氯化钙/硅胶和氯化钙/凹凸棒土复合吸附剂的制备及性能对比

分别通过浸渍法和焙烧法制备了两种复合吸附剂氯化钙/硅胶和氯化钙/凹凸棒土。在温度40℃、相对湿度20%条件,氯化钙/硅胶复合吸附剂的吸水性能随样本中氯化钙含量的增加而增加。氯化钙/凹凸棒土的最佳焙烧条件为焙烧温度300℃,焙烧时间2 h。在相对湿度为20%,吸附时间分别为15,20 min时,氯化钙/凹凸棒土的SCP分别为140.26,128.92 W/kg,远大于同等条件下氯化钙/硅胶的SCP。两种吸附剂的吸附性能对比表明,氯化钙/凹凸棒土吸附剂由于其良好的吸水性能更加适用于低温驱动的吸附制冷机。     

太阳能吸附制冷用复合吸附剂制备及其吸附机理探讨

以乙醇为吸附质，选取13X分子筛、凹凸楱土和氯化锶等为主要吸附材料．通过混合法制备了一系列有着优良吸附能的复合吸附剂。测定了乙醇在主要吸附材料和自制复合吸附剂上的吸附量，用TG-DTA法对主要吸附材料的热稳定性和自制吸附剂DTA脱附乙醇峰端温度进仃了分析.对吸附剂原料复合比例和扩孔剂种类等制备条件进行了实验研究。结果表明：自制复合吸附剂比单一吸附材料对乙醇确着更大的吸附能力；DTA分析的脱乙醇峰端温度明显低于单一吸附材料；加入扩孔剂E1或E2，可增加自制复合吸附剂孔容和孔径，改善其吸附性能；自制复合吸附剂对乙醇的吸附量显著高于活性炭。其中，M4-0003和M1-0001复合吸附剂对乙醇的平衡吸附量约为活性炭的2．5～4倍；M1-0001—乙醇工质对的吸附制冷量是活性炭—乙醇的2～6倍。对吸附剂复合的机理初步探讨表明：增加复合吸附剂弱吸附中心数，可降低其脱附温度。     

固体吸附式制冷系统中吸附剂粒径及吸附床总孔隙率对吸附床传热性能的影响研究

文章采用数值模拟方法研究了圆筒型吸附床的二维非稳态脱附传热过程,并基于综合导热系数和接触热阻分析了吸附剂的粒径和吸附床的总孔隙率对吸附床传热性能的影响,以及吸附床的总孔隙率与吸附剂粒径的最优组合。分析结果表明:当吸附床的总孔隙率较大时,吸附剂粒径对吸附床传热性能的影响更为明显,且吸附剂粒径越小,吸附床的传热性能越好;随着吸附剂粒径逐渐增大,吸附床总孔隙率对吸附床传热性能的影响呈现出不同的变化趋势;当吸附剂的粒径较小且吸附床的总孔隙率较大时,吸附床的传热性能最优。     

余热制冷用氯化钙_硅胶复合吸附剂的制备及性能研究

为了开发出利用余热进行吸附制冷的高性能吸附剂,采用浸渍法在真空下将氯化钙担载于粗孔硅胶上,制备了硅胶/氯化钙复合吸附剂,测试了复合吸附剂的吸附等温线和吸附速率,测试结果表明:浸渍法得到的复合吸附剂对水具有更大的吸附能力,在20%的湿度下,复合吸附剂在2h的吸附量为15.64 g/100 g吸附剂,是单一硅胶在相同条件下吸附量的8.06倍。用制备的复合吸附剂制作了一台小型吸附制冷机并进行了测试,当热源温度为90℃,冷却水温度为35℃时,在整个循环周期内(15 min),制冷功率为0.705kW,单位质量吸附剂的制冷功率(SCP)为70.51 W/kg,COP为0.25。     

硅胶-LiCl复合吸附剂-水的吸附性能研究

为研究硅胶在复合LiCl之后用于储热装置的性能,以4种不同浓度的LiCl溶液浸渍硅胶而制成复合吸附剂,对这4种复合吸附剂以及原硅胶的物理性质及储热性能进行测试分析.结果表明:LiCl使硅胶的比表面积等参数发生变化.复合吸附剂的渗透率在储热装置的推荐值以上,在吸附量、吸附热以及储热密度等参数上相对于硅胶均有提升,适合应用...     

