高压静电场在水分蒸发和物料干燥方面的应用研究
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摘要
随着现代科学技术的发展，许多电磁加工方法得到广泛的应用。目前高压静电场干燥是一个崭新的研究领域。高压静电场下，物料中水分蒸发速度可以加快。但是在这个领域还有许多问题需要研究，例如电场下水分蒸发的规律、电场的作用范围、电场下的干燥的节能效果等等。为了更好的应用高压静电场，本文的研究主要着眼于深入的研究电场下蒸馏水的蒸发，电场的作用范围，以及物料在电场下干燥的能量消耗问题。
本论文的研究以物理学、电磁学、食品物性学、化工原理、静电技术、测试技术等多学科的理论为基础，主要开展了三个方面的研究工作：高压静电场下不同电极形状、不同电场方向、不同电极距离等条件下影响水分蒸发的因素；上电极采用针电极，下电极采用板电极(本文所涉及的实验中下电极都是板电极，故以后不再提及)形成电场的作用范围的研究；电场中物料干燥过程中的性质变化以及能量消耗。主要结果如下：
1)选用不同的电极形状(上极板分别采用线电极、针电极、板电极)，上电极接负极的情况下，电场对蒸馏水蒸发的促进效果优于上电极接正极或者交流电压的效果；上电极采用针电极接负极的情况下，电场对蒸馏水蒸发的促进效果要优于上极板采用线电极或板电极接负极的效果。高压静电场下蒸馏水和普通自来水蒸发速度没有明显的差别。
2)上电极采用单针电极的情况下，电场下蒸馏水的蒸发速度和以针尖正下方为圆心的半径成二次曲线关系。在针电极和板极之间的距离一定的情况下，在一定的半径(以针尖正下方水面为圆心)以外，电场的影响非常微弱。
上电极采用多个针电极的情况下，蒸馏水的蒸发速度比上电极采用单针电极情况下要快，但是并不是随着针电极的倍数增长而成倍的增长。在多个针电极的情况下，当针电极之间的距离变大时，电场下蒸馏水的蒸发速度也变大。
3)在常温下，高压静电场也可以促进琼脂中的水分蒸发，而且效果很明显。在60℃条件下，琼脂干燥时间可以节省40％的干燥时间。
4)在高压静电场中，豆渣的干燥过程主要是降速干燥阶段，豆渣在电场中干燥比对照节省50％的干燥时间。电场下豆渣的颜色变化较对照有所不同。电场下节能率非常明显，干燥初期为80％以上，随着干燥的进行节能率会降低，主要原因是虽然初始含水量一样，但是干燥过程中电场下豆渣干燥速度要快于对照的速度，使得电场下豆渣中水分的绝对含量一直是少于对照中的水分含量。
本文最后对利用高压静电场促进干燥提出了进一步研究的建议。
With the development of science and technology, many advanced electromagnetic processing technologies have been developed. One of the most popular research areas is drying under high voltage electrostatic field because the high voltage electrostatic field can promote the evaporating and drying procedure. But there are many problems which are not clear enough, such as the foodstuff drying process under high voltage electrostatics field, including the energy consume and the energy efficient ratio. In order to the better application of these technologies, the further research should focus on the detail and deep research on evaporation of distilled water, foodstuff drying procedure and energy economy under high voltage electrostatics field.
Based on theories of Physics, Electromagnetics, Food physics, Chemical Engineering, Electrostatics and Measurement technology, there are three parts addressed in the thesis: The frist is the study on factors of high voltage electrostatic field on evaporation of distilled water; the second is the effect area of high voltage electrostatic field formed with needles and a stainless steel plate; the last is colour change , energy economy and other effects during foodstuff drying procedure. The main results are as follows:
1. The electrostatic fields were formed by a line electrode, a needle electrode, a board electrode, respectively. By changing the distances between electrodes and changing the directions of electrostatic fields, different conditions of electrostatic field were gained. When the same electrodes were connected with negative voltage the promotion of evaporation is better than thai when they were connected with positive voltage or alternating voltage. When the needle electrode was connected with negative voltage the promotion of evaporation is better than that when the other two types of electrodes were connected with negative. So we can obtain that directions of electrostatic field and types of electrode are important factors which affect the evaporation of distilled water. The result of this article has some guiding significance in designing drying equipment using electrostatic field. The promotion of evaporation of the electric Held on distilled water and on tap water has no obvious difference.
