热泵废热再生转轮除湿空调系统的性能研究

建立空气源热泵与小型固体除湿转轮相结合的复合机组,利用压缩机的高温排气和冷凝热作为转轮除湿剂的再生能源,并应用于新风量较小、湿负荷较低的居住建筑。对热泵的排气温度与能量利用特性进行分析并对热泵废热利用情况下的除湿转轮进行模拟与实验研究,结果表明在夏季冷却除湿工况下,热泵系统的废热足够实现除湿转轮的再生并满足室内湿负荷的要求。将复合机组的一次能源利用率与传统系统进行对比,在冬季工况下,复合机组的一次能源利用率相较于空气源热泵高25%;在夏季工况下,复合机组的一次能源利用率相较于空气源热泵高36%。     

溴化锂溶液除湿系统再生过程实验研究

溶液除湿技术是解决空调热湿解耦控制以及将废热与太阳能引入空调的有效途径.溶液再生则是溶液除湿的一个关键过程.设计了一套溴化锂溶液再生实验装置,对溶液流量、进口溶液温度、空气流量、进口空气温度、进口空气相对湿度对系统的再生性能进行了实验研究.结果表明:对于一定结构参数和进出口溶液、空气参数的再生装置,溶液流量存在一个最佳...     

太阳能溶液除湿系统再生器的实验研究

结合工程实例进行了太阳能溶液除湿系统除湿溶液再生实验,研究了除湿溶液再生过程的热质交换特性,得到了不同溶液入口参数下再生器内部各测点温度,揭示了不同空气和溶液入口参数对出口溶液浓度的影响和填料对再生器热质交换的影响。文章可为太阳能溶液除湿系统再生器的设计提供依据。     

液体除湿空调再生性能试验分析

液体除湿空调中除湿剂再生过程的效率和稳定决定整个系统运行效率和稳定性.对空气与除湿溶液质量流量之比、除湿溶液温度、除湿溶液的溶质浓度对除湿溶液再生系统性能的影响进行了探讨.     

液体除湿系统的研究发展

液体除湿空调不仅可以对热负荷和湿负荷独立处理,而且不断循环的盐溶液还可以对空气起到很好的杀菌效果,这可以提高人们生活和工作的空气品质,避免由传统空调引起的温室效应。但是在溶液除湿和再生的过程中溶液表面的水蒸气压力与空气的水蒸气压力差不断减小,阻碍了除湿过程和再生过程的进行,所以为了得到更高的效率,需要探索新型的液体除湿装置。液体除湿系统主要由除湿器、再生器、循环溶液组成,其中再生器的性能直接影响到整个液体除湿系统的性能。简要介绍了传统液体除湿系统的再生器、除湿器、除湿溶液及新型液体除湿系统再生器的发展。     

相变蓄热型空气源热泵系统蓄、释热特性与供暖节能运行温度条件的研究

文章通过对典型城市最冷月的日逐时室外空气的平均温度进行分析,并结合空气源热泵的运行特性、建筑供暖负荷规律和人们的用能规律,提出了一种相变蓄热型空气源热泵系统,实现了通过日蓄、夜释的方式弥补低温时段空气源热泵供热能力不足的目的。文章设计了新型翅片管式相变蓄热器,开展了相变蓄热型空气源热泵系统蓄、释热特性实验。实验结果表明:翅片管式相变蓄热器蓄热时,相变蓄热材料温度分布均匀,空气源热泵的冷凝温度与相变蓄热材料之间的温度差为1.1℃,这有利于降低空气源热泵冷凝温度、提高空气源热泵性能系数;翅片管式相变蓄热器释热时,相变蓄热器入口水温对释热速度具有重要影响。同时,对相变蓄热型空气源热泵系统的蓄热能效进行分析,得到了相变蓄热型空气源热泵系统供暖节能运行温度条件。     

太阳能平板降膜型再生器的模拟和实验研究

在对液体再生机理研究的基础上,针对对流和辐射传热边界条件,建立了太阳能平板集热型再生器中逆流降膜再生过程的数学模型,并通过实验方法对该模型进行验证,实验采用CaCl2水溶液作为除湿剂,分析了各种进口参数对再生效果的影响.结果表明:模拟结果与实验数据能够较好地吻合;太阳辐射强度、空气温度、空气含湿量和溶液浓度等均对再生过程有不同程度的影响.     

