纳米颗粒强化氨水鼓泡吸收性能的机理与影响因素

摘要

基于Danckwerts的界面更新模型和Langevin方程,分析了纳米颗粒对氨水鼓泡吸收性能影响的非均相膜传递和液相内传递过程,初步解释了纳米颗粒强化氨水鼓泡吸收性能的机理.认为纳米颗粒对氨水鼓泡吸收的强化过程包括液相强化和界面强化两个同时进行的子过程,而对于界面传递,由于纳米颗粒引起的Marangoni对流,使其强化系数要高于液相传递.结合机理,对可能影响纳米颗粒强化氨水鼓泡吸收性能的各因子进行了实验研究.结果表明:纳米颗粒悬浮液性能的稳定性是强化吸收的关键;以质量浓度为0.1% 配比制备的FeO、Al2O3纳米颗粒悬浮液,分别获得了较好的强化吸收效果;0.1%FeO+0.1%CTAB的强化吸收效果没有0.1%FeO +0.1%ACT明显;基液氨水浓度越大,有效吸收率越大;氨气流量变化,对有效吸收率影响呈现不规律特征;溶液温度较高时,纳米颗粒强化吸收效果比较明显;吸收器内起始压力或入口氨气压力不同,会对整个吸收过程产生很大影响.本研究为纳米颗粒对气体在固液悬浮体系中传递影响研究以及氨水吸收式制冷机鼓泡吸收器小型化研制提供参考.%Based on the Danckwerts interface refresh matrix and Langevin equation, the influences of nanoparticles on the heterogeneous phase film transfer process and liquid phase transfer process of ammonia bubble absorption were analyzed preliminarily, which can explain the mechanism of nanoparticles enhancing ammonia bubble absorption performance reasonably. According to the analysis, it was found that the process of nanoparticles enhancing bubble absorption performance includes two sub-processes of liquid phase transfer enhancement and interface transfer enhancement. Since the nanoparticles induce the interface Marangoni convection, the enhancing coefficient of interface transfer is higher than that of liquid phase transfer. According to the enhancement mechanism, the experimental studies of the possible factors influencing on the nanoparticles enhancing ammonia bubble absorption performance were conducted. The results show that the stability of the nanofluid is one of the key factors for the enhancement of the absorption process, and using nanofluid with FeO or Al2O3 nanoparticles of 0.1％ (mass fraction) individually can have better enhancing absorption effect. The enhancing effect of nanofluid with nanoparticles of 0.1％FeO+0.1％ CTAB is less than that of nanofluid with nanoparticles of 0.1％FeO+0.1％ACT. The effective absorption ratio increases with the increase of the concentration of the base ammonia solution; and keeping other conditions unchanged, the absorption ratio increases with increasing ammonia gas flow, but the changes of effective absorption ratio show ruleless. The enhancing effect also increases with the increase of solution temperature, and the difference of the inlet NH3 pressure or initial pressure in the absorber has great influence on the whole absorption process too. This paper provides a reference for subsequent research on mechanism of nanoparticles influencing the transfer process of gas in solid-liquid suspending system, and also for the mini-type absorber design of ammonia absorption refrigerator.