热泵干燥条件下刺参有效扩散系数的研究
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摘要
有效扩散系数D_(eff)是干燥传质研究的重要基础数据之一,现有D_(eff)研究大多侧重于考虑干燥温度t而忽视干基含水率X、收缩变形的影响。本文建立了刺参干燥有限元模型和D_(eff)计算模型,以X数据的模拟值与实验值之差最小为优化目标,计算得到D_(eff),对比分析了收缩变形、t和X对刺参D_(eff)的影响。研究表明:收缩变形、t及X均对D_(eff)影响较大,同时考虑上述3个影响因素得到的D_(eff)比仅考虑t及X影响时小3.9%～14.6%,而考虑收缩变形和t影响得到的D_(eff)比仅考虑t影响时小8.7%～14.5%,且刺参D_(eff)均随t和X的升高而增加。考虑收缩变形、t和X等对D_(eff)的影响后,刺参干燥模型模拟得到的X与实验值吻合最好,相关系数高于0.994。模拟得到的刺参内部D_(eff)按由内向外逐渐降低的规律分布,干燥从1 h进行至15 h,内外D_(eff)差值由6.4×10~(-10) m~2/s降至0.9×10~(-10) m~2/s,中心处D_(eff)则由14.6×10~(-10) m~2/s降至8.9×10~(-10) m~2/s。
The effective diffusivity(D_(eff)) is an important parameter for mass transfer research on the drying of sea cucumber. The dependence of the D_(eff) on drying temperature(t) has been adopted in current studies, while the effects of dry-based moisture content(X) and drying shrinkage have often been ignored. Therefore, in this paper, a finite element dry model is built and the D_(eff) determination method based on the model is applied to study the D_(eff) in sea cucumber heat pump drying. The influences of shrinkage during heat pump drying, t and X on D_(eff) have been studied and analyzed. The results show that the drying shrinkage, t, and X affect the D_(eff) greatly. The effective diffusivities, as determined by considering the effects of drying shrinkage, t and X, are 3.9%-14.6% lower than those considering the effects of t and X. The D_(eff) determined by considering the effects of drying shrinkage and t are 8.7%-14.5% lower than those only considering the effect of t. The D_(eff) increases with both t and X. Models considering drying shrinkage and influence of t and X on D_(eff) can preferably predict X variation in line with the experimental values, with a coefficient of correlation higher than 0.994. The D_(eff) decreases along the radial direction in the sea cucumber. As drying proceeds from 1 h to 15 h, the difference in D_(eff) between the center and the surface of sea cucumber reduces from 6.4×10~(-10) m~2/s to 0.9×10~(-10) m~2/s, and the D_(eff) in the center decreases from 14.6×10~(-10) m~2/s to 8.9×10~(-10) m~2/s.
The effective diffusivity(D_(eff)) is an important parameter for mass transfer research on the drying of sea cucumber. The dependence of the D_(eff) on drying temperature(t) has been adopted in current studies, while the effects of dry-based moisture content(X) and drying shrinkage have often been ignored. Therefore, in this paper, a finite element dry model is built and the D_(eff) determination method based on the model is applied to study the D_(eff) in sea cucumber heat pump drying. The influences of shrinkage during heat pump drying, t and X on D_(eff) have been studied and analyzed. The results show that the drying shrinkage, t, and X affect the D_(eff) greatly. The effective diffusivities, as determined by considering the effects of drying shrinkage, t and X, are 3.9%-14.6% lower than those considering the effects of t and X. The D_(eff) determined by considering the effects of drying shrinkage and t are 8.7%-14.5% lower than those only considering the effect of t. The D_(eff) increases with both t and X. Models considering drying shrinkage and influence of t and X on D_(eff) can preferably predict X variation in line with the experimental values, with a coefficient of correlation higher than 0.994. The D_(eff) decreases along the radial direction in the sea cucumber. As drying proceeds from 1 h to 15 h, the difference in D_(eff) between the center and the surface of sea cucumber reduces from 6.4×10~(-10) m~2/s to 0.9×10~(-10) m~2/s, and the D_(eff) in the center decreases from 14.6×10~(-10) m~2/s to 8.9×10~(-10) m~2/s.
引文
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[14]姬长英,蒋思杰,张波,等. 辣椒热泵干燥特性及工艺参数优化[J]. 农业工程学报,2017,33(13):296-302.(JI Changying, JIANG Sijie, ZHANG Bo, et al. Heat pump drying properties of chili and optimization of technical parameters[J]. Transactions of the Chinese Society of Agricultural Engineering, 2017, 33(13): 296-302.)
[15]NGUYEN DINH DUC,李保国,薛雅萌.木鳖果热泵低温干燥工艺研究[J].制冷学报,2014,35(6):109-113.(NGUYEN DINH DUC, LI Baoguo, XUE Yameng. Study on heat pump low temperature drying of Momordica fruit[J]. Journal of Refrigeration, 2014,35(6):109-113.)
