三维变形管换热器在压缩机中间冷却器中的应用研究

中间冷却器是提高压缩机效率的一种重要设备,在对三维变形管换热器的结构和传热特点进行介绍的基础上,对其在压缩机中间冷却器中的应用进行了可行性分析。采用三维变形管换热器对中石化某年产100万吨延迟焦化装置用富气压缩机中间冷却器进行了技术改造,并进行了实际运行测试和考核分析。结果表明:三维变形管换热器有效解决了管束的振动问题,在换热面积减少37. 4%、气体阻力降低36. 9%的情况下,气体出口温度达到生产工艺要求,起到了良好的节能节材效果。     

于海鲜酱杀菌的折流板波纹管换热器传热与流动性研究

为了开发用于液体食品杀菌的新型换热器,通过实验研究了螺旋折流板波纹管换热器用于海鲜酱杀菌过程中的传热与流动性能。研究结果表明:在水-海鲜酱的热交换中,螺旋折流板波纹管换热器总传热系数比波纹管换热器提高了10%～50%,比光管换热器提高了30%～130%;管侧海鲜酱综合性能系数α/Δp值波纹管大于光管,壳侧水的综合性能系数α/Δp值螺旋折流板波纹管结构换热器比波纹管结构的和光管结构的都大,证明了螺旋折流板波纹管换热器用于液体食品杀菌具有良好的应用前景。     

用于海鲜酱杀菌的折流板波纹管换热器传热与流动性研究

为了开发用于液体食品杀菌的新型换热器,通过实验研究了螺旋折流板波纹管换热器用于海鲜酱杀菌过程中的传热与流动性能。研究结果表明:在水-海鲜酱的热交换中,螺旋折流板波纹管换热器总传热系数比波纹管换热器提高了10%～50%,比光管换热器提高了30%～130%;管侧海鲜酱综合性能系数α/Δp值波纹管大于光管,壳侧水的综合性能系数α/Δp值螺旋折流板波纹管结构换热器比波纹管结构的和光管结构的都大,证明了螺旋折流板波纹管换热器用于液体食品杀菌具有良好的应用前景。     

波纹管换热器管束支撑结构

根据各种管束支撑结构的特点,找出与之相适应的波纹管管型,分析不同的组合结构对波纹管换热器壳程性能的影响,指出对波纹管换热器进行优化设计和实现整体强化传热的途径。     

波纹管对管壳式换热器内流体传热及流动特性的影响

为解决传统管壳式换热器换热效率低的问题,采用数值模拟的方法对波纹管换热器进行了数值模拟分析。研究表明:管壳式换热器壳程进口流量超过2 257 kg/h时,采用增加壳程进口流量来强化换热器内换热的方式整体经济性较差;与直壁管换热器相比,波纹管换热器的对流换热系数提高45.2%～51.1%,壳侧压降反而降低了2.6%～13.1%。同时发现,整个研究范围内性能评价指标EEC1; EEC受进口流量影响较大,其最优值出现在1 250～1 500 kg/h范围内。本研究结果为波纹管换热器在工业中的应用提供重要参考价值。     

U型波纹埋管对于增强土壤源热泵换热性能的研究

为了增强土壤源热泵系统地下埋管换热器的换热性能,通过CFD方法,探讨改用波纹管对地下换热所产生的影响,首次提出采用波纹管代替光管作为强化地下埋管换热器换热效率。     

新型不锈钢波纹管性能及强化传热的实验研究

新型不锈钢钢波纹管是经特殊工艺胀波凸起成型为多层波纹管,管内流动呈等直径流束型式和弧形流束型式,使流速和压力周期性的变化,冷热流体产生强烈扰动,实现了复合强化换热。文中对该波纹管进行了承压能力试验,并在水-水换热条件下,对波纹管强化换热规律进行了实验研究,分析了新型波纹管的强化传热机理,并给出该管的优化尺寸范围,为波纹管在换热器中的应用提供了理论依据。     

