提出一种基于物化热效应的制冷新循环,该循环利用氨基甲酸铵分解反应以及反应产物汽化的吸热效应进行制冷,利用该反应的逆反应实现放热。对不同运行工况下循环的热力性能进行了理论计算与分析,结果表明,吸、放热过程温差不宜高于40℃,中间压力、中间温度对循环热力性能影响显著,存在最佳的中间压力使循环热力性能达到最大,同时确定了该循环的最佳中间压力,且最佳中间温度为该压力下的平衡温度。与单级蒸汽压缩式制冷的理论循环相比,该循环的性能系数提高约20%,与液体汽化相变制冷循环相比,具有更高的能效。

Liquid desiccant is a new means of controlling air humidity with significant energy-saving potential. However, direct contact between the salt solution and the treated air may cause carryover droplets that degrade the indoor air quality, and this is a major obstacle to widespread application. This paper experimentally investigates how dehumidification and regeneration using LiCl solution affect the mass concentration of micro-particles in the treated air. The results show that dehumidification tends to remove micro-particles with sizes of 0?2.5 ?m rather than carryover droplets, especially for PM2.5 by 7.73%. However, larger micro-particles with sizes of 2.5?10 ?m are generated during regeneration of the liquid desiccant, which indicates that the change in the amount of micro-particles depends on the direction of moisture migration. Increasing the rate of air or solution flow increases moisture migration during regeneration to release more micro-particles. Additionally, the amount of micro-particles released during counter flow is less than that during parallel flow, because the larger particles settle down during the former. This investigation should help to understand the behavior of carryover droplets in liquid-desiccant air-conditioning systems and inspire new methods for controlling humidity and particles.

A liquid desiccant air dehumidifier (LDAD) with both high efficiency and low desiccant carryover is of vital significance to indoor environment. However, the instability introduced by desiccant film flow tends to deteriorate the droplets entrainment in product air and remains to be solved. In this study, a novel disk-type liquid desiccant air dehumidifier with no film flow (DLDAD) was developed to radically eliminate the apparent desiccant film flow. The distribution and refreshing of liquid desiccant on wetted surface is realized by the rotation of the disks rather than the film flow of liquid desiccant. The performance of DLDAD was numerically evaluated under varied dehumidifier parameters, including stage number, immersion depth, rotation speed and air and solution parameters. The results show that an increase in the stage number can increase dehumidification performance, ensuring the air outlet humidity ratio below 10 g/kg. The dimensionless immersion depth of 0.4 and the rotation speed of 3 r/min are suggested for better dehumidification performance in this case. Increasing solution concentration or decreasing solution temperature can effectively reduce the air outlet humidity ratio. All these results can support the structural design and practical application for LDADs with higher efficiency and lower desiccant carryover in the future.

提出一种基于溶液除湿的消除湿烟羽系统.该系统由烟气冷凝过程和烟气溶液除湿过程构成,利用盐溶液对待处理烟气进行除湿达到消除湿烟羽的技术标准,同时回收待处理烟气自身显热和潜热驱动溶液循环,不需要消耗额外热能,还能够回收烟气中水资源.建立了系统主要部件的数学模型,研究了待处理烟气温度tg,in、相对湿度RHg,in以及室外空气温度ta,amb、相对湿度RHa,amb对排放烟气参数、系统消除湿烟羽性能以及回收水分的影响.结果表明,随着tg,in和RHg,in的增大,消除湿烟羽性能逐渐降低,回收水分逐渐增多;当RHa,amb增大时,排放烟气温度、含湿量以及回收水分几乎无变化,但消除湿烟羽性能会逐渐降低;当ta,amb增大时,排放烟气温度和含湿量逐渐增大,消除湿烟羽性能逐渐增强,回收水分逐渐减少.

针对改善溶液除湿空调系统中填料表面润湿性的问题,通过CFD模拟研究了填料表面倾斜角、接触角和表面形态对LiCl-H2O降膜润湿性及临界喷淋量的影响.模拟结果表明:填料表面的倾斜角越小,溶液液膜表面波动性越小,润湿性越好;填料表面的接触角越小,润湿性越好,达到满膜流动所需的临界喷淋量越小;接触角从40°变化到60°时临界喷淋量的增长量最大.在小喷淋量下,波形填料表面的润湿性较平板填料表面有显著提升;当喷淋量为0.288 m~3/（m·h）时,5 mm波高的波形填料表面的润湿率比平板表面增加超过50%;波高增大,润湿率虽有提高,但增加量仅在5%左右.另外,由于波形表面上液膜的稳定性较差,故满足满膜流动所需的临界喷淋量要比平板表面大.

