静电场中极板表面液膜蒸发特性研究
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摘要
以静电场中水分子的极化和受力特性为基础,对热干烟气中极板表面液膜内水分子输运过程进行分析。考察了电场特征、液膜物性对静态高压电场中液膜蒸发特性的影响并提出了蒸发模型;同时研究了多场(温度、速度和静电)耦合作用下液膜蒸发过程中的主导作用机制。结果表明:离子风为静态高压电场中液膜蒸发的主要动力,蒸发速率是自然蒸发的6.7倍(25 kV)。液膜蒸发为等速过程,蒸发速率与电场强度呈正相关关系;液膜加入溶质,蒸发过程受抑制,蒸发模型变为等速和降速两个过程,最终液膜表面析出溶质;流场耦合静电场作用下,液膜蒸发速率随电压升高先缓慢上升(U<20 kV)后快速上升(U>20 kV),流速和电压分别是这两阶段的主要影响因素;温度场耦合静电场作用下,蒸发速率大于单场叠加数值。研究结果为热干烟气中极板表面稳定成膜、系统水耗及空间电场中温湿度分布等问题的研究提供理论支撑。
Based on the polarization and force characteristics of water molecules in the electrostatic field, the transport process of water molecules in the liquid film on the surface of the plate in hot dry flue gas is analyzed.Besides, the effect of electrical field parameters on the evaporation characteristics and the dominant influence factors in the evaporation process under multi-field coupling effect(temperature, velocity and electrical field) were all studied. Eventually an evaporation model was proposed. The results showed that the ion wind is the main power source in the process of water film evaporation and the electric evaporation rate is 6.7 higher than the natural evaporation rate(25 kV). Water film evaporated at a constant rate and there was a positive relationship between evaporation rate and electrical field intensity. Evaporation process can be inhibited by the dissolved solute in the water film and the process was divided into two periods: constant rate period and falling rate period. The solute precipitated firstly on the water film surface. Under the coupling effect of velocity and electrical field, the evaporation rate increases slowly(U<20 kV) and then increases rapidly(U>20 kV) with increasing the voltage,velocity and voltage is the main influence factor in this two processes respectively. Under the coupling effect of temperature and electrical field, the evaporation rate is higher than the superposition of these two single fields. All these results can provide a theoretic support for the water film forming and consumption, humidity distribution in the unsaturated flue gas.
Based on the polarization and force characteristics of water molecules in the electrostatic field, the transport process of water molecules in the liquid film on the surface of the plate in hot dry flue gas is analyzed.Besides, the effect of electrical field parameters on the evaporation characteristics and the dominant influence factors in the evaporation process under multi-field coupling effect(temperature, velocity and electrical field) were all studied. Eventually an evaporation model was proposed. The results showed that the ion wind is the main power source in the process of water film evaporation and the electric evaporation rate is 6.7 higher than the natural evaporation rate(25 kV). Water film evaporated at a constant rate and there was a positive relationship between evaporation rate and electrical field intensity. Evaporation process can be inhibited by the dissolved solute in the water film and the process was divided into two periods: constant rate period and falling rate period. The solute precipitated firstly on the water film surface. Under the coupling effect of velocity and electrical field, the evaporation rate increases slowly(U<20 kV) and then increases rapidly(U>20 kV) with increasing the voltage,velocity and voltage is the main influence factor in this two processes respectively. Under the coupling effect of temperature and electrical field, the evaporation rate is higher than the superposition of these two single fields. All these results can provide a theoretic support for the water film forming and consumption, humidity distribution in the unsaturated flue gas.
引文
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[19]王翔,常景彩,徐纯燕,等.线-板式静电除尘器芒刺电晕线放电特性[J].高电压技术,2017,43(2):533-540.Wang X,Chang J C,Xu C Y.Discharge characteristic research for barbed electrodes in wire-plate electrostatic precipitator[J].High Voltage Engineering,2017,43(2):533-540.
[20]Ieta A C,Kucerovsky Z,Greason W D.Current density modeling of a linear pin-plane array corona discharge[J].Journal of Electrostatics,2008,66(11):589-593.
