结构参数对液体除湿器性能的影响

建立了带内冷却的竖直板降膜液体除湿器的传热传质数学模型。并进行了相应的数值计算。计算结果表明,除湿器的结构参数竖直板长度和板间距对除湿性能的影响比较大,且都存在一个使除湿器性能最佳的值。     

逆流填料式液体除湿系统设计计算的ε-NTU法

在热力学盐球温度和盐球比热容基础上，提出逆流填料式液体除湿系统的设计计算方法ε-NTU法，给出算例，并将计算结果与文献的数值模拟结果进行了比较，认为ε能够在保证较高计算精度的前提下大大提高计算效率，具有工程应用价值。     

液体除湿空调系统除湿剂再生性能影响因素

液体除湿空调系统中,除湿剂再生过程的效率和稳定性决定空调系统运行效率和稳定性.探讨了液气比、除湿剂喷淋温度、除湿剂的溶质质量分数及再生空气状态对除湿剂再生性能的影响.     

液体除湿再生性能的理论与实验差异性分析

以实际液体除湿空调系统为对象,进行了数值模拟和实验对比研究,结果表明,实验值和模拟值有相同的变化趋势;在诸多的入口参数中,溶液的温度、浓度以及空气含湿量对再生溶液浓度变化影响较大;溶液出口温度的实验值偏小于理论值,浓度变化的实验值偏大于理论值.重点分析了理论数据和实验数据产生差异的原因.     

小型液体除湿空调系统实验研究

对小型液体除湿空调系统,从居住建筑除湿负荷及经济性角度出发,采用CaCl2溶液进行液体除湿实验,研究CaCl2除湿和再生的动态特性。研究发现除湿与再生的3个重要因素为溶液温度、溶液浓度和空气进口含湿量。在实验工况下,CaCl2溶液的除湿量为32 g/kg,再生性能优于除湿性能,约为除湿的1.3～9倍。对实验进行总结后,认为CaCl2作为除湿剂进行液体除湿还有很大改进空间和推广潜力。     

叉流除湿器中溶液与空气热质交换模型

建立了简化数学模型 ,空气出口温度和含湿量、溶液出口温度和质量分数的数值计算结果与实验结果的偏差在± 1 0 %以内 ,全热效率和除湿效率的偏差在± 2 0 %以内。通过分析除湿器内部温度场和浓度场得出 :在叉流除湿器中 ,不能忽略空气温湿度沿溶液流动方向和溶液温度沿空气流动方向的变化 ;传质驱动势要采用积分平均湿差的方法计算 ,而不能简单地采用对数平均湿差来表示     

液体除湿空调除湿性能影响分析

以液体除湿空调系统为实验对象,改变系统中除湿器入口空气及溶液的参数,得出空气出口温、湿度随之变化的状况.与理论模拟计算值比较,发现实验值和理论值有相同的变化趋势.由此得出各入口参数中,溶液的温度和流量的变化对空气出口温、湿度影响较大,空气的出口温度实验值偏小于理论值,空气的出口湿度实验值偏大于理论值.这将对液体除湿空调系统的性能分析和设计提供帮助.     

平板降膜除湿场协同性分析

溶液除湿方式在节能领域有广阔的发展前景,对溶液除湿涉及的传热传质耦合过程进行研究可以完善相关理论知识。本文采用Fluent数值模拟方法,在渗透理论模型的基础上,从场协同的角度,利用协同角评价标准分析了不同工况下平板降膜溶液除湿过程。对不同入口速度、入口温度、入口浓度、入口含湿量进行了数值模拟。研究结果表明:选定工况范围内,浓度场和速度场的协同性随着入口溶液温度、入口空气流速的升高而减弱,随着入口空气含湿量、入口溶液浓度的增加而增强。该数值模拟为溶液除湿研究提供了新的研究角度。方差法分析得到各因素对协同性影响程度由大到小排序为溶液温度、溶液浓度、气流速度、空气含湿量。     

