叉流除湿器热质传递性能实验研究

在太阳能溶液除湿蒸发冷却空调系统实验台上,以LiCl溶液为除湿剂,用空气进出口含湿量差和除湿效率作为除湿过程的性能评价指标,来研究叉流除湿器的除湿性能。通过实验数据分析了溶液、空气进口参数对除湿性能的影响,并利用实验数据建立适用于LiCl溶液的叉流除湿器的除湿效率和传质系数的实验关联式,发现与实验结果的吻合程度很好,误差在15%以内,能够利用这些关联式来准确的计算叉流除湿器的除湿性能,可供叉流除湿器设计参考使用。最后将实验结果与相关文献进行比较,结果表明:不同的除湿剂对叉流除湿器的除湿性能的影响基本相同。     

叉流除湿器传质性能实验研究

除湿器是液体除湿空调系统的核心部件。这里搭建了叉流除湿器性能测试实验台,利用Celdek规整填料作为汽液接触介质,除湿剂选用LiCl-H2O溶液,选取除湿量和除湿效率作为传质性能的评价指标。实验分析了空气、溶液进口参数对传质性能的影响,并利用实验数据建立了适用于LiCl-H2O溶液的叉流除湿效率的实验关联式。最后将实验结果与相关文献中的相关结果进行了比较。发现在实验范围内:与叉流形式相比,逆流除湿器中LiCl-H2O溶液表现出更强的传质性能;在叉流形式的除湿器中,LiCl-H2O溶液的传质性能最优,LiBr-H2O溶液次之,CaCl2--H2O溶液最差。     

多级矩阵结构冷却除湿器的除湿性能研究

为了降低空分系统压缩机功耗,提高压缩机运行可靠性,本文提出一种用于压缩机进气除湿的多级矩阵结构的冷却除湿器,并搭建了多级冷却除湿实验台,测试了除湿器的除湿性能。实验结果表明,在进口空气含湿量和温度固定为11.7 g/(kg干空气)和24.4 ℃时,当空气质量流量由0.48 kg/s增至0.78 kg/s,空气出口含湿量由7.1 g/(kg干空气)增至7.7 g/(kg干空气);在进口空气质量流量和温度固定为0.53 kg/s和25.2 ℃时,当冷却水温度由6.9 ℃升至11.9 ℃,空气出口含湿量由7.1 g/(kg干空气)增至9.4 g/(kg干空气)。同时,建立了除湿器内部传热传质过程的稳态数值模型,将模拟结果与实验结果进行对比。结果表明,该模型对于除湿器出口空气含湿量和温度的平均误差分别为8.6%和2.1%,显示出较好的可靠性。进一步模拟研究了多级矩阵结构与单级叉流结构冷却除湿器的除湿性能,发现采用多级结构可以有效提高除湿效率,在进口空气流量和冷却水质量流量分别为0.53 kg/s和0.3 kg/s时,多级结构的除湿量可以提高4.3%,除湿效率可以提高2.5%;通过增加填料模块的长度,可以提高除湿效率。当长方体填料模块体积固定为0.054 m3,模块长度由0.14 m增至0.28 m时,传质系数可由4.3 g/(m2?s)增至6.5 g/(m2?s),除湿效率由66.4%升至79.2%。     

中空纤维膜萃取器的分离效率

本文以不同体积浓度的TBP(煤油)—苯酚—水为实验体糸,研究了中空纤维膜萃取器的分离效率。结果表明,由于体系的萃取相平衡常数m值很高,过程的膜阻得到有效的控制,其分离效率相当可观。本文还计算比较了中空纤维膜萃取器和填料萃取柱的工况。中空纤维膜萃取器提供了巨大的传质比表面积,其HTU值很低,一般与填料萃取柱的研究中报道的最低限值相当。     

液体除湿空调除湿器性能研究

在液体除湿空调中,除湿器是系统的核心部件。本文搭建可用于实验研究的液体除湿空调系统中除湿器的实验台,对塔径300 mm、填料高度800 mm,以Li Cl溶液为除湿剂的除湿器布置测点进行实测。基于Mercel理论,根据热质平衡并结合D.I.Stevens的有效模型,建立适用于该液体除湿空调系统中的除湿器传热传质模型。从实验和理论模型两个方面分析除湿器进口各项参数对除湿量的影响,结果表明:理论值和实验值有很好的一致性,且数据差异较小,说明计算模型适应性良好,能准确的用于该除湿器的性能模拟测试,将实验与理论计算结果进行对比可知:在一定的工况范围内,除湿器的除湿量受进口溶液温度、浓度、质流密度等参数影响较大,其中溶液进口温度越低,除湿效果越显著,溶液进口浓度越低,除湿效果越好;溶液进口质流密度需控制在一定范围进行调节,才能显著提高除湿器性能;空气入口风速、干球温度以及含湿量对除湿出口的空气状态参数影响较弱。     

