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This paper investigated a desiccant solution regenerator using hot air to concentrate diluted desiccant solution, aiming to utilize the waste heat of hot air, such as the hot air from the condensers of vapor compression refrigeration systems. To verify the feasibility of the utilization of the hot air for the desiccant solution regeneration and disclose the performance of such kind of regenerators, performance analysis was conducted numerically by a validated mathematical model and parametric distribution of the air in a typical case was explored. The results showed that it was possible to use hot air for the desiccant solution regeneration when the requirement of the lowest inlet solution temperature was met and a typical case showed that the suggested hot air temperature was around 65 °C. Effects of main operation parameters on the regeneration thermal efficiency and regeneration rate were discussed and the result showed the regeneration thermal efficiency could achieve the maximum (ηreg, max) when the R was around 8 and lower flow rate of the desiccant could achieve higher ηreg, max. In addition, effects of dimensions of the regenerator on the regeneration performance were disclosed and some suggestions of design of the regenerators were introduced based on the study. 相似文献
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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. 相似文献
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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. 相似文献
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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. 相似文献
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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。 相似文献
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《Journal of Building Performance Simulation》2013,6(3):149-162
Using solar thermal energy is an interesting option for heat-driven air conditioning, e.g. desiccant cooling. In this article, the autonomous operations of a solar desiccant cooling plant powered by direct-flow vacuum-tube collectors are investigated. A model of the solar installation and the desiccant air handling unit is presented and implemented in the SPARK simulation environment and then it is validated experimentally. The overall cooling efficiency of the system is evaluated using simulation for humid and moderately humid climates and the effect of increasing the regeneration temperature on the cooling capacity, the overall cooling efficiency is studied and finally the overall efficiency of the collectors is calculated for the studied cases. 相似文献
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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. 相似文献
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This study deals about the investigation of a solar-powered desiccant dehumidification system coupled with variable frequency drive (VFD). The proposed design of the system consists of two evaporative air coolers. One cooler performs as an absorber and the other one as desiccant regenerator coupled with a solar water heater. The VFD is connected with the first evaporative air cooler. In this work, using solar energy, a zeolite is regenerated as part of the investigation. Regeneration cycle for hot water absorption is explained and analysed. A simple expression for the cycle is proposed. System efficiency is derived with consideration of flow of work and heat to and from the system. The operating concentration of desiccant used greatly affected regeneration temperature limits and mass of strong solution for unit mass of vapour produced. 相似文献
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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. 相似文献
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Theoretical investigation on the performance of lithium chloride (LiCl) absorption cooling system using an artificial neural network (ANN) model is presented. Tabulated data from the literature are used to construct the ANN model. Solar collector desiccant/regenerator is applied to re-concentrate the working solution. Using the proposed model, the effect of system design parameters; namely regenerator length, and air flow rate on the performance of the system is demonstrated. The variation of the thermo-physical parameters along the regenerator length is highlighted. 相似文献
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Simulation and experimental analysis of a fresh air-handling unit with liquid desiccant sensible and latent heat recovery 总被引:1,自引:0,他引:1
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. 相似文献
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选取民用空调常用的两种吸附材料-硅胶和4A分子筛,在实验的基础上,对比分析了硅胶和4A分子筛两种吸附材料的除湿量、吸附能效以及脱附能效,结果表明:4A分子筛在整个吸附阶段都能保持较高的单位除湿量,比较适于二次除湿或深度除湿工作。而硅胶在很快时间内达到吸附平缓值,较适用于表面除湿及一次除湿工作。在相同的吸附和再生条件下,硅胶较4A分子筛有着更高的吸附和脱附能效,因此将硅胶作为民用空调系统的除湿材料较4A分子筛节能效果更佳。 相似文献
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This paper presents an experimental test along with procedures to investigate the validity of a developed simulation model in predicting the dynamic performance of a condenser heat recovery with a photovoltaic/thermal (PV/T) air heating collector to regenerate desiccant for reducing energy use of an air conditioning room under the prevailing meteorological conditions in tropical climates. The system consists of five main parts; namely, living space, desiccant dehumidification and regeneration unit, air conditioning system, PV/T collector, and air mixing unit. The comparisons between the experimental results and the simulated results using the same meteorological data of the experiment show that the prediction results simulated by the model agree satisfactorily with those observed from the experiments. The thermal energy generated by the system can produce warm dry air as high as 53 °C and 23% relative humidity. Additionally, electricity of about 6% of the daily total solar radiation can be obtained from the PV/T collector in the system. Moreover, the use of a hybrid PV/T air heater, incorporated with the heat recovered from the condenser to regenerate the desiccant for dehumidification, can save the energy use of the air conditioning system by approximately 18%. 相似文献
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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。 相似文献