循环周期对吸附制冷管性能的影响与分析

设计制作了一种类似于热管、以13X分子筛-水为工质对的吸附制冷单管,吸附制冷单管直径为19 mm,吸附制冷单管由吸附床段和蒸发\冷凝段组成,其中吸附床段长800 mm,蒸发冷凝段长260 mm。吸附制冷系统由吸附制冷单管、管式电炉和数据采集装置组成,利用本装置对影响吸附制冷单管性能的循环周期、吸/脱附时间比进行了一系列实验研究,并利用数值模拟对分析结果进行了理论分析。研究表明:当吸附时间和脱附时间相等时,在不同脱附温度下,循环周期存在一个相应的最佳值,脱附温度越高,相应的最佳循环周期越长;适当增加一个循环周期内吸附时间所占比例可有效提高单元管制冷功率。对于此吸附单元管,在脱附温度为310℃时,吸附时间35 min、脱附时间25 min时,吸附制冷单管制冷功率达到最大值4.97 W,其单位质量吸附剂的制冷功率SCP为57.73W/kg,比吸附时间和脱附时间均为30 min时的制冷功率提高6.65%。     

太阳能固体吸附式制冷吸附床的设计及数值模拟分析

设计了管内填充吸附剂,管外走传热介质的新型吸附床结构,建立了相应的数学模型.以太阳能为驱动热源,分析了吸附床内温度在某时刻的静态分布以及温度、压力和脱附速率随时间的动态变化.通过对吸附床传热效果的分析指出该吸附床结构有较好的传热效果.     

肋板式吸附床传热性能的数值模拟

设计了新型肋板式结构吸附床,建立了吸附床在非第一类边界条件的三维传热传质数学模型.应用计算流体动力学中有限控制体积方法对吸附床内传热特性进行了模拟计算,并通过研究吸附床内温度随时间的动态变化,分析了换热流体参数和吸附剂导热系数变化对床层传热特性的影响.计算结果表明,吸附剂的导热系数,换热流体流速、温度对床层传热特性影响显著且肋板式吸附床传热效率高,吸附床内温度分布均匀.     

化学吸附式制冷系统传热传质的数值模拟和实验研究

运用多孔介质理论分析了化学吸附式制冷系统中的吸附床,按多孔介质的质量、动量和能量传递过程建立了吸附床内流动、传热和传质耦合求解的数学模型,并根据吸附剂在吸附床内多孔介质中的流动特性,采用比经典的Darcy模型更精确的多孔介质流动模型-Ergun模型。所建立的数学模型较之现有的吸附床传热传质数学模型能更全面、准确的描述吸附床的传热传质特性。将所建立的模型对化学吸附制冷样机进行了模拟计算,计算结果和测试结果吻合得较好。数学模型和计算结果有助于深入认识吸附床的传热传质特性,并可进一步用于吸附床和系统的优化设计。     

基于13X沸石分子筛/MgCl_2的复合吸附剂性能实验研究

复合吸附剂的吸附性能是吸附制冷循环过程中的一个重要参数,基于测试整体成型复合吸附剂吸附性能的需要,本文设计搭建了一种整体成型吸附剂性能测试装置,对复合吸附剂MgCl_2-13X进行了吸附性能测试实验。结果表明:该实验装置中吸附床外侧底部的温度变化速率较接近吸附床内部底部吸附剂的温度变化速率,二者温度变化速率相差0.01~1.9℃/min,整个吸附和脱附过程二者温度的平均值相差约3.24%,能够满足吸附剂性能测试实验的要求。吸附剂性能测试实验及电镜下吸附剂的微观结构表明:浸泡法制备的复合吸附剂的吸附性能与MgCl_2溶液的浓度有关,MgCl_2能够改善13X沸石分子筛的吸附性能,本实验测得当MgCl_2溶液的浓度为15%时所制得复合吸附剂MX3性能最优,其最大吸附量为0.32 g/g,最大吸附速率0.59 g/min,相比单一吸附剂13X沸石分子筛提高了20%。     

