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膜式液体除湿技术可以有效解决传统气液直接接触除湿器中气液夹带问题。在膜式液体除湿技术中,除湿溶液与空气被防水透气膜隔离,在保证溶液吸收空气中水蒸气的同时,防止溶液渗透到空气中。文中详细综述了现有膜式液体除湿系统研究中所用的除湿溶液,以及其中常用的膜组件,并从理论模型和试验研究两方面分别对在室内配置和室外配置的平板式和中空纤维膜式膜组件的性能展开了分析。最后还对膜式液体除湿组件未来发展方向进行了展望。 相似文献
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能源塔吸热过程的实质是塔内波纹填料表面液相降膜与逆流气相接触发生热质交换,为探究填料表面液膜流动对能源塔内气液两相热质交换过程的影响机制,文中建立了波纹填料表面液相降膜流动模型,模拟了不同气液相入口参数以及不同波纹结构的填料表面的液膜流动过程,通过对比各工况下填料表面稳定液膜的特性,分析了影响液膜流动的关键因素,从增强气液相接触角度出发,寻求更加合理的气液相入口参数和波纹结构。 相似文献
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污水源热泵将淋激式换热器作为热泵蒸发器是实现物理抑垢、污水换热温差较小保持较高的换热性能的新方法。在淋激式换热器中,采用水平的换热管,污水以液膜形态在水平换热管上和管间流动,换热表面上降膜的流动状态是影响其表面换热性能的关键因素。国内外对较长发展段的降膜破裂、降膜流动状态定性参数相关研究成果仍有限。针对污水源热泵取热相关工况条件,对总长度为100 mm的多根水平放置的水平换热管外表面重力降膜的破裂和流动状态、换热管间降膜流动状态进行试验观测,得到有利于污水热泵蒸发器取热的临界雷诺数R_e、管间距,给出降膜流动状态的边界R_e的试验关联式,试验工质为水,试验雷诺数为100~600。 相似文献
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《Planning》2016,(17)
基于VOF方法,利用CFD软件FLUENT对倾斜壁面上二维气-液两相流进行数值模拟,分析了三角形高度和结构间距均为1mm的6种尺寸壁面上的液膜流动特性,获得了三角形结构的壁面上液膜自由液面的分布图以及不同结构宽度w对液膜流动特性的影响规律。结果表明:与平壁面上液膜流动相比,三角形结构壁面上液膜自由液面位置随三角形结构呈规律性变化;在三角形结构壁面上,气体漩涡存在于液膜和壁面之间,当三角形结构宽度w改变时,漩涡的形状和位置均发生变化。 相似文献
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《煤气与热力》2018,(12)
针对制冷系统中降膜蒸发器的两种不同管形的换热管(圆形管和滴形管)管外液膜流动情况进行研究。通过Fluent软件,建立二维模型,以制冷剂R134a为介质,进行数值模拟。通过不同的换热管管形、不同的布液高度、不同的布液器出口初始流速及不同的管间距组合下的多种工况,分析换热管管外成膜情况、液膜的流动情况和成膜厚度。结果显示:在各模拟条件相同的情况下,滴形管的成膜管排数比圆形管多,且滴形管管外制冷剂流动的扰动较少,成膜更加均匀。滴形管成膜管排数随着布液高度的增大而减少;液膜厚度随布液高度的增大而减小;但是布液高度不应过大。滴形管液膜厚度随初始流速增大呈现增大的趋势,柱状流成膜范围也加大。滴形管成膜管排数、液膜厚度均随着管间距增大而减少。 相似文献
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针对制热工况,建立横流热源塔传质传热数学模型。对数学模型的计算准确性进行实验验证。选取重庆、长沙、杭州、西安、南京、青岛6座城市作为计算对象,分析计算热源塔显热换热量、潜热换热量的影响因素以及一定计算条件下的显热换热量、潜热换热量。计算结果与实验测量结果偏差很小,数学模型的计算结果可信。进口防冻液温度的影响:当防冻液、空气质量流量一定时,6座城市的显热换热量、潜热换热量均随进口防冻液温度的升高而减小。进口防冻液温度相同时,显热换热量、潜热换热量由大到小的城市均为重庆、长沙、杭州、南京、西安、青岛。防冻液质量流量的影响:重庆、长沙、杭州、南京、西安、青岛的进口防冻液温度分别选取-4、-8、-9、-11、-12、-14 ℃,空气质量流量一定时,6座城市热源塔显热换热量、潜热换热量均随防冻液质量流量的增大而增大,但潜热换热量增大幅度非常小。空气质量流量的影响:重庆、长沙杭州、南京、西安、青岛的进口防冻液温度分别为-4、-8.-9、-11、-12、-14℃,防冻液质量流量一定时,6座城市热源塔显热换热量、潜热换热量均随空气质量流量增大而增大。空气质量流量对重庆热源塔潜热换热量的影响最明显,其次分别为长沙、杭州、南京、西安,对青岛热源塔潜热换热量的影响微弱。一定计算条件下,6座城市热源塔显热换热量差别比较小,而潜热换热量差别明显,室外空气含湿量越大的城市热源塔潜热换热量越大。 相似文献
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为了提高间接蒸发冷却器换热效率,提出了将气-水雾化喷嘴应用于间接蒸发冷却器改进换热器表面水膜的均匀性,实验研究了扇形两相(气-水)喷嘴在不同空气压力和水压下的特性,测出了不同压力时喷嘴雾化角和气水质量流量值,得出了其变化规律,确定出了最佳的喷雾气水压力比和雾化角等参数。 相似文献
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《Energy and Buildings》2004,36(7):696-708
In the current work, two different types of evaporative systems are shown. A returning air recovery system is used. The indirect systems have two independent airflows, the primary airstream is used to refrigerate and the secondary flow is in direct contact with water in order to improve heat and mass transfer. The first equipment (the indirect evaporative refrigerator) works like a flat interchanger made of aluminium and there is only heat transfer in the primary airflow.The second equipment (the semi-indirect evaporative refrigerator) is made of solid porous ceramic pipes which separate the two airstreams, thus allowing that, in the primary airflow (apart from the heat transfer), there is also a mass transfer. It should also be mentioned that this system is free of legionella, because the pipes perform the role of a filter material, making it impossible for the bacterium to enter premises. This system has been named a semi-indirect evaporative system due to the permeability of the porous pipes which allow a higher or lower water diffusion and therefore a mass transfer depending on the specific humidity of the primary airstream. 相似文献
