蒸发冷冻海水淡化技术的热质传递特性研究

发布时间：2018-03-29 23:24

本文选题：蒸发冷冻　切入点：海水淡化　出处：《中国矿业大学》2015年硕士论文

【摘要】：面对当前严峻的淡水危机,寻求高效节能的海水淡化方法成为能源与水资源领域国内外共同关注的焦点。本文在对现有海水淡化方法分析的基础上,给出了一种新型高效的冷冻淡化方法-湿度差驱动的蒸发冷冻海水淡化方法,并对该淡化过程的传热传质特性进行了研究。论文给出了湿度差驱动的蒸发冷冻热质传递模型,分析了影响海水溶液冻结的主要因素。讨论了蒸发冻结过程中空气与水的热质传递过程,推导出蒸发冷冻法海水淡化的理论耗能量,并对显热与潜热传递对溶液蒸发冷冻产生的驱动势进行了对比分析。应用Fluent软件分析了蒸发冷冻过程中水、水蒸气、冰三相的分布状态及蒸发冻结现象,讨论了对流传质系数与结冰量之间的关系。分析了空气湿度差、空气流速与水槽长度对蒸发冷冻过程中的传质通量与传质系数的影响,讨论了空气流动过程中雷诺数与传质系数的关系。搭建了湿度差驱动的蒸发冷冻海水淡化试验装置,对不同湿度差与气流流速作用下海水溶液的冻结进行了试验研究,将试验结果与理论模拟结果进行了对比分析,两者具有较好的一致性。研究结果表明:蒸发冷冻法海水淡化过程中结冰量的主要影响因素为空气进出口湿度差与气流流速,相同条件下湿度差越大,结冰量越大;气流流速越大,结冰量越大。同时,水槽长度也是影响蒸发传质效果的重要因素,水槽长度越大,热质交换完成度越好。
[Abstract]:In the face of the severe freshwater crisis, it has become a common focus in the field of energy and water resources to seek high efficiency and energy saving desalination methods. Based on the analysis of existing desalination methods, In this paper, a new and efficient desalination method, evaporative desalination method driven by humidity difference, is presented, and the heat and mass transfer characteristics of the desalination process are studied. A model of evaporative freezing heat and mass transfer driven by humidity difference is presented in this paper. The main factors affecting the freezing of sea aqueous solution are analyzed. The heat and mass transfer process between air and water during evaporation and freezing is discussed, and the theoretical energy consumption of evaporative freezing desalination of seawater is deduced. The driving potential of solution evaporation and freezing produced by sensible heat transfer and latent heat transfer are compared and analyzed. The distribution state and evaporation freezing phenomenon of water, water vapor and ice in the process of evaporation and freezing are analyzed by Fluent software. The relationship between convection mass transfer coefficient and ice formation is discussed, and the effects of air humidity difference, air velocity and flume length on mass transfer flux and mass transfer coefficient during evaporation and freezing are analyzed. The relationship between Reynolds number and mass transfer coefficient during air flow is discussed. An evaporative desalination test device driven by humidity difference is built, and the freezing of seawater solution under different humidity difference and airflow velocity is studied experimentally. The experimental results are compared with the theoretical simulation results, and the results show that the main factors affecting the ice content in the process of seawater desalination by evaporative freezing method are the difference of air inlet and outlet humidity and the air flow velocity. Under the same conditions, the greater the humidity difference, the greater the freezing amount, the greater the flow velocity, the greater the ice concentration. At the same time, the length of the tank is also an important factor affecting the effect of mass transfer of evaporation. The larger the length of the tank, the better the degree of heat and mass exchange.
【学位授予单位】：中国矿业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P747

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