利用金属辐射网强化换热器烟气侧传热的研究

提出了用金属辐射网来强化高温烟气／空气换热器传热的方法，并通过实验研究了金属辐射网对其传热特性的影响。得出了烟气温度越高、流速越低、空气侧传热系数越大，则辐射网的效果越好等结论，为换热器传热的强化提供了一个新的途径。     

波纹板式换热器传热与流动特性分析

通过数值模拟的方式,对一种用于低粘度流体的波纹板式换热器的传热特性和阻力性能进行分析,以控制变量法分析了流体速度对传热特性及阻力性能的影响;搭建了板式换热器测试平台,验证了数值模拟结果的正确性和可行性;用等速法拟合了Nu-Re与Eu-Re的相关准则式,并采用JF因子评价换热器综合性能。结果表明：模拟结果与实验结果相比误差在10%以内;当流体流速小于1.0 m/s时,换热器传热系数和压降随着流速的增大而增大,但综合换热性能逐渐变差,在此流速范围内,总传热系数随冷流体进口温度升高而增大。     

间壁式换热器传热的强化

介绍了传热强化的基本原理和有效措施。指出，综合传热系数是换热器的重要经济技术指标，是评价一个换热器性能好坏的决定性参数。要强化换热器的传热，必须同时强化空气侧和烟气侧的传热才会产生最佳的效果，得到较高的综合传热系数。     

金属换热器经济选择分析

本文以系统节能和提高综合经济效益的观点，分析了影响金属换热器传热系数的诸因素及其提高途径，以及气流阻力与动力消耗，传热面积与投资的定量关系。为正确选用不同结构金属换热器及其性能提供了依据     

板壳式换热器流固耦合换热的数值模拟

以型号为IPS24的波纹板壳式换热器为研究对象,应用CFD软件ANSYS FLUENT16.0进行流体流动及耦合换热的数值模拟。结果表明:人字形波纹板结构对板壳式换热器传热性能有显著的增强,且能够有效地防止结垢;随着入口流速的增加,总对流传热系数增加,但也会导致压力损失增加,在流速为1.0 m/s时总传热系数达到1 519 W/(m~2·K),冷、热流体进出口压降也分别高达81.2和83.1 kPa。     

基于模块化的氟塑料换热器优化布置研究

对1 000MW火力发电机组中间热媒体烟气换热器(media gas-gas heater,MGGH)系统中脱硫塔前的氟塑料换热器展开设计计算,从交叉次数的角度对氟塑料换热器模块化以及优化布置展开研究.结果表明:水侧阻力与交叉次数的平方成正比;随着介质交叉次数的增加烟气侧压降降低管外总换热面积、联箱总开孔数和模块单元联箱开孔数均减少,且当交叉次数由2增加到4时上述参数均大幅降低,当交叉次数大于4以后降幅均相对较小,即氟塑料换热器的换热性能、阻力性能及联箱结构在交叉次数为4时得到优化,结合热膨胀因素建议在工程应用中尽量采用2个U形换热模块单元布置成W形.     

板式换热器性能的数值模拟

建立了人字形板式换热器冷热双流道的流体流动与传热计算模型,利用计算流体力学软件对5组不同速度工况下换热器内流体的流动和传热进行了数值模拟,分析了换热器流道内的速度场、温度场和压力场.结果表明:数值模拟得到的板式换热器进、出口温差和压降与试验测量值的误差均小于6%;换热器内流体的流动和传热存在明显的不均匀性,导致其进、出口的另一侧出现明显的传热"死区";换热器的总传热系数和流道阻力均随着流体流速的增大而增大.     

板壳式换热器传热准则关系式的分析与实验研究

假设板壳式换热器为特殊板式换热器,介绍了板壳式换热器传热准则关系式的研究方法.分析比较了壁面温度测定法、等雷诺数法、威尔逊法和等流速法等的适用性,确定了利用等流速法来进行实验研究,并分别进行了测定实验和验证实验,测定实验控制进出口流速相同,验证实验控制热侧流速不变,改变冷侧流速,采用实验获得的数据拟合传热准则关系式,计算出传热系数的相对误差.结果表明:传热系数的相对误差小于5%,所得传热准则关系式是合理的,表明板式换热器的研究方法适用于板壳式换热器.     

