Ohmic Heating Experiments And Simulation’s Preliminary Study Of Soybean Milk

Heating of food materials which directly relates to the final quality of products, energyconsuming during processing and production cost, is an important operation in foodprocessing. Ohmic heating of food materials is a new technology in food engineering. Inohmic heating process, foods serve as a part of an electric circuit through which alternatingcurrent flows, causing heat to be generated within the foods due to the electrical resistance ofthe foods. Ohmic heating technique research began relatively early in abroad, and continuousohmic heating apparatus are being used successfully in USA, UK, and Japan. Up to now, theresearch of ohmic heating technique in our country is a beginning state, and there are noohmic heating devices introduced. With the development of computer technology andnumerical calculation technology, finite element analysis has been an effective method tosolve complex problem of physical fields. The temperature distribution in materials duringohmic heating can be learned directly by the simulation and analysis of numerical modelwhich also saves much testing time and cost. Therefore, it is significant to study theapplication of numerical simulation in continuous ohmic heating for the better development ofohmic heating.Two aspects are studied in this paper. The first, using the small detachable continuousohmic heating device and static ohmic heating device,regarding soybean milk as the researchobject, is to study the effects of voltage on different conditions. The second is to simulate theohmic heating process of soy milk with finite element analysis software.1）The continuous ohmic heating system of liquid food had been designed, the soybeanmilk was heated by the continuous ohmic heating system. The results showed that the soybeanmilk was evenly and quickly heated, the voltage sensor, current sensor and data acquisitiondevice with T thermocouple acquire voltage, current and temperature signal in the process ofohmic heating. The continuous ohmic heating system worked perfectly in the heating process,was removed and cleaned conveniently after the experiment is complete. 2）The rule of the conductivity with temperature in the same heating meaning, highfrequency and different electric field intensity in the process of ohmic heating was researchedwith the ohmic heating system of liquid food, which was connected to the heating room ofstatic ohmic heating. The results showed that the soybean milk conductivity increased withthe electric field intensity in the high frequency.3）The influence of power waveform and electric field intensity on the soybean milkohmic heating was researched in low frequency. The result shows that soybean conductivityin the same power waveform was same; the sine wave conductivity was greater than thebipolar square wave in the same electric field intensity, in addition, the temperature rise speedof sine wave was higher than that of bipolar square wave in the same electric field intensityand position.4）The finite element method was applied in ohmic heating process, the numericalsimulation of soybean milk static ohmic heating compared to the experimental value to verifythe numerical simulation of the results. The results showed that the finite element methodcould accurately predict the heating rule in the process of the soybean milk static ohmicheating.5）The velocity field of soybean milk in the heating room of the continuous ohmicheating was numerically simulated, the soybean milk flowing regime in the heating room wasvisually displayed in the result of numerical simulation. The soybean milk flowing regime inthe different shape heating room was numerically simulated, so that the heating chambershape, which the study needed, was gotten, thus the manpower and material resources waseffectively saved and the cycle of experiment or ohmic heating equipment development wasconsumedly shorten.