Ohmic Heating And Simulation Of Solid-liquid Mixtures

With the development of computer technology and numerical calculation technology, finite element analysis has been an effective method to solve complex problem of physical fields. The temperature distribution in materials during ohmic heating can be learned directly by the simulation and analysis of numerical model which also saves much testing time and cost. Therefore, it is significant to study the solid and liquid-state admixture numerical simulation for the better development of ohmic heating.Two parts were included in this paper. The first part, regarding pork ribs as the research object, discussed the effect of pork ribs direction and solution concentration on solid and liquid-state admixture's heating rate and electric conductivity. The other was establishing solid and liquid-state admixture's three-dimensional finite element model and getting some numerical simulation results such as the transient temperature field using ANSYS, then verifying the results through experiments.1. The influence of the concentration of NaCl solution to pork ribs'heating rate by no-direct-contact heating test setup was explored. The results showed that the critical concentration of NaCl was 0.03 mol/L. The sample's average heating rate was faster than solution's when the concentration was under 0.03 mol/L and the phenomenon was impossible to conventional heating. The results also showed that the average heating rate of sample's different parts was unequal and the muscle's was the fastest while the bone marrow's was the slowest. When the concentration was 0.05 mol/L, the heating rate of sample's other parts in addition to muscle were slower than the solution's and the slowest part was the center of central bone marrow.2. The effect of pork rids'axial to heating rate by no-direct-contact heating test setup was studied. The results showed that the heating rate when the sample's axis was parallel to the electrical field was higher than the rate when the axis was vertical to the electrical field in the concentration of 0.01mol/L but the law was not clear in other concentrations.3. The influence of the pork rids'axial and solution concentration to solid and liquid-state admixture's electrical conductivity by no-direct-contact heating test setup was researched. The results showed that the relationship between the electrical conductivity of solid and liquid-state admixture and the temperature was linear.4. The conductivity of pork tenderloin and NaCl solution was measured by the contact ohmic heating setup and the no-direct-contact heating test setup. The results showed that the pork tenderloin's conductivity was almost the same to the conductivity of NaCl solution whose concentration was 0.07mol/L.5. The conditions and control equations of the pork tenderloin and NaCl solution were established. The pork tenderloin's temperature, current density, potential contours in different NaCl solution of 0.05 mol/L, 0.07 mol/L, 0.09 mol/L were simulated by ANSYS. The results showed that, when the solution concentration was 0.05 mol/L, the sample's conductivity was higher than the solution's and the cold spot was in the solution which was just above the sample axis's center and the highest point of heating rate was in the two sides closing to the plate of the sample. The sample's conductivity was lower than the solution's and the cold spot was in the two sides closing to the plate of the sample and the highest point of the heating rate was in the solution which was just above the sample axis's center when the solution concentration was 0.09 mol/L. The mixture of the sample and solution was heated uniformly and there was no cold plot and hot plot and the sample axial had little influence to the heating rate when the solution concentration was 0.07 mol/L. The heating effect was best when the sample's fiber direction was parallel to the electrical field and solution concentration was 0.07 mol/L.6. The mathematical models of pork tenderloin with lipid and NaCl solution in 0.07 mol/L were established and the heating process of solid and liquid-state admixture was simulated by ANSYS. The results showed that lipid had remarkable effect to the pork tenderloin and solution heating. There was great temperature difference in mixture and the lipid damaged the ohmic heating uniformity.7. The simulation result was verified by the experiment using the no-direct-contact heating test setup. The results showed that the temperature distribution and heating law of solid and liquid-state admixture could be predicted accurately by finite element analysis.