2. There is a effect area of high voltage electrostatic field formed with a needle electrode connected with negative voltage and a stainless steel plate connected with ground. Under this kind of electric field the relationship between the evaporation rate of distilled water and the semidiameter is pure quadratic. When using more than one needle electrodes, the evaporation rate of distilled water is 10%-35% faster than that under the situation of one needle electrode. With the increase of the distance among the needle electrodes, the evaporation rate of distilled water also increases.
3. At normal temperature the electrostatic field can promote the evaporation of agar. At
60℃ the time of drying of agar can save 40%.
4. Under electrostatic field the process of drying okara is mainly falling drying rate period and the lime of drying can save 50%. The colour changes are different between the experimental okara cakes and the control one. The energy efficient ratio is about to 80% at the beginning of drying and then decrease. The main reason is that though the initial moisture of okara is the same, the evaporation rate under electrosatic field is faster that that of the control., the absolute mass of okara under electrosatic field is less than that of the control.
Some proposals of further study on electrostatic drying were mentioned as well in the thesis.
本论文的研究以物理学、电磁学、食品物性学、化工原理、静电技术、测试技术等多学科的理论为基础，主要开展了三个方面的研究工作：高压静电场下不同电极形状、不同电场方向、不同电极距离等条件下影响水分蒸发的因素；上电极采用针电极，下电极采用板电极(本文所涉及的实验中下电极都是板电极，故以后不再提及)形成电场的作用范围的研究；电场中物料干燥过程中的性质变化以及能量消耗。主要结果如下：
1)选用不同的电极形状(上极板分别采用线电极、针电极、板电极)，上电极接负极的情况下，电场对蒸馏水蒸发的促进效果优于上电极接正极或者交流电压的效果；上电极采用针电极接负极的情况下，电场对蒸馏水蒸发的促进效果要优于上极板采用线电极或板电极接负极的效果。高压静电场下蒸馏水和普通自来水蒸发速度没有明显的差别。
2)上电极采用单针电极的情况下，电场下蒸馏水的蒸发速度和以针尖正下方为圆心的半径成二次曲线关系。在针电极和板极之间的距离一定的情况下，在一定的半径(以针尖正下方水面为圆心)以外，电场的影响非常微弱。
上电极采用多个针电极的情况下，蒸馏水的蒸发速度比上电极采用单针电极情况下要快，但是并不是随着针电极的倍数增长而成倍的增长。在多个针电极的情况下，当针电极之间的距离变大时，电场下蒸馏水的蒸发速度也变大。
3)在常温下，高压静电场也可以促进琼脂中的水分蒸发，而且效果很明显。在60℃条件下，琼脂干燥时间可以节省40％的干燥时间。
4)在高压静电场中，豆渣的干燥过程主要是降速干燥阶段，豆渣在电场中干燥比对照节省50％的干燥时间。电场下豆渣的颜色变化较对照有所不同。电场下节能率非常明显，干燥初期为80％以上，随着干燥的进行节能率会降低，主要原因是虽然初始含水量一样，但是干燥过程中电场下豆渣干燥速度要快于对照的速度，使得电场下豆渣中水分的绝对含量一直是少于对照中的水分含量。
本文最后对利用高压静电场促进干燥提出了进一步研究的建议。
With the development of science and technology, many advanced electromagnetic processing technologies have been developed. One of the most popular research areas is drying under high voltage electrostatic field because the high voltage electrostatic field can promote the evaporating and drying procedure. But there are many problems which are not clear enough, such as the foodstuff drying process under high voltage electrostatics field, including the energy consume and the energy efficient ratio. In order to the better application of these technologies, the further research should focus on the detail and deep research on evaporation of distilled water, foodstuff drying procedure and energy economy under high voltage electrostatics field.
