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     

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.     

利用冷凝热再生的复合除湿空调除湿潜力分析

简要描述了利用冷凝热再生的复合除湿空调系统形式及其节能性特点;在热力学第一定律和热力学第二定律的基础上,分别以冷凝器和除湿转轮为控制体,建立了复合除湿空调的系统热力学模型,并给出模型求解框图,从而可以求得复合除湿空调系统的除湿量;最后,计算了在不同转轮效率和室内单位面积显热负荷下的系统单位面积除湿量,并讨论了新风量大小对结果的影响;结果表明,在现有转轮效率和常见单位面积负荷指标下,转轮的除湿量小于新风湿负荷（1次/h）,而降低新风量后（0.5次/h）,当转轮效率较高和室内显热负荷较大时,转轮能够承担新风湿负荷。     

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。     

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.     

Artificial neural network based modelling of desiccant wheel

In this article, the concept of artificial neural network and goal oriented design have been used to propose a computer design tool that can help designers to evaluate performance of desiccant cooling system and behaviour of the desiccant wheel. Based on the experimental observations on desiccant wheel, a neural network model has been developed using a neural network toolbox of MATLAB^® with feed forward back propagation method. The model has been validated against experimental data sets. A number of training algorithms with feed forward back propagation method have been used for the modelling of desiccant wheel to identify a training algorithm with least mean square error (MSE). The performance of all training algorithms has been analyzed and training algorithm trainlm (Levenberg-Marquardt back propagation) is found most suitable for the prediction of outputs which have least mean square error of 0.064462 and 0.007575 for specific humidity and temperatures respectively. The proposed model can predict the specific humidity and temperature at the outlet of desiccant wheel within the range of experimental values.     

Desiccant wheels as gas-phase absorption (GPA) air cleaners: evaluation by PTR-MS and sensory assessment

Two experiments were conducted to investigate the use of the co-sorption effect of a desiccant wheel for improving indoor air quality. One experiment was conducted in a climate chamber to investigate the co-sorption effect of a desiccant wheel on the chemical removal of indoor air pollutants; another experiment was conducted in an office room to investigate the resulting effect on perceived air quality. A dehumidifier with a silica-gel desiccant wheel was installed in the ventilation system of the test chamber and office room to treat the recirculation airflow. Human subjects, flooring materials and four pure chemicals (formaldehyde, ethanol, toluene and 1,2-dichloroethane) were used as air pollution sources. Proton-Transfer-Reaction--Mass Spectrometry (PTR-MS) and sensory subjects were used to characterize the effectiveness of chemical and sensory pollution removal of the desiccant wheel. The experiments revealed that all the measured VOCs were removed effectively by the desiccant wheel with an average efficiency of 94% or higher; more than 80% of the sensory pollution load was removed and the percentage dissatisfied with the air quality decreased from 70% to 20%. These results indicate that incorporating a regenerative desiccant wheel in a ventilation system is an efficient way of removing indoor VOCs. PRACTICAL IMPLICATIONS: This study may lead to the development of new air cleaners and validates a new concept for the design of ventilation systems that can improve indoor air quality and reduce energy consumption.     

Proposal for a new hybrid control strategy of a solar desiccant evaporative cooling air handling unit

Correctly controlled solar desiccant evaporative cooling is an interesting option for achieving savings in building air-conditioning consumption. The operation of this system (open loop cooling cycle) is strongly influenced by indoor and outdoor air conditions. This influence is characterized using numerical simulations. First the air conditioned room and the cooling system are simulated using a validated model of the desiccant wheel. Then the influence of each parameter of the desiccant air handling unit is evaluated. The third step is to assess the system cooling power for each operating mode with fluctuating outdoor and indoor air conditions. This allows for making relevant choices for a new control strategy taking into account both indoor and outdoor air conditions. This control strategy is tested for a whole cooling season and compared to a reference compression system with promising results, allowing for energy savings of about 40% for French climate.     

固体转轮除湿与冷凝除湿的适用性研究

针对不同工况,对固体除湿转轮进行吸湿与再生的性能实验;根据实验结果,采用空气源热泵作为冷热源,通过理论计算得出不同条件下固体转轮除湿与冷凝除湿两种方式的性能。结果表明,相同工况除湿量相同时,转轮除湿相对于冷凝除湿功耗大、效率低;随着室内空气湿度的增大,2种除湿系统能耗都减小,效率增大,冷凝除湿效率改善更明显;室外空气湿度增大,对冷凝除湿性能影响较小,转轮除湿功耗变大,效率降低;室外空气温度升高,冷凝除湿功耗增大,转轮除湿功耗减小,但两者的效率均增大。     

Energy savings potential of a desiccant assisted hybrid air source heat pump system for residential building in hot summer and cold winter zone in China

In hot summer and cold winter zone in China, air conditioning system has four running modes yearly including cooling with dehumidification, cooling, dehumidification and heating in residential buildings. The conventional air source heat pump (ASHP) system is not designed to independently control temperature and humidity, and is not very suitable for the dehumidification mode in the view of building energy consumption. A novel ASHP system combining radiant cooling/heating for residential buildings was presented. The main feature of this hybrid ASHP system is that desiccant wheel and cooling coil accomplish dehumidification process together, and the regenerative heat needed by the desiccant wheel is supplied by the condenser dissipated heat. Based on simulation studies and performance analysis, this paper predicts the primary energy consumption of the hybrid ASHP system in comparison with the conventional ASHP system during the cooling and heating seasons. It was found that primary energy requirement can be reduced by more than 8% in cooling with dehumidification mode, by 50% in dehumidification mode, and by more than 14% in heating mode. The study results prove that the hybrid ASHP system can keep great energy saving and running cost saving yearly, especially in the dehumidification process.     

