Effect of ultrasonic oscillation combined with atomization on enhancing ammonia-water falling film process and performance of absorption refrigeration system

Abstract

The ammonia-water absorption refrigeration system (AARS) can utilize low-grade heat sources to drive the generation of high-grade energy. The enhancement of the coupled heat and mass transfer is the key to improving the system performance, thereby reducing energy consumption and the size of components. High-frequency ultrasonic waves can generate fine droplets, increasing the mass transfer area of gas-liquid contact. Medium and low-frequency ultrasonic oscillations can enhance the disturbance and heat and mass transfer within the falling film solution, increasing the driving potential for mass transfer, and thus realizing the improvement of the system performance. Therefore, a thermodynamic mathematical model of the system was established, and the reliability of the model was verified through a constructed experimental system. The coefficient of performance (COP) and exergy efficiency (COE) were used to describe the system energy consumption and irreversible losses. The size reduction rate was used to measure the reduction of the system size, and economic evaluation indicators were used to assess the investment and operating costs of the system operation. The results show that the installation of atomizers and oscillators has a positive impact on the system performance, making the system more compact and efficient. The COP can be improved by up to 37.12 %, the irreversible losses can be reduced by up to 43.82 %, the size of the main components can be reduced by up to 39.5 %, and the annual operating cost can be reduced by up to 30.85 %, providing a strong basis for the practical application of ultrasonic waves in AARS.