Based on theories of Physics, Electromagnetics, Food physics, Chemical Engineering, Electrostatics and Measurement technology, there are three parts addressed in the thesis: The frist is the study on factors of high voltage electrostatic field on evaporation of distilled water; the second is the effect area of high voltage electrostatic field formed with needles and a stainless steel plate; the last is colour change , energy economy and other effects during foodstuff drying procedure. The main results are as follows:
1. The electrostatic fields were formed by a line electrode, a needle electrode, a board electrode, respectively. By changing the distances between electrodes and changing the directions of electrostatic fields, different conditions of electrostatic field were gained. When the same electrodes were connected with negative voltage the promotion of evaporation is better than thai when they were connected with positive voltage or alternating voltage. When the needle electrode was connected with negative voltage the promotion of evaporation is better than that when the other two types of electrodes were connected with negative. So we can obtain that directions of electrostatic field and types of electrode are important factors which affect the evaporation of distilled water. The result of this article has some guiding significance in designing drying equipment using electrostatic field. The promotion of evaporation of the electric Held on distilled water and on tap water has no obvious difference.
2. There is a effect area of high voltage electrostatic field formed with a needle electrode connected with negative voltage and a stainless steel plate connected with ground. Under this kind of electric field the relationship between the evaporation rate of distilled water and the semidiameter is pure quadratic. When using more than one needle electrodes, the evaporation rate of distilled water is 10%-35% faster than that under the situation of one needle electrode. With the increase of the distance among the needle electrodes, the evaporation rate of distilled water also increases.
3. At normal temperature the electrostatic field can promote the evaporation of agar. At
60℃ the time of drying of agar can save 40%.
4. Under electrostatic field the process of drying okara is mainly falling drying rate period and the lime of drying can save 50%. The colour changes are different between the experimental okara cakes and the control one. The energy efficient ratio is about to 80% at the beginning of drying and then decrease. The main reason is that though the initial moisture of okara is the same, the evaporation rate under electrosatic field is faster that that of the control., the absolute mass of okara under electrosatic field is less than that of the control.
Some proposals of further study on electrostatic drying were mentioned as well in the thesis.
引文
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[2] Ashim K. Datta, P. Michael Davidson. Microwave and radio frequency processing. Journal of Food Science-Supplement. 2000, 65(8): 32～41
[3] Humberto Vega-Mercado, M. Marcela Góngor-Nieto, Gustavo V. Barbosa-Cáovas. Advances in Dehydration of Foods.Journal of Food Engineering, 2001, 49(4): 271～289