[16]食品安全国家标准-食品中水分的测定: GB/T 5009.3—2016 [S]. 北京:中国标准出版社,2016. (National standard for food safety-determination of moisture content in foods: GB/T 5009.3—2016 [S]. Beijing: China Standard Press, 2016.)
[17]盛骤,谢式千,潘承毅.概率论与数理统计[M]. 4版.北京:高等教育出版社,2008.(SHENG Zhou, XIE Shiqian, PAN Chengyi. Probability theory and mathematical statistics[M]. 4th ed. Beijing: Higher Education Press,2008.)
[2] 朱文学.食品干燥原理与技术[M].北京:科学出版社, 2009.(ZHU Wenxue. Principle and technology of food drying[M]. Beijing: Science Press, 2009.)
[3] CHEN Dengyu, ZHENG Yan, ZHU Xifeng. Determination of effective moisture diffusivity and drying kinetics for poplar sawdust by thermogravimetric analysis under isothermal condition[J]. Bioresource Technology, 2012, 107(3):451-455.
[4] ERBAY Z,ICIER F. A review of thin layer drying of foods: theory, modeling, and experimental results[J]. Critical Reviews in Food Science and Nutrition, 2010, 50(5):441-464.
[5] SCHSSLER K, JGER H, KNORR D. Effect of continuous and intermittent ultrasound on drying time and effective diffusivity during convective drying of apple and red bell pepper[J]. Journal of Food Engineering, 2012, 108(1): 103-110.
[6] 赵海波,杨昭.热泵干燥条件下种子有效扩散系数的研究[C]//高等教育学会工程热物理专业委员会第二十一届全国学术会议论文集——传热传质学专辑.2014.(ZHAO Haibo, YANG Zhao. Researches on effective diffusivity of seeds with heat pump drying[C]//Proceedings of the 21st National Academic Conference of Engineering Thermophysical Specialized Committee of Higher Education Society: Heat and Mass Transfer Album. 2014.)
[7] 母刚,张国琛,邵亮.热泵干燥海参的初步研究[J].渔业现代化,2007,34(5):47-52.(MU Gang, ZHANG Guochen, SHAO Liang. Preliminary study of sea cucumber heat pump drying[J]. Fishery Modernization, 2007,34(5):47-52.)
[8] MUJUMDAR A S. Study on a combination drying technique of sea cucumber[J]. Drying Technology, 2007, 25(12):2011-2019.
[9] JANGAM S. Advances in heat pump-assisted drying technology edited by vasile minea[J]. Drying Technology, 2017,35(4):522-523.
[10]杨世铭,陶文铨.传热学[M].4版.北京:高等教育出版社,2006.(YANG Shiming, TAO Wenquan. Heat transfer[M]. 4th ed. Beijing: Higer Education Press,2006.)
[11]INCROPERA F P, DEWITT D P, BERGMAN T L, et al. Fundamentals of heat and mass transfer[M]. 6th ed. New York:John Wiley & Sons,2007.
[12]MINEA V. Improvements of high temperature drying heat pumps[J]. International Journal of Refrigeration, 2010, 33:180-195.
[13]薛雅萌,李保国.黄粉虫热泵低温干燥特性及干燥数学模型[J].制冷学报,2015,36(3):108-113.(XUE Yameng, LI Baoguo. Drying characteristics and mathematical model for heat pump low temperature drying of Tenebrio Molitor[J]. Journal of Refrigeration, 2015,36(3):108-113.)
[14]姬长英,蒋思杰,张波,等. 辣椒热泵干燥特性及工艺参数优化[J]. 农业工程学报,2017,33(13):296-302.(JI Changying, JIANG Sijie, ZHANG Bo, et al. Heat pump drying properties of chili and optimization of technical parameters[J]. Transactions of the Chinese Society of Agricultural Engineering, 2017, 33(13): 296-302.)
[15]NGUYEN DINH DUC,李保国,薛雅萌.木鳖果热泵低温干燥工艺研究[J].制冷学报,2014,35(6):109-113.(NGUYEN DINH DUC, LI Baoguo, XUE Yameng. Study on heat pump low temperature drying of Momordica fruit[J]. Journal of Refrigeration, 2014,35(6):109-113.)
[16]食品安全国家标准-食品中水分的测定: GB/T 5009.3—2016 [S]. 北京:中国标准出版社,2016. (National standard for food safety-determination of moisture content in foods: GB/T 5009.3—2016 [S]. Beijing: China Standard Press, 2016.)
[17]盛骤,谢式千,潘承毅.概率论与数理统计[M]. 4版.北京:高等教育出版社,2008.(SHENG Zhou, XIE Shiqian, PAN Chengyi. Probability theory and mathematical statistics[M]. 4th ed. Beijing: Higher Education Press,2008.)
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