PV/T和GHP再生的转轮除湿空调系统仿真模型研究

首先利用MATLAB软件模拟出了除湿转轮子系统、GHP子系统和PV/T子系统的仿真模块,并根据子系统建立一整套系统的仿真模型;对于再生温度不同时除湿转轮出口空气的温度与湿度、冷凝器入口水温不同时系统的冷凝温度和冷凝压力以及不同时刻空气集热器出口的温度进行了仿真模拟,并将结果和实验数据进行对照,吻合较好。     

基于溶液除湿的粮食干燥机组性能仿真

针对目前粮食干燥过程能耗高、存在粮食浪费问题,设计基于溶液除湿的新型粮食干燥机,机组使用氯化锂作为除湿溶液,利用热泵驱动溶液的除湿和再生;对机组空气处理装置进行仿真,研究LiCl溶液的温度、浓度和质量流量对系统除湿性能的影响。结果表明：环境参数稳定时,结合溶液再生要求,采用14℃、27%的LiCl溶液,质量流量控制为4 kg/s时,机组能够获得最佳粮食干燥性能。     

太阳能再生式除湿换热器动态除湿性能研究

提出了一种新型再生式除湿换热器,建立了物理和数学模型。通过实验得到了该除湿换热器的实际动态除湿性能;将除湿器除湿性能的模拟结果与实验结果进行比较,验证了数学模型的可靠性。研究结果表明:该文研制的再生式除湿换热器具有良好的除湿性能,在给定工况(温度为24.7℃,含湿量为12.41g/kg)下除湿率可达到43.8%;还分析了处理风速、再生温度以及除湿换热器厚度对除湿性能和压降的影响,获得了使除湿换热器性能最佳的管排、翅片间距和迎面风速参数。     

基于溶液除湿的风冷热泵系统性能分析

为了克服利用冷却除湿的风冷热泵空调系统机器露点过低、需要再冷和过热、难以适应显热潜热比例的变化、不能蓄能等缺点,提出基于集热再生器溶液除湿的热泵空调系统。通过济南某工程实例研究表明,与冷却除湿空调系统相比较耗电量减少12.3%,利用太阳能加热溶液除湿具有降低空调除湿能耗、利用可再生能源、减少高品位能源消耗等优势。证明太阳能溶液除湿在空调系统中是处理潜热负荷的理想选择,具有较好的节能性。     

Analysis and Modeling of a Novel Hybrid Solid–Liquid Dehumidifier System

A novel waste-heat-driven hybrid solid–liquid dehumidifier (HSLD) system is proposed and its performance modeling is carried out. This new type of dehumidification system can be efficiently driven by low-temperature heat sources such as solar energy, while achieving high dehumidification performance due to its unique serial dehumidification and regeneration processes. The process airflow is first dehumidified by a liquid dehumidifier and then by a solid one; at the same time, the regeneration air first regenerates the solid dehumidifier and then the liquid one. The reason is because the liquid dehumidifier is more efficient to dehumidify humid air with low-temperature regeneration heat, while the solid dehumidifier can effectively dehumidify drier air with higher temperature regeneration heat. Theoretical analysis and performance analysis of the HSLD system are carried out under varied process air conditions and regeneration temperatures. The results show that this new HSLD system is promising for dehumidification performance improvement with low-temperature regeneration heat. It can be efficiently driven by waste heat as low as 60～70°C with a satisfactory dehumidification performance. For the HSLD system, the dehumidification ratio between the liquid and the solid dehumidifiers varies according to the regeneration temperature and process air inlet conditions.     

Development of a novel two-stage liquid desiccant dehumidification system assisted by CaCl2 solution using exergy analysis method

Air conditioning system based on liquid desiccant has been recognized as an efficient independent air humidity control HVAC system. To improve thermal coefficient of performance, a novel two-stage liquid desiccant dehumidification system assisted by calcium chloride (CaCl₂) solution is developed through exergy analysis based on the second thermodynamic law. Compared with the basic liquid desiccant dehumidification system, the proposed system is improved by two ways, i.e. increasing the concentration variance and the pre-dehumidification of CaCl₂. The exergy loss in the desiccant–desiccant heat recovery process can be significantly reduced by increasing desiccant concentration variance between strong desiccant solution after regeneration and weak desiccant solution after dehumidification. Meanwhile, the pre-dehumidification of CaCl₂ solution can reduce the irreversibility in the regeneration/dehumidification process. Compared to the basic system, the thermal coefficient performance and exergy efficiency of the proposed system are increased from 0.24 to 0.73 and from 6.8% to 23.0%, respectively, under the given conditions. Useful energy storage capacity of CaCl₂ solution and LiCl solution at concentration of 40% reach 237.8 and 395.1 MJ/m³, respectively. The effects of desiccant regeneration temperature, air mass flux, desiccant mass flux, etc., on the performance of the proposed system are also analyzed.     

Experimental and Numerical Study on Heat and Mass Transfer of Cross-Flow Liquid Desiccant Dehumidifier/Regenerator

Abstract

A liquid desiccant air dehumidification system driven by heat pump was established. The performance of cross-flow dehumidifier/regenerator was experimentally investigated. The empirical correlations of Sherwood number for dehumidification/regeneration were obtained by fitting the experimental data. On the basis of the empirical correlations of Sherwood number and thermodynamics analysis of heat and mass transfer process for dehumidifier/regenerator, a cross-flow heat and mass transfer model was established. The effects of air and solution parameters on the dehumidification/regeneration performance were analyzed. The number of mass transfer units and the height-to-length ratio of the packing module were also studied. The results show that there exist optimal number of mass transfer units and height-to-length ratio in the dehumidifier/regenerator.     

