理出发,建立了一种基于离散单元法的丝状颗粒传热传质数学模型。利用该模型对滚筒横向截面中丝状物料的温度和含水率的变化过程进行了分析计算,并通过实验验证了数学模型的有效性。研究结果表明:筒壁温度的变化对丝状颗粒传热传质特性有着直接且重要的影响;在干燥的初始阶段,颗粒彼此间温度的不均匀性迅速增大,但随着干燥的进行,颗粒之间的温度差别又呈现出逐渐缩小的趋势。颗粒间含水率的不均匀性在干燥的初始阶段同样迅速增大,当满足一定的干燥条件或一定的干燥时间,筒体内部丝状颗粒的干燥程度将会越来越均匀;丝状颗粒在滚筒中所获取的热量主要来自于与高温壁面(特别是与筒体之间)的接触导热;与升举式抄板相比,均布式抄板可使颗粒在滚筒横截面上的分布及颗粒间的温度和含水率更加均匀。
針對絲狀物料在滾筒內榦燥不均等問題,從榦燥機理齣髮,建立瞭一種基于離散單元法的絲狀顆粒傳熱傳質數學模型。利用該模型對滾筒橫嚮截麵中絲狀物料的溫度和含水率的變化過程進行瞭分析計算,併通過實驗驗證瞭數學模型的有效性。研究結果錶明:筒壁溫度的變化對絲狀顆粒傳熱傳質特性有著直接且重要的影響;在榦燥的初始階段,顆粒彼此間溫度的不均勻性迅速增大,但隨著榦燥的進行,顆粒之間的溫度差彆又呈現齣逐漸縮小的趨勢。顆粒間含水率的不均勻性在榦燥的初始階段同樣迅速增大,噹滿足一定的榦燥條件或一定的榦燥時間,筒體內部絲狀顆粒的榦燥程度將會越來越均勻;絲狀顆粒在滾筒中所穫取的熱量主要來自于與高溫壁麵(特彆是與筒體之間)的接觸導熱;與升舉式抄闆相比,均佈式抄闆可使顆粒在滾筒橫截麵上的分佈及顆粒間的溫度和含水率更加均勻。
침대사상물료재곤통내간조불균등문제,종간조궤리출발,건립료일충기우리산단원법적사상과립전열전질수학모형。이용해모형대곤통횡향절면중사상물료적온도화함수솔적변화과정진행료분석계산,병통과실험험증료수학모형적유효성。연구결과표명:통벽온도적변화대사상과립전열전질특성유착직접차중요적영향;재간조적초시계단,과립피차간온도적불균균성신속증대,단수착간조적진행,과립지간적온도차별우정현출축점축소적추세。과립간함수솔적불균균성재간조적초시계단동양신속증대,당만족일정적간조조건혹일정적간조시간,통체내부사상과립적간조정도장회월래월균균;사상과립재곤통중소획취적열량주요래자우여고온벽면(특별시여통체지간)적접촉도열;여승거식초판상비,균포식초판가사과립재곤통횡절면상적분포급과립간적온도화함수솔경가균균。
On account of drying inequality problem of filamentous materials in the rotary, a mathe-matical model for heat and mass transfer of filamentous particles based on the discrete element meth-od was proposed according to drying mechanisms, and then it was used to numerically study the tem-perature and moisture content evolution of filamentous materials in the transverse section of a rotary dryer.The effectivity of this model was verified by experiments.The results show that the change of the temperature of the cylinder wall has a direct and significant impact on the heat and mass transfer characteristics of filamentous particles.At the initial stage of drying, the standard deviation of the particles temperature increases rapidly, but then it reduces gradually with the dying time.And the standard deviation of the moisture content also increases rapidly at the initial stage of drying.When the certain drying conditions or the drying time is met, the uniformity of moisture content of filamen-tous particles inside the cylinder will be better and better.The heat flux of filamentous particles mainly obtains from the high temperature wall, especially from the cylinder wall.Compared with the lifting type baffle, the uniform type baffle can make the temperature distribution and the moisture content distribution of the particles on the transverse section of the cylinder more uniform.