Parameters optimization of the parallel and series mode ultrasonic atomizer on the ammonia-water absorption system

The application of the ammonia-water absorption refrigeration systems is limited by the absorption effect of the absorber. Installing atomizer at the absorber can significantly enlarge the liquid-vapor contact area. In this paper, we develop a mathematical model of system energy consumption coupled to absorption process, in which the effect of the atomizer on the mass and heat transfer is taken into account. The effect of the droplet parameters on the absorption effect and the energy efficiency of the system are discussed separately for the parallel and series installing strategies. Although the size reduction can improve the absorption effect, the increment of ammonia absorbed rate changes insignificantly with a smaller diameter of droplets. For each droplet diameter, a larger atomization ratio for the series model implies better absorption, but there is an optimal atomization ratio for the parallel model to reach the maximum ammonia absorbed rate, and the relationship between the droplets diameter and atomization ratio is also introduced. Meanwhile, the primary energy efficiency is used as an evaluation metric, then the droplets parameters in parallel and series modes are optimized by taking into account the energy input of the atomizer. The optimal parameter combination of parallel model is droplets diameter of 12.4 mu m and atomization ratio of 0.823. At this time, the atomizer power is 0.51 W, and the system PEE is increased by 35.99 %. Whereas, the optimal atomizer power is a function of the droplet size in the series mode. As the droplets diameter of 0-100 mu m, the optimal atomizer power decreased and the maximum value of the PEE increased with the droplet diameter.