波纹管降膜蒸发器强化传热技术

本文描述了管式换热器的强化传热技术，并从传热机理出发，对波纹管降膜蒸发器的结构特点和强化传热特性进行了分析，阐述了波纹管降膜蒸发器的防除垢性能及其存在的问题。     

板翅式换热器在燃气轮机进气冷却系统中的应用

将板翅式换热器应用于吸收式燃气轮机进气冷却系统中，降低燃气轮机压缩机进口温度，提高燃气轮机高温条件下的出力，在国内尚无先例。针对板翅式换热器，简要介绍了结构、布置形式和性能。通过实测的运行数据，对板翅式换热器和管式换热器的性能进行了对比。结果表明：板翅式换热器在传热系数、体积、进气阻力等方面，性能优于管式换热器，是一种值得发展的换热设备。最后提出了该板翅式换热器在实际应用中存在的一些问题及对应的处理方法。     

波纹管容积式换热器的失效及控制

1　前　言波纹管容积式换热器是热能工程广泛使用的热交换设备Ⅰ类压力容器。 1998年 7月江苏某压力容器厂制造一台编号为P980 96波纹管容积式换热器 ,该设备运行 2年后用户反映设备出现渗漏 ,而不能使用。现场观察发现设备筒体的 3条环缝两侧有较多的细小裂纹 ,整个壳体和封头表面不同程度也存在细小裂纹 ,但数量比 3条环焊缝侧要少。用检验榔头敲击壳体时 ,声音已失去了金属清脆的响声。针对此情况做出对该换热器报废处理决定并对水质进行取样分析 ,结果水中C1- 含量达 5 5mg/L ,超出《容规》规定的 2 5mg/L。据用户反映在自来水水箱中…     

螺旋槽管凝结换热器的研究与应用

通过对螺旋槽管凝结换热器的试验研究,得到了螺旋槽管涉及相变时管内对流换热、管外凝结换热准则关联式以及管内流动阻力关联式,并依据试验结果,将螺旋槽管应用于电站凝结换热器,取得了满意的效果。     

Analysis of Fouling in Six-Start Spirally Corrugated Tubes

Abstract

Fouling on heat exchanger surfaces can weaken the heat-transfer capability, increase the energy consumption, and even cause the failure of the whole system. In coaxial heat exchangers, spirally corrugated tubes perform better than smooth ones concerning heat transfer and antifouling. In this article, a parametric study on the antifouling performance of a six-start spirally corrugated tube is carried out with a solid–liquid two-phase model. First, comparisons between a smooth tube and a specific sample six-start spirally corrugated tube on the solid particle volume fraction distributions are carried out. Then, the effects of solid particle diameter, the main geometric parameters, including pitch and the corrugation depth, are investigated. Analyzing the solid particle volume fraction with different geometries, solid particle diameters and Reynolds number, the roles played by the centrifugal force, drag force, and gravity of solid particles on fouling performance in six-start spirally corrugated tubes are obtained. In addition, the corrugation depth affects the volume fraction range more while the pitch affects more on the steady range of particle volume fraction. This work is of significance for further design of spirally corrugated tubes and analysis of fouling problems in heat exchangers.     

Correlations for evaporation heat transfer coefficient and two-phase friction factor for R-134a flowing through horizontal corrugated tubes

Correlations for the evaporation heat transfer coefficient and two-phase friction factor of R-134a flowing through horizontal corrugated tubes are proposed. In the present study, the test section is a horizontal counter-flow concentric tube-in-tube heat exchanger with R-134a flowing in the inner tube and hot water flowing in the annulus. Smooth tube and corrugated tubes with inner diameters of 8.7 mm and lengths of 2000 mm are used as the inner tube. The corrugation pitches are 5.08, 6.35, and 8.46 mm and the corrugation depths are 1, 1.25, and 1.5 mm, respectively. The outer tube is made from smooth copper tube with an inner diameter of 21.2 mm. The correlations presented are formed by using approximately 200 data points for five different corrugated tube geometries and are then proposed in terms of Nusselt number, equivalent Reynolds number, Prandtl number, corrugation pitch and depth, and inside diameter.     

