共查询到18条相似文献,搜索用时 125 毫秒
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设备小型化发展的不断深入和高热流密度换热的需要促使了具备更高换热性能的小管径冷凝换热的研究。基于Nusselt膜状冷凝传热理论,构建了水平圆管从管外冷凝换热直到管内对流换热的计算模型和程序,并借助已有文献的试验结果完成了计算模型和程序的校验。随后,文章重点探讨了水平圆管管外冷凝换热的热阻分布,揭示当前管外冷凝换热热阻在单管整体换热热阻中所占比重较小的事实。通过进一步计算和比较本文认为,管外冷凝换热系数适度的退化对小管径水平圆管的整体换热影响较小,并不能改变小管径管外冷凝换热的优势。本数值分析可为小管径壳管换热器的研制以及微小管径冷凝换热试验的设计提供理论支撑。 相似文献
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PCHE(Printed Circuit Heat Exchanger)型混合工质冷凝器是浮式液化天然气装置中冷凝器的首选型式。本文通过构建混合工质冷凝试验系统,完成了PCHE混合工质冷凝器冷凝试验。以混合工质冷凝平衡模型理论为基础,采用BellGhaly方法与Shah冷凝准则方程进行微通道内混合工质冷凝计算。对比分析理论计算与试验结果表明:在高雷诺数情况下,Bell-Ghaly-Shah方法计算的混合工质冷凝传热系数与试验结果偏差为3.11%。本文研究内容对PCHE型混合工质冷凝器热力设计具有重要借鉴意义。 相似文献
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钟向阳 《机械工人(热加工)》2001,(2)
1.问题的提出 我公司生产的管壳式水冷冷凝器是制冷系统中的主要热交换器,设计上选用的换热管材料为纯铜管(材料代号T2,管径16mm,壁厚1.5mm),换热管与管板之间采用机械胀管连接。为提高换热管的热效率,除胀接部分余留一定长度外,其余部分均轧制成高肋螺纹。其外径大于换热管的原始外径和管板孔的孔径,因此,在组装完毕后换热管是不能更换的。否则,高肋螺纹部分将断裂成铜屑掉进冷凝器壳体内部,严重地影响系统的正常工作。 但在实际生产中,由于换热管轧制后没有严格试压或漏检,在组装焊接、胀管完毕后,试压过程中换热管单根或多根泄漏的现象屡有发生。此时,如果采用将两端堵塞的办法,将严重影响冷凝器的换热效果;否则只有报废处理,损失较大,两者都 相似文献
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介绍了如何建立R410A热力物性和输运特性数据模块、管内冷凝换热和管外空气换热模型,并采用Visual Basic语言建立翅片管冷凝器换热模型与R410A物性数据模块间的调用关系,开发出了适用于R410A翅片管冷凝器设计软件。它克服了传统手工算法造成的计算过程繁琐费时的缺点及经验估算带来的可靠性低的不足。通过对该软件的开发将有助于缩短新工质R410A翅片管冷凝器的设计研发时间,提高设计人员的设计水平。 相似文献
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本文论述了氟里昂卧式壳管式冷凝器的计算机模拟。建立了传热的数学模型。通过对偏微分耦合方程的求解,得出了内部温度场,局部换热量及换热系数变化的规律。这一模型可用来预测冷凝器的换热性能和优化结构参数。为验证数字模型的正确性,在实验用的冷凝器上进行了温度分布的测定。结果表明与模拟计算吻合较好。 相似文献
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针对R290的性能特点,设计了R290/CO2复叠式制冷循环的R290水冷式冷凝器;并在R290/CO2复叠式制冷循环实验台上进行实验,得到R290出口温度,冷却水出口温度及冷却水进出口温度差随冷却水流量和冷却水进口温度的变化关系,通过计算得到了R290和冷却水的对流换热系数随冷却水流量与冷却水进口温度的变化关系,得出了R290的对流换热系数对R290冷凝器换热性能影响较大,应加强R290侧的换热. 相似文献
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Byong Joo Kim 《Journal of Mechanical Science and Technology》1998,12(2):281-290
In the present work turbulent film condensation of nonazeotropic binary mixtures inside a horizontal tube is studied theoretically.