低温工况热源塔热泵系统应用试验分析

针对热源塔换热能力及热源塔联立热泵主机制热情况分别进行试验研究,并与风冷热泵的制热变化性能进行比较分析。结果表明,控制热源塔进口气液温差恒定的情况下,塔从空气中吸收的热量随环境温度的降低而增加,溶液中溶质的挥发对热源塔吸热量有重要影响;热源塔进口气液温差随环境自然变化的情况下,环境温度与蒸发温度的温差随环境温度的降低而减小,热源塔从空气中吸收的热量也随之减少。在低温工况下,虽然空气含湿量较少,但热源塔热泵系统相比于其他空气作为热源的热泵系统,在潜热换热方面有较大优势。     

Effectiveness of heat and mass transfer in packed beds of liquid desiccant system

A liquid desiccant system (using CaCl₂) is presented for air dehumidification using solar energy or any other low grade energy to power the system. The system utilizes two packed beds of counterflow between an air stream and a solution of liquid desiccant for the processes of air dehumidification and solution regeneration. To simplify the prediction of the performance of the system an effectiveness of heat transfer and an effectiveness of mass transfer in the packed beds are defined. A finite difference model is developed to model the heat and mass transfer in packed beds during the air dehumidification mode and the solution regeneration mode. This finite difference model is used to calculate the effectiveness of heat and mass transfer in the packed beds at various bed heights, various air and solution flow rates, various inlet temperatures of air and solution to the bed, and various concentrations of CaCl₂ solution at the bed entrance. Charts of the effectiveness of heat and mass transfer are presented in a convenient form. A designer of a liquid desiccant system may use the charts in predicting the performance of these systems without having to use the finite difference model for this purpose.     

Control performance of a dedicated outdoor air system adopting liquid desiccant dehumidification

Liquid desiccant is energy efficient for dehumidification in air-conditioning systems. In this study, a novel dedicated outdoor air system (DOAS) adopting lithium chloride solution as liquid desiccant is proposed to process supply air. The DOAS mainly consists of a membrane-based total heat exchanger, a liquid dehumidifier, a regenerator and a dry cooling coil. It can realize independent temperature and humidity controls for supply air. Control strategies for the supply air dehumidification and cooling process as well as the desiccant solution regeneration process in the DOAS are developed and verified. The control performances of the proposed dedicated outdoor air system are investigated at different operation conditions by simulation tests. The results show that the DOAS is more suitable for hot and humid climates. The effects of the total heat exchanger on the performance of the DOAS are also evaluated. It can improve the system energy performance by 19.9–34.8%.     

Measurements of Frost Thickness and Frost Mass on a Flat Plate under Heat Pump Condition

This study measured the frost thickness and frost mass on a flat plate to propose the correlation equations for the local and average frost thickness, frost density, and frost mass. Key parameters were the cooling surface temperature of the flat plate from 258.2 to 268.2 K, absolute humidity of air from 2.98 to 4.16 g/kg_DA, air temperature from 273.5 to 280.2 K, and air velocity from 1.0 to 2.5 m/s. A 50% ethylene glycol aqueous solution was used as a coolant. The sensitivity analysis of the parameters such as air temperature, air humidity, air velocity, and surface temperature on the frost thickness and frost mass were experimentally investigated under the heat pump condition. Correlation equations for the local and average frost thickness and frost mass under the heat pump condition were proposed. The values predicted by the correlation equations under the freezer condition were larger by a maximum of 30–50% than the values predicted by the present correlation equations under the heat pump condition. The proposed correlation equations might be applied to the part of the freezer condition.     

Study of an aqueous lithium chloride desiccant system: air dehumidification and desiccant regeneration

Desiccant systems have been proposed as energy saving alternatives to vapor compression air conditioning for handling the latent load. Use of liquid desiccants offers several design and performance advantages over solid desiccants, especially when solar energy is used for regeneration. For liquid–gas contact, packed towers with low pressure drop provide good heat and mass transfer characteristics for compact designs. This paper presents the results from a study of the performance of a packed tower absorber and regenerator for an aqueous lithium chloride desiccant dehumidification system. The rates of dehumidification and regeneration, as well as the effectiveness of the dehumidification and regeneration processes were assessed under the effects of variables such as air and desiccant flow rates, air temperature and humidity, and desiccant temperature and concentration. A variation of the Öberg and Goswami mathematical model was used to predict the experimental findings giving satisfactory results.     

空气源热泵热水器与电热水器耦合选型研究

阐述了空气源热泵热水器选型的影响因素,对冷热水温度、干球温度、相对湿度和设备COP、结霜等影响因素进行了说明,给出了空气源热泵热水器和电热水器耦合使用时的选型方法,并利用贴现指标法对二者按不同配置时的经济效益进行比较分析,从而获取最优配比。