Flow topology,heat transfer characteristic and thermal performance in a circular tube heat exchanger inserted with punched delta winglet vortex generators

To improve the heat transfer rate and thermal performance, the punched delta winglet vortex generators, DWVGs, were inserted in the middle of the circular tube heat exchanger. The effects of the flow attack angles and the flow directions were investigated numerically for the Reynolds number Re = 100–2000. The finite volume method and the SIMPLE algorithm were used to study. The results are reported in terms of the flow structure, heat transfer behavior and thermal performance evaluation and also compared with the smooth tube with no vortex generators. As the numerical results, the use of the DWVGs in the tube can improve the heat transfer rate and thermal performance by creating the vortex flow through the tested section. The rise of the flow attack angle results in the increasing strength of the vortex flows. The flow attack angle of 25° performs the highest heat transfer rate and thermal performance, while the flow attack angle of 0o gives the reversed results. The computational results reveal that the optimum thermal enhancement factor is around 2.80 at Re = 2000, α = 25°, with the winglet tip pointing downstream. The correlations on both the Nusselt number ratio and friction factor ratio for the DWVG in the tube heat exchanger are presented.     

Heat transfer enhancement for fin-tube heat exchanger using vortex generators

Vortex generators are fabricated on the fin surface of a fin-tube heat exchanger to augment the convective heat transfer. In addition to horseshoe vortices formed naturally around the tube of the fin-tube heat exchanger, longitudinal vortices are artificially created on the fin surface by vortex generators. The purpose of this study is to investigate the local heat transfer phenomena in the fin-tube heat exchangers with and without vortex generators, and to evaluate the effect of vortices on the heat transfer enhancement. Naphthalene sublimation technique is employed to measure local mass transfer coefficients, then analogy equation between heat and mass transfer is used to calculate heat transfer coefficients. Experiments are performed for the model of fin-circular tube heat exchangers with and without vortex generators, and of fin-flat tube heat exchangers with and without vortex generators. Average heat transfer coefficients of fin-flat tube heat exchanger without vortex generator are much lower than those of fin-circular tube heat exchanger. On the other hand, fin-flat tube heat exchanger with vortex generators has much higher heat transfer value than conventional fin-circular tube heat exchanger. At the same time, pressure losses for four types of heat exchanger is measured and compared.     

Determination of optimum winglet height of longitudinal vortex generators for the best thermo-hydraulic performance of compact heat exchangers

The effect of winglet height on the thermal-hydraulic performance of finned tube heat exchanger (FTHE) is investigated numerically. The rectangular winglet pairs (RWPs) having 5° attack angle are placed in common flow up (CFU) manner adjacent to the tubes for analysis. The air-side performance evaluation has been done based on the area goodness factor (j/f). The working fluid (air) is considered as incompressible fluid. Additionally, MOORA (multi objective optimization on the basis of ratio analysis) method is employed to get the best performance order of various configurations by taking Nusselt number (Nu) and area goodness factor (j/f) as beneficial attributes and friction factor (f) as a non-beneficial attribute having equal significances. The present study reveals that the rectangular vortex generators having 60 % of the channel height provides the better thermal hydraulic performance compared to the other considered cases.

     

Numerical investigation of convective heat transfer characteristics of circular and oval tube banks with vortex generators

Journal of Mechanical Science and Technology - The present work represents a 3-D numerical investigation of forced convection heat transfer over circular and oval tube banks with longitudinal...     

Experimental and numerical studies on heat transfer enhancement for air conditioner condensers using a wavy fin with a rectangular winglet

Journal of Mechanical Science and Technology - The air side thermal performance of wavy fins with rectangular winglets are studied using experimental and numerical methods. The following parameters...     

高效节能钢带式果蔬绿色干燥装备翅片管换热器的传热计算

翅片管换热器是高效节能钢带式果蔬绿色干燥装备的供热装置,通过对翅片管换热器的翅化比、对流换热系数、传热系数及阻力的计算,得到了翅片管换热器的压降及翅片管的管数,计算结果表明翅片管换热器换热能力强,传热系数高。     

管壳式换热器的振动特性分析及模态试验

针对某一型号管壳式换热器管程入口和出口处容易损坏的问题,采用有限元模态分析和试验模态分析相结合的方法,对其动态特性进行了分析。研究结果表明其固有频率在180Hz以上,避开了流体诱导振动产生的激振频率,但需加强其管程入口和出口处的刚度和壳体螺栓连接部位的连接强度。有限元模态分析方法可为其他类型管壳式换热器的动态特性快速评价和可靠性优化设计提供参考。     

Experimental analysis on performance assessment of a hybrid double cross flow tube arrangement in a shell and tube heat exchanger

Journal of Mechanical Science and Technology - The article presents the evolution of a novel configuration of tube placements in a shell and tube heat exchanger (HX). A CFD analysis on a double...     

Evaluation of heat storage and release in a double shell and tube heat exchanger with a PCM layer

Journal of Mechanical Science and Technology - In this study, a thermal storage type heat exchanger that combines heat storage and heat exchange functions has proposed and the heat transfer...     