炭化活化温度对活性炭-CaCl2复合吸附剂性能的影响

为研究并开发高性能的吸附剂,本文以CaCl₂和杉木木屑为原料,采用炭化活化造孔的方法制备复合吸附剂,考察了炭化活化温度对复合吸附剂性能的影响,炭化活化温度分别选择400℃、500℃、600℃和700℃。扫描电镜照片和元素分布图表明,复合吸附剂具有发达的孔隙结构而且CaCl₂分布均匀。NH₃吸附性能实验表明,吸附剂4 h的NH₃吸附量随炭化活化温度的升高而增加。而对于吸附制冷而言,500℃炭化活化温度下制备的复合吸附剂具有最好的性能,其30 min的吸附量达到0.488 g/g。     

新型吸附式制冷系统吸附床的研究进展

吸附床的传热传质性能是提高吸附式制冷效率的关键,优化吸附床的结构能够有效提高整个吸附床的传热传质效率,减少热量损失,提高系统的制冷效率（coefficient of performance, COP）和单位质量吸附剂制冷量（specific cooling power, SCP）。本文介绍了近年来几种新型吸附床的类型,综述了吸附剂侧的固化吸附剂和涂层吸附剂,以及换热器侧的新型换热器结构。最后阐述新型吸附床的未来发展方向和研究重点。     

新型复合吸附剂SiO2·xH2O·yCaCl2与常用吸附剂空气取水性能的对比实验研究

提出了一种便携式吸附空气取水器 ,并为其提出了一种新型复合吸附剂SiO2 ·xH2 O·yCaCl2 。介绍了这种吸附剂的配制方法 ,分析了它吸附湿空气中水蒸气的原理。通过实验表明 :在空气温度恒为 2 5℃、相对湿度 4 0 %的条件下 ,这种复合吸附剂的平衡吸附量we(H2 O干吸附剂 )可达 0 .4 ,是粗孔球形硅胶的 5 .7倍、细孔球形硅胶的 2 .1倍、人工沸石 13X的 1.9倍、椰壳活性炭的 6 .8倍。通过对比分析它们的吸附速度曲线表明 :这种复合吸附剂的吸附特点是吸附量大、吸附速度快。分析结果表明 :采用这种复合吸附剂的空气取水器即使在我国西北地区 7月份的干燥气候条件下也能够有很高的出水量。而且这种复合吸附剂的解吸温度低 (6 0～ 80℃ ) ,可用太阳能加热解吸 ,是一种理想的取水用吸附剂     

新型固体吸附制冷吸附床的结构比较研究

参考国内外现有的固体吸附床结构 ,利用相似原理比较了气 -液、气 -气、液 -液换热器结构的传热特点 ,得出板翅式和翅片管式固体吸附床比管壳式固体吸附床具有传热系数高和传热面积大的优点。本文提出在逐渐解决固体填充和加工工艺困难的前提下 ,板翅式和翅片管式固体吸附床具有很好的应用前景     

一种新颖的太阳能制冷管及其性能实验研究

一种新颖结构的太阳能吸附制冷管,其吸附床由一种具有高强度,高吸附性能和导热性能,并对太阳能具有高吸收率的复合吸附剂块组成,与已有的太阳能制冷系统相比,每根冷管生成一个制冷系统,结构简单,密封性好,同时吸附床可直接吸收太阳辐射,提高了对太阳能的有效利用。实验表明,在未采用专门的集热装置,吸附床向阳面温度仅为７５℃左右的情况下,冷管的性能,系数可达８％左右。     

Composite adsorbents of CaCl2 and sawdust prepared by carbonization for ammonia adsorption refrigeration

Composite adsorbents of CaCl₂ and sawdust prepared by carbonization for adsorption refrigeration with NH₃ as refrigerant are tested, and the effects of carbonization temperature on the sorption capacity and rate are analyzed. The results show that the amount of pores in the sawdust of the composite adsorbents carbonized, apart from the content of CaCl₂, is the most dominant factor influencing the NH₃ sorption on composite adsorbents. The optimum carbonization temperature is 700°C, which gives the maximal NH₃ sorption capacity as high as 0.774 kg of NH₃ per kg of the composite, and the specific cooling power is approximately between 338 and 869 W/kg with the cycle duration varying from 5 to 20 minutes. The present study demonstrates that the composite absorbent of CaCl₂ and sawdust prepared by carbonization is more promising and competitive for adsorption refrigeration application.     