固体吸附式制冷系统中吸附床内的传热传质过程分析和强化

利用多孔性物质的吸附分离原理分析了固体吸附式制冷系统中吸附剂颗粒和整个吸附床的传热传质特性,并在此基础上介绍了目前国内外强化吸附床传热传质性能的主要措施。     

以硫化石墨为吸附剂基质的再吸附制冷性能分析

相比于传统的吸附式制冷,再吸附制冷作为一种新型的制冷方式,其结构更加简单,并且其制冷性能系数也比相同条件下的吸附式制冷系统要高,故有较好的应用前景。但受到吸附剂的传热传质性能的限制,难以实现高效的再吸附制冷。本文利用硫化石墨作为吸附剂的基质,对其导热系数以及渗透率进行了测试比较,优选吸附剂。并且针对再吸附制冷系统建立了相关数学模型,分析不同工况条件下吸附剂工质对的性能。对整个再吸附制冷过程进行模拟仿真,从而得到不同工况下的制冷性能。结果表明,采用新型复合吸附剂的再吸附系统,COP最大可达到0.3以上,SCP最大可达到161 W/kg。     

固体吸附式制冷系统新型针刺板吸附床数值模拟研究

固体吸附式制冷系统中吸附床内填充的吸附剂是一种多孔材料,由于多孔结构的存在,床体与吸附剂颗粒及吸附剂颗粒之间存在较大的热阻,因而存在传热速率慢,传热不均匀的缺点;在已有的板翅式吸附床基础上提出了一种新型针刺板吸附床,利用针刺丰富的扩展表面作为传热面,解决吸附剂内传热速率慢、温度场不均匀的问题。     

套管式吸附床传热性能的数值模拟

建立吸附床的传热数学模型,对套管式吸附床的传热性能进行数值模拟,并对影响吸附床传热性能的因素进行分析。结果表明:吸附剂导热系数是影响吸附床传热性能的关键因素,减小床层厚度和缩小套管的尺寸也能够明显改善吸附床的传热性能。     

温度场均匀性对吸附床吸附/脱附性能的影响

根据吸附制冷的特性,从理论上研究了吸附床温度场均匀性对吸附/脱附性能的影响;研究结果表明:温度场的均匀分布可提高吸附床的吸附/脱附性能,对今后吸附床的优化设计提供了理论依据.     

吸附式制冷工质对的吸附性能测试研究

吸附剂的性能是吸附制冷技术中最重要的参数之一,而吸附量和吸附速率是吸附剂性能的2个重要指标。准确测定吸附剂的性能对于吸附制冷机的设计起着至关重要的作用。本文结合国内外对吸附剂性能的测试方法以及本课题对汽车余热吸附制冷所用吸附剂的性能进行测试,着重阐述吸附剂性能测试所用方法的特点以及使用范围,旨在为吸附剂性能的准确测试提供参考。     

Numerical simulation of unsteady continuous countercurrent adsorption system with nonlinear adsorption isotherm

A theoretical dispersed plug flow model that includes a mass-transfer resistance represented by a linear driving force approximation is developed for unsteady-state continuous countercurrent adsorption systems having nonlinear equilibrium isotherms. The model is solved from unsteady state to steady state using Danckwert's boundary conditions. The system consists of two sections having 11 adsorption columns. The model is used to investigate the effects of various process parameters on the performance of the system. It is demonstrated that as the nonlinearity changes, the optimal choice of bed length, feed and eluent flow rates, and switch times must be suitably adapted. The results are compared with the “pore diffusion” and “equilibrium” models of Morbidelli et al.¹⁴ and are found to lie between these two models. To establish the consistency of the model the results are compared with one of the limiting asymptotes, namely, the linear isotherm with the experimental data of Ching and Ruthven^12,13 and are found to agree well.     

变压吸附系统吸附剂吸附容量的实验研究

运用实验的方法对变压吸附系统中吸附剂的吸附容量进行了研究.分析不同因素对吸附剂吸附容量的影响,包括吸附温度、吸附压力,给出吸附容量在这些因素影响下的变化规律,同时比较了不同吸附剂的吸附容量.实验结果可对工业选用吸附剂以及变压吸附系统的优化设计提供必要的数据.     

Multicomponent and adsorption calculations

A comprehensive treatment of incorporating multicomponent equilibrium theories into adsorption calculations is presented. The theories considered include the Langmuir, the Langmuir-Freundlich, the ideal adsorbed solution, and the potential theories. Procedures of calculating equilibrium concentrations under the three most common conditions based on these theories were given and sample calculation results presented to illustrate these procedures.     