Analysis of coiled-tube heat exchangers to improve heat transfer rate with spirally corrugated wall

Steady heat transfer enhancement has been studied in helically coiled-tube heat exchangers. The outer side of the wall of the heat exchanger contains a helical corrugation which makes a helical rib on the inner side of the tube wall to induce additional swirling motion of fluid particles. Numerical calculations have been carried out to examine different geometrical parameters and the impact of flow and thermal boundary conditions for the heat transfer rate in laminar and transitional flow regimes. Calculated results have been compared to existing empirical formulas and experimental tests to investigate the validity of the numerical results in case of common helical tube heat exchanger and additionally results of the numerical computation of corrugated straight tubes for laminar and transition flow have been validated with experimental tests available in the literature. Comparison of the flow and temperature fields in case of common helical tube and the coil with spirally corrugated wall configuration are discussed. Heat exchanger coils with helically corrugated wall configuration show 80–100% increase for the inner side heat transfer rate due to the additionally developed swirling motion while the relative pressure drop is 10–600% larger compared to the common helically coiled heat exchangers. New empirical correlation has been proposed for the fully developed inner side heat transfer prediction in case of helically corrugated wall configuration.     

Numerical study of an exhaust heat recovery system using corrugated tube heat exchanger with twisted tape inserts

The purpose of this work is to investigate gas to liquid heat transfer performance of concentric tube heat exchanger with twisted tape inserted corrugated tube and to evaluate its impact on engine performance and economics through heat recovery from the exhaust of a heavy duty diesel generator (120 ekW rated load). This type of heat exchanger is expected to be inexpensive to install and effective in heat transfer and to have minimal effect on exhaust emissions of diesel engines. This type of heat exchanger has been investigated for liquid to liquid heat transfer at low Reynolds number by few investigators, but not for gas to liquid heat transfer. In this paper, a detail of heat transfer performance is investigated through simulations using computer software. The software is first justified by comparing the simulation results with the developed renowned correlations. Simulations are then conducted for concentric tube heat exchanger with different twisted tape configuration for optimal design. The results show that the enhancement in the rate of heat transfer in annularly corrugated tube heat exchanger with twisted tape is about 235.3% and 67.26% when compared with the plain tube and annularly corrugated tube heat exchangers without twisted tapes respectively. Based on optimal results, for a 120 ekW diesel generator, the application of corrugated tube with twisted tape concentric tube heat exchanger can save 2250 gal of fuel, $11,330 of fuel cost annually and expected payback of 1 month. In addition, saving in heating fuel also reduces in CO₂ emission by 23 metric tons a year.     

极地船波纹换热管冲蚀磨损研究与防护

针对极地船波纹管换热器中进入冰晶颗粒对管路产生严重腐蚀磨损问题,采用CFD中欧拉-拉格朗日离散框架的DPM模型及腐蚀磨损模型研究流速、冰晶颗粒直径和含冰率条件变化对水平直波纹管磨损特性的影响。结果表明:波纹管磨损严重位置发生在波纹与直管衔接处、波谷处以及与流速相对的波峰面,且出口直管段磨损最为严重,而水平光滑圆管顶部位置磨损比较严重,但波纹管的磨损率均大于相同条件下光滑直管的磨损率;流速对磨损率影响最大,可使波纹管使用寿命减少10倍以上;冰晶颗粒直径对波纹管磨损影响较小;含冰率对管壁磨损也有很大影响,含冰率为10%时波纹管使用寿命比含冰率为2%时的减少4.2倍。根据以上研究结果提出了相应的防护措施。     

Experimental determination of shell side heat transfer coefficient and pressure drop for an oil cooler shell-and-tube heat exchanger with three different tube bundles

In this paper, the heat transfer coefficient and pressure drop on the shell side of a shell-and-tube heat exchanger have been experimentally obtained for three different types of copper tubes (smooth, corrugated and with micro-fins). Also, experimental data has been compared with theoretical data available. Correlations have been suggested for both pressure drop and Nusselt number for the three tube types. A shell-and-tube heat exchanger of an oil cooler used in a power transformer has been modeled and built for this experimental work in order to investigate the effect of surface configuration on the shell side heat transfer as well as the pressure drop of the three types of tube bundles. The bundles with the same geometry, configuration, number of baffles and length, but with different external tube surfaces inside the same shell were used for the experiment. Corrugated and micro-fin tubes have shown degradation of performance at a Reynolds number below a certain value (Re < 400). At a higher Reynolds number the performance of the heat exchanger greatly improved for micro-finned tubes.     

