基于CFX对管式换热器在烟气余热回收中的改进

通过对换热器结构特点的分析,提出在换热管外壁添加圆形翅片以此来提高管式空气换热器的余热回收。利用CFX软件模拟分析新型换热器的传热特性,通过分析翅片厚度、翅片间距、翅片高度得出,翅片厚度为0.8mm、翅片间距为3mm、翅片高度为12.5mm,换热器的换热性能最佳。     

顺排H型翅片圆管的传热与流动分析

通过模拟计算并比较数据得出结果：随着迎面风速增大,Re 数增大,Nu 数增大,摩擦系数f 减小,传热热阻R 也减小;随着翅片间距增大, Nu 数减小,摩擦系数f 减小,对传热热阻R 的影响较小;随着翅片厚度增大,Nu 数增大,摩擦系数f 明显减小,传热热阻R 也显著减小;随着翅片高度增加,Nu 数增加,摩擦系数f 也增加,而传热热阻R减小,在本文中研究的影响因素中优先考虑的因素为：翅片间距、翅片厚度及翅片高度。     

板翅式EGR冷却器耦合传热模拟研究

利用气-固-液耦合传热的数值模拟方法对板翅式EGR冷却器进行换热仿真分析,研究了平直翅片厚度、节距对换热和压降的影响,对比了不同类型翅片的换热效果,并对单程和双程的流动布置形式进行了比较。结果表明随着翅片厚度增加和翅片节距减小,换热效果增强,压力降增大;波形翅片比平直翅片有更好的换热效果和更大的压力降;双程流动与单程流动相比较,对增强换热具有显著影响,但压力降也急剧增加。     

横向管间距对开缝翅片管性能的影响及降噪方法的探讨

在分析窗式和分体式空调器特点的基础上,探讨两种家用空调器的优缺点。应用SIMPLE算法对空调用开缝翅片管表面的传热及流动阻力特性进行了三维数值模拟,研究了横向管间距对空调器换热和阻力性能的影响,在翅片间距和进口流量保持不变的情况下,计算了横向管间距从10.5mm变化到12.5mm等五种工况,得出随着横向管间距的增大,换热器两端压降减小,换热略有增加以及单位泵功换热量先增加然后减小的结论。计算结果表明,当横向管间距为11.97mm时单位泵功换热量最大。     

铜翅片管热水器的特性研究

以铜翅片管换热器为研究对象,通过合理的简化模型,以相邻2片换热片(取半片)及其之间的烟气通道作为计算区域,利用流体力学软件CFX对烟气通道的流动状况和换热情况进行了数值模拟。研究了管径、翅片厚度和翅片间距对排烟温度的影响,结果表明随着管径和翅片间距的增大排烟温度升高,随着翅片厚度增大排烟温度降低,排烟温度的升高或降低将影响排烟损失的大小,从而影响热效率。该数值模拟结果对改进翅片结构以提高热效率有一定指导意义。     

平直翅片管式换热器的传热数值模拟研究

以平直翅片管式换热器为研究对象,采用计算流体力学(CFD)方法进行建模和模拟计算,通过对正交试验结果进行极差和方差的分析,综合考虑了翅片厚度、翅片间距、管横向间距和管纵向间距对努赛尔数Nu和阻力系数的影响程度和显著水平,并结合综合性能评价指标进行分析,结果显示:翅片厚度、翅片间距和管横向间距对换热器的传热性能影响显著,管纵向间距对换热器的传热性能无显著影响。当翅片厚度为2mm,翅片间距为9mm,管横向间距为65mm,纵向间距为115mm时传热性能最佳。     

柔性管板计算方法与几何尺寸优化

利用ANSYS 15.0软件对柔性管板进行热-应力耦合分析,得到柔性管板整体应力分布规律,对柔性管板厚度、换热管中心间距、过渡圆角半径进行优化,并对国内外管板计算方法进行对比分析.结果表明:西德AD方法计算出的管板厚度最小;随着柔性管板厚度的增加,薄膜应力先减小后增大,薄膜加弯曲应力逐渐增大;随着换热管中心间距的增大,...     

过渡流下多列叉排圆柱列流动传热特性对比研究

为了在过渡流状态下对小型化换热器叉排管束群的传热强化机理进行研究,对三列、五列叉排圆柱列的流动传热特性的数值模拟结果进行了对比研究。使用Fortran程序对基于复合网格系统的三列、五列叉排模型在不同横向间距(Ps/D)下的流动传热特性进行数值模拟。研究结果表明(1)当Ps/D=3时,五列叉排圆柱列的传热强化效果最好,Ps/D=4时,三列叉排圆柱列的传热强化效果最好;(2)在叉排管束群中,第二列圆柱列的对流换热效果最好,后排圆柱列的对流换热效果依次降低。(3)在叉排管束群中,当圆柱列列数增加时,Ps/D增大时,传热强化效果不明显。     

平直翅片热管散热器的正交数值模拟优化

文中以平直翅片热管散热器为研究对象,研究了翅片厚度、翅片间距、翅片高度、翅片宽度和热管直径 5 个结构参数对翅片换热性能和阻力特性的影响,采用正交实验设计的方法设计了上述结构参数的 15 个组合方案,利用 CFD 数值模拟的方法对每个组合方案下翅片的流动换热性能进行了模拟。以努塞尔数 Nu 、阻力系数f、传热性能综合评价指标(Performance Evaluation Criteria, PEC)作为评价指标,在每个评价指标下利用极差分析挑选出性能最优的组合方案。 该方法能快速获得散热器结构的优化方案,并分析出主要影响因素,对工程应用有一定的指导意义。 结果表明:影响 Nu 和 f 的最主要因素是热管直径,影响 PEC 的最主要因素是翅片厚度。 对于本文研究的散热器,其最优参数组合方案为:翅片厚度为 0. 6 mm,翅片间距为 2. 2 mm,热管直径为 6 mm,翅片高度为 65 mm,翅片宽度为 28 mm。     

胀接工艺和片距对金属复合管换热器接触热阻影响的数值研究

金属复合管换热器制造过程中的胀接工艺会在管与翅片间产生接触热阻,该接触热阻对换热能力的负面影响较为显著.采用一种适用于工程上的结合换热性能试验和模拟仿真的计算方法,针对不同胀接工艺(Type-A型和Type-B型)和不同片距(2.0,2.2 mm)金属复合管的接触热阻数值问题开展研究工作.研究结果表明:片距2.0 mm...     

