共查询到18条相似文献,搜索用时 250 毫秒
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针对双排对折型微通道换热器,建立三维分布参数模型,基于双排对折的独特结构分别划分换热区和集流管的控制单元,并创新性提出一种基于流程的制冷剂流路描述方法。调研并整理了公开发表文献中记载的适用于微通道换热器的制冷剂侧和空气侧的换热及压降关联式,使模型能够应用于各类工况。建立模型的控制方程,并开发一种换热-压降交替迭代的快速求解算法,基于此计算换热器性能,并用试验数据验证模型的计算精度。结果表明,基于此仿真模型计算的换热器平均换热误差小于5%,制冷剂侧平均压降误差小于10%,满足实际工程需求。 相似文献
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补气增焓制冷系统具有系统能效比高、运转费用低等优势,被广泛应用于现代飞机的环境控制系统中。为了指导系统的设计与控制,开发了机载补气增焓制冷系统的动态性能仿真模型,并开展了实验验证。通过将补气压缩机工作过程分解,建立了基于物理机理的补气压缩机显式计算模型;通过制冷剂相区划分,建立了蒸发器和冷凝器的移动边界模型;并开发了基于质量引导的系统动态求解算法。实验验证表明,模型能够准确反映系统压力和温度的动态变化趋势;在系统动态响应时间内,模型对于系统压力和温度的时均预测偏差分别为2.55%和-3.29℃。 相似文献
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为降低机柜的散热负荷,减小散热系统的体积和质量,并且提高冷却系统的能量利用效率,提出利用微通道平行流换热器泵驱动两相回路热管系统方案,基于AMESim软件研究质量流量、换热器风量、环境温度、冷凝器结构参数对系统换热性能的影响。研究结果表明:制冷剂质量流量过大、换热器风量过大对系统制冷量无显著影响。室外温度是系统换热性能的重要影响因素,室外温度由10℃增加至35℃时,制冷量降低了57.9%。冷凝器流程布置和扁管排布需要考虑换热性能和流动阻力之间的平衡,平行流冷凝器为3流程,扁管数目为(12,12,10)时,系统运行性能最佳。 相似文献
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建立了一种R1233zd(E)卧式冷凝器的动态仿真模型,其相比于稳态模型在预测系统运行特性方面具有明显优势。详细介绍了建模所用控制方程、离散方法、运算逻辑等,模型可以计算出冷凝器在每一时间步长下,每一个控制体内制冷剂、管壁、冷却水的状态参数。由于模型涵盖了换热管的几何参数,因此改变几何参数可以模拟采用不同换热管结构对冷凝器性能的影响,比较了采用不同齿距的换热管对换热器内部相区分布、换热量、出水温度的影响。模拟结果得出,采用齿距为1.3 mm的低肋管时,出水温度较光管提升1.5℃以上,达到稳定输出的时间提前1 min以上,换热量提升2.3倍。R1233zd(E)作为新型环保工质,缺乏相关的热泵模型研究,因此搭建该冷凝器模型是完成R1233zd(E)高温热泵模型的重要基础。 相似文献
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As one of the main reasons causing leakage heat load in a refrigerator, mass and heat transfer through refrigerator door seal is of great importance to be studied. In this paper, a model is presented for numerical simulation of mass and heat transfer process through refrigerator door seal, and an experiment apparatus is designed and set up as wel for comparison. A two-dimensional model and tracer gas method are used in simulation and experiment, respectively. It can be found that the relative deviations of air infiltration rate between the simulated results and experimental results were less than 1%, and the temperature difference errors at two special points of the door seal were less than 2.03 °C. In conclusion, the simulated results are in good agreement with the experimental results. This paper initially sets up a model that can accurately simulate the heat and mass transfer through the refrigerator door seal, and the model can be used in refrigerator door seal optimization research in the follow-up study. 相似文献
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Numerical study on gas and liquid slugs for Taylor flow in a T-junction microchannel 总被引:1,自引:0,他引:1
The rapid development of microfabrication techniques creates new opportunities for applications of microchannel reactor technology in chemical reaction engineering. The extremely large surface-to-volume ratio and the short transport path in microchannels enhance heat and mass transfer dramatically, and hence provide many potential opportunities in chemical process development and intensification. Multiphase reactions involving gas/liquid reactants with a solid as a catalyst are ubiquitous in chemical and pharmaceutical industries. The hydrodynamics of the flow affects the reactor performance significantly; therefore it plays a prominent role in reactor design. For gas/liquid two-phase flow in a microchannel, the