Ultrasonic defrosting theory and technology for finned-tube evaporator

Aiming at the high energy consumption, low thermal comfort of traditional reverse cycle defrosting technology, a new ultrasonic defrosting technology for finned-tube evaporator, is investigated. Combining the MATLAB numerical method with the finite element analysis method of piezoelectric-structure coupling simulation, the dispersion curve in the evaporator structure is analyzed and the type, mode and transmission characteristics of ultrasonic wave in the evaporator structure are determined. The ultrasonic frequency dispersion curve analysis results and finite element simulation results are compared. It is found that the A0 and S0 mode of Lamb wave and SH0 mode of SH wave exist in the fin when the excitation is less than 250 kHz, and the crushing stress and the shear stress at the interface between fin and frost layer are excited by Lamb wave and SH wave, respectively. The vibration mode in the fin is primarily the S0 mode of Lamb wave, the symmetrical longitudinal mode obviously appears in the tube, and the finite element simulation results coincide well with the calculation results of ultrasonic dispersion curve. The ultrasonic defrosting experiments and energy consumption analysis indicates that the ultrasonic defrosting energy consumption is less than 1/22 of the traditional reverse cycle defrosting and the defrosting efficiency is improved more than 7 times.