بررسی تاثیر دوره تناوب بر تنش های خشک شدن در خشک شدن تناوبی خاک رس با تغییرات دوره‌ای رطوبت نسبی

نوع مقاله : مقاله پژوهشی

نویسندگان

دانشکده مهندسی، دانشگاه بیرجند، بیرجند، ایران

چکیده

خشک‌شدن تناوبی در صورت طرح‌ریزی مناسب یک راهکار موثر برای بهبود سینتیک خشک شدن، کیفیت قطعات خشک شده و مقدار مصرف انرژی می‌باشد. تعیین دوره تناوب، دامنه تناوب و زمان شروع تناوب چالش‌های اصلی در طرح‌ریزی فرایند خشک شدن تناوبی می‌باشند. هدف این مطالعه بررسی تاثیر دوره تناوب بر سینتیک و تنش‌های خشک شدن در خشک شدن تناوبی خمیر رسی با تغییرات دوره‌ای رطوبت نسبی می‌باشد. همچنین تنش‌های حرارتی و رطوبتی مورد مقایسه قرار گرفته است. تغییرات پارامترهای خشک شدن نسبت به رطوبت و دما در مدلسازی لحاظ گردیده است. مطابقت مناسب متغیرهای متعدد تجربی و شبیه‌سازی نشان دهنده صحت و درک کامل هر سه جنبه فرایند خشک شدن توسط مدل ریاضی ارائه شده می‌باشد. نتایج شبیه‌سازی نشان می‌دهد که در هنگام شکسته شدن لوله‌های موئین قطعه باید در دوره خشک شدن با نرخ کمینه قرار داشته باشد. با توجه به شکست تدریجی لوله‌های موئین در دوره گذار، خشک شدن تناوبی روی نقاط مختلف اثر متفاوتی می‌گذارد. از این رو نقاط مستعدد ترک برداشتن باید به صورت هم‌زمان مورد بررسی قرار گیرند. تنش‌های حرارتی در مقایسه با تنش‌های رطوبتی بسیار ناچیز هستند و می‌توان از مدلسازی آنها در فرایند خشک‌شدن صرف نظر کرد.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Relative Humidity Period Influence on Drying Induced Stresses in Intermittent Drying of Clay

نویسندگان [English]

  • mohsen heydari
  • khalili khalili
  • Yousef Ahmadi-Brooghani
1 Ph.D. Student, Mech. Eng., University of Birjand, Birjand
چکیده [English]

Intermittent drying is an effective strategy for improving the drying kinetics, energy consumption as well as, the quality of the dried products. The aim of this study is to investigate the effect of the period of intermittent drying on the drying kinetics and the induced stresses. To this end, a clay like material is used and by changing the air relative humidity periodically, the stresses induced were determined. Parameters variation with moisture and temperature are considered in modeling. Good agreement between experimental and simulation variables results reveals that the model developed is valid and accurate. Simulation results suggest that the drying rate should be kept at its minimum at the stage of disruption of hydraulic continuity. Due to the gradual disruption of capillary tubes in transition period, the part is affected gradually, and this necessitates the possible crack deformation points of the part to be sought simultaneously. Also, the current work studied the magnitude of each of stresses induced by non-uniform moisture distribution and stresses induced by non-uniform temperature distribution. It is shown that the thermal stresses are negligible compared to the moisture stresses and can be neglected in drying modeling.

کلیدواژه‌ها [English]

  • Intermittent drying
  • convective drying
  • drying stress
  • mathematical modeling
  • Clay
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