[4] 曹崇文．中国农业大学干燥技术研究进展．第七届全国干燥会议论文集．1999，济南，3
[5] Y. Asakawa. Promotion and retardation of heat transfer by electric fields. Nature, Vol. 261, May 1976: 220～221
[6] Yuonhong Chen, Nayana N. Barthakur, Neville P. Arnold. Electrohydrodynamic (EHD) Drying of Potato Slabs. Journal Food Engineering, 1994, 23:107～119
[7] Fumio Hashinaga, Ganga Prasa, Ryuichi Shintani. Effect of Ordinary Frequency High Electric Fields on Evaporation and Drying. Food Sci. Technoi., Int., 1995, 1(2): 77～81
[8] Fumio Hashinaga, T. R. Bajgai, S. Isobe, N. N. Barthakur. Electrohydrodynamic (EHD) Drying of Apple Slices. Drying Technology, 1999, 17(3): 479～495
[9] 梁运章，那日，白亚乡等．静电干燥原理及应用．物理．2000，29(1)：39～41
[10] 李里特，李法德，辰巳英三．高压静电场对蒸馏水蒸发的影响．农业工程学报，2001，(2)：12～15
[11] 陈家森，朱晓波，刘万红．一项在农业生产中有应用前景的技术——电晕放电技术．物理．1997，26(11)：671～674
[12] 孙目珍．电介质物理基础．广州：华南理工大学出版社，2003年3月第1版，158～160
[13] 李法德．食品物料通电加热及高压电场节能干燥的应用研究：[博士学位论文]．北京：中国农业大学，2002
[14] 李里特．食品物性学．北京：中国农业出版社，1998年2月第1版，404～407
[15] J A Cross. Electrostatically assisted heat transfer. In: Electrostatics (Ed. J. Lowell), Inst. Phys. Conf., Series 48,(1979): 191～199
[16] 徐学基，诸定昌．气体放电物理．1996，上海：复旦大学出版社，1996年8月第1版，20
[17] N. N. Barthakur. Electrohydrodynamic Enhancement of Evaporation from NaCl Solutions. Desalination, 1990, 78: 455～465
[18] H. R. Carlon, J. Latham. Enhanced Drying Rates of Wetted Materials in Electric Field. Journal of Atmospheric and terrestrial Physics, 1992, 54(2): 117～178
[19] Yuonhong Chen, Nayana N. Barthakur, Neville P. Arnold. Electrohydrodynamic(EHD) Drying of Potato Slabs. Journal Food Engineering, 1994, 23:107～119
[20] Fumio Ashinaga, Ganga Prasa, Ryuichi Shintani. Effect of Ordinary Frequency High Electric Fields on Evaporation and Drying. Food Sci. Technol., Int., 1995, 1(2): 77～81
[21] J.Seyed-Yagoobi,etal. Electrohydronamically Enhanced Heat Transfer in Pool Boiling. Journal of Heat Transfer. 1996,118(2): 233～237
[22] 董守绂，梁运章．电晕电场对物料干燥的试验．高电压技术．1996，22(2)：69～71
[23] Yang Tiqiang, Liang Yunzhang, Dong Soufu. The experiment and physics analysis on drying vegetables in the electric field. The 3rd International Conference on Applied Electrostatics. Shanghai, 1997, 196～200
[24] S. Isobe, N. Barthkur, T. Yoshino, L. Okushima, S. Sase. Electrohydrodynamic Drying Characteristics of Agar Gel. Food Sci. Technol. Res .1999, 5(2): 132～136
[25] Li Lite, Li Xiuqu, K.Uemura, E.Tasumi. Electroosmotic Dewatering of Okara in Different Electric Fields. International Conference in Agricultural Engineering (99-ICAE) 12,14～17,1999,Beijing China Ⅳ58～63
[26] X. Xue, N. N. Barthakur, I. Alli. Electrohydrodynamiclly-dried Whey Protein: an Electrophoretic and Differential Calorimetric analysis. Drying Technology, 1999, 17(3): 467～478
[27] 梁运章．静电干燥技术的研究．第七届全国干燥会议论文集．1999，济南：343～348
[28] 那日，杨体强等．静电干燥特性的研究．内蒙古大学学报(自然科学版)1999，30(6)：699～705
[29] 梁运章，那日，白亚乡，李玉峰．静电干燥原理及应用．物理．2000，29(1)：39～41
[30] Lite Li, Fade Li, Eizo Tatsumi. Effect of High Voltage Electrostatic Field on Evaporation of Distilled Water and Okara Drying. Biosystem Studies, 2000, 3(1); 43～52
[31] T. R. Bajgai, F.Hashinaga. Drying of Spinach with a High Electric Field. Drying technology, 2001, 19(9): 2331～2341
[32] 李里特，李法德，辰巳英三．高压静电场对蒸馏水蒸发的影响．农业工程学报．2001，17(2)：12～15
