Research on Intelligent Defrost Control Based on Parallel Plate Capacitor Principle

A novel intelligent defrosting control strategy based on the parallel-plate capacitor principle was investigated to address the issue of the "erroneous defrosting" of an evaporator. A mathematical model of a parallel-plate capacitor was established in the process of frosting and defrosting of the evaporator, and a theoretical analysis of the effects of the air/frost/water intermediate medium proportions on the capacitance value was conducted. The capacitance value showed a gradual linear growth during the frosting process, whereas it first rose and then fell during the defrosting process. This study considered a cold storage evaporator as the research object and constructed a capacitance defrosting control system. The experimental results were consistent with the theoretical analysis results for the capacitance variation trend. The results showed that 32.0 pF and 19.0 pF could be used as the start and stop points for intelligent defrosting control, respectively. The fluctuation range for the central temperature in the cold storage was reduced by 12.0 ℃. The defrosting cycle time was shortened by approximately 4 min. The defrosting efficiency increased by approximately 22%. The defrosting power consumption was reduced by 36.74%, and the total power consumption of the refrigeration system was reduced by 19.8%.