LDV散热器传热特性的分析研究

散热器是发动机是重要部件总成。本文对上海汽车商用车技术中心LDV车用散热器的传热性能进行风洞试验,由实测试验数据,将管外横掠管簇的对流换热系数从传热系数中分离出来,整理成无量纲准则式,为散热器的优化设计提供参考依据。另外,对一些未做过性能试验的散热器的设计计算也能提供帮助。     

Effects of aspect ratio on mixed convection in a horizontal rectangular duct with heated and cooled side walls

This paper describes the effect of aspect ratio on mixed convection in a horizontal rectangular duct with heated and cooled side walls numerically and experimentally. In the numerical analysis, fluid flow and temperature distributions for Ri=1.61, Pr=6.99, Re=100 and aspect ratio, Ar=0.2–10, were obtained by solving dimensionless governing equations using the SIMPLE procedure. The QUICK scheme was applied to the convective term of these equations. In the experimental analysis, the flow behavior for A_r=0.5–2 was visualized by the dye‐injection method. Numerical results showed that the swirl flow was generated along the flow direction, and its pitch length was influenced by A_r. The pitch length was the shortest when A_r=0.5–1, and this tendency was the same in numerical results and experimental results. The heat transfer behavior was also discussed corresponding to the flow, and the heat transfer ratio was highest at A_r=1 in 0.2 ≤ A_r ≤ 10. © 2012 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.20391     

自激振荡脉冲对流换热的实验研究

将Helmhotz共振腔应用于换热器来增强换热是一种新的强化换热方法。设计了一种换热效果较好的Helmhotz共振腔,并通过实验研究了Helmhotz共振腔对换热器的换热强化效果,分析了水力参数和结构参数对换热效果的影响,结果发现：对一定结构的共振腔,配以适当的水力参数,就可以产生自激振荡;对于同一结构的共振腔,水力参数不同,产生自激振荡的强弱也不同,随着压力的增加,自激振荡的强度也增加;将共振腔产生的自激振荡流引入换热器后,当自激振荡达到一定的强度时,能够破坏层流底层,从而可以强化换热;Helmhotz共振腔在绝大多数工况下能将管内换热系数提高10%-30%。     

平行平板间有圆台形蜂窝板的不同组合体时自然对流传热的实验研究

报道了平行平板间装有圆台形蜂窝及其不同组合体时自然对流传热的实验研究工作，介绍了实验装置及实验方法，比较了有无蜂窝及蜂窝的不同组合方案对自然对流传热的影响。实验结果表明，采用本工作研究的蜂窝结构，可有效地抑制空气夹层的自然对流传热。     

一种熔融铝液辐射余热回收用集热器的性能仿真研究

以回收熔融铝液辐射热量的集热器为研究对象,建立了集热器热力学过程理论模型,并采用Workbench和Fluent软件对集热器辐射传热过程和对流传热过程进行仿真分析。结果表明：当辐射距离为400~900 mm时,壁面平均温度在190~350 ℃之间;出口压力和壁面温度增加导致对流传热系数减小,而流量增加则使对流传热系数增加;流量和出口压力增加导致出口温度降低;系统流量增加造成压缩空气压降增大,出口压力增大导致压降减小,而壁面温度对压降没有影响。     

电晕放电强化气体对流换热研究进展

在气体中施加高压电场后,引起气体放电,产生的电晕风可以强化空气的对流换热。综述了国内外电晕风强化气体对流换热方面的研究进展,概括了以往研究的特点,指出了目前研究所存在的问题,对今后在该领域的研究方向及重点提出了建议。     

Research on convective condensation heat transfer for a gas mixture in a vertical tube

This paper discusses the convective condensation of a gas mixture in a vertical tube. A mathematical model was derived by combining a modified film model and Nusselt's condensation theory. The effect of wall temperature on film thickness and interfacial temperature was predicted and film thickness was calculated. When compared with the gas phase resistance method, the film model is better. The phenomenon of SO₂ absorption into condensate is illustrated and discussed. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(4): 219–228, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20011     

波纹板强化换热装置中带水膜饱和烟气对流传热的实验研究

为了探讨糖厂的烟气水膜除尘耦合换热技术实施的可行性,建立了带水膜湿烟气与空气之间的换热实验装置,进行带水膜湿烟气的对流传热实验研究。在该换热装置中,烟气在矩形通道中流动并喷入雾化热水,通过换热面加热另一侧的空气,同时,在烟气侧通道安装波纹板强化单元,以强化热质传递。实验确定最佳液气比,通过改变波纹板峰高、波纹段高、段数及烟气流速,研究带水膜饱和烟气的对流传热系数。结果表明:饱和烟气对空气的换热量显著;最佳液气比为3.3~4.2 L/m~3;烟气流速和波纹板添加段数的增加显著增大对流传热系数。回归了最佳液气比下的传热准则关联式。     

管内对流换热过程的热优化分析

对管内对流换热过程的温差换热和粘性摩擦引起的熵产进行了分析和优化计算 ,对换热设备和传热技术的设计和优化组织具有一定的指导意义。     

回转式空气预热器蓄热元件传热特性实验研究

回转式空气预热器热力性能主要取决于蓄热元件,在蓄热元件传热特性试验台上,通过分段均匀电加热蓄热元件模拟其在锅炉烟道中的温度并控制其在不同的温度水平上,对不同蓄热元件板形在不同壁温、不同雷诺数下传热特性进行了比较试验,并对结果做出了简要分析.     

