| Ohmic heating of food material is a rising technique in food engineering. Food material is considered as conductor and the heat is produced in term of the Joule Rule. Ohmic heating technique research began relatively early in abroad, and continuous ohmic heating apparatus are being used successfully in USA, UK, and Japan. Up to now, the research of ohmic heating technique in our country is a beginning state, and there are no ohmic heating devices introduced. In order to reduce the gap in this field, it is urgent to develop an ohmic heating device with self intelligent property right. The electrical conductivity of foods is one of the main factors which determine the heat in ohmic heating, so most of the research on ohmic heating is focus on electrical conductivity. At present, the key factor that influences the practicality of ohmic heating is the heating rate and the electrode fouling. The main purpose of this article is to research the temperature distribution and electrode fouling in continuous ohmic heating.Based on theories of Physics, Physical Properties of Foods, Electrics, Fluid Mechanicals, Heat Transfer, Physical Chemistry, Engineering Material, etc., two research task are developed, one is to design and manufactured an ohmic heating system for liquid foods; the other is to research temperature field and electrical conductivity of tap water and soybean milk during continuous ohmic heating. The main content is as follows.1. A knock-down continuous ohmic heating system for liquid foods is designed and manufactured, using this system, the temperature of food material and electrode surface was researched. The results showed that this system could heat tap water and soybean milk rapidly in subsection. The heating process was stable and the operation run well.2. The average temperature of tap water and soybean milk in each heating room was researched. The results showed that the whole heating processes can be divided into three phases. In the first heating stage, the food temperature risen quickly, and the average temperature with heating time was exponential; During the second heating stage, the temperature risen slowly, the average temperature with heating time is logarithmic; In the last heating phase, the temperature kept constant, and the temperature with the heating length is linear. The heating rate becoming decrescent because of the different electrical field, and the heating rate of soybean milk was higher than the tap water because of the electric conductivity.3. The temperature of electrode surface during continuous ohmic heating process was measured. In the beginning heating stage, the temperature in surface center and 1/2R on the same electrode is similar, and no"over heating"phenomenon appeared; But"over heating"appeared on electrode when the temperature arrived at stable state, and the"over heating"of soybean is serious than tap water. The"over heating"mitigated when make use of electrode drilled with cross whole.4. The calculate method for electrical conductivity and simulate circuit model for liquid foods with load Y connection was suggested. Electrical conductivity of soybean an tap water was calculated according to measured data, the result showed that electrical conductivity with temperature was linear, and the electrical conductivity of soybean milk is bigger than tap water.5. Compared with"18-8"stainless steel, the erosion of stainless filled with titanium was more severe and polluted foods material very serious;"18-8"stainless steel can be used in continuous ohmic heating apparatus because it can bear erosion preferable.6. Attach phenomenon on electrode appeared during experiment with soybean milk. The attach phenomenon has relationship to surface roughness of electrode. Attach phenomenon is more severe when the surface roughness is big. And because there were some manufacture and fixing error, and soybean attach phenomenon on electrode, the three-phase load was not balance.7. Some proposals for further study were suggested finally.
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