Ammonia-water absorption refrigeration system has much more superiority in environmental protection and energy saving. However the coefficient of performance (COP) of ammonia-water absorption refrigeration system is relatively low. Absorption enhancement is an effective way to improve COP of ammonia-water absorption refrigeration system. In this study, Magnetic field was employed in the falling film absorption outside vertical tube with ammonia-water. Firstly, the mathematical model of ammonia-water falling film absorption in magnetic field has been built up. Magnetic field force was introduced to the mathematical model. In the process of modeling, the variation of falling film thickness, the variation of physical characteristics of ammonia-water and the convection in the direction of the film thickness were considered. The distribution of temperature, velocity and concentration in falling film were acquired through numerical derivation. Then, the micro mechanism of effect on ammonia-water solution and its absorption was analyzed. The numerical results show that the velocity along falling, the thickness and the concentration of falling film all increased in magnetic field. The micro mechanism analysis show that external magnetic field will increase the activity of solution. External magnetic field has positive effect on the falling absorption of ammonia-water.
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