新型吸附床的研究进展

吸附床是吸附式制冷装置的核心部件,其性能的优劣直接关系到吸附式制冷装置的制冷效果.通过吸附床的热阻分析,得出强化吸附床传热的措施.文中重点介绍了提高吸附剂与换热壁面的换热系数和吸附剂间的导热系数来强化吸附床传热的方法,详细介绍了填充式吸附床、涂抹式吸附床以及固化式吸附床的结构特点,比较分析3种吸附床的传热传质特点,并阐...     

新型高效复合吸附剂开发及系统仿真

针对一种新型高效复合吸附剂开展了吸附性能实验研究,并假想将该复合吸附剂装填于一固体吸附式空调样机吸附床内进而开展仿真研究。对比研究表明该复合吸附剂不但具有比硅胶强得多的吸附能力,而且再生温度较低。装填该复合吸附剂的吸附式空调不但可以获得比装填纯硅胶时高得多的比制冷功率SCP,而且系统性能系数COP也明显高于纯硅胶系统。     

吸附式制冷中吸附剂传热传质的强化

对吸附式制冷系统中吸附剂的两种关键性能－有效吸附量及导热系数进行了实验及理论研究。测量了几种吸附剂的上述性能并进行了数据拟合,分析了吸附剂吸附性能及导热系数对吸附制冷系统效率的影响,提出了以吸附制冷最佳经济效率为目标函数的吸附剂性能强化手段,并进行了一些实验研究,取得了较好的效果。     

一种高效吸附床的设计及二维传热数值模拟分析

设计了一种特殊的高效换热的板翅式吸附床,用于硅胶-水连续循环的吸附式制冷系统中。建立了吸附床的二维数学模型。因硅胶-水吸附式制冷系统具有很快的吸附和解吸过程,热量的及时传递成为极其关键的因素。因此在该模型中,只考虑了快速加热和冷却的传热过程,以寻求提高传热速度的途径。对于吸附床的各关键尺寸对换热性能的影响进行了对比和分析,并对实验结果也进行了对比分析。理论研究表明,吸附床的各参数的最优尺寸为：翅片间距为3～6 mm,翅片高度为6～12 mm,翅片厚度为0.03～0.15 mm。实验结果表明,使用这种吸附床结构,系统的循环时间可短至420 s。在硅胶的热导率仅为0.175 W·(m²·℃)^-1的情况下,吸附床的总传热系数可提高至相似文献   

一种新型太阳能吸附式制冷系统的设计及性能模拟

为了解决传统的双床连续吸附制冷系统中因在制冷剂环路使用真空挡板阀而存在的制冷剂压降的问题,使吸附式制冷系统更适合于应用太阳能,提出了利用硅胶-水作为吸附工质对的新型太阳能制冷系统.系统热源由40 m²的热管式真空管集热器提供,制冷机为特殊设计的吸附制冷系统,在上海典型日照条件下该系统可以较为稳定地提供5～8 kW的制冷量,系统COP达0.2以上.通过对系统的动态模拟和理论分析,证实了以硅胶-水为工质对的吸附式系统更适合利用太阳能,研究结果为进一步实验和改进系统性能提供理论指导.     

固体吸附式制冷系统制冷剂的解吸特性

搭建了以活性炭-甲醇为工质对的单床吸附式制冷实验系统,对圆柱形吸附管内的吸附剂在不同解吸温度和不同解吸时间条件下的解吸量进行实验研究。解吸温度分别为84、89、94℃,解吸时间分别为4、5、6、7 h。实验结果表明,解吸温度、解吸时间和制冷剂的解吸量对吸附式制冷系统制冷循环性能有着重要影响。在热源温度为84℃加热时间4 h时,系统的制冷性能系数COP最小为0.053。系统在解吸温度为94℃,解吸时间为6 h时,系统的制冷性能系数COP最大为0.19,此时的解吸温度和解吸时间为最佳解吸温度和解吸时间。继续增加解吸时间,解吸量的增长率小于耗能的增长率,COP减小。     

吸附式制冷装置中吸附床传热传质的研究

本文根据吸附式制冷装置中吸附床的操作特性,建立了吸附床在受热解吸过程中的传热传质数学模型.在这个模型中,假设吸附床是均质的,吸附床的导热系数可用一个当量寻热系数表示,并考虑吸附床中吸附剂与传热片之间的接触热阻.以本文作者所建立的吸附式制冰机为例,对此数学模型进行了计算,计算值与实验结果吻合得较好.     