低温烟气换热器传热特性的试验研究

ND钢作为优良耐硫酸腐蚀钢已被广泛用于低温烟气余热回收,而目前尚缺乏其传热相关数据,故搭建小型传热试验台,研究了工质与烟气流速、进口烟温和管材质对光管、外螺纹管、螺旋翅片管传热特性的影响。结果表明:工质流速对传热影响不大;烟气流速从4.1增大到7.4 m/s时,总换热系数分别增大了1.86倍、1.7倍、1.44倍,且外螺纹管、螺旋翅片管的总换热系数分别是光管的1.05~1.15倍和1.52~2倍;进口烟温从75℃升高到190℃时,总换热系数分别增大了31%、33%、20%;不同管材质通过接触热阻影响换热性能。     

基于ANSYS FLUENT的板式换热器性能仿真

板式换热器作为海水淡化设备的关键部件，换热器的结构对于整个设备的正常运行、使用寿命以及海水淡化处理的效果都起着关键作用。但长期以来板式换热器的结构设计主要依赖于经验公式，缺乏可靠的设计分析方法。因此，根据板式换热器的结构，通过质量守恒方程、动量守恒方程以及能量守恒方程建立换热器的能量传递数学模型，采用湍流(RNG k-ε)模型建立质量传递模型。使用ANSYS FLUENT建立了板式换交换器的三维几何模型。并模拟了不同工况下的热力学性能。根据模拟结果分析了压力场、温度场、速度场和流动情况。比较分析了换热器在不同流量和冷热流体温差下的传热性能和阻力性能。为了提高板式换热器的效果可通过增加冷流体的流速和增加冷流体和热流体之间的温差来确保更大的传热系数，从而提升换热器的热交换性能。研究结果为不同工况条件板式换热器使用及设计提供了理论支持。     

Numerical studies on flow and heat transfer in membrane helical-coil heat exchanger and membrane serpentine-tube heat exchanger

The flow and heat transfer characteristics of synthesis gas (syngas) in membrane helical-coil heat exchanger and membrane serpentine-tube heat exchanger under different operating pressures, inlet velocities and pitches are investigated numerically. The three-dimensional governing equations for mass, momentum and heat transfer are solved using a control volume finite difference method. The realizable k-ε model is adopted to simulate the turbulent flow and heat transfer in heat exchangers. There flows syngas in the channels consisting of the membrane helical coils or membrane serpentine tubes, where the operating pressure varies from 0.5 to 3.0 MPa. The numerically obtained heat transfer coefficients for heat exchangers are in good agreement with experimental values. The results show that the syngas tangential flow in the channel consisting of membrane helical coils is significant to the heat transfer enhancement to lead to the higher average heat transfer coefficient of membrane helical-coil heat exchanger compared to membrane serpentine-tube heat exchanger. The syngas tangential velocity in the membrane helical-coil heat exchanger increases along the axial direction, and it is independent of the gas pressure, increasing with the axial velocity and axial pitch rise and decreasing with the radial pitch rise.     

An experimental study on vapor condensation of wet flue gas in a plastic heat exchanger

An experimental system investigating condensation heat transfer of wet flue gas was set up, and the heat transfer performance of vapor‐gas mixture with vapor condensation was discussed. The experimental results of laminar flow in a plastic longitudinal spiral plate heat exchanger were obtained and are in good agreement with the modified classical film model. It is shown that the plastic air preheater can avoid acid corrosion in the low‐temperature field for the boiler using fuel containing sulfur and recover latent heat of the water vapor of the wet flue gas. Also some SO₂ was scrubbed during the vapor condensing process in the heat exchanger. © 2001 Scripta Technica, Heat Trans Asian Res, 30(7): 571–580, 2001     

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。     

低温烟气凝结换热及对天然气热效率的影响实验研究

为研究烟气露点附近及以下的低温烟气对流凝结换热规律与烟气换热对天然气利用热效率的影响,建立了烟气在翅片管换热器内对流凝结换热实验系统,研究了不同烟气温度、水蒸气含量对烟气凝结换热的影响,得出了烟气凝结换热实验准则关联式,分析对比了天然气利用热效率实验值与理论值。实验结果表明:当被加热水温度为23℃,烟气出口温度为73℃,比烟气露点53℃高20℃时已开始冷凝;过量空气系数1.3,烟温由54.1~73.4℃降到28.7~57.8℃,被加热水进口温度21~25℃的条件下,烟气中水蒸气质量含量降低了27%~76%,潜热换热占总换热51%~63%;天然气利用低热值热效率实验值比理论值高1.04%~8.74%。为低温烟气对流凝结换热规律研究与烟气余热回收利用技术开发及应用提供理论依据和数据资料。     

径向热管换热器在天然气工业炉低温烟气中的应用

当前我国的能源形势紧张,能源利用状况令人担忧.在一些高耗能的企业,工业生产中排放的中低温烟气余热由于回收难度高、回收成本大等问题,一直得不到合理的利用,如何合理回收成为亟待解决的难题之一.简要介绍了一种新型余热利用换热设备——径向热管换热器,提出了计算热管换热器经济性评价指标的方法,并以某工厂低温烟气余热回收工程为实例,对烟气余热的回收利用进行了技术和经济效益分析.实践应用证明,径向热管换热器在工业低温烟气余热回收中有很好的实用性和可行性.     

