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建立了错流中空纤维膜液体除湿组件的二维传热、传质数学模型,引入研究传质过程质量积耗散的湿阻来衡量溶液除湿过程中水分传递的不可逆性。通过分析膜法除湿组件中除湿与传热耦合的湿空气水分传递过程,得到了热湿传递过程中传质的阻力表达式。通过一个典型设计实例,得出了可以降低中空纤维膜除湿组件不可逆传质损失的管长、根数、管间距、排列方式等设计参数。 相似文献
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《工程热物理学报》2018,(12)
由于NH3-H20-LiBr三元溶液中溴化锂的存在会使溶液性质发生改变,易于发生过程的进行,但阻碍了吸收氨的传质过程,对吸收性能不利.对此提出了一种膜分离技术,可将溴化锂从进入吸收器的溶液中分离出来,进而改善吸收性能.为检验对溴化锂的分离效果,采用装有3363/3364异相离子交换膜堆的膜分离装置进行实验。实验结果表明NH3-H20-LiBr三元溶液在膜分离器中一次循环后分离溴化锂的效率达90%,两次循环后分离效率达95%以上。基于上述实验中的分离效率,利用Aspen Plus模拟器,进一步模拟分析了带有这种膜分离装置的NH3-H20-LiBr三元吸收式制冷系统,并计算其性能系数.结果表明,与普通三元吸收式制冷系统相比,采用膜分离技术后,NH3-H20-LiBr吸收式制冷系统的性能系数可提高近10%. 相似文献
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《工程热物理学报》2021,42(9):2216-2226
为强化膜式溶液除湿器的性能,本文基于膜的渗透特性,建立了多级内冷型膜式溶液除湿器的传热传质模型。经模型验证后,采用遗传算法对不同设计工况下的膜式除湿器结构进行了优化,并通过引入传热传质分布不均因子,分析了各运行控制参数与空气状态参数对膜式除湿器的传热传质性能影响。结果表明,除湿器处理的空气流量越大,所需的最优层数越多,最优级数越小。在最优结构下增大溶液流量与降低冷却水温度虽可提高总效能,但也加剧了传热传质驱动力的分布不均。在处理低湿度空气时,该系统总效能可达0.64。该研究揭示了传热传质效能与驱动力分布不均之间的内在关系,有助于膜式溶液除湿器的性能强化。 相似文献
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The process of direct manufacturing by selective laser melting basically consists of laser beam scanning over a thin powder layer deposited on a dense substrate. Complete remelting of the powder in the scanned zone and its good adhesion to the substrate ensure obtaining functional parts with improved mechanical properties. Experiments with single-line scanning indicate, that an interval of scanning velocities exists where the remelted tracks are uniform. The tracks become broken if the scanning velocity is outside this interval. This is extremely undesirable and referred to as the “balling” effect. A numerical model of coupled radiation and heat transfer is proposed to analyse the observed instability. The “balling” effect at high scanning velocities (above ∼20 cm/s for the present conditions) can be explained by the Plateau-Rayleigh capillary instability of the melt pool. Two factors stabilize the process with decreasing the scanning velocity: reducing the length-to-width ratio of the melt pool and increasing the width of its contact with the substrate. 相似文献
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真空冷冻干燥机冷阱中的气体换热分析 总被引:1,自引:0,他引:1
从理论上分析了螺旋盘管式冻干机冷阱中气体的换热。对真空冷阱中处于滑流区的气体换热 ,应考虑温度跳跃和速度滑移对换热的影响。基于冷阱内表面定热流和恒壁温的假设 ,建立了相应的分析模型 ,导出了冻干机冷阱内处于滑流区的气体换热 Nusselt数表达式 ,认为随着冷阱压力的降低 ,换热 Nusselt数将不断减小 相似文献
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Sidi El Bcaye Maïga Cong Tam Nguyen Nicolas Galanis Gilles Roy 《Superlattices and Microstructures》2004,35(3-6):543
In the present work, we consider the problem of the forced convection flow of water– γAl2O3 and ethylene glycol– γAl2O3 nanofluids inside a uniformly heated tube that is submitted to a constant and uniform heat flux at the wall. In general, it is observed that the inclusion of nanoparticles has increased considerably the heat transfer at the tube wall for both the laminar and turbulent regimes. Such improvement of heat transfer becomes more pronounced with the increase of the particle concentration. On the other hand, the presence of particles has produced adverse effects on the wall friction that also increases with the particle volume concentration. Results have also shown that the ethylene glycol– γAl2O3 mixture gives a far better heat transfer enhancement than the water– γAl2O3 mixture. 相似文献
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通过适当假设,推导出了结霜等截面环肋传热的数学模型,然后得到其传热热问题的修正解,同时给出其相应的热流量计算公式。与一般简化的肋传热计算公式相比,该解提高了计算精度,并且表达形式简单,可以很方便的应用于工程实践;对结霜肋片的设计有一定的理论指导作用,并可以推广到其他类似的传热等问题中。 相似文献
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Prabal Talukdar D. Trimis 《Journal of Quantitative Spectroscopy & Radiative Transfer》2004,84(4):527-537
This paper deals with the heat transfer analysis of a 2-D rectangular porous radiant burner. Combustion in the porous medium is modelled as a spatially dependent heat generation zone. The gas and the solid phases are considered in non-local thermal equilibrium, and separate energy equations are used for the two phases. The solid phase is assumed to be absorbing, emitting and scattering, while the gas phase is considered transparent to radiation. The radiative part of the energy equation is solved using the collapsed dimension method. The alternating direction implicit scheme is used to solve the transient 2-D energy equations. Effects of various parameters on the performance of the burner are studied. 相似文献
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Heat transfer over a stretching surface with uniform or variable heat flux in micropolar fluids is investigated in this Letter. The boundary layer equations are transformed into ordinary differential equations, and then they are solved numerically by a finite-difference method. The effects of the material parameter K, Prandtl number Pr, velocity exponent parameter m, and heat flux exponent parameter n on the heat transfer characteristics are studied. It is found that the local Nusselt number is higher for micropolar fluids compared to Newtonian fluids. 相似文献
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针对微槽式芯片冷却器,建立三维仿真模型,分析其稳态工况下的传热情况,获得其温度和热应力分布.分析了五种不同结构形式芯片冷却器工作性能的影响,比较了纯铜和氮化硅复合物两种材质对散热性能的影响.结果表明,铜质冷却器散热性能较好,但内部热应力却高于复合材质冷却器.通过将原冷却通道分割成两个相同的小通道,可提高冷却性能,且应将... 相似文献