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螺旋槽管管内流阻和传热特性的研究 总被引:1,自引:0,他引:1
本文以空气为工质,在雷诺数Re=10~4~10~5以及较大的管参数范围内对13条螺旋槽管进行了阻力和传热实验。实验结果证明就强化管内单相流体的湍流传热而言在粗糙雷诺数e~+=10~500范围内,螺旋角β≈90°的单头管比多头管具有更好的强化传热性能。用热线风速仪测定了螺旋槽管中的速度分布,定性地分析了管内沿轴向方向湍流强度的强弱,用壁相似定律、混合长理论以及热动量传递相似理论推导了螺旋糟管的阻力和传热模型。最后对螺旋槽管的管参数进行最优化计算,并讨论了Pr数对最佳管参数和最佳操作雷诺数的影响。 相似文献
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螺旋槽管与折流栅组合的高效水冷器的传热和阻力特性与其管、壳程的结构因素密切相关,本文就螺旋槽管槽深对水冷器管、壳程传热与阻力特性的影响进行了实验研究.结果表明:壳程流速变化对水冷器传热系数的影响更加明显,即壳侧热阻相对较大,强化传热应以强化壳侧换热为主要目标;螺旋槽管槽深对水冷器传热系数的影响很大,应在实际工程设计中确保实际槽深符合设计要求;槽深越深,管壳程阻力也相应增加,即传热的强化是以阻力增加为代价.根据实验结果还得到了不同结构水冷器的管、壳程换热与阻力计算关联式. 相似文献
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为解决干气密封(DGS)端面型槽优化中未考虑型槽几何参数之间对目标函数交互影响而导致几何参数优化结果不准确的问题,研究了不同速度条件下DGS螺旋槽中其他几何参数对某一几何参数优选值的交互影响。基于气体润滑理论,建立了螺旋槽DGS的几何模型和数学模型,数值求解获得端面膜压分布和稳态性能参数,定义了综合表征螺旋槽几何结构的特征参数。以气膜刚度最大为优选目标,获得了不同速度条件下DGS螺旋槽中某一几何参数优选值随其他几何参数的变化规律。结果表明:DGS螺旋槽各几何参数两两之间呈现出复杂的交互影响关系,不过总体符合趋向于降低槽内实际通流面积、槽长宽比和槽长深比3个综合参数变化幅值的原则;与单因素优化方法相比,在给定算例参数条件下所提出的考虑几何参数交互影响的优化方法所获得气膜刚度最优值提高11.4%。 相似文献
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<正> 引言 螺旋槽管是一种优良的换热元件.许多学者对其换热强化机理比较一致的看法是:一方面由于螺旋槽的引导作用使得近壁处流体发生旋转,加强了径向扰动;另一方面,发生了绕流脱体,形成了回流区,在再附点处换热最强.同时由于流体的旋转和脱体使得摩擦阻力较大地增大.流体在管内流动过程很复杂,对螺旋槽管的研究基本上是以实验为主的数据拟合,有的学者虽对其进行了数学分析并建立了相应的关联式,但不能表征出流体在管内旋转和脱体的实际流动情况,因此不能对二者的相互耦合进行定性或定量的分析.本文以流体在螺旋槽管内的流态为基础,以期建立能够反映其流动特性的阻力和换热计算公式. 相似文献
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《Chemical Engineering Communications》2007,194(7):975-993
This article presents the modeling of heat transfer of upward annular flow in a smooth tube and a spirally internally ribbed tube. First, analytical models of two-phase flow dynamics and heat transfer of annular flow in flow boiling were derived from the liquid film momentum and energy equations for smooth tubes. Combined with empirical correlations for liquid droplet entrainment and deposition rates in annular flow, modeling of heat transfer of upward annular flow in the smooth tube was conducted. The predicted heat transfer coefficients of annular flow agree with the experimental results very well for the smooth tube. Based on the heat transfer model for smooth tubes, a simplified annular flow heat transfer model for the spirally internally ribbed tube was proposed by modifying the interfacial friction factor. The predicted heat transfer coefficients by the modified heat transfer model for the spirally internally ribbed tube agree with the experimental results to some extent. It is suggested that the heat transfer model for the spirally ribbed tube be further improved by modifying the correlations for liquid droplet entrainment and deposition rates in annular flow, which should describe the feature of annular flow in the spirally internally ribbed tube. Extensive experimental data are needed for this purpose. 相似文献
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Lixin Cheng 《Chemical Engineering Communications》2013,200(7):975-993
This article presents the modeling of heat transfer of upward annular flow in a smooth tube and a spirally internally ribbed tube. First, analytical models of two-phase flow dynamics and heat transfer of annular flow in flow boiling were derived from the liquid film momentum and energy equations for smooth tubes. Combined with empirical correlations for liquid droplet entrainment and deposition rates in annular flow, modeling of heat transfer of upward annular flow in the smooth tube was conducted. The predicted heat transfer coefficients of annular flow agree with the experimental results very well for the smooth tube. Based on the heat transfer model for smooth tubes, a simplified annular flow heat transfer model for the spirally internally ribbed tube was proposed by modifying the interfacial friction factor. The predicted heat transfer coefficients by the modified heat transfer model for the spirally internally ribbed tube agree with the experimental results to some extent. It is suggested that the heat transfer model for the spirally ribbed tube be further improved by modifying the correlations for liquid droplet entrainment and deposition rates in annular flow, which should describe the feature of annular flow in the spirally internally ribbed tube. Extensive experimental data are needed for this purpose. 相似文献
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Based on finite volume method, the pressure drop and heat transfer characteristics of one smooth tube and ten different axisymmetric corrugated tubes, including two with uniform corrugation and eight with non-uniform corrugation, have been studied. A physical model of the corrugated tube was built, then the numerical simulation of the model was carried out and the numerical simulation results were compared with the empirical formula.The results show that: the friction factor decreases with the increase of Reynolds number ranging from 6000 to 57000, the value of which in the corrugated tubes with non-uniform corrugation(tube 03–10) are smaller than those with uniform corrugation(tube 01–02). The geometry parameters of tube(01) have advantages on the heat transfer enhancement in low Reynolds number flow region(from 6000 to 13000) and tube(07–08)have advantages on the heat transfer enhancement in high Reynolds number flow region(from 13000 to 57000). The vortex, existed in each area between two adjacent corrugations called second flow region, is the root of the enhancement on heat transfer in the corrugated tubes. The effectiveness factor decreases with the increasing of Reynolds number and the performances of the corrugated tubes with pitch of 12.5 mm have advantages than these of 10 mm under the same corrugation geometric parameter. 相似文献
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在凝结换热实验台上 ,采用恒壁温法和恒热流法对油品在大粗糙度横肋管中的层流与湍流摩擦阻力与传热特性进行了实验研究 .实验过程中Re为 5 0~ 6 2 0 0 ,Pr为 75~ 2 6 0 ,管子粗糙高度为 5mm ,导程为 30mm .实验结果表明 ,由于实验管特殊几何结构 (大粗糙度 )和油品物性参数的相互作用 ,使其表现出与以水或空气为工质的常用强化管不同的流动传热规律 ,并且实验方法对实验结果的影响不大 .根据实验结果 ,提出了层流区和湍流区油品量纲 1摩擦系数及传热系数的关联式 ,并将实验数据与Ravigururajan和Bergles关联式的计算值进行了比较 .研究结果可用于大粗糙度横肋管换热器的设计及运行参数优化 . 相似文献