固体吸附式制冷系统制冷剂的解吸特性

搭建了以活性炭-甲醇为工质对的单床吸附式制冷实验系统,对圆柱形吸附管内的吸附剂在不同解吸温度和不同解吸时间条件下的解吸量进行实验研究。解吸温度分别为84、89、94℃,解吸时间分别为4、5、6、7 h。实验结果表明,解吸温度、解吸时间和制冷剂的解吸量对吸附式制冷系统制冷循环性能有着重要影响。在热源温度为84℃加热时间4 h时,系统的制冷性能系数COP最小为0.053。系统在解吸温度为94℃,解吸时间为6 h时,系统的制冷性能系数COP最大为0.19,此时的解吸温度和解吸时间为最佳解吸温度和解吸时间。继续增加解吸时间,解吸量的增长率小于耗能的增长率,COP减小。     

一种吸附式空气取水装置的性能实验

基于大气中水的吸附与解吸循环,设计出吸附式空气取水装置,并对其进行了实验研究。该装置主要由太阳能集热器、吸附床和冷凝器等组成。晚上吸附剂吸附空气中的水,白天由太阳能提供热量进行解吸。实验制备了硅胶（SC）-CaCl₂、SC-LiCl、活性炭纤维毡（ACF）-CaCl₂、ACF-LiCl 4种新型复合吸附剂,并对其进行了实验测试。结果表明：由ACF制备的复合吸附剂性能比由SC制备的复合吸附剂性能要好;ACF-LiCl的吸附与解吸性能最好,在吸附床出口温度为90℃时,解吸6 h的产水率是0.412 kg水·（kg吸附剂）^-1。     

一种吸附式空气取水装置的性能实验

基于大气中水的吸附与解吸循环,设计出吸附式空气取水装置,并对其进行了实验研究。该装置主要由太阳能集热器、吸附床和冷凝器等组成。晚上吸附剂吸附空气中的水,白天由太阳能提供热量进行解吸。实验制备了硅胶(SC)-CaCl_2、SC-LiCl、活性炭纤维毡(ACF)-CaCl_2、ACF-LiCl 4种新型复合吸附剂,并对其进行了实验测试。结果表明:由ACF制备的复合吸附剂性能比由SC制备的复合吸附剂性能要好;ACF-LiCl的吸附与解吸性能最好,在吸附床出口温度为90℃时,解吸6h的产水率是0.412kg水·(kg吸附剂)~(-1)。     

余热制冷吸附床的一个新传热传质模型

在既考虑吸附剂颗粒内部的传质阻力,又考虑吸附剂颗粒之间的外部传质阻力的前提下,建立了余热吸附制冷系统中吸附床的三维非平衡传热传质数学模型,它包括加热/冷却流体传热模型、换热管传热模型、肋片传热模型、吸附剂颗粒床传热传质模型4部分;通过对模型的数值求解,获得了吸附床内部的温度演变曲线和性能指标,与实验结果基本吻合。     

Effect of Adsorbent Diameter on the Performance of Adsorption Refrigeration

Adsorbents are important components in adsorption refrigeration. The diameter of an adsorbent can af-fect the heat and mass transfer of an adsorber. The effect of particle diameter on effective thermal conductivity was investigated. The heat transfer coefficient of the refrigerant and the void rate of the adsorbent layer can also affect the effective thermal conductivity of adsorbents. The performance of mass transfer in the adsorber is better when pressure drop decreases. Pressure drop decreases with increasing permeability. The permeability of the adsorbent layer can be improved with increasing adsorbent diameter. The effect of adsorbent diameter on refrigeration output power was experimentally studied. Output power initially increases and then decreases with increasing diameter under different cycle time conditions. Output power increases with decreasing cycle time under similar diameters.     

HEAT AND MASS TRANSFER IN THE ADSORBENT BED OF AN ADSORPTION HEAT PUMP

The heat and mass transfer equations governing an adsorbent bed in an adsorption heat pump and the mass balance equation for the adsorbent particles in the adsorbent bed were solved numerically to simulate the cycle of a basic adsorption heat pump, which includes isobaric adsorption, isosteric heating, isobaric desorption, and isosteric cooling processes. The finite difference method was used to solve the set of governing equations, which are highly nonlinear and coupled. The pressures of the evaporator and condenser were 2 and 20 kPa, respectively, and the regeneration temperature of the bed was 403 K. Changes in the temperature, adsorptive pressure, and adsorbate concentration in the adsorbent bed at different steps of the cycle were determined. The basic simulated cycle is presented in a Clausius-Clapeyron diagram, which illustrates the changes in average pressure and temperature of the adsorbent bed throughout the cycle. The results of the simulation indicated that the most time-consuming processes in the adsorption heat pump cycle were isobaric adsorption and isobaric desorption. The high thermal resistance of the bed slows down heat transfer, prolonging adsorption and desorption processes.     