综合管廊通风除湿有效时长研究

为了解综合管廊通风除湿有效时长的变化规律,利用数值模拟以通风换气效率、通风除湿效率作为技术性评价指标进行比选,以最优通风形式评价6个不同影响因子作用下的综合舱通风除湿效果,判断其与通风除湿有效时长之间的相关性,基于多元回归分析搭建通风除湿有效时长预测模型。结果表明:“一端进风一端排风”通风形式的除湿表现最优;通风分区长度和通风换气次数达到一定值后除湿效果趋缓;进风温度与廊内温度初始值的差值越小除湿效果越好;对于相关性系数:进风相对湿度＞断面宽高比＞通风分区长度＞通风换气次数＞廊内相对湿度初始值＞进风温度;模型预测的通风有效时长拟合值与数值模拟结果之间的误差为0.43%,回归模型拟合效果较好。     

液体除湿与排风热回收相结合的新风处理系统

该系统能实现温度湿度独立控制,提高空调冷水温度。介绍了液体除湿独立处理新风和液体除湿与全热换热器共同处理新风的焓湿图和系统流程图。结合对某工程的节能改造,分析了节能效益及减排量。结果表明,应用该系统在设计工况下可获得冷量1.36GJ/h,CO2减排量132.5kg/h,节能减排效果显著。     

叉流平板式间接蒸发冷却过程数值模拟

建立了数学模型,对叉流平板式间接蒸发冷却过程进行了数值模拟分析,得到了分别沿一、二次空气流动方向一次空气干球温度和二次空气干湿球温度的分布,以及水膜温度的变化情况。     

埋地钢管气密性试验过程温度场的数值模拟

建立埋地钢质管道气密性试验过程温度场模拟的物理模型,确定温度场水平方向与垂直方向的边界条件。采用有限元分析软件,对埋地钢质管道气密性试验过程的温度场分布进行瞬态数值模拟。气密性试验开始阶段,管内气体温度下降较快,埋地管道对土壤温度场的影响范围逐渐增大,1．5h后管内外温度场基本达到稳定,根据数值模拟的结果,拟合得到了温度场达到稳定后管内外温度的关系式,数值模拟结果与试验结果基本吻合。     

置换通风系统室内温度分布的实验研究

实验研究了置换通风系统送风参数和环境参数对室内温度场分布特性的影响.测量了不同送风量、送风温度和夹层空气温度下室内不同测点及人体不同部位上的竖直温度分布,并将实验值与CFD模拟结果进行比较,结果表明二者吻合较好.不同参数条件下的实验结果表明,随着送风量的增大,热分层高度相应提高,但送风量达到一定值后,其对竖直温度梯度的影响明显减小;送风温度的变化只对室内整体温度产生影响,而几乎不影响室内温度梯度;夹层空气温度的升高对室内下部温度影响不大,而上部区域温度升高明显.     

大型展览大厅空气分布模拟分析(Ⅱ)

通过对4个方案在非等温条件下的数值模拟分析,比较了非等温条件下与等温条件下速度场的差异;总结了为达到温度场均匀,区域送风量的分配原则;分析了同侧送风与回风的空气分布模式下回风口高低对温度场的影响。     

夏季空调房间气流组织的数值模拟

应用计算流体力学方法对夏季空调房间两种送风参数下的室内气流组织进行了数值模拟,给出了速度场和温度场的分布状况,通过对比分析,指出舒适性空调夏季采用较低的送风速度能使室内温度场和速度场分布更均匀。     

Numerical study on temperature stratification in a room with underfloor air distribution system

In this study, numerical prediction using computational fluid dynamics (CFD) was utilized to investigate air temperature stratification in a room with an underfloor air distribution (UFAD) system. The numerical modeling using CFD computation was validated with physical test in a full size experimental room with an UFAD system. The different supply air conditions and heat loads were discussed. The results show that the effect of three parameters, heat load, supply volume flux and supply air velocity, on room air temperature would be expressed by the length scale of the floor supply jet. When the length scale increased from 0.8 to 1.56 m, the ratio of vertical temperature difference between 2.5 and 0.1 m at the occupied zone to the difference between return and supply air temperature decreased from 0.62 to 0.25. When there was only one local heat source in the room, there was a thermal stratified interface at the occupied zone. The interface height was about 1.42 times the length scale. The results may suggest ways to optimize UFAD design and operation.     

