Experimental Measurement and Analysis of Performance of Heat Pipe Heat Exchanger Used in a Turbocharged Engine with Intercooling

Turbocharging technology with higher compression ratio has been widely applied in engines and the strength loss of an aluminum charge air cooler becomes a problem attracting increased attention. The heat pipe charge air cooler (HPCAC) is a new type of CAC that can withstand high temperature. An experimental study of a gravity-assisted HPCAC was performed. Several configurations of heat pipe heat exchangers were constructed and tested under different operation conditions on the testing rig. The effects of tube pitch, heat pipe line, and condenser length on the performance were investigated and an optimal configuration in this study was obtained. Then effects of inlet cooling air velocity, inlet compressed air temperature, and velocity on the heat transfer and pressure drop for a fixed tube pitch and condenser length were analyzed, and the results were compared with the theoretical simulation. The experiment results showed that the HPCAC could remove the heat load efficiently to ensure that the aluminum CAC works under a safe temperature, which indicated that HPCAC is a suitable approach and effort to solve aluminum strength loss at high temperature.     

套管换热器对流换热的数值模拟研究

本文建立了一种复杂的数学模型用于预测套管式换热器内流体的流动及传热特性。数学模型包括计算流体力学模型和计算传热学模型。其中,计算传热学模型中的湍流扩散系数是利用温度方差t2和温度方差耗散率εt来求解,而不是利用通常采用的Pr数假设值或实验测定值来求解。为验证新建立模型预测结果的准确性,本文将数值模拟结果与文献中的实验结果进行了比较,结果吻合较好。     

管壳式换热器换热性能的数值模拟研究

在水的雷诺数Re从1900~25000范围变化的情况下,选择换热效果比较好的Φ25/Φ19波纹管,并对其换热性能进行了数值模拟与实验研究。结果显示波纹管的换热系数是直管的1.1~1.8倍,且随着雷诺数的增加,倍数值逐渐减小;波纹管的压降损失是直管的2~3倍。     

用于电子元件散热的集成热管换热特性研究

本文对应用于电子元件散热的热管换热器在不同的加热功率、不同风量情况下的传热特性进行了实验研究，从而得出换热量、总热阻、翅片表面阻力系数、换热系数、总热阻与加热功率及风道内空气肫数的关系，并与市场上的SP-94型热管散热器及传统纯铜散热器进行了比较，发现该热管换热器无论是散热量、平均换热系数还是总热阻都有明显的优势。因此，这种散热器在实际工程应用中必将有着广泛的潜力。     

非对称翅片管换热器传热和阻力特性的数值分析

基于COMSOL软件建立了一种非对称翅片管换热器的三维模型,对空气侧的流动和传热特性进行了数值研究,与平直翅片管换热器进行对比,并进一步分析了不同雷诺数下交错角β对非对称翅片管换热器性能的影响.结果表明:在Re为3 239~9 700内,与平直翅片管换热器相比,非对称翅片管换热器的传热因子增大,平均增大量为13.95%,阻力因子减小,且随着Re增大其减小效果更加明显,平均减小量为4.80%;以MJF作为评价标准,且其他结构参数不变时,β=30°时MJF最大,换热器的综合性能最好.     

有机酸清洗剂去除换热设备污垢实验研究

以A、B、C三种有机酸清洗剂为研究对象,筛选出性能较好的清洗剂并优化其清洗工艺参数,结果表明,清洗剂C与水的体积比为1∶20、清洗温度为20~40℃、清洗时间为1 h时,除垢率达97%,且对碳钢和不锈钢的腐蚀率为三种清洗剂中最低,满足化学清洗对腐蚀率的要求.在此基础上,建立动态除垢实验装置考察实际清洗效果,结果表明,清洗剂C实际清洗效果较好,除垢后清洗试件在管程流速分别为0.5、0.7、0.9、1.1 m·s-1时,传热系数分别提高6.01%、6.98%、6.93%、9.04%.     