Indirect thermosiphon flat-plate solar collector performance based on twisted tube design heat exchanger filled with nanofluid

Stationary solar collector such as flat-plate collector is a thermal device, which traps solar energy and converts it into heat that can be used in industrial and domestic applications such as water heating. Flat-plate collector thermal performance enhancement is investigated in this research paper. Two cross-sectional geometries of the tube in the heat exchanger were investigated; a normal circular tube and a twisted tube were used in the experiment. The aim of the twisted tube exchanger is to enhance the performance of heat transfer of the tubes and to reduce the shell pressure drop; flat-plate solar collector is the used application to study the heat exchanger performance. Both twisted tubes heat exchanger and normal circular tubes heat exchanger were examined in the same location and conditions with the same solar collector, both were used in the heat exchanger to study their effect, with two different working fluids, which are distilled water and multiwalled carbon nanotube (MWCNT)/water nanofluid. The system shows an increase in the performance when twisted tubes were used in the system compared with the circular tubes in both distilled water and MWCNT/water nanofluid by 12.8% and 12.5%, respectively, with an improvement by 34% for twisted tubes with MWCNT compared with normal circular tubes with distilled water.     

多管型套管式换热器传热与流阻性能试验研究

多管型套管式换热器是在大尺寸外管的内部布置多根内管所构成的换热设备 ,与单根内管的套管式换热器相比 ,流量大幅增加 ,选用螺纹内管和管间折流板可以强化传热。对于多管型套管式换热器的传热性能试验 ,采用修正威尔逊法进行试验计算 ,得出了两种多管型套管式换热器的传热与流动阻力性能试验结果。     

Numerical investigation of heat transfer and pressure drop in enhanced tubes

This study investigates passive heat transfer enhancement techniques to determine the distribution of temperature and static pressure in test tubes, the friction factor, the heat flux, the temperature difference between the inlet and outlet fluid temperatures, the pressure drop penalty and the numerical convective heat transfer coefficient, and then compares the results to the experimental data of Zdaniuk et al. It predicts the single-phase friction factors for the smooth and enhanced tubes by means of the empirical correlations of Blasius and Zdaniuk et al. This study performed calculations on a smooth tube and two helically finned tubes with different geometric parameters also used in the analyses of Zdaniuk et al. It also performed calculations on two corrugated tubes in the simulation study. In Zdaniuk et al.'s experimental setup, the horizontal test section was a 2.74 m long countercurrent flow double tube heat exchanger with the fluid of water flowing in the inner copper tube (15.57–15.64 mm i.d.) and cooling water flowing in the annulus (31.75 mm i.d.). Their test runs were performed at a temperature around 20 °C for cold water flowing in the annulus while Reynolds numbers ranged from 12,000 to 57,000 for the water flowing in the inner tube. A single-phase numerical model having three-dimensional equations is employed with either constant or temperature dependent properties to study the hydrodynamics and thermal behaviors of the flow. The temperature contours are presented for inlet, outlet and fully developed regions of the tube. The variations of the fluid temperature and static pressure along tube length are shown in the paper. The results obtained from a numerical analysis for the helically tubes were validated by various friction factor correlations, such as those found by Blasius and Zdaniuk et al. Then, numerical results were obtained for the two corrugated tubes as a simulation study. The present study found that the average deviation is less than 5% for the friction factors obtained by the Fluent CFD program while Blasius's correlation has the average deviation of less than 10%. The corrugated tubes have a higher heat transfer coefficient than smooth tubes but a lower coefficient than helically finned tubes. The paper also investigates the pressure drop penalty for the heat transfer enhancement.