固体转轮与溶液调湿过程的对比及热学分析

发布时间：2018-03-08 04:07

本文选题：转轮　切入点：逆流型溶液填料塔　出处：《清华大学》2015年硕士论文　论文类型：学位论文

【摘要】：本课题的研究对象为转轮和逆流型溶液填料塔这两种装置的调湿方式,研究的主要内容是二者应用于全热回收时的性能特点、应用于除湿时模块结构、运行参数对系统组成的影响,以及利用火用参数对转轮除湿系统进行评价、衡量部件传热传质能力的具体方法和思路。在此基础上,本文主要研究工作如下:首先,利用全热回收转轮和除湿转轮的实验数据对转轮的双扩散数学模型进行验证,并利用逆流型填料塔装置的实验数据对逆流型溶液与空气的传热传质模型验证,两个模型均具有较高准确性;详细测试了转速、新回风焓差、湿差、回风风量对全热回收转轮的热回收效率的影响,找出了最关键的影响因素。其次,在以上模型为研究工具的基础上,分析全热回收过程中转轮与空气传热传质过程随转速变化规律,以及逆流型填料塔中溶液温度和等效含湿量沿程分布随溶液循环流量的变化。对于转轮来说,转速即代表了吸湿材料的质量流量;转轮热回收效率随转速增加而增加,逆流型填料塔存在最优的溶液/空气流量比,在此基础上,得到二者的理想最大全热回收效率与传质单元数(NTUm)具有相同的关系,但取得最大热回收效率的条件不同。同时因规整填料的比表面积比转轮蜂窝状结构的来得小,所以实际装置中,填料塔的NTUm是限制逆流型溶液热回收装置效率的另一重要因素。再次,利用火用参数对转轮除湿系统进行分析,系统包括转轮、热回收器、加热器和表冷器,其中热回收器用于回收转轮出口处温度较高的被处理空气的显热;提出将部件的火用损失分为两类,由有限传热/传质能力引起的和不匹配系数引起的,在此基础上更加清晰地指出系统火用损失的主要原因和明确改善短板部件的途径。最后,比较了通过空气投入冷热量的转轮除湿系统和通过加热和冷却溶液的逆流型溶液除湿系统的差异:前者中转轮引起的冷热抵消量较小,会随着转轮体量增加、转速增大而增加;后者在除湿/再生模块NTUm较小时、溶液循环流量较大时产生冷热抵消。除湿/再生模块NTUm分别影响转轮的再生温度,和溶液循环中的冷热量需求;横向对比两个系统,转轮系统需求更高的热源温度,溶液除湿系统需求更多的冷热量;又因转轮的近等焓除湿过程、填料塔的NTUm较小,因此两个系统设置热回收器均十分必要。
[Abstract]:The research object of this subject is the humidification mode of the runner and countercurrent solution packing tower. The main content of the research is the performance characteristics of the two devices applied to total heat recovery and the module structure of dehumidification. The influence of operation parameters on the system composition, and the specific methods and ideas for evaluating the heat and mass transfer ability of the components by exergy parameters to evaluate the dehumidification system of the runner are presented. On this basis, the main research work of this paper is as follows: first, The double diffusion mathematical model of the runner is verified by the experimental data of the total heat recovery runner and the desiccant runner, and the heat and mass transfer model between the countercurrent solution and the air is verified by the experimental data of the counter flow packed tower. The effects of rotational speed, enthalpy difference of new return air, humidity difference and return air volume on the efficiency of heat recovery of total heat recovery runner are tested in detail, and the most important factors are found out. On the basis of the above model, the variation of heat and mass transfer between runner and air with rotating speed in the process of total heat recovery is analyzed. The distribution of solution temperature and equivalent moisture content in counterflow packed tower varies with the circulating flow rate of solution. For the runner, the rotational speed represents the mass flow of the hygroscopic material, and the heat recovery efficiency of the runner increases with the increase of the rotational speed. On the basis of optimal solution / air flow ratio in countercurrent packed column, the ideal maximum total heat recovery efficiency and the number of mass transfer units have the same relationship. But the conditions for achieving maximum heat recovery efficiency are different. And because the specific surface area of the regular packing is smaller than that of the honeycomb structure of the runner, the actual installation, The NTUm of the packed tower is another important factor that limits the efficiency of the countercurrent solution heat recovery device. Thirdly, the exergy parameters are used to analyze the desiccant system of the runner, which includes the runner, the heat collector, the heater and the surface cooler. The heat collector is used to recover the sensible heat of the treated air at the runner outlet, and the exergy loss of the parts is divided into two categories, which are caused by the limited heat / mass transfer ability and the mismatch coefficient. On this basis, the main causes of system exergy loss and the ways to improve the short plate parts are pointed out more clearly. Finally, The difference between the desiccant desiccant system with air cooling heat and the countercurrent desiccant system with heating and cooling solution is compared. In the former, the cooling and heat cancellation caused by the runner is smaller, and the speed increases with the increase of the volume of the runner. The latter produces cold and heat cancellation when the NTUm of the desiccant / regeneration module is small and the flow rate of the solution cycle is larger. The NTUm of the dehumidification / regeneration module affects the regeneration temperature of the runner and the cold heat requirement in the solution cycle, respectively. The higher heat source temperature is required in the runner system, the more cold heat is required in the solution dehumidification system, and the NTUm of the packed tower is smaller because of the near isothermal dehumidification process of the runner, so it is very necessary for the two systems to set up the heat recovery unit.
【学位授予单位】：清华大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU834.9

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