太阳能吸附制冷空调吸附床温度场数值模拟与传热分析

建立了吸附床几何模型和数学模型,通过Fluent软件数值模拟得到床层温度分布的变化情况,并深入分析床层参数变化对床层温度分布的影响。结果表明,吸附剂的物性参数对床层温度分布影响显著;换热流体流速、温度对床层温度影响不大。在床层径向上存在着较大的温度梯度,但在轴向上温度分布比较均匀。在吸附剂的物性参数中,导热系数对床层温度变化影响最大。因此为了提高吸附床传热效率,应尽量增大吸附剂的导热系数,以及采取多种措施强化吸附床的传热效率。     

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。     

非平衡吸附特征的吸附床传热传质特性

建立椰壳活性炭-甲醇吸附式制冷系统吸附床传热传质数学模型,应用该模型进行具有非平衡吸附特性的吸附床传热传质研究,利用数值方法对数学模型进行求解,讨论了吸附床在冷却过程中吸附剂温度、吸附速率、吸附量、制冷系数以及单位质量吸附剂制冷功率与时间的关系,吸附床在加热过程中吸附剂温度、脱附速率及脱附量与时间的关系.研究结果表明:吸附床在整个吸附过程中的吸附速率存在一个峰值0.001 2 ks/s,吸附床在整个脱附过程中的脱附速率存在一个峰值0.001 7ks/s,吸附剂温度变化率在换热阶段趋于平缓,制冷系数值在吸附阶段近似呈线性增长,而单位质量吸附荆制冷功率在吸附阶段存在一个峰值35 kW/kW.     

吸附式制冷中固定床导热性能改进研究

本文对吸附式制冷系统中固定床的传热机理进行了实验探索.利用苯胺单体在吸附剂颗粒表面化学氧化聚合,形成均匀连续的高分子导热网,使吸附剂的有效导热系数提高到原来的4-10倍,对吸附剂的吸附性能无明显影响.实验分析了改性的吸附剂挤压成型强化吸附床层的传热,利用导热胶降低吸附剂与吸附换热器表面间接触热阻的效果,获得了一种较全面改进热交换性能的技术方法,在强化传热和热传导的同时,未影响吸附剂的传质性能,为吸附式制冷系统的产业化提供了新的技术路线.     

天然气吸附储存脱附过程的动态模拟

通过热动力学计算,认识了脱附过程当中储罐内温度剖面分布的典型特征:储罐轴心处的温度下降幅度最大。分析了脱附过程当中储罐壁的热交换、吸附剂的导热系数以及储罐内的初始压力对储罐内的温度剖面的影响。结论是加强储罐外壁的热交换、增大吸附剂的导热系数皆能改善吸附储罐内的温度剖面。     

螺旋板式吸附床的结构分析和传热性能研究

分析了螺旋板式吸附床的优缺点,采用逆流型的流动换热方式,针对制冷量为15kW的制冰工况对螺旋板式吸附床结构进行分析计算和优化设计,并理论研究其传热过程和冷热源的需求量,结果表明,螺旋板式吸附床的传热能力较其它吸附床结构形式有很大提高、体积较小,若能有效解决加工困难和传质通道的设置,则可以得到广泛应用,推动吸附制冷技术的产品化和商业化。     

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。     

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。     

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.     

新型复合吸附剂传热性能的强化

以氯化钙和杉木屑为原料,通过炭化活化的方法制备具有发达孔隙结构的吸附剂,然后加入膨胀石墨以强化吸附剂的传热性能。石墨的含量从0%到50%变化,通过氨吸附性能实验考察石墨含量对吸附量和吸附速率的影响。实验结果表明,在四个小时内,复合吸附剂对氨气的吸附量随着膨胀石墨含量的增加而减小,吸附速率随膨胀石墨含量的增加先增加后减小,而导热系数随膨胀石墨含量的增加单调的增加。对吸附制冷而言,膨胀石墨含量为30%的复合吸附剂具有最佳性能,其导热系数达到0.193W/(m?K),吸附时间为15 min时对应的吸附量达到0.431 g/g。     