液体除湿空调再生性能分析

液体除湿空调的再生性能具有重要意义,再生过程的效率和稳定决定整个系统运行效率和稳定性。本文建立逆流填料式液体除湿系统传热传质的数学模型基础上,用实验分析各参数对再生的影响并分析再生性能,得出较好的结论。试验结果表明,液气比和溶液温度对再生过程的作用比较大。     

液体除湿空调再生性能分析

液体除湿空调的再生性能具有重要意义,再生过程的效率和稳定能决定整个系统运行效率和稳定性。本文在建立逆流填料式液体除湿系统传热传质的数学模型基础上,用实验分析各参数对再生的影响并分析再生性能,得出较好的结论。试验结果表明,液气比和溶液温度对再生过程的作用比较大。     

叉流再生器性能试验研究

搭建叉流再生器性能试验台,利用Celdek规整填料作为气液接触介质,再生剂选用LiCl-H2O溶液,选取再生量和再生效率作为再生性能的评价指标。试验分析空气、溶液进口参数对再生性能的影响,并利用试验数据建立适用于LiCl-H2O溶液的再生效率和传质系数的试验关联式。最后将试验结果与文献中的相关结果进行比较,结果表明:不同的再生剂对再生性能的影响基本相同;当溶液浓度较低时(LiCl-H2O溶液≤32%),使用LiCl-H2O溶液比使用LiBr-H2O溶液的再生量大,而溶液浓度较高时,情况反之。     

CO_2水平管外池沸腾换热的实验研究

对自然工质CO2在不同沸腾压力下的光管、机械加工表面强化管(Turbo-EHP)水平单管管外电加热池沸腾进行了实验研究。从核态沸腾的角度分析了光管、强化管管外沸腾换热系数随热流密度、沸腾压力的变化规律,通过对热流密度在10~50k W/m2、蒸发压力在2~4 MPa范围内的换热数据分析拟合得出光管时CO2在该范围下的换热关联式,拟合关联式的计算值和实验值的误差在±8.73%以内。新的拟合关联式的计算值与已有关联式的预测值的偏差在±15%之内。在热流密度范围内强化管的强化倍率在1.50~1.72之间。研究结果对进一步深入研究CO2池沸腾换热及蒸发器的设计具有指导意义。     

利用冷凝热再生低浓度除湿溶液的实验研究

为了获得系统重要运行参数对利用冷凝热实现低浓度除湿溶液再生性能的影响,本文在热泵驱动溶液除湿空调系统实验平台上,以低浓度的Li Cl水溶液作为再生盐溶液,再生量和冷凝热利用率作为再生性能的评价指标,对利用冷凝热实现溶液再生过程进行了实验研究。结果表明:空气流量、温度和溶液流量、温度的增加都有利于提高再生量。在夏季典型工况下,当溶液浓度为21.20%~24.91%时,冷凝热利用率在0.416~0.507波动,降低溶液浓度有利于提高冷凝热利用率。并根据实验数据拟合出了利用冷凝热再生除湿溶液过程中的耦合传热传质系数关联式,为后续如何在溶液再生过程中充分利用冷凝热提供了实验依据。     

An experimental study on the dehumidification performance of a counter flow liquid desiccant dehumidifier

This paper presents an experimental study on the dehumidification performance of a counter flow liquid desiccant dehumidifier using structured packing with a high specific surface area (650 m² m⁻³). New empirical equations correlating the moisture effectiveness and the enthalpy effectiveness with critical inlet parameters are developed, which can be used to conveniently predict the performance of a similar dehumidifier. The empirical correlations are validated using the experimental data of this study, and compared with the experimental data reported by another researcher. The deviations are within ±10% for the former and within ±15% for the latter. The performance of the present type of packing is also compared with other two types of structured packing available in literature. The influences of the inlet conditions of the air and the desiccant as well as the packing height on the dehumidification performance are also investigated and compared with the results reported in previous studies.     

New mass transfer performance data of a cross-flow liquid desiccant dehumidification system

This paper presents new mass transfer performance data of a cross-flow liquid desiccant dehumidification system using a structured packed tower. The structured packing consists of cross-corrugated cellulose paper sheets with a surface area per unit volume ratio of 608 m² m^?3. The liquid desiccant, viz. calcium chloride, flows through the pad from top to bottom, while the air flows horizontally making it a cross-flow configuration. The experimental dehumidification effectiveness from the present study was compared with the widely used Chung's correlation (although developed for counter flow arrangement, as opposed to cross-flow in the current study) and Liu et al.'s correlation. A new empirical correlation was developed for the dehumidification effectiveness, which fitted the experimental data to within ±10%. The effect of varying air and solution inlet conditions and flow rates on the system performance was also quantified in the paper.     

