溶液除湿蒸发冷却空调系统及其若干重要问题

从系统流程的构建、系统性能的研究、系统关键部位的优化等方面介绍了溶液除湿蒸发冷却空调系统的研究情况,探讨了进一步研究中的关键问题.     

溶液除湿空调系统蓄能性能分析

介绍了溶液除湿蒸发冷却空调系统的蓄能原理,分析了蓄能密度的影响因素。与冰蓄冷、水蓄冷和气体水合物蓄冷等常规蓄冷方式的比较结果表明,溶液除湿空调系统在蓄能方面有明显的优势,其蓄能密度远大于常规蓄冷方式。该系统可以利用太阳能作为再生能源,白天蓄存浓溶液用于夜间制冷,节能效果显著。     

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.     

Study on a novel thermally driven air conditioning system with desiccant dehumidification and regenerative evaporative cooling

Existing desiccant cooling systems reduce the temperature of process air either by adopting evaporative coolers or incorporating vapor compression systems. While the former is restricted by inaccurate control, the latter still consumes certain quantity of electric power. To solve this problem, a thermally driven air conditioning system, which combines the technologies of rotary desiccant dehumidification and regenerative evaporative cooling, has been proposed and investigated. In addition to dehumidification, the system is capable of producing chilled water, thereby realizing separate temperature and humidity control without increasing electrical load. To find out the characteristics of produced chilled water and evaluate the feasibility and energy saving potential of this novel system, a mathematical model has been developed. Case studies have been conducted under Air conditioning and Refrigeration Institute (ARI) summer, ARI humid and Shanghai summer conditions. It is found that the system can achieve a thermal COP higher than 1.0 and an electric COP about 8.0. The temperature of chilled water produced by the system is around 14–20 °C. This chilled water can be used with capillary tube mats for radiant cooling. It is suggested that the system can also be designed as a standalone chilled water plant. As a desiccant dehumidification-based chilled water producing technology, this would expand desiccant cooling to a boarder niche application. The effects of chilled water flow rate, air distribution ratio, inlet air conditions and regeneration temperature have been analyzed in detail. Reachable handling regions, which will be helpful to system design and optimization, have been obtained.     

The effects of operational conditions of the desiccant wheel on the performance of desiccant cooling cycles

A desiccant cooling model is developed and applied to the ventilation, recirculation, makeup, and mix modes of the operating system. The mathematical model is based on the transient coupled heat and mass transfer and is used to predict the performance of the system under various design and operational conditions. The numerical results are validated using experimental measurements. The effects of the regeneration temperature and rotational speed of the desiccant wheel on the COP and output cycle temperature are investigated. The results show the availability of an optimum regeneration temperature and rotational speed in which the output cycle temperature has a minimum value. The optimum regeneration temperature and rotational speed are detected and shown on the Psychrometric charts. Calculating these values has a significant effect on the energy use of these cycles.     

利用盐溶液制备冷水的冷水机组

在间接蒸发冷却装置的基础上,设计了利用盐溶液制备冷水的冷水机组,使得间接蒸发冷却技术能够应用于非干燥地区,并运用了热回收技术达到节能目的。通过对不同室外工况下冷水机组性能的模拟,发现COP对室外空气含湿量最敏感。最后模拟分析了在北京地区使用时此冷水机组的整体性能。     

Application of desiccant systems for improving the performance of an evaporative cooling-assisted 100% outdoor air system in hot and humid climates

The purpose of this study was to enhance the energy-saving potential of an indirect and direct evaporative cooling-assisted 100% outdoor air system (IDECOAS) by integrating it with either a solid or liquid desiccant system. The desiccant system can be installed either at the scavenger air side of the indirect evaporative cooler (IEC) to enhance its effectiveness or at the primary air side of the IEC to reduce the latent load of outdoor air. The operating energy consumption affected by the location and type of the desiccant unit integrated with IDECOAS was simulated under three different hot and humid climates using TRNSYS 17 integrated with commercial equation solver programme. And then, the most energy-conservative configuration was selected for each climate zone as the proposed system. The simulation results showed that configurations with the desiccant dehumidification unit located upstream of the IDECOAS consume 76–85% less cooling coil energy than those with the desiccant unit located downstream of the IDECOAS. It was also found that the liquid desiccant system saves 21–50% more primary energy than the solid one, when it is integrated with IDECOAS.     