吸附式制冷循环的分析

以吸附式制冷循环的热力过程为依据，使用火用分析的方法对连续回热循环做了分析，对循环中各部分火用损进行了比较。指出了连续回热循环中火用损的主要部位，并探讨了回热率及吸附床的传热性能对循环火用效率的影响。     

A dynamic model of heat and mass transfer in a double-bed adsorption machine with internal heat recovery

This paper presents the results of a predictive two-dimensional mathematical model of an adsorption cooling machine consisting of a double consolidated adsorbent bed with internal heat recovery. The results of a base-case, taken as a reference, demonstrated that the COP of the double bed adsorption refrigeration cycle increases with respect to the single bed configuration. However, it was verified that, in order to maximize also the specific power of the machine, the adsorbent beds must have proper thermo-physical properties.Consequently, a sensitivity analysis was carried out, studying the influence of the main heat and mass transfer parameters on the performance of the machine. The results obtained allowed us to define the adsorbent bed design that maximizes its heat and mass transfer properties, as well as the most profitable heat recovery conditions.     

变压吸附空分制氧过程非等温模拟

建立了变压吸附空分制氧过程非线性、非等温模型,并进行了数值模拟,计算结果与实测值吻合较好.在此基础上探讨了变压吸附过程中床层内温度和体积分数的动态行为,考察了吸附时间、吸附床高度、进气流速、清洗比等工艺参数对过程性能的影响.结果显示,对于本研究中的小型变压吸附装置,吸附热对产品气的影响不太大.     

一种新型的平板式太阳能制冷吸附器复合体设计

在成功研究太阳能固体吸附式制冷循环的基础上,结合平板式太阳能热水器集热芯片的制造技术,提出了一种新型的吸附器设计方法,并成功地实现了新型吸附器复合体的制造。实验表明,新制作的吸附器复合体结构合理,操作简便,能够有效地实现太阳能固体吸附制冷过程中供热与制冷联合循环的新思路,为太阳能固体吸附制冷技术吸附床的有效设计做了一次全新的尝试。     

Forced convection adsorption cycle with packed bed heat regeneration: Cycle à adsorption à convection forcée avec régénération thermique du lit fixe

The convective thermal wave is part of a patented cycle which uses heat transfer intensification to achieve both high efficiency and small size from a solid adsorption cycle. Such cycles normally suffer from low power density because of poor heat transfer through the adsorbent bed. Rather than attempting to heat the bed directly, it is possible to heat the refrigerant gas outside the bed and to circulate it through the bed in order to heat the sorbent. The high surface area of the grains leads to very effective heat transfer with only low levels of parasitic power needed for pumping. The new cycle presented here also utilises a packed bed of inert material to store heat between the adsorption and desorption phases of the cycle. The high degree of regeneration possible leads to good coefficients of performance (COPs). Thermodynamic modelling, based on measured heat transfer data, predicts a COP (for a specific carbon) of 0.90 when evaporating at 5°C and condensing at 40°C, with a generating temperature of 200°C and a modest system regenerator effectiveness of 0.8. Further improvement is possible. Experimental heat transfer measurements and cycle simulations are presented which show the potential of the concept to provide the basis of a gas-fired air conditioner in the range 10–100 kW cooling. A research project to build a 10-kW water chiller is underway. The laboratory system, which should be operational by June 1997, is described.     

Application of an embossed plate heat exchanger to adsorption chiller

The present research conducted a parametric study on an embossed plate heat exchanger (plate HX) type adsorption chiller with SWS-1L and water pair, using a numerical method. The plate HX has a relatively high heat transfer capacity and compact size, and this study is a first attempt to apply the plate HX as a new type of adsorption chiller, as an improved alterative to the fin-tube type heat exchanger. A feasibility study was conducted on the base model and the result is comparable to the value for existing fin-tube type adsorption chillers. Furthermore, a parameter study was conducted for seven important design parameters, embossing diameter ratio, embossing height, embossing pitch, bed thickness, plate thickness, heating temperature and heat transfer fluid velocity. The results provided guidelines for the optimal designs of plate HX type adsorption chiller. The optimal values of COP and SCP were 0.5118 and 662.8 W kg⁻¹, respectively.