流化床用树脂基球形活性炭及其VOCs吸附性能

以聚苯乙烯树脂为原料,采用水蒸气活化、氯化锌活化及水蒸气?氯化锌协同活化方法制备了3种流化床用树脂基球形活性炭,采用固定床反应器考察了活性炭对乙酸乙酯的动态吸附行为,对比了其传质区长度,并利用Yoon?Nelson模型对实验数据进行了拟合. 结果表明,3种活性炭的摩擦磨损指数均小于0.1%,耐磨性能出色,物理、化学协同活化活性炭比表面积高达1702.49 m2/g,对二甲苯的静态吸附容量达0.86 g/g.     

硅胶及其混合吸附剂——水吸附工质对性能测试

测试了硅胶-水吸附制冷工质对的等量吸附线,且利用各类吸附方程对实验测量数据进行拟合以用于硅胶-水冷水机组的整体系统的数值模拟。实验还通过在纯硅胶颗粒中添加黏结剂或膨胀石墨形成混合吸附剂来提高传热性能。研究表明混合吸附剂（黏结剂的含量为1.1％）在解吸过程中前5min的解吸量相对于纯硅胶颗粒吸附剂提高了13.8％;解吸15min时,混合吸附剂的解吸量相对于纯吸附剂仅提高2.5％。表明混合吸附剂有利于缩短吸附循环周期。在添加剂质量分数相同的情况下,利用膨胀石墨作添加剂形成的混合吸附剂与通过浸泡于黏结剂溶液中形成的混合吸附剂的吸附性能相同,但有其各自的优缺点。     

A 3-zone model for protein adsorption kinetics in expanded beds

The adsorption behavior of expanded beds is more complex than that of fixed beds, since the adsorbent particle size, local bed voidage and liquid axial dispersion will vary axially with expanded height. Models applicable to fixed beds maybe not adequately describe the hydrodynamic and adsorption behavior in expanded beds. In this paper, a 3-zone model is developed, in which the model equations are written for the bottom zone, middle zone, and top zone of the column, respectively, and the model parameters, such as the adsorbent particle diameter, bed voidage and liquid axial dispersion coefficient, are zonal values. In-bed breakthrough curves are predicted by the 3-zone model, and tested against literature data for lysozyme adsorption on Streamline SP in an expanded bed.Model parametric sensitivity is analyzed. The effects of film mass transfer resistance, liquid axial dispersion and adsorbent axial dispersion on the breakthrough curves are weaker than that of protein intraparticle diffusion resistance for stable expanded beds. Adsorbent particle size axial distribution and bed voidage axial variation significantly affect in-bed breakthrough curves, therefore, model parameters should not be assigned uniform values over the whole column; instead the model should account for the adsorbent particle size axial distribution and bed voidage axial variation.     

Performance analysis of an adsorption refrigerator using activated carbon in a compound adsorbent

To improve the performance of the adsorption refrigeration of CaCl₂-ammonia adsorption system, activated carbon has been distributed uniformly in the mass of CaCl₂, thereby helping to enhance mass transfer and uplift the cooling power density. A multifunctional heat pipe adsorption refrigerator, in which activated carbon-CaCl₂ is used as compound adsorbent and ammonia as refrigerant, is designed. Water and acetone are used as working liquids for the heat pipe. This paper presents a study on the adsorption refrigeration performances of this adsorption refrigerator under two different working conditions, ice-maker for fishing boat driven by the waste heat from exhaust gases, and solar ice-maker driven by solar water heating. The obtained average SCP (specific cooling power) and the COP (coefficient of performance) of the refrigerator were measured to be 770.4 W/kg and 0.39 at about −20 °C of evaporating temperature for the former working condition, and they were 161.2 W/kg and 0.12 at about −15 °C of evaporating temperature for the later working condition.     

Adsorption of carbon dioxide using polyethyleneimine modified silica gel

To find an ideal adsorbent for carbon dioxide capture, a new polyethyleneimine modified silica gel material was synthesized with a simple procedure. Three silica gel materials with various particle sizes (15, 25 and 40–63 μm) were prepared and functionalized with polyethyleneimine. The carbon dioxide adsorption amounts of modified silica gel and non-modified silica gel were calculated using a mass balance equation at three different temperatures (298.15, 308.15 and 318.15 K), respectively, and the influence of gas pressure and particle size on adsorption was discussed. Experimental data showed that the carbon dioxide adsorption capacity of modified silica gel was better than non-modified silica gel, and the adsorption capacity gradually decreased with increasing particle size. The smaller particle size (15 μm) PEI modified silica gel had the largest adsorption capacity, at 298.15 K, and the adsorption amounts of various particle sizes of PEI-silica better fit the Langmuir isotherm model.