The combined heat and mass transfer involved is analyzed through an integral formulation of the continuity, momentum, energy
and diffusion equations. As the mass velocity of refrigerant mixtures increases, the condensation heat transfer coefficient
increases. The heat transfer coefficient becomes smaller at higher mass quality. As the mole fraction of the more volatile
component in binary mixtures increases, the back-diffusion mass flux of the more volatile component reduces in the vapor.
As a result the condensation heat transfer coefficient improves with the increase of the inlet mole fraction of the more volatile
component especially in the upstream of condenser. The results of the present study show good agreement with the experimental
data available. 相似文献
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管束效应对HFC245fa与HCFC123膜状凝结换热影响 总被引:2,自引:0,他引:2
建立试验系统、改进试验方法,试验研究HFC245fa与HCFC123在光管与3种强化换热管(2D-A,3D-A与3D-B)管束外冷凝换热特性。试验管束由4列排深为5排的列管构成,换热管公称外径为19.05 mm、有效换热长度为500 mm。试验中,利用改进的Wilson图解法获得水侧对流传热系数,通过轮转试验方法消除管束试验中各试验管换热本构差异等因素对管束效应测试分析的影响。试验结果表明,Kern模型预测值与HFC245fa与HCFC123光管管束外凝结换热结果偏差随试验热通量升高而增大;管束效应对光管与三维表面强化管(3D-B)凝结换热影响比其对二维表面低肋管(2D-A)影响显著;管束效应对HFC245fa在3D-B管外凝结换热影响在n>3后超过Nusselt管束模型预测值;HFC245fa在3D-B管束外凝结换热性能随管排深度的变化规律与其在光管管束外的变化规律及Nusselt模型显示规律明显不同。 相似文献
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Jehee Lee Goon-Cherl Park Hyoung Kyu Cho 《Journal of Mechanical Science and Technology》2018,32(3):1015-1023
In the containment of nuclear power plants, wall film condensation occurs with non-condensable gases under accident conditions. With non-condensable gases, condensation heat transfer on the containment wall can be degraded significantly because of the accumulation of non-condensable gases near the condenser wall; therefore, an investigation into the wall condensation heat transfer is of great importance to nuclear reactor safety. In this study, wall film condensation with non-condensable gases was simulated using the CUPID code. To evaluate the heat and mass transfer coefficients, a wall function approach was adopted to save the computational cost. To validate the model, a COPAIN condensation experiment was simulated using CUPID. The calculation results were compared with the COPAIN experiment data and results from the commercial CFD code (STAR-CCM+) results, which used the resolved boundary layer approach. From the comparison, good agreements were obtained between the CUPID code and the other results. 相似文献
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通过分析国外对R290水平光滑管内和强化管内的流动凝结换热的研究,得出R290管内换热系数较常规工质高,而强化管内的凝结换热系数明显高于光滑管。另外还列举了一些典型的凝结换热关联式,并提出了进一步研究工作的建议。 相似文献
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以一台变转速热泵空调器为研究对象,测试其在冬季用R32做制冷剂时机组的能效及换热器的传热性能,以研究制热工况下空调系统中用R32作为替代制冷剂的可行性。试验测量参数包括蒸发器(室外机)和冷凝器(室内机)的传热系数、换热量、总压力降以及整机制热工况下的COP。通过结构匹配的室内、外侧两换热器在系统运行中同步测量,结果表明:冬季名义制热工况下,R32空调系统的制热能力比用R410A高出约3.0%,蒸发器、冷凝器的传热系数也有所提高,其中蒸发器的传热性能提高约6.0%,冷凝器传热性能提高约6.7%,而压降对比则变化不大。 相似文献
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The heat transfer phenomenon occurring during stratified condensation inside an inclined tube is investigated theoretically
and numerically. Differential equations governing the kinematic, dynamic, and thermal aspects for vapor condensation inside
inclined tubes, which are derived from a thin film flow modeling, are solved simultaneously. These solutions are achieved
by applying an explicit finite difference numerical method to predict the condensation heat transfer coefficient variations
along the tangential and axial coordinates. The inclination angle is found to have a significant effect on condensation heat
transfer coefficient inside inclined tubes. In addition, in accordance with the given physical and thermal condition of working
fluids, there is a specific optimum inclination angle. In this study, the 30°–50° range from the horizontal position is found
to be the range of the optimum inclination angle for achieving the maximum condensation heat transfer coefficient, with R134a,
R141b, and R11 as the working fluids. The results of the present study are compared with experimental data, and a good agreement
is observed between them. 相似文献