溶液除湿空调系统中叉流再生装置热质交换性能分析

再生器是溶液除湿空调系统中的重要传热传质部件。搭建了叉流再生器性能测试的实验台,并建立了叉流再生器中传热传质过程的数学模型。以溴化锂溶液为除湿剂,采用总换热量、全热效率描述再生器的热质交换总体效果,采用再生量、再生效率描述传质效果,实验测试了溶液和空气的进口参数对再生器性能的影响,并与逆流再生器的实验结果进行了比较。以实验得到的量纲一传质系数作为数学模型的输入条件,数值计算结果与73组实验数据吻合很好,全热效率和再生效率的偏差均集中在±15%以内。     

金属填料型吸收式除湿器的除湿性能研究

通过理论和实验相结合的方式,对金属填料型吸收式除湿器的除湿性能进行了研究,分析和讨论了空气和溶液的进口状态参数对出口状态参数的影响.依据双膜理论建立了该除湿器的传热传质数学模型,并进行了理论研究.实验测试与模拟计算结果表明,溶液的状态参数对除湿器传热传质的影响较大.实验过程中除湿器运行稳定,具有应用的可行性.     

利用蒸发式冷凝器再生除湿溶液时传质系数的实验研究

建立了溶液再生式蒸发冷凝器实验台,利用冷凝热再生氯化锂除湿溶液,对影响空气与除湿溶液之间传质系数的主要因素进行了实验测试.在大量实验数据基础上,分析了除湿溶液质量流速及空气迎面风速对空气与液膜之间传质系数的影响,并回归得到了传质系数的经验公式,为利用低品位热源再生除湿溶液提供理论依据.     

叉流除湿器中溶液与空气热质交换模型

建立了简化数学模型 ,空气出口温度和含湿量、溶液出口温度和质量分数的数值计算结果与实验结果的偏差在± 1 0 %以内 ,全热效率和除湿效率的偏差在± 2 0 %以内。通过分析除湿器内部温度场和浓度场得出 :在叉流除湿器中 ,不能忽略空气温湿度沿溶液流动方向和溶液温度沿空气流动方向的变化 ;传质驱动势要采用积分平均湿差的方法计算 ,而不能简单地采用对数平均湿差来表示     

太阳能除湿溶液再生方式及装置的分析与研究

简介了太阳能除湿溶液再生的发展历史,归纳总结了除湿溶液的再生方式和再生装置,根据除湿溶液再生过程是否直接与外界接触,将太阳能除湿溶液再生装置划分为开式集热型再生器、闭式集热型再生器和封闭式再生器三种。两级式集热型再生器溶液的再生量大于单级式集热型再生器,且再生效率有所提高;溶液温度可调单元喷淋模块结构简单,便于制作,兼有除湿和再生的功能,同时还可以与热泵组合实现多级并用,提高了系统的效率。     

复合型太阳能溶液除湿空调的性能模拟

结合热湿地区的气候特点,设计了复合型太阳能溶液除湿空调系统,并通过数值模拟,分析了除湿器和再生器入口空气参数对系统性能的影响.结果表明,除湿器入口空气温、湿度从36℃和80%冷却减湿预处理到26℃和90%时,除湿器的体积可减小约63%,溶液循环量减小约58%;使用房间排风作为再生空气源,可明显提高溶液的再生效率和浓度,有效降低再生热源温度.     

液体除湿器的数值模拟分析

建立了带填充物的液体除湿器的传热传质数值模型,并进行了相应的数值计算。计算结果表明,溶液入口温度和浓度对除湿性能有显著影响,进而影响液体除湿冷却空调的送风温度。     

小型液体除湿空调系统实验研究

对小型液体除湿空调系统,从居住建筑除湿负荷及经济性角度出发,采用CaCl2溶液进行液体除湿实验,研究CaCl2除湿和再生的动态特性。研究发现除湿与再生的3个重要因素为溶液温度、溶液浓度和空气进口含湿量。在实验工况下,CaCl2溶液的除湿量为32 g/kg,再生性能优于除湿性能,约为除湿的1.3～9倍。对实验进行总结后,认为CaCl2作为除湿剂进行液体除湿还有很大改进空间和推广潜力。     

溶液除湿系统再生性能的研究进展

溶液除湿系统不存在温室效应,对环境友好,实现了热负荷和湿负荷的独立处理,提高了人们生活和工作环境的空气品质。但在溶液吸湿的过程中,溶液浓度会不断降低,溶液表面与空气之间的水蒸气分压力差会逐渐减小,溶液失去除湿能力,需要对溶液进行再生才能循环使用。再生器是盐溶液提浓循环使用的重要场所。本文简要介绍了溶液除湿系统再生性能的研究现状以及一些不同于传统再生的方法。     

溶液再生回流比例对溶液除湿系统性能的影响

给出了可调节再生回流比例的除湿系统流程,建立了系统各主要部件的数学模型。模拟得到了夏季工况不同除湿负荷、不同溶液再生回流比例下系统的能耗和性能系数(COP)。结果表明:降低溶液再生回流比例可提高除湿系统性能;在较低的溶液再生温度和较低的除湿负荷条件下,降低溶液再生回流比例对系统性能的改善作用较大;再生回流比例的降低受再生温度的限制,存在合理的较优再生回流比例。     

Performance analysis on the internally cooled dehumidifier using liquid desiccant

Dehumidifier is one of the most important components in liquid desiccant air-conditioning systems. Previous study shows that the internally cooled dehumidifier may have better mass transfer performance than the adiabatic unit. The effect of flow pattern, especially the flow direction of air to desiccant on the internally cooled dehumidifier performance is numerically analyzed in detail. The result shows that counter-flow configuration of air to desiccant has better dehumidification performance, and parallel-flow configuration performs the poorest with the same conditions, due to more uniform mass transfer driving force expressed in the counter-flow configuration. The decrease of the desiccant concentration is the main factor that influences the internally cooled dehumidifier's performance, while the increase of the desiccant temperature is the main performance restricting factor in adiabatic dehumidifier. Internally cooled dehumidifier has better mass transfer performance compared with adiabatic dehumidifier plus external heat exchanger.     