Liquid desiccant dehumidification has been prevalent for many years to remove moisture in the air. The application and enhancement of the involved absorption processes depend on the understanding of heat and mass transfer between liquid desiccants and air. In order to unravel the mystery of energy and mass transport during dehumidification, vapor absorption processes were simulated by molecular dynamics under different solution concentrations and temperatures. Energy characteristics and interaction components were further analyzed to obtain dominant particles in LiBr solutions during absorption. It is found Br- contributes the most in terms of the accumulated interactions when the water vapor molecule just enters into the interface for within 10 ps. This can be attributed to the occurrence of a OH bond directing to the liquid bulk with a high possibility of about 80%. However, after the absorbed water molecule entering into the interface for a longer time about 250 ps, the accumulated interactions caused by Li+ will be the largest under conditions with low concentrations and high temperatures. This is because the absorbed water molecule will gradually diffuse close to Li+ in the liquid desiccants and adjust the orientation around Li+. This study helps understand the absorption from microscopic level.

A comparative study is conducted to find that there are significant prediction deviations of single liquid desiccants vapor pressure at high concentration and regeneration temperature (high temperature) based on existing typical models. Some factors affecting water activity are not taken into account in these models, and they become more significant at high temperature and high concentration. This paper proposes a modified LIQUAC model to improve the prediction accuracy of single liquid desiccants vapor pressure at high temperature and high concentration. In the modified thermodynamic model, the middle-range interaction is derived by enhancing temperature and concentration dependence. By analyzing the prediction results of three typical liquid desiccants, it is found that the theoretical framework of the novel model is better than that of two typical models (using same data base for parameterization) at high temperature and high concentration. The interaction parameters in the modified model have precise physical meanings and make the model can be extended to other electrolyte solutions. (C) 2020 Elsevier B.V. All rights reserved.

Understanding heat and mass transfer between LiBr aqueous solution and vapor is a crucial issue in absorption refrigeration and air dehumidification for the purpose of intensifying transfer and conversion. This is difficult to be realized by macro experiments due to failing to catch detailed information of water molecules. Molecular dynamics has been resorted to for exploring mechanisms of chemical processes but the used force field dominates the simulation accuracy. In order to discover suitable force fields to describe interactions in LiBr solution, three recent models developed based on infinite dilution were evaluated in terms of static and transport properties. Results show that all models could predict the density with high accuracy. The model of Koneshan et al. achieves most properties with satisfactory accuracy and is the best one to simulate the surface tension, which indicates good interfacial performance. Further, by selecting the model of Koneshan et al., the energy and mass transport phenomenon through liquid–vapor interface was simulated and analyzed. Four behaviors of water molecules including absorption, release, replacement and reflection were observed near the interface of LiBr solution. It is found that the replacement behavior only occurs under high liquid temperature conditions and the reflection behavior is characterized by a steep energy ravine. This research provides data reference for the force field selection, setting a solid foundation for studying heat and mass transfer between LiBr solution and vapor by molecular dynamics. This research could also disclose the molecular behaviors between aqueous solution and air.
© 2019 Elsevier Ltd and IIR

Because the weight of interactions in liquid desiccants varies with solute type and concentration, it is difficult for existing typical models to accurately quantify the interactions in mixed liquid desiccants near saturated solubility. A statistical thermodynamic model is proposed to predict the vapor pressure of mixed liquid desiccant solutions near saturated solubility by re-quantifying the weight of interactions between all species in solution. The model considers that charge interaction and non-charge interaction are still dominant, and charge-dipole interaction between ions and solvent molecules increases with the increase of solute concentration. Rigorous expressions are given to calculate the interactions: ion-ion charge interaction is described by modifying the Fowler-Guggenheim theory, charge-dipole interaction is expressed by combining the McMillan-Mayer theory with the Debye-Hückel theory, and non-charge interaction is calculated based on the extended UNIQUAC equation. The prediction accuracy comparison between the new model and two typical models shows that the new model has better accuracy, and the superiority of the model increases with the increase of solute concentration and temperature. The model can be recommended for the liquid desiccant solutions consisting of Li+, Ca2+, Cl− or Br− with concentration ranging from infinite dilution to near saturation and temperature ranging from 283.15 to 353.15 K. © 2019 Elsevier Ltd

Understanding heat and mass transfer between LiBr aqueous solution and vapor is a crucial issue in absorption refrigeration and air dehumidification for the purpose of intensifying transfer and conversion. This is difficult to be realized by macro experiments due to failing to catch detailed information of water molecules. Molecular dynamics has been resorted to for exploring mechanisms of chemical processes but the used force field dominates the simulation accuracy. In order to discover suitable force fields to describe interactions in LiBr solution, three recent models developed based on infinite dilution were evaluated in terms of static and transport properties. Results show that all models could predict the density with high accuracy. The model of Koneshan et al. achieves most properties with satisfactory accuracy and is the best one to simulate the surface tension, which indicates good interfacial performance. Further, by selecting the model of Koneshan et al., the energy and mass transport phenomenon through liquid–vapor interface was simulated and analyzed. Four behaviors of water molecules including absorption, release, replacement and reflection were observed near the interface of LiBr solution. It is found that the replacement behavior only occurs under high liquid temperature conditions and the reflection behavior is characterized by a steep energy ravine. This research provides data reference for the force field selection, setting a solid foundation for studying heat and mass transfer between LiBr solution and vapor by molecular dynamics. This research could also disclose the molecular behaviors between aqueous solution and air. © 2019 Elsevier Ltd and IIR