The heat and mass transfer performance of facile synthesized silica gel/carbon-fiber based consolidated composite adsorbents developed by freeze-drying method

A series of experimental investigations had been performed to analyze the heat and mass transfer performance for two novel types of silica-based consolidated composite adsorbents developed by the freeze-drying method. The first type of adsorbent is silica gel consolidated with carboxymethyl cellulose (CMC) (SC), while the other is silica gel consolidated with CMC and carbon fiber powder (SCC). Results indicate that the thermal conductivity of consolidated composite adsorbents increases with the mass proportion of carbon fiber powder, while it decreases with the increasing moisture content in the preparation process of the adsorbents. When the mass ratio of silica gel, CMC, and carbon fiber powder is 4:1:4, the highest thermal conductivity of consolidated composite adsorbent obtained from experiments reaches 1.66 W m^?1 K^?1, which is 13.4 times greater than that of pure silica gel. Furthermore, the results of macroporous properties analysis of typical samples including SC20 and SCC20 (where the 20 means that the undried samples have a water content of 20% by mass during the preparation process) show that heat transfer additives effectively improve the macroporous porosity and permeability of the consolidated composite adsorbents. The study on adsorption dynamic performance indicates that the freeze-drying method helps to improve the adsorption performance including adsorption rate and equilibrium water uptake. The experimental results also show that the mass transfer coefficient K of the two typical samples are approximately stable at 5 × 10^?3 s^?1 when the adsorption temperature is ranged between 30 and 40°C, which are almost twice the corresponding values of the samples developed by heating–drying method. Therefore, the proposed approach which is the consolidation with heat transfer additives combined with freeze-drying method is effective for simultaneously enhancing the heat and mass transfer performance of the silica gel adsorbents.     

Computational study of a novel continuous solar adsorption chiller: performance prediction and adsorbent selection

A novel solar adsorption chiller intended for domestic use is presented. The chiller can be integrated with existing solar systems based on flat plate collectors, and, contrary to commercial chillers, it operates continuously. A detailed analysis of both the simple and the heat‐integrated cycle is carried out so as to select the optimal adsorbent and operating conditions. The employed integral thermodynamic model takes into account the inert masses that limit the performance of the chiller, such as the metal frame, the thermo‐fluid, and the non‐adsorbed steam, by introducing heat capacity effects. Given the adsorption equilibrium data, the energy balances, the performance, and the useful thermal loads of the system can be calculated at any operating conditions. The results indicate that silica gel Type A is a more efficient adsorbent compared to silica gel Type RD or Type 3A. Furthermore, the total porosity has a slight effect on system performance, while optimal operation can be achieved when the condenser temperature is less than 326 K and the evaporator temperature greater than 280 K. Copyright © 2006 John Wiley & Sons, Ltd.     

Parametric study on the silica gel–calcium chloride composite desiccant rotary wheel employing fractal BET adsorption isotherm

In this paper a family of new silica gel–calcium chloride composite adsorbents is presented for desiccant rotary wheel in dehumidification system. For these desiccants the water sorption equilibrium has been measured in a wide relative vapour pressure range. This experimental study shows that the vapour adsorption properties of the composites using calcium chloride as impregnated salt can be controllably modified by varying the amount of the salt inside the pores. The thermodynamic performance of such desiccant rotary wheel is analysed based on the adsorption equilibrium equations obtained through nonlinear regressions using fractal BET theory. The simulation results show that the new composite desiccants can be effectively used in a rotary wheel dehumidifier and to improve its performance, various optimum operational/system parameters have been identified. Copyright © 2005 John Wiley & Sons, Ltd.     

