Numerical analysis of heat and mass transfer in ammonia distillation process enhanced with ultrasonic atomization technology

Energy-efficient and environmentally economic ammonia absorption refrigeration systems (AARS) are driven by low-grade energy, but efficiency and equipment volume are constrained by the low performance of the ammonia distillation process. According to the ultrasonic-assisted application, the ultrasonic atomization is widely applied in absorption, dehumidification, desiccation process. In this study, ultrasonic atomization technology is employed in the ammonia rectification process of AARS. This rectification model has been conducted with EES program and solved by Visual Basic programs. The enhancement factor gamma and average volumetric mass transfer coefficient KLaave v are analyzed in ammonia rectification process. Moreover, the effects of inlet solution mass fraction, cooling water temperatures, ultrasonic atomization droplets diameters and droplets quantities were investigated. The results compared with packed column, enhance the purity of ammonia by 0.39 & pertenk; because v is increased by 4.22 % to 58.5 %. The effective heat and mass transfer area are 146.79 m2/m3 to 239.14 m2/m3 leading to a 4.05 % to 36.9 % volumetric reduction. Low cooling water temperatures, high reflux ratios, smaller droplet sizes and higher droplet quantities allow for improved mass enhancement.While avoiding the occurrence of liquid flooding, the smaller ammonia droplets sizes are also limited by the atomizer frequency. Additionally, ultrasonic atomization decreases the solution concentration at the distillation column outlet, enhancing the coefficient of performance (COP) of the absorption refrigeration system (AARS) by up to 3.52 %. In conclusion, the ultrasonic atomization technology employed in ammonia distillation is presented, which improves the mass and heat transfer, fills the gap of distillation process enhanced by ultrasound and reduces the manufacturing column volume.