Experimental study of thermal performance improvement in a cross-flow heat exchanger by using copper foam

In this study, copper foam was used as a porous medium in place of traditional aluminum fins. A comparison between the two heat exchangers—one with fins and the other with copper foam—was conducted under various conditions. The air inlet velocity ranged from 0.9 to 9.3 m/s, and the water inlet temperature ranged from 10°C to 18°C. Different water flow rates were tested. A comparison was made between the performance of copper foam and aluminum fins by calculating several parameters, including thermal resistance, heat exchanger effectiveness, Colburn factor, Nusselt number, friction factor, and area goodness factor (AG). The experimental results showed that at low air velocities, the heat transfer coefficient for both types of heat exchangers was almost equal. However, at high air velocities, the copper foam exhibited a higher heat transfer coefficient. The Colburn factor was higher for the heat exchanger with copper foam than in the conventional fins, where it was equal to 0.1959 for the copper foam and 0.1186 for the fins. On the other hand, the AG was higher in the case of fins than in the heat exchanger with copper foam.     

开缝布置方式对开缝翅片管换热器 传热与阻力特性的影响

为了获得开缝布置方式对开缝翅片管换热器传热与阻力特性的影响规律,对5种不同翅片管换热器进行了数值模拟研究,并进行了模化试验验证。结果表明：增加开缝会提高翅片管换热器的传热性能,但阻力也随之增加;与开缝位置相比,开缝数量对开缝翅片管换热器传热与阻力特性的影响更大;在Re=4800~7500日时,开缝翅片管换热器综合流动传热性能 随着Re数的增大而增大;在5种翅片中,开缝翅片的综合流动传热性能高于普通平直翅片;数值模拟与试验结果偏差较小,采用数值模拟方法能够比较准确地分析开缝翅片管换热器的传热与阻力特性。     

径向热管换热器壳程压降数值模拟及参数优化

通过对径向热管换热器壳程压力场的数值模拟,分析入口烟气速度对换热器压降的影响规律,并对换热器结构参数进行优化。结果表明:换热器迎风侧压力高于背风侧压力,沿烟气流动方向压力逐渐降低且呈线性分布;换热器压降随入口烟气速度的增加而增加,且其增加速率也相应增大。通过改变换热器结构参数,对换热器壳程压降进行分析研究,得到其结构优化参数:翅片高度小于26.5mm,翅片间距大于6.5mm,热管横向间距108～111mm,纵向间距120～125mm。     

Experimental study on titanium heat exchanger used in a gas fired water heater for latent heat recovery

In general, latent heat recovery is usually accompanied by the corrosion of the heat exchanger, which is caused by the strongly acidic condensate when the temperature of the flue gas is lowered below the acid dew point. The present study has been conducted to investigate the heat and mass transfer characteristics in a titanium heat exchanger with excellent corrosion resistance used for waste heat recovery with the condensation arranged in a gas fired water heater. In addition, the thermal efficiency of the gas fired water heater was evaluated based on the net calorific value at the maximum rated output during latent heat recovery from the exhaust flue gas. Parametric studies were conducted for the flue gas flow rate, inlet temperature and mass flow rate of the supplied water, respectively. Different arrangements of the tubes of the heat exchanger including in-line and staggered configurations were investigated. The experimental results indicate that the thermal efficiency of the gas fired water heater with a latent heat recovery (LHR) heat exchanger was enhanced by about 10% compared with conventional instantaneous water heaters, i.e., water heaters without heat recovery. In addition, in terms of the Nusselt number and the Sherwood number, the heat and mass transfer performance of the staggered tube bank type were approximately 50% and 10% higher than that on the in-line tube bank type when the Reynolds number of the flue gas was 10³.     

湿法烟气脱硫系统的烟气换热器设置分析

通过对上海地区燃煤电厂湿法烟气脱硫系统安装和不安装烟气换热器(GGH)的运行分析,证实了安装GGH后的烟囱腐蚀,明显低于无GGH烟囱,尤其是针对GGH发生结垢、堵塞和腐蚀等问题采取的六大技术措施,能够达到环保考核要求,同时论述了脱硫系统取消GGH后,会给周边环境和生产运行安全带来隐患。为此,结合国家环保政策,提请各燃煤电厂在建设脱硫系统时,不应盲目取消脱硫系统的GGH装置。