利用热管强化吸附床内的传热传质

为了强化吸附式制冷吸附床内的传热传质，设计了利用高效传热元件热管作为内翅片的吸附床。在能量守恒关系和吸附平衡方程的基础上建立了吸附床的数学模型，并对此模型用数值方法进行了求解。求解结果表明利用热管元件可以显著的改善吸附床内的传热传质过程，缩短了吸附式制冷的循环时间，提高了系统的效率，该数学模型为吸附床的设计参数的选择和优化等提供了依据。     

太阳能固体吸附式制冷循环的吸附床内传热传质耦合计算

用多孔介质理论方法分析了太阳能固体吸式制冷循环的吸附床并相应地按多孔介质的质量、动量、能量传递过程建立了太阳能固体吸附式制冷循环吸附床内传热传质耦合求解的数学模型。用本文建立的方法,可对吸附式制冷循环的吸附床进行了热动力学分析与计算,并可进一步用于系统的优化设计中。     

太阳能固体吸附式制冰机热动力学性能分析模型及实验

分析了太阳能固体吸附式制冷装置中吸会床的传热传质计算过程,给出了求解模型的具体方法,运用数值传热学的方法,计算了在一定日照国徽能量条件下,系统装置的吸附床内的温度场分布,实验表明,所建立的模型能对太阳能固体吸附式制冷装置进行了性能动态模拟,为系统装置的优化设计提供了参考。     

翅片管整体传热传质强化的太阳能吸附式制冷系统性能研究

针对太阳能金属管式吸附床传热传质存在的不足,采用增加吸附管传热翅片及增大传质通道的方法,提出一种整体强化传热传质的新型翅片管设计方法,分别设计两种结构形式的太阳能吸附集热器,建立采用活性炭-甲醇为工质对的太阳能吸附式制冷系统。实验表明,采用吸附管横放、两端分别连接汇流导管形式的太阳能翅片管式吸附集热床可明显改善系统制冷性能,其吸附制冷效率是采用吸附管纵向放置、从翅片管上部通过导管连接到汇流导管的吸附床的太阳能吸附式制冷系统的3.56倍。采用性能较好的吸附床可构建太阳能吸附式制冷系统,并在晴朗无云、晴天有时有云、多云辐射强烈及多云辐射微弱4种典型天气情况下,进行吸附制冷系统运行特性和制冷性能实验研究,结果表明前三种天气条件下吸附床维持较高温度(≥80℃)超过4 h,制冷剂解吸较为充分,均产生制冰效果,制冷效率较高,COP最高达0.129;在多云太阳辐射微弱天气条件下,虽然吸附床维持在较高温度(≥80℃)时间不到2 h,但COP可达0.039,体现出该翅片管式吸附床良好的天气适应性。     

固体吸附式制冷系统中吸附床传热传质研究进展

总结了近２０年来国内外吸附式制冷循环系统中吸附床传热传质研究的发展及现状。将吸附床传热传质数学模型分为３类进行了讨论：（１）均匀温度场模型；（２）均匀压力场模型；（３）非均匀温度场和压力场模型。以具体的吸附器结构为例，详细描述了不同数学模型的前提建模方法和适用范围，指出了吸附床传热传质数值研究的发展趋势。     

吸附床传热传质数学模型研究

在固体吸附制冷循环中,实际的吸附(解吸)过程都是非平衡吸附过程,与理论循环之间存在较大差距.建立吸附式制冷系统吸附床传热传质数学模型,利用数值方法对数学模型进行求解.采用SCP(单位质量吸附剂的制冷功率)优先,同时兼顾COP(性能系数,即制冷量与加热量的比值)的策略,依据建立的吸附床传热传质数学模型进行计算,从而确定吸附式制冷系统循环的最佳周期是24 min,并分析了吸附单元管的长度尺寸对整个制冷系统循环性能的影响.     

变压强化传质太阳能吸附制冷特性研究

为深入分析太阳能吸附制冷变压工况对制冷性能的影响,在管道泵强化传质太阳能吸附制冷系统实验平台基础上,开展对太阳能吸附制冷系统强化传质变压工况下解吸量、制冷量的实验分析,并与自然传质恒压工况进行对比,获得强制循环下太阳能吸附制冷系统变压制冷特性。实验结果表明:在同等加热量情况下系统运行10 h,吸附制冷系统加装强化传质管道泵后,白天加热解吸阶段随着吸附床温度的提高,吸附床在强化传质工况下与自然传质工况下相比压力降低约10 kPa,从而使得强化传质比自然传质解吸率提高21.7%、解吸量提高1000 mL,制冷循环系数COP_(solar)提高18.8%。     