[21]Long Z,Yao Q,Song Q.Three-dimensional simulation of electric field and space charge in the advanced hybrid particulate collector[J].Journal of Electrostatics,2009,67(6):835-843.
[22]Kudra T,Martyneko A.Energy aspects in electrohydrodynamic drying[J].Drying Technology,2015,33(13):1534-1540.
[23]Hashinaga F,Kharel G,Shintani R.Effect of ordinary frequency high electric fields on evaporation and drying[J].Food Science and Technology International,Tokyo,1995,1(2):77-81.
[24]Blanchard D,Atten P,Dumitran L M.Correlation between current density and layer structure for fine particle deposition in a laboratory electrostatic precipitator[J].IEEE Transactions on Industry Applications,2002,38(3):832-839.
[25]Jaworek A,Krupa A,Czech T.Modern electrostatic devices and methods for exhaust gas cleaning:a brief review[J].Journal of Electrostatics,2007,65(3):133-155.
[26]Barthakur N N.Electro-hydrodynamic enhancement of evaporation from NaCl solutions[J].Desalination,1990,78(3):455-465.
[27]Farnoosh N,Adamiak K,Castle G S P.Three-dimensional analysis of electro-hydrodynamic flow in a spiked electrode-plate electrostatic precipitator[J].Journal of Electrostatics,2011,69(5):419-428.
[28]Lai F C,Sharma R K.EHD-enhanced drying with multiple needle electrode[J].Journal of Electrostatics,2005,63(3/4):223-237.
[29]Mantach S,Adamiak K.A double-vortex EHD flow pattern generated by negative corona discharge in point-plane geometry[J].Journal of Electrostatics,2018,93:118-124.
[30]Dong M,Zhou F,Zhang Y,et al.Numerical study on fine-particle charging and transport behaviour in electrostatic precipitators[J].Powder Technology,2018,330:210-218.
[2]常景彩,王翔,王鹏,等.纤维水膜极板表面颗粒沉积脱落特性[J].化工学报,2018,69(10):4302-4310.Chang J C,Wang X,Wang P,et al.Deposition and exfoliation characteristics of collected particles on wet fabrics collector[J].CIESC Journal,2018,69(10):4302-4310.
[3]龚秀娟.物料干燥系统热湿传递及其交叉作用的热力学分析[D].兰州:兰州理工大学,2017.Gong X J.Thermodynamic analysis of heat and moisture transfer and crossing of material drying system[D].Lanzhou:Lanzhou University of Technology,2017.
[4]Saadi S N,Zhai Z J.Modeling phase change materials embedded in building enclosure:a review[J].Renewable and Sustainable Energy Reviews,2013,21:659-673.
[5]Mandal S,Song G.Thermal sensors for performance evaluation of protective clothing against heat and fire:a review[J].Textile Research Journal,2015,85(1):101-112.
[6]Asakawa Y.Promotion and retardation of heat transfer by electric fields[J].Nature,1976,261(5557):220-221.
[7]李里特,李法德.高压静电场对蒸馏水蒸发的影响[J].农业工程学报,2001,17(2):12-15.Li L T,Li F D.Effect of high voltage electrostatic filed on evaporation of distilled water[J].Transactions of the Chinese Society of Agricultural Engineering,2001,17(2):12-15.
[8]季旭,冷从斌,李海丽.高压电场下玉米的干燥特性[J].农业工程学报,2015,31(8):264-271.Ji X,Leng C B,Li H L.Drying characteristics of corn in high voltage electric field[J].Transactions of the Chinese Society of Agricultural Engineering,2015,31(8):264-271.
[9]Cao W,Nishiyama Y,Koide S.Electro-hydrodynamic drying characteristics of wheat using high voltage electrostatic field[J].Journal of Food Engineering,2004,62(3):209-213.
[10]Lai F C,Lai K W.EHD-enhanced drying with wire electrode[J].Drying Technology,2002,20(7):1393-1405.
[11]那日,杨体强.静电干燥特性的研究[J].内蒙古大学学报:自然科学版,1999,30(6):699-705.Na R,Yang T Q.Study of the characteristics of electrostatics drying[J].Acta Scientiarum Naturalium Universitatis NeiMongol,1999,30(6):699-705.