Similarity of coupled heat and mass transfer between air–water and air–liquid desiccant direct-contact systems

Packed-bed heat and mass transfer devices are widely used in air-conditioning systems, such as cooling tower, evaporative cooler of air–water direct-contact devices, dehumidifier and regenerator of air–liquid desiccant direct-contact devices. Similarities of heat and mass transfer characteristics between air–water and air–liquid desiccant devices are considered and investigated in this paper. Same reachable handling region of outlet air can be obtained for both air–water and air–liquid desiccant devices, which is among three boundary lines, isenthalpic line of inlet air, iso-relative humidity line of inlet fluid (water or desiccant), and the connecting line of inlet statuses of air and fluid. Inlet conditions of air and fluid affect heat and mass transfer characteristics to some extent, so that a zonal method is proposed only according to the relative statuses of inlet air to inlet fluid. Four zones, dehumidification zones A, D and regeneration zones B, C, are divided for air-desiccant direct-contact devices. The first three zones A, B and C are divided for air–water direct-contact devices, with the same zonal properties as those of air-desiccant devices. In order to obtain better humidification performance, fluid should be heated (in zone C) rather than air (in zone B). And fluid should be cooled (in zone A) rather than air (in zone D) to obtain better dehumidification performance. Counter-flow pattern should be applied for best mass transfer performance in the same conditions within the recommended zone A or C, while parallel-flow pattern is the best in zone B or D.     

Modeling and simulation of desiccant wheel for air conditioning

This paper presents the modeling of a desiccant wheel used for dehumidifying the ventilation air of an air-conditioning system. The simulation of the combined heat and mass transfer processes that occur in a solid desiccant wheel is carried out with MATLAB Simulink. Using the numerical method, the performance of an adiabatic rotary dehumidifier is parametrically studied, and the optimal rotational speed is determined by examining the outlet adsorption-side humidity profiles. The solutions of the simulation at different conditions used in air dehumidifier have been investigated according to the previous published studies. The model is validated through comparison the simulated results with the published actual values of an experimental work. This method is useful to study and modelling of solid desiccant dehumidification and cooling system. The modeling solutions are used to develop simple correlations for the outlet air conditions of humidity and temperature of air through the wheel as a function of the physically measurable input variables. These correlations will be used to simulate the desiccant cooling cycle in an HVAC system in order to define the year round efficiency.     

Experimental study on dehumidifier and regenerator of liquid desiccant cooling air conditioning system

A new type of air conditioning system, the liquid desiccant evaporation cooling air conditioning system (LDCS) is introduced in this paper. Desiccant evaporation cooling technology is environmental friendly and can be used to condition the indoor environment of buildings. Unlike conventional air conditioning systems, the system can be driven by low-grade heat sources such as solar energy and industrial waste heat with temperatures between 60 and 80 °C. In this paper, a LDCS, as well as a packed tower for the regenerator and dehumidifier is described. The effects of heating source temperature, air temperature and humidity, desiccant solution temperature and desiccant solution concentration on the rates of dehumidification and regeneration are discussed. Based on the experimental results, mass transfer coefficients of the regeneration process were experimentally obtained. The results showed that the mean mass transfer coefficient of the packing regenerator was 4 g/(m² s). In the experiments of dehumidification, it was found that there was maximal tower efficiency with the suitable inlet humidity of the indoor air. The effective curves of heating temperature on the outlet parameters of the regenerator were obtained. The relationships of regeneration mass transfer coefficient as a function of heating temperature and desiccant concentration are introduced.     

除湿器研究进展

介绍了冷凝除湿设备、固定床除湿器、转轮除湿器、热泵和电化学除湿器、液体除湿设备、膜除湿器、HVAC除湿系统的研究进展。分析了各种除湿设备的原理、应用领域及优缺点。指出了除湿设备的发展方向。     

Comparative study on internally heated and adiabatic regenerators in liquid desiccant air conditioning system

Liquid desiccant regeneration has important effect on performance of a liquid desiccant air conditioning system. Compared with conventional packed regenerator, internally heated regenerator is proposed to achieve better regeneration performance. This study emphasized on both regeneration rate and regeneration thermal efficiency to evaluate the performance of both regenerators. A validated heat and mass transfer model was used to analyse and compare the performance of internally heated and adiabatic regenerators. The results indicated that internally heated regenerator not only could increase the regenerate rate, but also could exhibit higher energy utilization efficiency. Different from adiabatic regenerator, internally heated regenerator can provide comparable regeneration efficiency and regeneration rate at low desiccant flow rate, so it should be a good alternative to avoid carryover of desiccant droplets. Higher air flow rate would result in a deduction of regeneration thermal efficiency although achieving higher regeneration rate. Suitable flow rate of the air should be considered carefully in liquid desiccant regeneration. The internally regenerator could have considerable prospect in liquid desiccant air conditioning application.