基于板翅式换热器的百叶窗高翅片的设计与制造

百叶窗翅片的制造高度过高会造成翅片强度不足,导致换热器产品的强度不足,无法使用。传统百叶窗翅片的制造高度限制在10 mm以下。通过对连续型折弯式百叶窗高翅片的设计与制造进行尝试,设计了一种全新的翅片结构,并给出了翅片的制造方法。采用上述制造方法,可以得到,弯折角度0°~45°可控、翅片高度9~19 mm可控、翅片峰距1.5~4 mm可控的任意组合的翅片,提高了翅片的原料利用率和换热器的传热效率。     

有限元分析在管壳式换热器定期检验中的应用

换热器常处于高温高压的工作环境下,并且受力复杂。在定期检验工作中比较难以掌握它的受力情况。应用有限元分析对管壳式换热器在机械场和耦合场两种不同工况下进行应力分析,分别确定应力集中位置,得出应力集中位置应力最大理论值。通过对两种工况的比较,分析得出热载荷是换热器应力值增大的主要影响因数,并且把应力集中位置作为定期检验工作的重点,从而提高缺陷的检出率,消除检验死角,为检验师制定全面检验方案提供理论基础。     

组合涡发生器在螺旋板式换热器上的强化传热研究

在螺旋板式换热器螺旋通道内设置三角翼和椭圆柱组合涡发生器,利用流体计算软件Fluent进行三维数值模拟。研究了Re为4000～7000内组合涡发生器对通道平均Nu和平均阻力系数f的影响,并应用场协同原理进行了分析。与只加装椭圆柱涡发生器的螺旋板式换热器进行对比,结果表明,纵向涡发生器产生的二次流能改善螺旋通道内的速度场与温度场的协同性,起到强化换热作用。在正三角形排列方式下,组合涡发生器通道的平均Nu比椭圆柱涡发生器的平均Nu增大8.7%,阻力因子f减小23.7%,强化换热的效果较好。     

管壳式换热器管束与管板连接问题的探讨

就管壳式换热器在使用过程中，管束经常出现的几个问题进行了分析，提出了在设计、制造管束的过程中，易出现的问题并采取应对措施加以防范，避免换热器在使用中出现泄漏，以满足生产装置安、稳、长、满、优运行的需要。     

绕管式换热器管束模态试验

通过建立绕管式换热器模态试验测试系统,研究缠绕管的固有振动特性.根据缠绕管的几何特性不同,将缠绕管划分为曲管与绕管.在同一测试位置,曲管两方向上的固有频率接近,阻尼比总体上分布在1.1％附近.靠近收口段的绕管固有频率远大于中间绕管区域,并且在各测点位置,径向的固有频率均略大于轴向的固有频率,表明绕管沿换热器轴线方向更易...     

斜截半椭圆柱面涡发生器在管道中的传热数值模拟研究

管内设置一种斜截半椭圆柱面涡发生器,利用计算软件F luent进行数值模拟研究,研究以烟气为加热介质,冷空气为冷却介质的换热方式在不同Re数下不同攻角和倾角的传热及阻力特性,并与光管进行了对比。结果表明:斜截半椭圆柱面涡发生器能明显提高换热性能,在所研究的纵向涡发生器中,攻角为60°,倾角为15°时,涡发生器强化传热综合效果最佳。     

Thermal performance of a spirally coiled finned tube heat exchanger under wet-Surface conditions

This paper is a continuation of the authors’ previous work on spiral coil heat exchangers. In the present study, the heat transfer characteristics and the performance of a spirally coiled finned tube heat exchanger under wet-surface conditions are theoretically and experimentally investigated. The test section is a spiral-coil heat exchanger which consists of a steel shell and a spirally coiled tube unit. The spiral-coil unit consists of six layers of concentric spirally coiled finned tubes. Each tube is fabricated by bending a 9.6 mm diameter straight copper tube into a spiral-coil of four turns. The innermost and outermost diameters of each spiral-coil are 145.0 and 350.4 mm, respectively. Aluminium crimped spiral fins with thickness of 0.6 mm and outer diameter of 28.4 mm are placed around the tube. The edge of fin at the inner diameter is corrugated. Air and water are used as working fluids in shell side and tube side, respectively. The experiments are done under dehumidifying conditions. A mathematical model based on the conservation of mass and energy is developed to simulate the flow and heat transfer characteristics of working fluids flowing through the heat exchanger. The results obtained from the present model show reasonable agreement with the experimental data.     

热交换器高效冷边翅片研制方法探索

利用Fluent流体分析软件,通过平均壁面温度代替热边翅片影响的方法对板翅式热交换器结构进行简化分析,并将仿真分析结果与风洞试验结果进行对比,获得一套用于新型高效冷边翅片开发行之有效的分析方法。     

Evolution of flame shape to a vortex pair

The PSC (Propagation of Surfaces under Curvature) algorithm is adapted to the simulation of a flame propagation in a premixed medium including the effect of volume expansion across the flame front due to exothermicity. The algorithm is further developed to incorporate the flame anchoring scheme. This methodology is successfully applied to numerically simulate the response of an anchored V-flame to two strong free stream vortices, in accord with experimental observations of a passage of Karman vortex street through a flame. The simulation predicts flame cusping when a strong vortex pair interacts with flame front. In other words, this algorithm handles merging and breaking of the flame front and provides an accurate calculation of the flame curvature which is needed for flame propagation computation and estimation of curvature-dependent flame speeds.     

空调制冷换热器超大型胀管机

在我院多年开发胀管机的基础上 ,首次研制成功空调制冷换热器超大型胀管机 ,解决了大片距换热器由手工胀管转变为机械胀管的难题。     

岛津X荧光光谱仪CWC-16二重管式热交换器的再生处理

岛津X荧光光谱仪在使用多年后,它的CWC-16二重管式热交换器的效率就会逐步变低,导致内部循环水温度升高超限报警,X射线关闭,仪器无法正常使用,进而还会影响到X射线管及离子交换树脂的使用寿命。经实践探索,我们总结出了一套再生处理的方法：外接一台水泵,使用除垢剂,循环对二重管式热交换器的管壁进行清洁,可以有效地提高其热交换效率,做到修旧利废,快速地恢复仪器。