颗粒分布对吸附热变换器内传热传质的影响

采用直接接触法提高吸附热变换器内的传热传质速率，回收热水直接生成过热蒸汽。对蒸汽生成过程进行数值建模，耦合质量、能量和动量方程。气液固的三相计算被合理简化成两个由一个移动水-气界面连接的两相区域计算。模拟研究填充床内的沸石颗粒分布如松散-密集型和密集-松散型对蒸汽生成的影响。两种填充床生成蒸汽的总质量相同。密集-松散型生成蒸汽的时间短，但生成速率快。密集-松散型生成蒸汽与入水的时间比值为58.8%，生成的蒸汽均保持在峰值，最高温度达249℃，系统整体温升达139℃，而松散-密集型生成的蒸汽仅有1/3保持在峰值。密集-松散型出口处与水-气液面产生蒸汽的质量比值大，表明该床层的颗粒分布更有利于蒸汽的快速通过。

Effect of particle distribution on heat and mass transfer inside adsorption heat transformer

Adsorption heat transformer with zeolite-water working pair has been proposed to directly generate high-temperature superheated steam from unsaturated hot water. A concept of direct-contact method between adsorbent and working fluid is adopted in order to enhance heat transfer inside the packed bed with porous adsorbent. Steam generation process is modeled to investigate dynamic behavior by combining mass, heat and momentum governing equations. Three-phase calculations of zeolite, water and gas are performed in zeolite-water and zeolite-gas regions connected by a moving water-gas interface. Two typical packed bed with different particle distributions are presented for numerical discussions:fine-coarse bed (F-C bed) and coarse-fine bed (C-F bed). Overall mass of generated steam are the same for the two kinds of beds. In F-C bed steam generation rate is faster but generation time is shorter. Time ratio of steam generation to water input is 58.8% in F-C bed. Superheated steam at 249℃ with gross temperature lift of 139℃ is achieved for both beds. All of the steam is generated at the maximum value for F-C bed, while only one-third of that could be obtained at the peak for C-F bed. Mass ratio of generated steam from the outlet to the moving water-gas interface is larger for F-C bed. It's thus concluded F-C bed is more effective for steam generation with a considerable temperature lift.