利用吸收式热泵回收工业废热的探讨

吸收式热泵是一种利用热驱动的节能设备,在节约和充分利用能源方面具有显著的作用,具有很高的可推广性。阐述了吸收热泵的工作原理,对其技术情况作了分析,并对其节能和环保方面的应用作了介绍。     

微沟槽热管传热性能实验研究

为研究充液率、真空度和长度对热管传热性能的影响作用,利用基于虚拟仪器技术的热管传热性能测试平台对直径6mm的微梯形沟槽热管在不同充液率、不同真空度以及不同长度等条件下进行实验测试.实验表明:微沟槽热管的最佳充液率在(75～100)%之间.热管内必须具备足够低的真空度,且充液率需根据真空度的不同适当调整.热管长度缩短可以提高其传热性能,但长度较短时,需适当提高充液率.     

热管换热器在烟气余热回收中的应用

介绍了热管技术，并分析了其传热机理。热管换热器具有许多独特的优点，已经获得了广泛的工业应用，应用主要集中在中低温余热资源回收利用方面，应完善高温热管，以拓宽热管换热器在高温余热资源中的应用。     

Enhancement of the critical heat flux by using heat spreader

Direct immersion cooling has been considered as one of the promising methods to cool high power density chips. A fluorocarbon liquid such as FC-72, which is chemically and electrically compatible with microelectronic components, is known to be a proper coolant for direct immersion cooling. However, boiling in this dielectric fluid is characterized by its small value of the critical heat flux. In this experimental study, we tried to enhance the critical heat flux by increasing the nucleate boiling area in the heat spreader (Conductive Immersion Cooling Module). Heat flux of 2 MW/m² was successfully removed at the heat source temperature below 78°C in FC-72. Some modified boiling curves at high heat flux were obtained from these modules. Also, the concept of conduction path length is very important in enhancing the critical heat flux by increasing the heat spreader surface area where nucleate boiling occurs.     

Experimental study on heat transfer characteristics of water-spray-bed heat exchanger

An experimental study was conducted on a water-spray-bed heat exchanger to investigate the heat transfer characteristics. A laboratory-scale test rig was built and its heat transfer characteristics were investigated with respect to various design and operation parameters such as the water spray flow rate, exhaust gas flow rate and number of tube rows. It was found that the implementation of the water spray increased the heat transfer rate to about 1.3 - 2.2 times that of a heat exchanger without water spray, although with a slight increase in the pressure loss. It was thus confirmed that the water spray was effective for enhancing condensing heat recovery from an exhaust gas.

     

Laser heat treatment

This paper reviews recent developments in the application of high power lasers to materials processing technology. The use of fine beams of laser energy to modify the surface properties of metallic materials is described in detail with specific emphasis on transformation hardening, surface alloying, and laser glazing. The successful exploitation of this new technology points to a significant potential for manufacturing industry to develop wear resistant surfaces using these laser systems     

无机传热技术及其工业应用

无机传热技术具有钢-水热管技术的优点，并解决了钢-水热管应用温度范围窄、常用工质热管易爆管和使用寿命短的缺陷。用该技术制造的空气预热器、余热锅炉等设备已成功地应用于石油行业，用于回收余热或进行工艺加热，并取得了良好的社会效益。     

Topological design of heat dissipating structure with forced convective heat transfer

This paper discusses the use of the topology optimization formulation for designing a heat dissipating structure that utilizes forced convective heat transfer. In addition to forced convection, there is also natural convection due to natural buoyancy forces induced by local heating inside fluid. In the present study, the temperature distribution due to forced convection, neglecting buoyancy and viscous dissipation inside fluid, was simulated and optimized. In order to analyze the heat transfer equation with forced convective heat loss and the Navier-Stokes equation, a common sequential computational procedure for this thermo/hydraulic characteristic was implemented. For topology optimization, four material properties were interpolated with respect to spatially defined density design variables: the inverse permeability in the Navier-Stokes equation, the conductivity, density, and the specific heat capacity of the heat transfer equation. From numerical examples, it was found that the balance between the conduction and convection of fluid is of central importance to the design of heat dissipating structures.     

An analytical solution to heat conduction with a moving heat source

This paper deals with an analytical solution to heat conduction in the medium subjected to a moving heat source. It evaluates the temperature distribution around a rectangular shape source moving at a constant speed along the axis of a bar. The transient temperature field from a moving heat source was analyzed using a Fourier series procedure. The most interesting result of the theory, is the derivation of a single formula capable of predicting the cooling time and cooling rate with a fairly good accuracy for ranges of temperature. Because of the passage of the heat source, the rise of temperature produced at a given near the source, tends to rapidly become constant. Several sample problems are discussed and illustrated, and comparisons with numerical approaches where these can also be used made. The results show that these solutions are in good agreement with the numerical results.     

提高KZL4-13型锅炉发热量减少热损失

对老式KZL4-13型锅炉的辅机和内拱结构进行改造，提高了锅炉热效率，加强对供热系统管理，增加了企业效益。