油气散热器传热特性的分析研究

运用fluent软件对油气散热器管内流动的传热特性和阻力特性进行了数值模拟,得出了管内努赛尔数Nu和阻力与雷诺数Re的关系曲线,然后进一步对管内外的流动与换热进行试验研究,并根据试验数据将管内外的换热系数分离出来,得到了管外换热的关系准则式.将管内的传热和阻力特性的数值模拟和试验研究结果进行对比分析表明,两者具有很好的一致性.     

管壳式与板式水水换热器性能比较

通过对管壳式与板式换热器结构特点、设计参数、安装检修、技术经济性等方面的性能比较,得出板式换热器优于管壳式换热器的结论.     

空-空热管式中冷器设计与热力性能试验研究

依据热管式换热器的特点,编制了空-空热管式中冷器的设计程序,并设计了试验用热管式换热器样件对该设计程序进行试验验证。利用通用的传热系数计算公式程序所得的计算值与试验所得的实测值变化趋势基本一致,说明所编制的计算程序是实用和可靠的。根据试验结果对设计程序进行了修正,热空气出口温度最大偏差为0.5℃,热流量最大偏差为7W,表明修正后程序的计算结果与试验结果吻合较好。用试验数据分析了欧拉数与雷诺数的关系,拟合得到适合空-空热管式换热器的阻力计算的准则方程式,压降修正结果与实测值最大偏差为31.39Pa,误差不超过6%,说明在中冷器设计程序中可以利用拟合公式较好的分析压降。     

再生式换热器的实验研究与数值模拟

为了解再生式换热器工作特性,采用Matlab软件计算简化后的模型,对换热器内流体和固体的温度分布进行了数值模拟,并进行了实验验证.研究了蓄热体长度、比表面积、速度和蓄热体材质对换热效果的影响.结果表明,面积和流速对换热效果影响明显,而改变蓄热体材质基本无影响.     

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。     

换热器性能的火用经济评价

通过对换热器传热与流动过程的(火用)经济分析,提出了一项换热器性能(火用)的经济评价指标--单位传热量的总费用η,并对顺流、交叉流和逆流三种流型的换热器进行了(火用)经济分析和优化.本文的有关方法和结论可为工程上换热器的性能评价提供参考.     

Fast Simulation of a Vertical U-Tube Ground Heat Exchanger by Using a One-Dimensional Transient Numerical Model

An explicit one-dimensional transient numerical model has been built for a single-borehole ground heat exchanger, and two computing algorithms are given. The outlet temperature of the U-tube and the soil temperature can be predicted by using arbitrary time-varying load or inlet temperatures as inputs. This numerical model has been compared with analytical models and validated by using test data of three boreholes. Conclusions are that this numerical model is considerably accurate and efficient; the computational time of a one-year-period simulation is about 52 s; recommended is the discrete scheme with 60-s step time and spatial increment of 0.033–0.067 m.     

Numerical Analysis of Baffle Cut on Shell Side Heat Exchanger Performance with Inclined Baffles

In this work, an attempt has been made to decrease the pressure drop and to increase the heat transfer rate in a shell and tube heat exchanger (STHX) by tilting the baffle angle and by varying the baffle cut. The process of solving the simulation includes modeling, meshing, and analyzing the geometry of the STHX by using Pro-E, hypermesh, and computational fluid dynamics package of ANSYS Fluent, respectively. The objective of this study is to find a suitable baffle inclination and baffle cut for the efficient performance of the STHX. The baffle inclinations of 25°, 30°, 35°, and 40° were considered for three different baffle cuts of 25%, 30%, and 35% of shell inside diameter and the results were compared with segmental baffle of inclination angle 0°. The shell side flow with different inclination angles and baffle cuts results in a significant variation in heat transfer rate and pressure drop in the STHX. The results provide a clear idea that the heat transfer rate is maximum in inclined baffle heat exchanger compared to that of segmental baffle heat exchanger. Further it is found that the STHX with the configuration of 35º baffle inclination angle and baffle cut of 30% of shell inside diameter provides higher heat transfer rate with minimum pressure drop compared to all other configurations.     

