Application Of High Voltage Electrostatic Fields On Water Evaporation And Material Drying

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. At60℃ 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.