Performance of a solar-regenerated liquid desiccant ventilation pre-conditioning system

A solar-regenerated liquid desiccant ventilation pre-conditioning system has been proposed for use in hot and humid climates. The system aims to dehumidify the ventilation air which is the major source of latent load. A heat exchanger is used to cool the dehumidified air instead of typical evaporative cooling to maintain the dryness of the air. The use of solar energy at the regeneration process and cooling water from a cooling tower makes the system more passive. The simulation procedure for the proposed system has been presented. By inputting the climatic data and the physical parameters of all equipments, the operating parameters at each equipment and the performance parameters of the system can be evaluated. The simulation procedure is demonstrated by showing the daily profiles of the operating and performance parameters on a typical day as well as investigating the influence of the selected operating parameters on the system performance. The results suggest that the most influential parameters are solar radiation, ventilation rate, and desiccant solution concentration. The balance between the water removed at the dehumidifier and that evaporated at the regenerator needs to be considered to maintain uniform performance during continuous operation.     

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.     

某高压电机装配车间环境控制的实测分析与研究

通过对某高压电机装配车间进行实测,研究了空调风量对恒温恒湿车间工作区空气温湿度均匀性的影响;并与对空调冷负荷的分析相结合,进一步明确影响室内空气湿度最重要的因素是新风,影响室内空气温度最重要的因素是厂房内的工艺设备的散热量;根据高压电机生产车间的低湿环境要求,综合考虑技术性和经济性,对空调湿负荷的处理方式进行了优化研究,提出冷却除湿+转轮除湿复合除湿系统是能够达到此要求的最优化方法.     

转轮除湿与单元式空调机相结合的空气处理系统

本文介绍了转轮除湿与直接膨胀式单元机组相结合的复合空调系统的2种紧凑型组成形式:前置预冷与后置冷却,并在几种不同室外工况下,针对应用于独立新风系统,对比分析了这2种典型组成方案的性能特点。结果表明,这2种除湿方式在4种典型工况下的制冷能耗相差不明显,在10%以内;但后置冷却除湿在高温高湿工况下难以实现较大的单位除湿量,且再生空气温度高;而前置预冷除湿系统采用较小的除湿转轮尺寸,结构更紧凑,可明显降低初投资,且再生空气温度较低。因此,前置预冷除湿系统在较小流量空气处理应用方面更具优势,更具商品化发展潜力。     

数值模拟对直接蒸发冷却空调性能的分析

针对直接蒸发冷却空调机组,简化了物理模型并建立了控制方程和相应的边界条件。运用Ansys软件进行模拟计算后,将模拟结果与试验测试数据进行对比验证,表明了模拟的准确性。通过温度场分布图对试验测试的结果进行分析,发现被测机组填料厚度大,使机组出口空气的相对湿度过大,并且不利于节能。因此,通过数值模拟对直接蒸发冷却空调性能分析的方法是可行的。     

Simulation, performance analysis and optimization of desiccant wheels

Desiccant wheel is an important and crucial component that can be used in building HVAC systems in order to reach relevant energy savings and to use renewable sources. The optimization of air handling units based on desiccant wheels instead of conventional components is complex and it requires adequate simulation tools. In the present paper desiccant wheels performance and optimization are investigated. The analysis is carried out through a one-dimensional gas side resistance model which considers developing temperature and velocity profiles along the channels. Simulation results show a good agreement with experimental data available in literature in a wide range of operating conditions. The model is used to analyze the influence of working conditions on desiccant wheel performance and on the optimal revolution speed. Several performance criteria are introduced and each one of them is used to investigate and to find out the optimal desiccant wheel configuration. For each criterion the best process air angular sector and revolution speed are identified, and the obtained results are compared. Through a practical example it is finally shown how each criterion leads to different optimal configurations.     

使用天然气的除湿供冷系统

文章阐述了除湿供冷系统的结构和原理，并分析了影响除湿性能的一些因素。在与传统的制冷技术作比较的同时，评价了该系统的优越性。该系统不仅节约能源，还有助于提高室内空气品质和环保。     

燃气驱动的三级液体除湿空调系统及其特点分析

介绍了液体除湿空调系统的原理及其特点。基于分级除湿思想和能量梯级利用原则，提出了一种燃气驱动的三级液体除湿空调系统，系统由风机、除湿器、蒸发冷却器和再生器组成。除湿器采用三级液体除湿，通过对室内回风直接蒸发冷却进行全热回收，用回收的冷量冷却除湿过程，移去处理空气的潜热；蒸发冷却器由间接蒸发冷却器和直接蒸发冷却器两部分组成，前者间接冷却除湿后的空气，移去空气的显热，后者调节空气的温湿度；再牛器采用燃气驱动，实现沸腾蒸发和非沸腾蒸发结合的两效再生。该系统是一种节能环保的新型空凋系统，具有优化城市能源结构的功能。     

Experiences with a gas driven,desiccant assisted air conditioning system with geothermal energy for an office building

Thermal driven desiccant assisted air conditioning systems make use of waste heat to dehumidify humid outside air in a desiccant wheel. Within the scope of a research project, an investigation of a desiccant assisted air conditioning system was carried out, and a demonstration plant was built in an office building in Hamburg, Germany. The HVAC system consists of a small CHP-plant, a desiccant assisted ventilation system and an earth energy system (borehole heat exchangers) for cooling instead of an electric driven compression chiller. The radiant floor heating system of the building is used for cooling. In this paper, measurement results and investigations of performance, energy demand and operating costs will be presented. It was found that considerable primary energy savings can be achieved (70%) using desiccant air conditioning with borehole heat exchangers. But even if electric chiller is used, savings of 30% in primary energy can be accomplished. Starting costs for the demonstration plant were not higher than for a conventional system, but running costs could be reduced drastically.     

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.