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。     

太阳能固体吸附式制冷系统部件的实物设计

对太阳能固体吸附式制冰机系统的关键零部件吸附床、冷凝器、蒸发器加以分析,并进行了实物设计。实验结果表明,所设计的系统零部件在太阳能固体吸附式制冰机装置实际运行工况下具有较好的传热、传质特性,系统各子部件间运行时能够很好地匹配,为太阳能制冷空调的实用化奠定了良好的基础。     

固体吸附式制冷的关键技术研究

描述吸附容量的Ｄ－Ａ方程、吸附床内的传热传质、新型热力循环的潜力与可行性、吸附系统的技术经济性和优化控制、实际吸附循环理论以及双效／多效吸附式制冷等是吸附式制冷尚需进行研究的基础课题。本文对固体吸附式制冷机的关键技术进行了探讨。     

Experimental investigation and mathematical modelling of a solid adsorption refrigeration system

The objective of this work is to study the thermodynamic mechanism and performance of an engine exhaust-powered adsorption refrigeration system using CaCl₂ as adsorbent and NH₃ as refrigerant. A 6 kW nominal refrigerating capacity adsorption refrigerator was developed. The working performance of the refrigerator is presented. It is concluded that the refrigerating capacity at constant evaporating temperatures varies with the input heat into the generator, and the heat transfer affects strongly the mass transfer in the adsorbent, making it work in different mean generation and adsorption temperatures. A conventional test bed was developed for investigating the properties of CaCl₂–NH₃ adsorption/desorption unit tube. A mathematical model based on non-equilibrium thermodynamics was developed to describe the performances of the adsorption refrigerating system.     

吸附式制冷系统吸附床内非平衡态热力学分析

从非平衡态热力学角度，对以氯化钙—氨为工质对的固体吸附式制冷系统吸附床内传热传质过程进行了分析，建立了吸附床内热质耦合模型，并通过对模型的数值模拟，探讨了解吸／吸附过程中各热力学流之间的作用关系及其对吸附床熵产率的影响。     

基于平行流铝扁管吸附床传热性能的模拟研究

吸附床是吸附式制冷系统的关键部件。吸附床的换热能力对吸附式制冷系统的各项性能有显著影响。文章针对应用于吸附床的传统换热器和扁管换热器的不足之处,设计出一种新型平行流铝扁管吸附床,并建立了该吸附床的二维传热模型,以温度随时间的变化情况为分析指标,分析翅片的间距、高度、厚度,以及吸附剂体积分数等因素对吸附床传热性能的影响,从而优化调整吸附床的结构,提高其换热性能。分析结果表明:当翅片高度约为70 mm时,吸附床的换热能力达到峰值;当翅片厚度大于1.5 mm时,翅片厚度的增加对吸附床传热性能的影响比较微弱;当吸附剂体积分数由0.25逐渐增大至0.45时,吸附剂的等效传热系数约增加了50%。     

Thermodynamic analysis and performance study for adsorption refrigeration cycle driven by a fuel cell electric vehicle waste heat

Three kinds of adsorption refrigeration cycles are analyzed in this paper, a two‐bed continuous cycle, an adiabatic mass recovery cycle, and an isothermal mass recovery cycle. Operating parameters (including desorption temperature, adsorption temperature, cycle adsorption rate, COP, and period refrigerating capacity) with the change of the evaporating temperature, condensing temperature, heat capacity ratio, and heat resource temperature are discussed. The analysis indicates that performance differences between the mass recovery cycle and the two‐bed continuous cycle are reduced with an increasing of evaporating temperature and heat source temperature. By increasing the heat capacity ratio, COP values for the three kinds of cycle decrease. When the heat source temperature is between 70 and 90°C, the performance of the isothermal mass recovery cycle is best. Through study, this paper puts forward that the isothermal mass recovery cycle is the best cycle for adsorption refrigeration systems driven by fuel cell electrical vehicle waste heat. © 2010 Wiley Periodicals, Inc. Heat Trans Asian Res, 39(7): 523–538, 2010; Published online 16 July 2010 in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/htj.20315     