[12]Tada Y,Takimoto A,Hayashi Y.A review on heat transfer enhancement in a convective field by applying ionic wind[J].Journal of Enhanced Heat Transfer,2017,24(1-6):517-532.
[13]Singh A,Orsat V,Raghavan V.A comprehensive review on electro-hydrodynamic drying and high-voltage electric field in the context of food and bio-processing[J].Drying Technology,2012,30(16):1812-1820.
[14]Martynenko A,Kudra T.Electrically-induced transport phenomena in EHD drying-a review[J].Trends in Food Science&Technology,2016,54:63-73.
[15]梁运章,丁昌江.高压电场干燥技术原理的电流体动力学分析[J].北京理工大学学报,2005,(25):16-19Liang Y Z,Ding C J.EHD analysis of the high voltage electric field drying technology's principle[J].Transactions of Beijing Institute Technology,2005,(25):16-19.
[16]孙剑锋.高压静电场在水分蒸发和物料干燥方面的应用研究[D].北京:中国农业大学,2004Sun J F.Application of high voltage electrostatic fields on water evaporation and material drying[D].Beijing:China Agricultural University,2004.
[17]Taghian S,Havet M,Hamdami N.Drying of mushroom slices using hot air combined with an electro-hydrodynamic(EHD)drying system[J].Drying Technology,2014,32(5):597-605.
[18]丁昌江.电场对生物物料中水分子输运特性的实验及机理研究[D].呼和浩特:内蒙古大学,2004.Ding C J.The experiment and mechanism study of transport character of water molecule on electric field in bio-mateials[D].Huhhot:Inner Mongolia University,2004.
[19]王翔,常景彩,徐纯燕,等.线-板式静电除尘器芒刺电晕线放电特性[J].高电压技术,2017,43(2):533-540.Wang X,Chang J C,Xu C Y.Discharge characteristic research for barbed electrodes in wire-plate electrostatic precipitator[J].High Voltage Engineering,2017,43(2):533-540.
[20]Ieta A C,Kucerovsky Z,Greason W D.Current density modeling of a linear pin-plane array corona discharge[J].Journal of Electrostatics,2008,66(11):589-593.
[21]Long Z,Yao Q,Song Q.Three-dimensional simulation of electric field and space charge in the advanced hybrid particulate collector[J].Journal of Electrostatics,2009,67(6):835-843.
[22]Kudra T,Martyneko A.Energy aspects in electrohydrodynamic drying[J].Drying Technology,2015,33(13):1534-1540.
[23]Hashinaga F,Kharel G,Shintani R.Effect of ordinary frequency high electric fields on evaporation and drying[J].Food Science and Technology International,Tokyo,1995,1(2):77-81.
[24]Blanchard D,Atten P,Dumitran L M.Correlation between current density and layer structure for fine particle deposition in a laboratory electrostatic precipitator[J].IEEE Transactions on Industry Applications,2002,38(3):832-839.
[25]Jaworek A,Krupa A,Czech T.Modern electrostatic devices and methods for exhaust gas cleaning:a brief review[J].Journal of Electrostatics,2007,65(3):133-155.
[26]Barthakur N N.Electro-hydrodynamic enhancement of evaporation from NaCl solutions[J].Desalination,1990,78(3):455-465.
[27]Farnoosh N,Adamiak K,Castle G S P.Three-dimensional analysis of electro-hydrodynamic flow in a spiked electrode-plate electrostatic precipitator[J].Journal of Electrostatics,2011,69(5):419-428.
[28]Lai F C,Sharma R K.EHD-enhanced drying with multiple needle electrode[J].Journal of Electrostatics,2005,63(3/4):223-237.
[29]Mantach S,Adamiak K.A double-vortex EHD flow pattern generated by negative corona discharge in point-plane geometry[J].Journal of Electrostatics,2018,93:118-124.
[30]Dong M,Zhou F,Zhang Y,et al.Numerical study on fine-particle charging and transport behaviour in electrostatic precipitators[J].Powder Technology,2018,330:210-218.
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