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Packed-bed heat and mass transfer devices are widely used in air-conditioning systems, such as cooling tower, evaporative cooler of air–water direct-contact devices, dehumidifier and regenerator of air–liquid desiccant direct-contact devices. Similarities of heat and mass transfer characteristics between air–water and air–liquid desiccant devices are considered and investigated in this paper. Same reachable handling region of outlet air can be obtained for both air–water and air–liquid desiccant devices, which is among three boundary lines, isenthalpic line of inlet air, iso-relative humidity line of inlet fluid (water or desiccant), and the connecting line of inlet statuses of air and fluid. Inlet conditions of air and fluid affect heat and mass transfer characteristics to some extent, so that a zonal method is proposed only according to the relative statuses of inlet air to inlet fluid. Four zones, dehumidification zones A, D and regeneration zones B, C, are divided for air-desiccant direct-contact devices. The first three zones A, B and C are divided for air–water direct-contact devices, with the same zonal properties as those of air-desiccant devices. In order to obtain better humidification performance, fluid should be heated (in zone C) rather than air (in zone B). And fluid should be cooled (in zone A) rather than air (in zone D) to obtain better dehumidification performance. Counter-flow pattern should be applied for best mass transfer performance in the same conditions within the recommended zone A or C, while parallel-flow pattern is the best in zone B or D. 相似文献
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本文针对管外流体、空气和管内流体耦合换热情况的换热管换热性能进行研究,通过分析各参数的影响,运用控制变量法改变喷淋水流量进行了水平单管外流动水膜与空气之间对流传质系数的实验测定。实验结果表明,喷淋水流量对传质系数有较大的影响,并得到了实验数据拟合关系式。 相似文献
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Evaporation of water droplets while traveling in hot air layer will be studied. The air-droplet system is analyzed by solving
the mass, momentum and energy conservation equations for each phase. The droplet phase is described by the Lagrangian approach.
Two conditions of air flow in the smoke layer are assumed. Firstly, as commonly used in modeling fire suppression by water
spray, the smoke layer is assumed to be quiescent. Secondly, both gas cooling effect and air entrainment in the water spray
cone are included. The properties of gas phase related to evaporation are specific heat capacity, thermal conductivity and
dynamic viscosity. All these are evaluated by the one-third rule. The Runge–Kutta algorithm is used to solve the ordinary
differential equation group for the droplet motion with heat transfer. Droplet positions, velocities, temperatures and diameters
are calculated while traveling in the hot air reservoir. The effects of air temperature, water vapor mass fraction, thickness
of hot air reservoir, and initial diameter on the droplet behavior are analyzed. The quantity of heat absorbed by a single
droplet is calculated. Results are then calculated for a water spray by taking it has many droplets. The cooling effect of
the water vapor produced is considered. Water spray consisting of small droplets should absorb more heat while acting on the
hot air layer. The ratio of the heat for vaporization to the total heat absorbed by water can go up to 0.9 when all the droplets
are evaporated. Limited experimental data are selected to verify the mathematical model. Predicted results are useful for
studying fire suppression by water mist system. 相似文献
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针对回热式新风系统中多孔介质回热器在交替边界条件下的传热传质特性进行了研究。采用数值方法针对表面温、湿度交替变化的对流边界条件,对多孔床与空气的非稳态传热传质过程进行了模拟计算,获得了多孔床内温度场和含湿量场。在此基础上,分析了该类多孔床的传热传质特性,并比较了关键因素对多孔床内温度和含湿量变化的影响。计算结果表明,多孔床与空气之间的热质交换主要发生在交界面附近较浅的薄层,往底层的传递十分缓慢。多孔床与空气的热、质交换效果受气流流速影响较为明显。 相似文献
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为解决地铁站冷却塔设置难题,提出了一种采用低速电机驱动旋转布水装置的间接蒸发冷却器,在两种布置方式下,对其换热性能进行了单因素实验,并运用正交实验法对较优布置方式下影响换热器换热的因素进行了分析。结果表明:两种布置方式下,喷嘴与蒸发冷却器的间距、两组换热管束间距均存在最佳值,喷嘴双侧旋转布水优于单侧旋转布水;换热器平行气流布置且喷嘴双侧旋转布水为较优布置方式,此时,换热器换热量随喷水量、转速、空气速度、冷却水进口温度的增加以及喷水温度、空气温度的降低而增大,其中,冷却水进口温度对换热器换热影响最为显著,其他因素对其换热的影响从主到次顺序为:喷水量、空气温度、空气速度、喷水温度、转速、冷却水流量。 相似文献