翅片管式蒸发器超声波除霜理论与技术研究
Ultrasonic Defrosting Theory and Technology for Finned？？Tube Evaporator

针对传统逆除霜技术能耗高、热舒适度差的问题,研究应用于翅片管式蒸发器的超声波除霜新技术。结合MATLAB数值求解方法与有限元压电结构耦合仿真方法,分析蒸发器结构中的频散曲线,确定蒸发器结构中的超声导波类型、模态及导波传播特性,并将超声频散曲线分析结果与有限元仿真结果进行对比。研究结果表明,在激励频率小于250 kHz时,蒸发器翅片上存在Lamb波的A0和S0模态以及SH波的SH0模态,Lamb波在翅片与霜层界面处激发破碎应力,SH波激发剪切应力;翅片上振动以Lamb波的S0模态为主,铜管上可以清楚看到对称的纵向模态,有限元仿真结果与频散曲线分析结果完全吻合;超声除霜试验与能耗分析结果表明,超声除霜能耗不到传统逆除霜能耗的1/22,除霜效率至少提高了7倍,是一种高效、低能耗的翅管式换热器除霜新技术。
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