国内外蒸发冷却空调技术研究进展(3)

介绍了多级蒸发冷却空调系统、除湿与蒸发冷却相结合的空调系统、半集中式蒸发冷却空调系统、建筑物被动蒸发冷却技术、蒸发冷却自动控制系统及蒸发冷却水的水质处理。     

Overall cooling efficiency of a solar desiccant plant powered by direct-flow vacuum-tube collectors: simulation and experimental results

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.     

Numerical simulation of a semi-indirect evaporative cooler

This paper presents the experimental study and numerical simulation of a semi-indirect evaporative cooler (SIEC), which acts as an energy recovery device in air conditioning systems. The numerical simulation was conducted by applying the CFD software FLUENT implementing a UDF to model evaporation/condensation. The numerical model was validated by comparing the simulation results with experimental data. Experimental data and numerical results agree for the lower relative humidity series but not for higher relative humidity values.     

再循环蒸发冷却中再循环风量的实验研究

介绍了一种再循环蒸发冷却技术,其原理是利用一部分经间接冷却处理的空气作为二次空气直接蒸发制取冷水,用冷水反过来间接冷却室外空气。搭建了相应的实验台,针对夏季实际工况条件,实验研究了再循环风量比例对蒸发冷却效率的影响,给出了合适的再循环风量范围。     

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.     

基于TRNSYS的区域供冷能源站仿真控制研究

以泰州医药城区域供冷系统为研究对象,在TRNSYS中建立了区域供冷能源站模型。对能源站中的五台热泵机组采用组合式控制,模拟了冬夏季节的热泵机组联合运行时的供回水温度。     

CO2跨临界循环和除湿法冷却联合循环系统的研究

为有效回收和利用CO2跨临界循环的气体冷却器排气热量,提出了一种将除湿法冷却供冷和CO2跨临界循环结合起来的系统方式,介绍了系统的组成和特点,分析了系统的循环效率、可行性和经济性,指出该方式可有效提高系统的综合能源利用效率,并可满足全年的空调要求。     

蒸发冷却空调技术的研究状况

重点介绍了两级蒸发冷却及露点蒸发冷却空调技术的研究状况,此外还介绍了水蒸发冷却技术的两个较新的应用实例研究.     

Investigation of a hybrid system of nocturnal radiative cooling and direct evaporative cooling

In this paper, the results of a study on a hybrid system of nocturnal radiative cooling, cooling coil, and direct evaporative cooling in Tehran have been discussed. During a night, the nocturnal radiative cooling provides required chilled water for a cooling coil unit. The cold water is stored in a storage tank. During eight working hours of the next day, hot outdoor air is pre-cooled by means of the cooling coil unit and then it enters a direct evaporative cooling unit. In this period, temperature variation of the conditioned air is investigated. This hybrid system complements direct evaporative cooling as if it consumes low energy to provide cold water and is able to fulfill the comfort condition whereas direct evaporative alone is not able to provide summer comfort condition. The results obtained demonstrate that overall effectiveness of hybrid system is more than 100%. Thus, this environmentally clean and energy efficient system can be considered as an alternative to the mechanical vapor compression systems.     

蒸发冷却式空调在我国南方地区的应用分析

以广州某3层建筑为例,采用动态模拟方法,详细计算分析了其采用蒸发冷却式空调的可行性和使用蒸发冷却式空调后的节能效果.结果显示,在类似于广州的我国南方地区,可以采用间接利用蒸发冷却式技术的蒸发冷却空调集成系统.     

外冷型多级蒸发制冷空气处理机组性能分析

介绍了该机组的空气处理过程。机组夏季出风参数主要与进风参数、进水温度、风水比、直接蒸发制冷段效率有关。在分析影响因素的基础上,绘制了机组在不同地区应用时的夏季出风参数图,并给出了机组出风参数确定的一个实例。计算了机组的夏季性能参数。     

Experimental validation of a simplified approach for a desiccant wheel model

This work presents an experimental validation of a simplified approach for a desiccant wheel model, based on the concept of the analogy method and the formulation proposed by Jurinak for the respective combined potentials. The present work experimentally investigates the validity of the assumption of the efficiency factors of the wheel, with regard to the combined potentials, remaining constant over a sufficiently wide range of operation conditions. The results prove the validity of the discussed assumption. The same analysis is implemented with regard to the technical data about the performance of the wheel, usually provided by the manufacturer in the form of software, the results being also positive. Thus, the respective efficiency factors can be calculated through a limited number of measurements, or even simpler, through the use of the manufacturer's performance software accompanying the product.     

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.