New type of fresh air processor with liquid desiccant total heat recovery

A liquid desiccant total heat exchanger and small capacity refrigeration cycle combined fresh air processor is proposed here in this paper, in order to improve indoor air quality and decrease the energy consumption of the air-conditioning system. Operating principles of both the total heat recovery device and fresh air processor using liquid desiccant are presented in details. Experimental tests of the fresh air processor installed in a hospital show that energy efficiency ratio (EER) is around 6.3–7.3 in the summer experimental conditions and 4.7–5.0 in the winter experimental conditions. Hour-by-hour simulation, which is based on the climate data in Beijing, shows that the average EER is 5.3 and 4.3 in summer and winter period, respectively. Liquid desiccant has the potential to remove a number of pollutants, avoiding cross contamination. Furthermore, in summer fresh air is dehumidified by contacting liquid desiccant instead of 7 °C chilled water, which avoids wet surfaces in the air-conditioning system and much higher indoor air quality can be achieved.     

Simulation and experimental analysis of a fresh air-handling unit with liquid desiccant sensible and latent heat recovery

This article introduces a liquid desiccant fresh air processor. Its driving force is low-grade heat (heat obtained from 65 – 75°C hot water). Inside the processor, the air is dehumidified by the evaporative cooling energy of the indoor exhaust air. A four-stage structure is used to increase the efficiency of the combined sensible and latent heat recovery from the exhaust air. A mathematical model of the fresh air processor was set up using Simulink®. A liquid desiccant fresh air processor was constructed and tested for outside air conditions of 29.1 – 33.6°C, 13.7 – 16.7g/kg humidity ratio, and supply air conditions of 23.6 – 24.2°C, 7.4 – 8.6g/kg humidity ratio. The average measured COP _f was 1.6 (cold production divided by latent heat removed) for the range of conditions tested. The corresponding average COP _sys of the system including the regenerator was 1.3 (cold production divided by heat input). The detailed operating parameters of each part of the test unit were also measured. The test data was compared with the simulated performance. The characteristic coefficients (such as the volumetric mass transfer coefficient of the air-water evaporative cooling module, etc.) in the mathematical model were modified to calibrate the model output to the measured data. The calibrated simulation model was used to investigate the control strategy of the fresh air processor. The flow rate of the strong solution into the unit and the number of operation stages may be controlled separately or together to meet different indoor air requirements at different outdoor conditions. The hot water driven liquid desiccant air conditioning system was compared with a typical vapor compression system with an average COP of 4.5; the pump and fan power of the proposed system was 40% of the combined chiller, pump, and fan consumption. We achieved savings of over 30% of the power consumption compared with the traditional system under the designed outdoor air conditions.     

南海意库3#办公楼温湿度独立控制空调系统实测与分析

测试了温湿度独立控制空调系统主要设备的性能。结果显示,溶液除湿新风机组的平均COP为5.4,高温冷水机组的平均COP为8.9,水系统EER为5.1,典型房间室内空气参数均满足设计要求,室内空气露点温度低于冷水供水温度,干盘管处无凝水产生。空调系统单位面积年电耗为34.3kWh/m2,约为深圳甲级办公楼平均空调用电水平的69.3%。     

Optimization of a liquid desiccant based dedicated outdoor air-chilled ceiling system serving multi-zone spaces

A liquid desiccant based dedicated outdoor air-chilled ceiling (DOAS-CC) system is proposed to serve a multi-zone space. The outdoor airflow rate and the supply air humidity ratio are two crucial variables in such a system, which significantly influence indoor thermal comfort, indoor air quality and energy consumption. Two strategies are presented to optimize these two variables in the study. They are the demand-controlled ventilation (DCV) strategy and the supply air humidity ratio set-point reset strategy. To evaluate the performances of these two strategies, a basic control strategy, i.e., the strategy adopting constant ventilation flow rate and constant supply air humidity ratio, is selected as the benchmark. Performances of the two strategies in terms of indoor air temperature, relative humidity and CO₂ concentration as well as energy consumption are analyzed using simulation tests. The results show that the supply air humidity ratio set-point reset strategy is effective for the indoor air humidity control. It can save about 19.4% of total energy consumption during the whole year. The DCV-based ventilation strategy can further reduce about 10.0% of energy consumption.     

溶液调湿技术在昆明南站的应用

分析了昆明南站的溶液调湿通风系统,通过通风满足室内温度要求,通过溶液调湿系统满足室内湿度要求,并对溶液调湿通风系统进行数值模拟和运行工况分析。     

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.     

Performance analysis of liquid desiccant based air-conditioning system under variable fresh air ratios

In conventional air-conditioning system, fresh air volume is always restricted to save energy, which sacrifices indoor air quality (IAQ) to some extent. However, removing the latent load of air by liquid desiccant rather than by cooling is an alternative way of reducing energy consumption. Therefore, IAQ can be improved by increasing the volume of fresh air introduced into an air-conditioning system. In this paper, a liquid desiccant based air-conditioning system is studied, with the system performance under various fresh air ratios analyzed using simulation tests. In addition, the proposed system and a conventional system are compared. In the proposed system, with the increase in fresh air ratio, the heating load for solution regeneration rises, the dehumidification efficiency increases and the regeneration efficiency drops. The coefficient of performance (COP) of the liquid desiccant based system decreases sharply when the fresh air ratio exceeds 60%. The results also show that the proposed system can save power notably. The maximum power saving ratio is 58.9% when the fresh air ratio is 20%; however, the ratio drops when the fresh air ratio increases. These findings will be beneficial in the selection of fresh air ventilation strategies for liquid desiccant based air-conditioning systems.     

