Falling-film absorption ammonia-water magnetic field

Abstract

Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.

Absorption refrigeration systems, despite having numerous advantages, are generally characterized by low Coefficient of Performance (COP). Absorption enhancement has been considered an effective way of improving the COP of the refrigeration systems, and magnetic enhancement is one of these. The literature is sparse on the use of magnetic field for the enhancement of absorption refrigeration systems. A numerical model of magnetic field enhancement in ammonia- water absorption systems is presented in this paper. The flow within the film thickness to the absorber wall was considered as two-dimensional steady laminar flow. A finite difference model was developed based on the conservation of mass, momentum, energy equations and mass transport relationship. Macroscopic magnetic field force was introduced in the model equations. The model was validated using data obtained from the literature on ammonia solution. Changes in the physical properties of ammonia solution while absorbing, both in the direction of falling film and across its thickness, were investigated. The distribution of the physical properties of ammonia solution within the film-thickness was not significantly different (p<0.05) from results in the literature. The magnetic field was found to have positive effect on the ammonia-water falling film absorption to some degree. When magnetic induction intensity at the solution’s inlet was 1.4 and 3Tesla (T), the increments in concentration of ammonia solution at outlet was 0.004 and 0.01, respectively. Relative to 0.0 Tesla, the COP of simple ammonia solution absorption refrigeration system increased by 1.9% and 3.6% for magnetic induction of 1.4 and 3.0 Tesla respectively. A numerical model for the magnetic field enhancement of the ammonia absorption system was developed. Absorption performance enhancement increased with magnetic intensity in ammonia solution.