微尺度热传导理论及金属薄膜的短脉冲激光加热

概述了微尺度热传导理论的几种模型及其求解方法。以金属薄膜的短脉冲激光加热为例,分析了固体材料在微尺度条件下的热响应特征,主要包括短脉冲激光加热条件下金属薄膜中的热平衡时间、薄膜中热传递的波动性特征和微尺度条件下热传递的尺寸效应;同时讨论了对流热损失对金属薄膜热行为的影响。     

浅谈PCB图形转移中的短路现象

研究了一种少见的PCB短路现象,及解决问题的全过程.     

栅格式方孔翅片自然对流换热的数值模拟

为改善电子器件的散热情况,提出了一种新型结构的栅格式方孔翅片,并对其在自然对流条件下的散热特性进行了研究。利用正交试验法和Fluent数值模拟,模拟了102种不同翅片高度与间距比H/S、不同孔边长与翅片厚度比b/δ的散热情况。研究得到:大空间自散热条件下,H/S=2、b/δ=0～4时的Gr-Nu的关系图;有限空间散热条件下,b/δ=1.5、H/S=1～16/3时的Gr-Nu的关系图。结果表明,格栅式方孔翅片可以改善电子器件的散热,并为LED照明等电子器件散热设计提供新的思路和理论依据。     

厚膜片状电阻器开路失效分析

分析了厚膜片状电阻器波峰焊时开路失效的原因 ,并提出了相应的解决方法。     

电子元器件中热传递功能的声学评价

半导体电子元器件的内部缺陷会影响其散热效率从而导致元器件失效。为了检测元器件的内部缺陷,采用声学显微镜来检测塑料封装集成电路器件的芯片胶接层和倒装芯片散热片与芯片间的热界面材料,结果显示,前者的胶接层的孔隙率达46.22%。而后者的热界面材料中发现有孔隙。对热界面材料的厚度通过参考回声的方法进行了测量,结果显示其厚度为30~75μm,均在要求范围之内。     

散射性半透明介质内红外热辐射与相变耦合换热

半透明介质的相变传热必须考虑介质内红外热辐射传输的影响.研究了二维矩形吸收、发射、各向同性散射性半透明介质的凝固过程.假设凝固发生在某一温度区间,因此须考虑液、糊、固三个区域.采用有限体积法求解基于焓的能量方程,蒙特卡洛法求解红外热辐射传输.一维相变导热、二维瞬态红外热辐射与导热耦合换热的结果与文献进行了比较,吻合较好...     

Examination of natural convection plumes from partially heated PCB plates and estimation of the heat transfer coefficients

Accurate values of convection heat transfer coefficients are required for the simulation of the thermal characteristics of printed circuit boards. This paper presents the results of experiments carried out using a Schlieren apparatus to examine the natural convection plumes from a horizontally positioned partially heated printed circuit board plate. It has been demonstrated that for a board with a centrally positioned resistor, the convection coefficients may be approximated to two values, one over the heated resistor area and another over the rest of the plate. These observations were then used in an optimization process to estimate the convection coefficients from such surfaces. Values of 4 W/m²K and 13.5 W/m²K were obtained for the resistor and the adjoining unheated sections, respectively. It is concluded that it is not generally satisfactory to assume a uniform value for convection coefficients during thermal simulation of electronic structures. However, a simplifying assumption of two values for convection coefficient appears to be acceptable; the lower value applying in the region of convection plumes and the higher value elsewhere.     

微通道的流动阻力分析

针对在恶劣温度条件下工作的芯片热控制问题,提出由微泵、微通道、热电模块、智能控制单元、散热片以及液体管道等构成的微通道对流换热设计思想。数值仿真分析了换热微通道结构的速度和压力分布,计算了管道、微通道等部件的阻力损失和换热系统的流动阻力曲线,确定了系统必需的微泵工作性能参数,求解了微泵的最佳工况点。最后,制作了微通道对流换热装置,测得了系统流量和流动阻力,证实了可用经典流体理论来分析该系统的流动阻力。     

碲锌镉晶体生长全局热传递模拟模型准确度研究

在碲锌镉晶体生长技术开发方面,数值模拟软件发挥着越来越重要的作用。以全局热传递模型为基础进行晶体生长模拟能够极大的提高模拟结果的实用性,缩短晶体生长设备及生长工艺的开发周期。但其前提是采用的全局热传递模型的准确度较高。因此,本文主要研究了几何模型、物性参数、边界控温条件等对模型准确度的影响,并根据模型计算值与炉体中心测温比较结果,修正了上述模型各参数,获得了在多种温度设定条件下,计算结果都能与实际过程很好的吻合的全局热传递模型。采用修正后的模型应用于碲锌镉晶体生长过程模拟,最终晶体生长模拟结果的温度与实际监测温度差距在2 ℃以内。     

电子产品散热器的设计

对电子产品使用的散热器的散热原理、主要影响因素进行了分析,建立了数理模型,并对如何选择散热器提供了一些可行的依据.     