Numerical analysis of outdoor thermal environment around buildings

Simulation of thermal environment around buildings is of great importance for residential microclimate study. In this article, a numerical method is proposed to simulate the outdoor thermal environment around buildings. By the method, temperature distributions of the outdoor air, building surfaces and ground surfaces are achieved by combining computational fluid dynamics (CFD) calculation of air flow and energy balance equations calculation of surfaces. In every computing time step, the outdoor air distribution is calculated as quasi-steady condition. And the surface temperatures of buildings and ground are simplified as “shadow zone temperature” and “sunshine zone temperature” to reduce the calculating time and memory space. Response factor method is employed to deal with the transient heat transfer between outdoor air and surfaces of buildings and ground. The numerical method is validated by the measured data of outdoor thermal environment around one single building and the simulated temperature distributions are illustrated and analyzed at different time in a day.     

Numerical and experimental study of velocity and temperature characteristics in a ventilated enclosure with underfloor ventilation systems

Airflow and temperature distributions in an enclosure with heat sources ventilated by floor supply jets with floor or ceiling air exit vents were investigated using experimental and numerical approaches. These ventilation configurations represent the floor return or the top return underfloor ventilation systems found in real applications. Experiments and numerical simulations were performed on a full-sized environmental chamber. The results reveal that the temperature stratification in the enclosure highly depended on the thermal length scale of the floor supply jets. When the thermal length scale of the supply jet was >1, temperature stratification was minor for all tested heat densities and air distribution methods. Significant vertical temperature gradients occurred when the jet thermal length scale was <1. Changes in air distribution methods also became significant for temperature stratification at small supply jet thermal length scales. Temperature stratification also affected the terminal height of the momentum-dominant region of the vertical buoyant supply jets. The applicability of these results to underfloor ventilation design was also discussed. PRACTICAL IMPLICATIONS: In designing underfloor ventilation systems, supply jet conditions and heat load density have to be considered to avoid thermal discomfort because of excessive temperature stratifications. This study demonstrated, by both numerical simulations and experiments, that thermal length scale can be used as a design indicator to predict thermal stratifications under a floor return and a top return underfloor ventilation setting.     

蒸发器总成流动与换热性能研究

针对某汽车空调蒸发器总成换热效率低问题,采用实验与数值模拟相结合的方法进行研究。蒸发器简化为多孔介质模型,应用star ccm+软件进行数值模拟,对比分析数值模拟结果与实验结果验证了数值模拟的可行性。应用star ccm+软件对蒸发器总成性能进行数值仿真,得到其内部速度,温度和压力分布,研究发现风道内存在涡流和偏流现象,风道结构对蒸发器的换热效率有很大的影响,并提出优化方向。     

Bestimmung des thermischen und hygrischen Zustands der Raumluft bei freier Konvektion

Determination of the thermal and hygric room air parameters considering buoyancy and free convection. The knowledge of the room air parameters concerning temperature and moisture already in the planning phase of a building is significant in various ways. Especially in high rooms a vertical gradient of temperature and moisture may occur. The influence of buoyancy and free convection should not be neglected in a calculation. Therefore suitable mathematical models are needed. A field model and a multi‐zone model were developed and the results were being compared with the measured data. The use of the field model leads to detailed information about the room air parameters at any position in the room; the numerical effort indeed is very high. By use of the multi‐zone model it is possible to calculate the room air parameters at some spaces in the room taking principle buoyancy effects into account; the numerical effort is low. The two models supplement each other and give the chance to adapt the numerical effort to the problem.