Effect of tabs on impinging heat transfer

The present work experimentally investigates the effect of vortex generators, in the form of small tabs projecting normally into the flow at the nozzle exit, on the fluid flow and heat transfer characteristics of an axisymmetric impinging air jet in the subcritical Reynolds number range. With this comes the expectation of a large eddy structure variation and the possibility of active control. Local heat transfer and static pressure were measured on a target plate for a round air jet issuing from a circular nozzle with rectangular tabs whose numbers and lengths changed at a constant nozzle‐to‐plate gap (L/d = 8) and jet Reynolds number (Re = 34,000). The main results are the following: When two tabs were set at the exit of the circular nozzle, Cpw and Nu profiles flatten in the direction of the tab setting. In the case of three tabs, however, among both Cpw and Nu profiles a concentric profile is found, as well as in the case without any tabs. © 2001 Scripta Technica, Heat Trans Asian Res, 30(7): 561–570, 2001     

混合气体管内对流凝结传热研究

研究了混合气体在垂直圆管内的对流凝结传热。利用修正的膜模型与Nusselt凝结理论建立了换热数学模型,预测了壁面温度对膜厚度和界面温度的影响,计算了凝结液膜厚度,并与报相热阻法进行比较,研究结果表明该模型更接近实验果,提出了混合气体对流凝结换热与Nusselt凝结的不同。     

Control of heat transfer on wall with wall jet

A heat transfer experiment on a wall with laminar flow was performed by using a wall jet. The wall jet was generated by a flow control plate placed near the wall. Heat transfer coefficients were measured by a Mach. Zehnder interferometer. Flow patterns and velocities were measured by a smoke-wire method and a laser Doppler velocimeter, respectively. The height of the plates was varied from 2 mm to 8mm. The clearances between the wall and plate were varied from O mm to 7.6 mm. The following results were obtained. The large plate height gave a large, local heat transfer coefficient. The local heat transfer coefficients were enhanced about 7 times as high as that without the place at h = 8 mm, 0 = 30 degrees, and c/(c + h) = 0.15. The optimum wall jet generator angle for large heat quantity was 30 degrees or 45 degrees. © 1997 Scripta Technica, Inc. Heat Trans Jpn Res. 25 (1): 1–11, 1996     

Electrochemical experimental method for natural convective heat and mass transfer in porous media

Natural convection driven by combined thermal and solutal buoyant forces in a fluid-saturated porous enclosure was studied experimentally. An electrochemical method was employed to establish the concentration gradients. The inside temperature profiles and heat and mass transfer coefficients on the vertical walls were determined experimentally. The effects of dimensionless parameter Ra, Le, N on flow, heat, and mass transfer are discussed in detail. © 1999 Scripta Technica, Heat Trans Asian Res, 28(4): 266–277, 1999     

Mechanism of convection heat transfer on a heated crystal surface

This paper considers the mechanism of convection heat transfer on a heated crystal surface. An attempt was made to divide the heat transfer process into three links. Phonon theory is used to study and define the "convective power" of a crystal. The results indicate that the convection heat transfer process is discrete. The order of convective power of the crystal is extremely high and is approximately proportional to T ∼︁ T. It can be regarded that the energy exchange is finished in the course of one collision between the heated solid and media particles that is demonstrated by thermal conduction in the gas. The value of the heat transfer coefficient depends on the properties, states, and motion of the media. © 2000 Scripta Technica, Heat Trans Asian Res, 29(7): 573—580, 2000     

相变微胶囊功能流体相变区间的影响因素和变化趋势分析

相变微胶囊功能流体所具有的相变区间是影响其强化传热效应和工程应用价值的主要因素。采用双流体数学模型通过数值模拟发现:在层流条件下,双流体模型能够很好地模拟颗粒相体积分数、管径和R e对相变区间的影响。功能流体的相变段长度和总吸热量都随着这三个因素的增大而显著增大。同时相变段长度还取决于入口温度和边界条件等因素。以直链烷烃为相变材料的功能流体在相变段的蓄热能力相近。但在同R e下,功能流体的相变段长度和总吸热量都随着囊芯材料相变温度的升高而减小。入口温度是影响相变材料熔化速度的重要因素。相变段的长度、总温升和总吸热量与流体入口过冷度都呈线性关系。在第一类边界条件下,相变段长度与壁面过热度呈指数为负的幂指数关系,而相变段总温升和总吸热量都随壁面过热度的增大而增大。