Experimental Study on Anti-Fouling Performance in a Heat Exchanger with Low Voltage Electrolysis Treatment

An innovative physical method to control fouling in heat transfer equipment—low voltage electrolysis anti-fouling (LVEAF) technology—is introduced. The objective of the present study is to testify the effect of LVEAF treatment in forced convective system and identify the operating mechanism. A series of fouling tests were carried out with and without LVEAF treatment. During the experiments fouling resistance was monitored, and the properties of test liquid were measured, including hardness, alkalinity, electrical conductivity, and pH. The main results were as follows: (1) The fouling was effectively restrained to form on the heat exchanger surface if the circulating water was treated with LVEAF. The scale inhibition ratios exceeded 90% in most cases. (2) The LVEAF technology is an active anti-fouling technology with lower energy consumption. The properties of treated test liquid were changed. (3) Electrochemical reactions occur near the electrode due to the low current existence in the water when the LVEAF device is working. A lot of fouling deposits formed in the test liquid near the cathode or on the inner surface of the treatment unit, but did not deposit on the heat exchanger surface.     

半圆柱空间异形孔板换热器热工水力性能的数值模拟

为研究半圆柱空间异形孔板换热器的流动与传热特性,建立换热器简化物理模型,运用ANSYS软件建立CFD模型进行数值模拟,分析了开孔形状与板间距的影响,并对比了半圆柱空间异形孔板换热器与弓形板换热器的联系与区别。研究结果表明：半圆柱异形孔板换热器壳侧流体呈纵向流动,壳侧流体通过孔隙形成射流冲刷管壁,具有强化传热作用;板间距一定,开孔面积相近时,开孔形状对壳侧压降的影响较小,对换热性能的影响稍大;板间距越小壳侧换热系数越高但其综合性能指标越小;圆头三角孔板换热器在板间距30 mm时的壳侧换热系数比40及50 mm方案分别高5.62%,10.06%,综合性能指标低1.44%,2.07%;异形孔板换热器的综合性能指标比弓形折流板换热器平均约高27.89%。     

Real Time Fouling Diagnosis and Heat Exchanger Performance

The issue of fouling in preheat trains of crude oil distillation units in Petrobras's refineries is a major concern—especially now, as heavier Brazilian crudes with higher asphaltene content are being refined. As the efficiency of the preheat train plays an important role in the energy consumption of a distillation unit, its performance must be tracked as precisely as possible in order to identify operational problems. This work describes an online heat exchanger performance evaluation system based on rigorous simulation of the equipment in order to predict both the operational and clean overall heat transfer coefficient. A real-time comparison between these two values indicates the actual performance of the heat exchanger and of the preheat train. The use of a rigorous process simulator (Petrox from Petrobras) together with a rigorous calculation of the global heat transfer coefficient (using the program Xist from HTRI) allows one to consider aspects that are not usually taken into account in this kind of evaluation. These aspects include crude vaporization after the desalters and variations of crude and products composition with the distillation unit run. The system is being implemented at the biggest Petrobras refinery (360,000 bpd) in a 25 heat exchanger preheat train.     

Thermal-Hydraulic Performance of Different Discontinuous Fins Used in a Printed Circuit Heat Exchanger for Supercritical CO2

In this study, four discontinuous fin configurations in parallel and staggered arrangements are investigated to classify their effects on the thermal-hydraulic performance of a printed circuited heat exchanger. Meanwhile, the formation mechanism of the flow resistance of supercritical CO₂ is studied in an airfoil fin printed circuited heat exchanger. It shows that the fin configurations have little effect on the overall thermal-hydraulic performance when the mass flow rate of supercritical CO₂ is low. The flow resistance dramatically increases during the heating process due to velocity increment caused by increased density, but is not significantly affected by the change in dynamic viscosity.     

AP1000非能动余热排出热交换器的焊接

针对我国引进的三代核电技术AP1000中主要核岛部件非能动余热排出热交换器(PRHR HX)的制造,介绍了PRHR HX的技术参数、结构特征、材料特点和所依据的规范技术条件。介绍了管板双面堆焊、封头不锈钢带极堆焊、接管-安全端异种金属镍基合金焊接、换热管-管板密封焊和不锈钢框架焊接等主要焊接技术难点和对应的焊接工艺。