Performance of temperature and humidity independent control air-conditioning system in an office building

The temperature and humidity independent control (THIC) system, which controls indoor temperature and moisture separately, may be an attractive alternative to existing conventional HVAC systems for its prominent improvement on the overall system performance and utilization of low grade energy resources. In order to verify the effectiveness of THIC system, a pilot project has been implemented in an office building in Shenzhen, China. In the system, liquid desiccant fresh air handling units driven by heat pumps are utilized to remove the entire latent load of outdoor air supplied for the whole building, and chilled water at the temperature of 17.5 °C from chiller is pumped and distributed into dry fan coil units and radiant panels to control indoor temperature. This paper presents the results of field test of the system, which shows that the system can provide a comfortable indoor environment even in very hot and humid weather. The COP of the entire THIC system can reach 4.0. According to the energy usage data recorded from the year 2009, the energy consumption of the THIC system in the tested office building was 32.2 kWh/(m² yr), which demonstrates magnificent energy-saving potential compared with the conventional air-conditioning system (around 49 kWh/(m² yr)).     

Performance comparison between two novel configurations of liquid desiccant air-conditioning system

This paper is concerned with performance investigation and comparison between two novel configurations (type A and type B) of liquid desiccant air-conditioning system driven by low grade thermal energies. Both of these configurations, compared with other liquid desiccant systems, may have some outstanding advantages: leading to improved indoor air qualities, possessing a compact structure and making the best use of space exhaust air to cool the process air. Computer simulation is performed to analyze the cycle performance of these two system configurations under the effect of five key variables. Simulation results show that type B configuration is superior when the supply air temperature and humidity ratio are required to be relatively low or the ambient air absolute humidity is relatively high. In contrast, system of type A configuration has higher performance under the lower ambient air absolute humidity conditions. For a typical hot and humid summer day of Zhuhai, a city of Guangdong Province in southern China, the supply air temperature of type B configuration is more stable.     

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.     

溶液除湿温湿度独立控制空调系统设计

该文叙述了溶液除湿温湿度独立控制空调系统的构成和溶液调湿技术,并针对各种实际场合提出了相应的系统形式。同时,详细介绍了温湿度独立控制空调系统的设计方法以及注意事项,为设计师进行温湿度独立控制空调系统设计提供一定的指导。     

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。     

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     

新风和回风对液体除湿空调系统的影响

采用十字正交实验法对液体除湿新风处理机组在高温高湿工况下的除湿量进行了测定分析,结果表明：除湿量受新风含湿量、风量影响较大,受新风温度和回风温度、风量影响较小;并随着进口空气流量、含湿量、温度和回风量的增加而增大,随回风温度的升高而降低。     

溶液全热回收装置与热泵系统结合的新风机组

提出了一种以溶液为媒介的全热回收装置和热泵系统相结合的新风处理机。安装于某医院的新风机性能测试结果表明：测试条件下，新风机夏季性能系数为6．3～7．3，冬季性能系数为4．7～5．0。新风机中吸湿溶液能去除空气中多种污染物，可避免新风和室内排风之间的交叉污染。     

溶液除湿空调在档案库房中的应用

本文首先对档案库房所需要的环境进行了分析,指出档案库房除了要满足基本的温度和湿度要求外,还必须有一定的洁净度、空气酸度和霉菌量的要求。而后剖析了常规冷凝除湿空气处理机组在档案库房空调应用中的弊端,研究提出了适应于档案库房的基于温、湿度独立控制技术的溶液除湿空气处理技术。最后通过对常规空调与溶液除湿空调的能耗分析,得出溶液除湿空调与常规空调相比可显著节能的结论。     

地源吸收式热泵夏季运行方式研究

针对现有的地源吸收式热泵在夏季运行工况时所出现的系统能耗高、空调房间易结露等问题,提出将集中热源驱动的新风溶液除湿机组和地埋管夏季免费供冷相结合,构成集中热源驱动的土壤源温湿度独立控制空调系统。选取北京地区某典型办公房间,以该系统为研究对象,建立各部分的数学模型,并模拟分析了新风量对系统性能的影响。结果表明:随着单人新风量的增加,地埋管水流量基本保持不变,除湿器入口溶液流量先是急剧下降,而后基本保持不变;再生器入口溶液温度逐渐升高,而再生器耗热量先是急剧下降,而后又逐渐上升,当单人新风量为30 m~3/(h·人)时,再生器耗热量达到最低;除湿器和再生器的湿传递效率均逐渐降低。     

温湿度独立调节技术在夏热冬冷地区的应用研究

通过研究分析,认为一体式热泵型溶液调湿热回收型新风机组加干式风机盘管结合地埋管地源热泵组成的温湿度独立调节空调系统应用效果较好,节能及节地优势明显,在夏热冬冷地区应用有较大的意义.并通过实例证实了研究结论.     

溶液除湿空调在高温高湿地区的应用研究

设计了一种新型的溶液除湿装置。综合利用太阳能、天然水源、热回收和溶液除湿技术,对新风进行分阶段除湿,同时,利用太阳能和室内排风对溶液进行再生,克服了传统溶液除湿空调技术在高温高湿地区应用过程中的局限性。结果表明,与传统溶液除湿方案相比,该系统的溶液循环量减小,运行能耗降低,对太阳能的依赖程度降低,溶液的吸湿效率和再生效率提高。     

对热舒适、空气感觉质量及能耗的模拟研究

室内空调设计温度和新风量对热舒适，室内空气质量及能耗量有重要影响，然而对它们之间相互关系进行研究的文献却较少。通过计算机模拟空调系统在7种室内设计温度和7种新风量条件下的运行情况，得到不同的设计条件组合对热舒适、人体感觉空气质量及建筑能耗量的影响。基于这项分析，提出了此办公建筑合理的室内设计温度和新风量取值。