Experimental study on the enhancement effect of ultrasonic oscillation on an ammonia-water falling film absorber

Ultrasound is widely used to enhance heat and mass transfer, while its impact on absorbers remains largely unexplored. To relieve the challenges posed by the large size and low performance of absorption refrigerators, a novel falling film absorber featuring direct ultrasonic action on solutions is proposed. A test platform was established to investigate the influence of ultrasonic oscillations on ammonia absorption. The results show that the absorption effects of the solution increased with the escalation of the ultrasonic power (UP) while the increase rate decreased. Given the inlet solution mass fraction of 0.3 and absorption pressure of 0.3 MPa, ammonia absorbed rate (ma,abs) and mass transfer coefficient (k) were increased by 17.07 % and 17.43, respectively, when UP was raised from 0 W to 50 W. When UP was increased from 50 W to 100 W, ma,abs and k were increased by 4.17 % and 10.6 %, respectively. The highest increase of the ma,abs per unit power was achieved when UP is 25 W. Overall, these findings provide data support for the design of absorption refrigerators integrated with the ultrasonic oscillator, contributing to the miniaturization and promotion of absorption refrigeration equipment.