Experimental research on dynamic operating characteristics of a novel silica gel-water adsorption chiller

A novel silica gel-water adsorption chiller consisting of two adsorption/desorption chambers and an evaporator with one heat-pipe working chamber is experimentally studied. The dynamic operating characteristics of the chiller and the thermodynamic characteristics of the adsorber are obtained. The experimental results show that the dynamic operating characteristics of the chiller and the thermodynamic characteristics of the adsorber are satisfactory and that the cycle is a novel and effective adsorption cycle. A mass recovery process increases the cyclic adsorption capacity of the system and improves adaptability of the chiller to a low-grade heat source. In addition, the experiment indicates that this novel chiller is highly suitable for an air conditioning system with a low dehumidification requirement or a system with a large cycle flowrate and an industrial cooling water system. Translated from Journal of Shanghai Jiaotong University, 2006, 40(2): 306–310 [译自: 上海交通大学学报]     

Mathematics model for heat and mass transfer on an adsorption bed

In a solid adsorption refrigeration system, the real cycle with non‐equilibrium adsorption is different from the ideal cycle with equilibrium adsorption. To investigate the heat and mass transfer process inside the adsorption bed, a model was established. Mathematical models were then solved by numerical method. The best cycle time of 24 minutes was ascertained through the strategy of SCP priority and paying attention to COP. The influence of the length of adsorption cell tube to the performance of refrigeration system is discussed. © 2009 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20271 Copyright © 2009 Wiley Periodicals, Inc.     

Heat-exchanger design and switching-frequency effects on the performance of a continuous type solar adsorption chiller

A transient one-dimensional model, capable of describing the performance of a newly-introduced adsorption chiller with continuous operation, is developed. Since the cycle time and the switching frequency have a great influence on chiller performance, a non-dimensional switching frequency is introduced and a systematic parametric study is carried out in order to determine regions of optimal operation. An optimization based on the thermodynamic efficiency yields a lower switching frequency than an optimization based on the maximum cooling capacity. In addition, the effect of the heat-exchanger design parameters on system performance is explored. An increase of either the bed’s Fourier number or the thermofluid’s Nusselt number has a positive effect on both COP and cooling capacity. An improvement of system performance can also be achieved by decreasing either the thermofluid’s Fourier number or the bed’s Biot number. Finally, the effect of space velocity of the thermofluid exhibits the most interesting behavior; an increase of the space velocity has a positive effect on cooling capacity and a negative effect on COP.     

Improvement of both adsorption performance of silica gel and heat transfer characteristics by means of heat exchange modulation for a heat pump

In order to provide high performance silica gel for an adsorption heat pump (AHP), gels were synthesized using the sol-gel process modified with a new method of controlling the primary gel particle growth by the addition of aluminum ion. In this process, the pores of the silica gel synthesized became smaller when aluminum ion was added in the washing process. Furthermore, this silica gel adsorbed more water at a low region of water vapor pressure and its adsorption ability did not change after 100 repetitive times of adsorping/desorping water vapor. The experimental results from the water vapor adsorption on the silica gel agreed well with theoretical results obtained under the Lump model for heat transfer and intraparticle diffusion model for mass transfer. A new direct heat exchange silica gel module (DS-module) for the AHP was provided, and the heat transfer characteristics during the operation for the adsorption of water vapor were both experimentally and theoretically determined. The period of the adsorption for the DS-module was shorter than that for a silica gel/tube module. Therefore, with the addition of the DS-module the heat transfer in the AHP adsorber was sufficiently enhanced and the maximum heat generation power for the 2-mm-thick DS-module was obtained. © 1997 Scripta Technica, Inc. Heat Trans Jpn Res, 25(7): 420–433, 1996     

Performance evaluation of multi-stage, multi-bed adsorption chiller employing re-heat scheme

This paper deals with the performance investigation of a silica gel/water-based multi-stage, multi-bed, six-bed adsorption chiller employing re-heat scheme. The innovative chiller is powered by waste heat or renewable energy sources of temperature between 50 and 70 °C along with a coolant of inlet temperature at 30 °C for air-conditioning purpose. The performance of the six-bed adsorption chiller using re-heat scheme is compared with that of the six-bed chiller without re-heat. With the same operating conditions, such as the heat transfer fluid inlet (HTF) temperatures, HTF flow rates, adsorption/desorption cycle time and same chiller physical dimension, it is found that both the cooling capacity (CC) and the coefficient of performance (COP) of the three-stage chiller with re-heat scheme are superior than those of the three-stage chiller without re-heat scheme.