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[2] Ashim K. Datta, P. Michael Davidson. Microwave and radio frequency processing. Journal of Food Science-Supplement. 2000, 65(8): 32～41
[3] Humberto Vega-Mercado, M. Marcela Góngor-Nieto, Gustavo V. Barbosa-Cáovas. Advances in Dehydration of Foods.Journal of Food Engineering, 2001, 49(4): 271～289
[4] 曹崇文．中国农业大学干燥技术研究进展．第七届全国干燥会议论文集．1999，济南，3
[5] Y. Asakawa. Promotion and retardation of heat transfer by electric fields. Nature, Vol. 261, May 1976: 220～221
[6] Yuonhong Chen, Nayana N. Barthakur, Neville P. Arnold. Electrohydrodynamic (EHD) Drying of Potato Slabs. Journal Food Engineering, 1994, 23:107～119
[7] Fumio Hashinaga, Ganga Prasa, Ryuichi Shintani. Effect of Ordinary Frequency High Electric Fields on Evaporation and Drying. Food Sci. Technoi., Int., 1995, 1(2): 77～81
[8] Fumio Hashinaga, T. R. Bajgai, S. Isobe, N. N. Barthakur. Electrohydrodynamic (EHD) Drying of Apple Slices. Drying Technology, 1999, 17(3): 479～495
[9] 梁运章，那日，白亚乡等．静电干燥原理及应用．物理．2000，29(1)：39～41
[10] 李里特，李法德，辰巳英三．高压静电场对蒸馏水蒸发的影响．农业工程学报，2001，(2)：12～15
[11] 陈家森，朱晓波，刘万红．一项在农业生产中有应用前景的技术——电晕放电技术．物理．1997，26(11)：671～674
[12] 孙目珍．电介质物理基础．广州：华南理工大学出版社，2003年3月第1版，158～160
[13] 李法德．食品物料通电加热及高压电场节能干燥的应用研究：[博士学位论文]．北京：中国农业大学，2002
[14] 李里特．食品物性学．北京：中国农业出版社，1998年2月第1版，404～407
[15] J A Cross. Electrostatically assisted heat transfer. In: Electrostatics (Ed. J. Lowell), Inst. Phys. Conf., Series 48,(1979): 191～199
[16] 徐学基，诸定昌．气体放电物理．1996，上海：复旦大学出版社，1996年8月第1版，20
[17] N. N. Barthakur. Electrohydrodynamic Enhancement of Evaporation from NaCl Solutions. Desalination, 1990, 78: 455～465
[18] H. R. Carlon, J. Latham. Enhanced Drying Rates of Wetted Materials in Electric Field. Journal of Atmospheric and terrestrial Physics, 1992, 54(2): 117～178
[19] Yuonhong Chen, Nayana N. Barthakur, Neville P. Arnold. Electrohydrodynamic(EHD) Drying of Potato Slabs. Journal Food Engineering, 1994, 23:107～119
[20] Fumio Ashinaga, Ganga Prasa, Ryuichi Shintani. Effect of Ordinary Frequency High Electric Fields on Evaporation and Drying. Food Sci. Technol., Int., 1995, 1(2): 77～81
[21] J.Seyed-Yagoobi,etal. Electrohydronamically Enhanced Heat Transfer in Pool Boiling. Journal of Heat Transfer. 1996,118(2): 233～237
[22] 董守绂，梁运章．电晕电场对物料干燥的试验．高电压技术．1996，22(2)：69～71
[23] Yang Tiqiang, Liang Yunzhang, Dong Soufu. The experiment and physics analysis on drying vegetables in the electric field. The 3rd International Conference on Applied Electrostatics. Shanghai, 1997, 196～200
[24] S. Isobe, N. Barthkur, T. Yoshino, L. Okushima, S. Sase. Electrohydrodynamic Drying Characteristics of Agar Gel. Food Sci. Technol. Res .1999, 5(2): 132～136
[25] Li Lite, Li Xiuqu, K.Uemura, E.Tasumi. Electroosmotic Dewatering of Okara in Different Electric Fields. International Conference in Agricultural Engineering (99-ICAE) 12,14～17,1999,Beijing China Ⅳ58～63
[26] X. Xue, N. N. Barthakur, I. Alli. Electrohydrodynamiclly-dried Whey Protein: an Electrophoretic and Differential Calorimetric analysis. Drying Technology, 1999, 17(3): 467～478
[27] 梁运章．静电干燥技术的研究．第七届全国干燥会议论文集．1999，济南：343～348
[28] 那日，杨体强等．静电干燥特性的研究．内蒙古大学学报(自然科学版)1999，30(6)：699～705
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