Simulation of an adsorption solar cooling system

A more realistic theoretical simulation model for a tubular solar adsorption refrigerating system using activated carbon-methanol (AC/M) pair has been introduced. The mathematical model represents the heat and mass transfer inside the adsorption bed, the condenser, and the evaporator. The simulation technique takes into account the variations of ambient temperature and solar radiation along the day. Furthermore, the local pressure, and local thermal conductivity variations in space and time inside the tubular reactor are investigated as well. A C++ computer program is written to solve the proposed numerical model using the finite difference method. The developed program covers the operations of all the system components along the cycle time. The performance of the tubular reactor, the condenser, and the evaporator has been discussed. Time allocation chart and switching operations for the solar refrigeration system processes are illustrated as well. The case studied has a 1 m² surface area solar flat plate collector integrated with a 20 stainless steel tubes containing the AC/M pair and each tube has a 5 cm outer diameter. In addition, the condenser pressure is set to 54.2 kpa. It has been found that, the solar coefficient of performance and the specific cooling power of the system are 0.211 and 2.326 respectively. In addition, the pressure distribution inside the adsorption bed has been found nearly uniform and varying only with time. Furthermore, the AC/M thermal conductivity is shown to be constant in both space and time.     

Numerical study of a combined heat and mass recovery adsorption cooling cycle

A new transient two-dimensional model for the simulation of a combined heat and mass recovery adsorption cooling cycle based on the zeolite NaX/water working pair is proposed in this paper. The model describes the transfer phenomena in the adsorber in detail and is solved by control volume method. Internal and external mass transfer limitations which are neglected by many researchers are considered in the model since they have significant effects on the performance of the adsorption cooling cycle. The numerical results show that the combined heat and mass recovery cycle between two adsorbent beds can increase the coefficient of performance (COP) of an adsorption cooling system by more than 47% compared to the single bed cycle. This numerical model can be used in system optimization and design of adsorption cycles.     

10kW吸附冷冻机组基本工作特性试验分析

为了对一台设计制冷量为10kW的吸附冷冻机进行试验分析和验证,搭建了一套完整的性能测试试验台,并利用试验台测定了机组的吸附床、冷凝器以及蒸发器工作工况下的相关数据,根据试验结果分析了系统各个主要部件的性能。试验结果和分析表明,被试机组各部件的性能良好,不过蒸发器和冷凝器的换热面积还可适当增加。根据设计工况下测量得到数据,计算得到机组制冷量和COP分别达到11．4kW和0．28,达到设计要求的1149／6和140％。     

Review of mathematical investigation on the closed adsorption heat pump and cooling systems

A mathematical model of the closed adsorption heat pump and cooling systems is particularly used to assist in interpreting the observed phenomena, to design the system, to predict the trends, and to assist in optimization. In this paper, various mathematical models mainly analyzing the heat and mass transfer process of an adsorption bed in closed adsorption heat pump and cooling systems are reviewed and classified based on complexity, into three main groups: i.e. thermodynamic model; lumped parameters model; heat and mass transfer model. The major characteristics of different models and assumptions used are presented and discussed. Also, the numerical methods and validation of the models are summarized and significant results obtained through mathematical model are detailed. Although the models have evolved to a point where several features of the process can be predicted, more effort is required before the models can be applied to define actual operating conditions as well as to further investigate new closed adsorption cycles.     

A dimensionless analysis of heat and mass transport in an adsorber with thin fins; uniform pressure approach

A numerical study on heat and mass transfer in an annular adsorbent bed assisted with radial fins for an isobaric adsorption process is performed. A uniform pressure approach is employed to determine the changes of temperature and adsorbate concentration profiles in the adsorbent bed. The governing equations which are heat transfer equation for the adsorbent bed, mass balance equation for the adsorbent particle, and conduction heat transfer equation for the thin fin are non-dimensionalized in order to reduce number of governing parameters. The number of governing parameters is reduced to four as Kutateladze number, thermal diffusivity ratio, dimensionless fin coefficient and dimensionless parameter of Γ which compares mass diffusion in the adsorbent particle to heat transfer through the adsorbent bed. Temperature and adsorbate concentration contours are plotted for different values of defined dimensionless parameters to discuss heat and mass transfer rate in the bed. The average dimensionless temperature and average adsorbate concentration throughout the adsorption process are also presented to compare heat and mass transfer rate of different cases. The values of dimensionless fin coefficient, Γ number and thermal diffusivity ratio are changed from 0.01 to 100, 1 to 10^− 5 and 0.01 to 100, respectively; while the values of Kutateladze number are 1 and 100. The obtained results revealed that heat transfer rate in an adsorbent bed can be enhanced by the fin when the values of thermal diffusivity ratio and fin coefficient are low (i.e., α^? = 0.01, Λ = 0.01). Furthermore, the use of fin in an adsorbent bed with low values of Γ number (i.e. Γ = 10^− 5) does not increase heat transfer rate, significantly.