Taylor slug flow regime is the most commonly encountered flow pattern. The present study deals with the numerical simulation of the Taylor flow in a microchannel, particularly on gas and liquid slugs. A T-junction empty microchannel with varying cross-sectional width (0.25, 0.5, 0.75, 1, 2 and 3 mm) served as the model micro-reactor, and a finite volume based commercial computational fluid dynamics (CFD) package, FLUENT, was adopted for the numerical simulation. The gas and liquid slug lengths at various operating and fluid conditions were obtained and found to be in good agreement with the literature data. Several correlations in the T-junction microchannel were developed based on the simulation results. The slug flows for other geometries and inlet conditions were also studied. 相似文献
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采用微通道换热器作为数据中心回路热管冷却换热器,在微通道冷凝器侧进行了蒸发冷却实验。实验利用焓差平台测量了不同因素对采用蒸发冷却技术的微通道冷凝器换热影响,并分析了室内外不同温差、室外不同湿度条件下采用蒸发冷却的微通道冷凝器及蒸发器的进出口空气温差。实验结果表明:采用蒸发冷却可使冷凝器入口空气温度实现大幅温降,并增加冷凝器及蒸发器的进出口空气温度差值,喷淋后可使流经热管空气降温0.3~1.9℃,增大2%~20%的系统换热量,冷凝器换热效率得以提升,并可扩大回路热管换热器使用地区,延长回路热管年利用时间。 相似文献
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Fluent软件的数值模拟结果显示伞形微通道结构比U形直线形微通道结构具有更加高效的混合效率,但该结构也存在流动死区,结合优化方向提出一种压降更小、混合效率较优更适用于液-液非均相反应的菱形微通道结构。同时,本文利用前述3种不同微通道结构反应器及常规反应器开展丙烯酸十四酯的合成评价对比实验,红外光谱及核磁谱图对反应产物的分析表征均证明了丙烯酸十四酯的生成。常规反应器和微反应器在相似工艺条件下,丙烯酸十四酯的收率仅为82%,停留时间更是长达300min,而微反应器中收率均达到90%以上,停留时间不超过3.5min,且菱形微通道结构反应器比U形直线形和伞形微通道结构反应器所得丙烯酸十四酯的收率都大,达到97%,说明菱形微通道结构更加有利于物料间的充分混合反应,这与菱形微通道结构数值模拟显示的结果是一致的,从而验证了数值模拟结果的可靠性。 相似文献
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显微成像条件下的三维流场测量是微通道流动等研究的基础,其难点在于颗粒深度位置的测量。由于显微镜头景深极小,成像时通道内大部分颗粒处于离焦状态。本文首先基于几何光学原理分析了显微成像前后离焦 不对称的特点,随后基于Inception V3卷积神经网络搭建了颗粒深度预测模型,并通过光线追踪方法生成粒径 1~10μm的10种颗粒在深度范围-50~50μm内的仿真显微图像,应用深度预测模型对其进行训练及预测,颗粒深度预测结果显示1~3μm颗粒的相对误差在±13%以内,4~10μm颗粒的相对误差小于±5%。最后在微通道中拍摄粒径分别为2.6μm和5μm的聚苯乙烯微球在深度范围-50~50μm内的显微图像,应用同一深度预测模型进行训练及预测,两种颗粒深度预测结果的相对误差分别为小于±15%和±5%。结果表明,所提出的基于深度学习的显微离焦图像法能够有效测量微通道内颗粒深度位置,为图像法流场测量技术增加了新的思路。 相似文献
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I. V. Derevich V. S. Ermolaev V. Z. Mordkovich D. D. Galdina 《Theoretical Foundations of Chemical Engineering》2012,46(1):8-19
Fluid dynamics in a microchannel of a new-generation Fischer-Tropsch reactor for artificial petroleum synthesis is reported.
Liquid and gaseous product downflows are modeled in the annular flow approximation. The conjugate flow of gaseous and liquid
products is investigated in terms of integral momentum balance equations with capillary effects and microchannel wall roughness
taken into consideration. A simulation procedure appropriate for the method of deposition of catalyst particles onto the inner
wall is suggested for modeling a random inner surface of the microchannel. The simulation procedure takes into account the
variation of the synthesis product composition and the variation of the thermal properties of the liquid and gas phases along
the microchannel length. A stable computational procedure has been devised for calculating fluid dynamic parameters of the
two-phase flow. The effects of the synthesis gas flow rate and conversion, microchannel diameter, chain propagation constant,
temperature, and pressure on the two-phase flow parameters and on the aerodynamic resistance of the gas have been investigated. 相似文献