Mathematical model and performance analysis of a novel outside evaporative cooling liquid desiccant dehumidifier

A numerical model of a novel outside evaporative cooling liquid desiccant dehumidifier (OECD) was developed and the effects of inlet parameters, including the inlet temperature and relative humidity of dehumidified air and evaporative cooling (EC) air, as well as the inlet mass flow rate of solution and so on, on the device performances were investigated in this paper. The results show that as the inlet temperature of solution increased from 31 to 42 °C, the moisture removal rates of OECD were increased by 14.0–18.0% and 31.1–101.5% compared to the non-evaporative cooling dehumidifier (NECD) and the adiabatic dehumidifier respectively, whereas the dehumidification rate was only decreased by about 1.6% with increase in the inlet temperature of LiCl solution from 24 to 44 °C. All these results can provide guidance for the structural design and performance analysis of the dehumidifier in the future.     

Experimental study on a new internally cooled/heated dehumidifier/regenerator of liquid desiccant systems

For providing good performance of dehumidifier and regenerator with certain dimensions, a new type of internally cooled/heated dehumidifier/regenerator based on the plate–fin heat exchanger (PFHE) was designed. To investigate the behavior of the new equipment, an experimental setup was established in an environment chamber with regulable temperature and humidity air. By the internally cooled dehumidification testing, effects of the cooling water temperature, the air flow rate and the desiccant temperature on the dehumidification performance and the cooling efficiency were presented. The behavior of internally cooled dehumidification process was compared with that of the adiabatic dehumidification process. The results suggested that the cooling efficiency decreased with the increasing of the cooling water temperature and desiccant with low temperature could bring more mass transfer coefficients. There is an optimal air flow rate to achieve the maximum absolute humidity decrease of the air. By the internally heated regeneration testing, effects of the air flow rate and the desiccant inlet temperature on the regeneration performance and air outlet parameters were discussed and also compared with those of the adiabatic regeneration process. It was concluded that the regeneration efficiency of internally heated regeneration was more than that of the adiabatic regeneration, and the internally heated regenerator could offer better thermal performance.     

Energy conservation research of dehumidification system for main cable anticorrosion of suspension bridge

The necessity of the main cable anticorrosion for suspension bridge is described, operating principles and composition of main cable dehumidification system is analyzed, and an idea using the waste heat of high temperature outlet air of dehumidification system to heat up regeneration air of rotary-type dehumidifier is put forward in this paper. The concrete scheme is to install a heat exchanger on air-out pipeline of Roots blower and air-in pipeline of regeneration electric heater of rotary dehumidifier. Air preheated by the heat exchanger enters regeneration electric heater of rotary-type dehumidifier. Energy conservation of main cable dehumidification system for the Yangtze River highway bridge was calculated, and the results showed that energy conservation rate reached 44%.     

Performance analysis of liquid desiccant dehumidification systems

Desiccant systems find applications in a very large variety of industrial and daily usage products including the new HVAC installations. An overview of liquid desiccant technology has been presented in this paper along with a compilation of experimental performance data of liquid desiccant dehumidifiers, empirical dehumidification effectiveness and mass transfer correlations in a useful and easy to read tabular format. The latest trends in this area suggest that hybrid systems are of current interest to HVAC industry, not only for high latent load applications but also for improving indoor air quality. The paper presents a comprehensive comparative parametric analysis of packed bed dehumidifiers for three commonly used desiccant materials viz. triethylene glycol, lithium chloride and calcium chloride, using empirical correlations for dehumidification effectiveness from the literature. The analysis reveals significant variations and anomalies in trends between the predictions by various correlations for the same operating conditions, and highlights the need for benchmarking the performance of desiccant dehumidifiers.     

Experimental characterization of the rectification process in ammonia–water absorption systems with a large-specific-area corrugated sheet structured packing

In this paper, the mass transfer performance of a large-specific-area corrugated sheet structured packing for ammonia–water absorption refrigeration systems (AARS) is reported. An experimental facility was used to test the performance of the packing. Experimental results of the temperature, ammonia concentration and mass flow rate of the rectified vapour are presented and discussed for different operating conditions including reflux ratio values from 0.2 to 1. The volumetric vapour phase mass transfer coefficient is calculated from the measured data and compared with different correlations found in the literature. A new correlation is proposed which was fitted from the experimental data. Finally, a comparison is made between the actual packing height used in the experimental setup and the height required to obtain the same ammonia rectification in AARS with different packings previously tested by the authors.     

新型除湿模式在国防工程中的应用

针对常规热湿联合处理技术应用于国防工程时出现的室内温湿度波动大、机组运行能效低等问题,提出利用温湿度独立控制理念构建国防工程新型除湿模式。该除湿模式由新风处理系统(全工况除湿机)和空气循环处理系统(一体化分流节能型除湿机)构成。计算分析表明与应用于常规热湿联合处理系统相比,同型号一体化分流节能型调温除湿机应用于温湿度独立控制系统(新型除湿模式构建的国防工程)时,其制冷量可增加约21.3%。