扰流小通道液冷冷板流动与传热特性的数值研究

为降低常规蛇形小通道液冷冷板的热阻,提高其对流换热能力,在流道内引入了一种强化换热结构,设计了扰流蛇形小通道液冷冷板,并利用数值模拟方法对两者进行了比较分析。相比于常规蛇形小通道液冷冷板,新的流道设计能够显著降低冷板的总热阻和进、出口压降,降幅分别可达9.2%和66.7%。此外,冷板平均努赛尔数(Nusselt, Nu)提高了17.2%。对冷板内部流动和传热情况进行了详尽的数值分析,研究了扰流小通道的强化传热效果及其作用机理。     

Bounding relations for natural convection heat transfer from vertical printed circuit boards

The simplicity and convenience of direct cooling with freely circulating air, as well as the ubiquity of such systems in the marketplace, make this the technique of choice for many thermal packaging tasks. While standard heat transfer correlations are generally unsuitable for determining the detailed thermal behavior of individual components, the maximum surface temperature of integrated circuit packages mounted on PCBs can often be shown to lie between two analytical bounds: an upper, "asymmetric isoflux," bound based on heat transfer from just one side of the PCB and a lower, "symmetric isoflux," bound based on identical thermal transport from both sides of each PCB. Following a brief review of the development and validation of the theoretical symmetric and asymmetric isoflux relations for smooth-plate channels, this study focuses on the application of the proposed bounding relations to widely and closely spaced component-carrying PCBs. Successful comparison with much of the available data demonstrates the acceptable accuracy of these analytical expressions, for all except the narrowest spacings, and their utility to the thermal designer of air-cooled PCBs.     

比较法研究微细尺度氮化硅表面自然对流换热

微细尺度的对流换热与常规尺度的有很大不同,采用比较法研究了微细尺度水平氮化硅表面空气自然对流换热的问题。利用标准CMOS工艺和简单的post-CMOS工艺制作出微热板(MHP)测试结构并实验测试,对测试方法的准确性进行了有限元仿真。结果表明：面积为43.5μm×43.5μm的水平氮化硅表面的自然对流的传热热导为2.63×10-5WK-1,由此计算出的自然对流系数高达1.39×104Wm-2K-1,远远高于常规尺度下空气自然对流系数。     

轴快流CO2激光器翅片管换热器强化换热研究

为了解决厚板切割领域中高功率轴快流CO₂激光器翅片管换热器压力损失大、传热效率低的问题,采用计算流体力学软件ANSYS分析了3种涡流发生器的换热特性,并对换热性能更佳的梯形小翼涡流发生器的形状、长度、高度和安装角度进行优化设计;通过一个开环的风洞实验平台验证了数值模拟数据的可靠性。结果表明,长度11mm、高度2.6mm的梯形小翼涡流发生器采用30°迎角渐缩方式布置时换热性能最佳,在雷诺数为600~1600范围内,和没有安装涡流发生器相比,梯形小翼涡流发生器的努塞尔数Nu提高了8%~22%,摩擦因子上升了16%~27%;8h稳定输出功率4216W,比额定输出功率高出5.4%。该研究提高了CP4000系列激光器的厚板切割能力。     

基于STM32的真空玻璃传热参数测试装置的研制

真空玻璃传热参数测试装置是一种专门测量真空玻璃传热参数的仪器设备。真空玻璃传热参数表征真空玻璃隔热保温、隔音降噪、防结霜结露等特性。以国标JC/T1079-2008为依据,并根据真空玻璃传热参数测试装置的组成结构,分别对其内部模块、电路控制系统、检测系统平台进行了研究、设计及制作;对真空玻璃在恒温条件下进行多次测试并研究分析了影响真空玻璃传热参数的一系列因素,测试出相应待测真空玻璃样品的传热参数。     

Convection heat transfer in electrostatic actuated liquid droplets for electronics cooling

In this paper, the internal flow and heat transfer inside the electrostatic actuated droplets are studied for different droplet velocities by means of detailed flow computations. It is shown that the internal droplet flow exhibits a parabolic characteristic at one hand and that the presence of two convection cells decreases the heat transfer to the lower part of the droplet, thereby limiting the overall heat transfer through the droplet. A typical enhancement of the heat transfer with a factor 2 is achieved with respect to the minimal value that would be obtained assuming heat conduction as the only means of heat transfer in the liquid. Further an analytic lumped model is presented to estimate the transient average droplet temperature with an accuracy of 5% compared to the full transient computational fluid dynamics modelling.     

Impact of radiative‐heat transfer on photovoltaic module temperature

The prediction and the optimization of the energy production of a photovoltaic (PV) module require a good knowledge of its optical, electrical, and thermal behavior. We build a complete multi‐physics model able to describe the behaviors of a PV module depending on the environmental conditions (ambient temperature, wind speed, total irradiance, and installation conditions). The model treats radiation heat transfer in participating media. This feature reveals the limits of the commonly used modeling. It also opens new possibilities on improvement of the PV module yield and may influence the design strategy. Copyright © 2015 John Wiley & Sons, Ltd.     

回路热管换热性能的实验研究

为研究回路热管(LHP)的换热性能,制作了简单的回路热管换热性能测试装置。采用不锈钢为回路热管的材料,500目铜丝网为吸液芯,实验研究了回路热管不同功率下对启动时间和热管热阻的影响。研究结果表明,回路热管的功率增大,启动时间越短,热阻也相应的减小;同时,回路热管冷凝器入口和储液室入口的温度在LHP启动后,会呈现相反的温度波动。研究结果为回路热管散热器的应用提供了理论依据和方便的测试手段。     

风对二维平面物体传热的影响

为了研究风对二维平面物体传热的影响,分析了此过程的传热机理并建立了理论模型;在不同风速情况下,用铁板和混凝土块进行了实验,验证了理论分析;最后对风这一因素的影响进行了总结,对研究意义作了展望.     

热流传感器信号采集系统硬件设计

为了解热流传感器的自身温度与输出的具体数量关系,设计一种基于C8051单片机的热流传感器信号采集系统。该系统增加专用的温度信号采集模块。使系统结构更小,功能更多,且数据采集更精确,从而为后续数据处理奠定基础。