Cadmium adsorption by coal combustion ashes-based sorbents--relationship between sorbent properties and adsorption capacity

A very interesting possibility of coal combustion ashes reutilization is their use as adsorbent materials, that can also take advantage from proper beneficiation techniques. In this work, adsorption of cadmium from aqueous solutions was taken into consideration, with the emphasis on the intertwining among waste properties, beneficiation treatments, properties of the beneficiated materials and adsorption capacity. The characterization of three solid materials used as cadmium sorbents (as-received ash, ash sieved through a 25 μm-size sieve and demineralized ash) was carried out by chemical analysis, infrared spectroscopy, laser granulometry and mercury porosimetry. Cadmium adsorption thermodynamic and kinetic tests were conducted at room temperature, and test solutions were analyzed by atomic absorption spectrophotometry. Maximum specific adsorption capacities resulted in the range 0.5-4.3 mg g(-1). Different existing models were critically considered to find out an interpretation of the controlling mechanism for adsorption kinetics. In particular, it was observed that for lower surface coverage the adsorption rate is governed by a linear driving force while, once surface coverage becomes significant, mechanisms such as the intraparticle micropore diffusion may come into play. Moreover, it was shown that both external fluid-to-particle mass transfer and macropore diffusion hardly affect the adsorption process, which was instead regulated by intraparticle micropore diffusion: characteristic times for this process ranged from 4.1 to 6.1d, and were fully consistent with the experimentally observed equilibrium times. Results were discussed in terms of the relationship among properties of beneficiated materials and cadmium adsorption capacity. Results shed light on interesting correlations among solid properties, cadmium capture rate and maximum cadmium uptake.     

Protein adsorption to titania surfaces

Titanium and its alloys are used widely in the manufacture of orthopaedic and dental implants. Their popularity is encouraged by the excellent biocompatibility of the surface oxide layer and the phenomenon of osseointegration that occurs following surgical implantation into bone. This term describes the fixation of a medical device through the formation of a direct interface with bone tissue. However, the processes that lead to osseointegration are not fully understood and, in particular, the contribution of selective protein adsorption to clinical success is the subject of debate. The aim of this study was, therefore, to investigate the adsorption of serum proteins to titanium oxide (titania) and to non-integrating surfaces as controls using a number of methods. In situ labelling of proteins with biotin and subsequent detection with avidin peroxidase on electroblots and an ELISA method gave the best results. Differences were observed between protein adsorption to the two classes of surfaces, with selective adsorption of vitronectin to the osseointegrating surfaces. It is suggested that this may influence the subsequent behaviour of cells and the process of osseointegration.     

Room-temperature water-vapor adsorption in niobium

Translated from Izmeritel'naya Tekhnika, No. 8, pp. 61–62, August 1990.     

Localized adsorption on heterogeneous surfaces

The general theory of localized adsorption on patchwise heterogeneous surfaces, in both the submonolayer and the multilayer range, is presented in this work.Exact and approximate mathematical methods for finding the binding energy distribution are considered for the Langmuir adsorption isotherm.It is shown that all the methods described (related to the solution of Fredholm integral equations of the first kind) can also be applied to the Brunauer-Emmett-Teller multilayer isotherm through the definition of the “enhanced pressure”.The physical interpretations are applied to the Dubinin-Radushkevich isotherm which consequently must be modified, with respect to the original formulation, in the very low pressure limit and in the multilayer range.     

Water vapor adsorption properties of amorphous cefditoren pivoxil evaluated by adsorption isotherms and microcalorimetry

Water vapor adsorption of ground cefditoren pivoxil was studied. The amount of water adsorbed increased with a decrease in the crystallinity of cefditoren pivoxil. It was found from the microcalorimetric measurements that the differential heat of water vapor adsorption at 1.5% adsorbed water increased with decreasing crystallinity of cefditoren pivoxil, suggesting that hygroscopicity of cefditoren pivoxil was enhanced by grinding. These results indicated that hydrophilic adsorption sites in cefditoren pivoxil increased through the grinding process. The results of infrared (IR) spectra examination suggested that the increment of hydrophilic adsorption sites through the grinding process resulted from the change of the environment of the carbonyl groups in two esters and amide.