Flat and U-Shaped Heat Spreaders for High-Power Electronics

To achieve a high heat-flux level and reduce manufacturing costs associated with conventional heat pipes, the concept of network heat spreaders employing a boiling heat-transfer mechanism in a narrow space had been proposed, and several flat-plate wickless heat spreaders had been designed and fabricated. The heat spreaders had been tested under different working conditions and orientations relative to gravity with very good results. The previously tested network heat spreaders, however, were based on plates with a relatively large size for general heat spreading purposes. In the present study, network heat spreaders with overall dimensions of 78 2 62 2 3.2 mm are designed and fabricated. Spreaders of this size are intended for use as heat sinks of high-power electronic components. External cooling fins are attached to enhance air-cooling heat transfer rate. The network heat spreaders are tested under various working conditions with water as the working fluid. The maximum heat input rate achieved is about 150 W with a corresponding heat flux of 60 W/cm 2 . Compared to the performance of a solid copper plate having the same overall size as the spreader, the maximum temperature difference over the surface is reduced from about 32°C to 3.3°C. The heat transfer performance of the spreader is also largely dependent on the filling ratio of the working fluid and the boiling heat transfer in the narrow space. For these reasons, boiling heat transfer mechanisms in a narrow space are analyzed, and a spreader design that would improve the performance in a horizontal position is described.     

单元式露点蒸发冷却装置的实验研究

本研究设计了一台由干、湿通道相结合的单元式露点蒸发冷却装置,通过实验研究了蒸发冷却装置在空气经过一级冷却的模式1和经过二级冷却的模式2两种运行模式下,不同空气入口参数时的换热效果。实验结果表明,空气的入口温度越高,换热效果越好;低湿度时空气的进出口温差比高湿度时大,但其湿球效率和露点效率反而较低,这说明2种效率并不适用于不同湿度间的冷却效果对比;模式2运行时的换热效果比模式1好。与已有研究成果对比表明,该单元式露点蒸发冷却装置的湿球效率和露点效率分别可以达到120%和88%,为露点蒸发冷却装置的优化设计提供理论依据和优化方向。     

冷辐射地板系统的实验研究

为了研究冷辐射地板系统的热工性能，测试了地板辐射供冷系统的运行工况，得到了地板表面的最低温度、室内的实感温度、热流密度等参数，并初步探讨地板辐射供冷系统结露现象及防治措施，通过实验分析指出这是一种舒适、节能的供冷方式。     

Experimental Study on Effectiveness of Celdek Packed Liquid Desiccant Cooling System

Dehumidifier and regenerator are the most important components in a liquid desiccant cooling system. Present paper is focused on study the effect of inlet process parameters on the effectiveness of dehumidifier and regenerator of liquid desiccant cooling system. Experimental study is performed with varying inlet process parameters; mass flow rate of air, desiccant solution flow rate, inlet air temperature, inlet solution temperature, inlet specific humidity and concentration of desiccant solution. Celdek structured pads as packing material and calcium chloride as liquid desiccant is investigated first time using counter flow of the desiccant solution and air. It is concluded from the results that the effectiveness of dehumidifier increases with solution flow rate, inlet specific humidity while decreases with increasing mass flow rate of air, inlet temperature of air and desiccant, temperature and concentration of desiccant solution. The effectiveness of regenerator increases with increasing solution flow rate and inlet desiccant concentration and it decreases with increasing inlet air temperature, air flow rate and inlet solution temperature. Present paper adds to effect of inlet specific humidity, inlet temperature of the air and solution on the effectiveness of desiccant cooling system on the past research.     

柴油机 EGR 电控冷却系统试验研究

研究了 CA498 柴油机在不同工况下EGR冷却温度对NOx等排放的影响规律,确定了各个工况下EGR的最佳冷却温度,据此设计出一套EGR冷却温度控制装置,可以通过单片机控制伺服电动水泵的转速来调节冷却水的循环量,确保不同工况下的最佳EGR冷却温度.将该电控冷却系统在CA498柴油机上进行了试验.结果表明,与未冷却的EGR系统相比,该EGR电控冷却系统在c0和Hc的排放略有增加的情况下,可以有效地降低NOx的排放、烟度和油耗率.     

车用锂离子电池液冷式热管理系统实验研究

锂离子电池组的热管理对电动汽车的性能和安全性具有重要意义。基于多通道蛇形波纹管液冷式热管理系统,以200个18650型锂离子电池组为热管理对象,对电池在各种充放电倍率下所需的冷却液流量、泵功消耗以及热管理收益进行了实验研究。结果表明,热管理系统对动力电池在各种充放电应用条件下都具有较好的热管理效果,电池最大温度和最大温差基本可控制在40℃以下和5℃以内。提高冷却水流速对系统热管理能力的提升具有一定的效果,但是随着流速增大,热管理能力提升的边际效益也更趋明显;而系统运行所消耗的泵功增加导致了热管理收益随冷却水流速增加而大幅降低。从电池的性能安全以及热管理有效性的角度综合考虑,各充放电倍率下热管理系统的冷却水流速都是以保证电池安全和性能指标的最低流速为优。     

装载机冷却系统控制装置设计与试验研究

设计了装载机冷却系统控制装置,将发动机冷却系统和液压油冷却系统分开布置,发动机冷却系统采用液力驱动,液压油冷却系统采用电机驱动,两冷却系统的风扇和水泵转速都由单片机控制,实现了冷却系统冷却能力的自动调节.液压油冷却系统采用晶闸管相控调压调速系统,建立了其控制模型.将此控制装置在ZL-50装载机进行了试验研究.结果表明:该控制装置可有效解决装载机发动机水温和液压油温同时过高的问题,还可将预热时间减少50%,预热阶段节约燃油43%.     

防倒流循环家用太阳能热水器的实验研究

以普通平板型自然循环家用太阳能热水器做对比,对作者设计的防倒流循环家用太阳能热水器进行了实验研究,结果表明：与普通平板型自然循环家用太阳能热水器相比,防倒流循环家用太阳能热水器具有较低的热损系数,且平均日效率较高。     

纳米悬浮液热虹吸管的传热性能试验研究

在相同的试验条件下,对比研究了纳米CuO-去离子水(DW)悬浮液重力热管与普通DW重力热管的启动性和等温性,研究了纳米工质热管的充液率和颗粒浓度对热管工作特性的影响,对纳米工质热管的强化传热机理进行了初步探讨。研究表明:纳米工质热管比普通热管启动快;纳米工质热管蒸发段外壁温的高低与充液率、纳米浓度和加热条件有关;纳米颗粒浓度和充液率对热管的传热性能影响较大,且存在最佳浓度(本研究为5%)和最佳充液率(本研究为44.3%);高浓度纳米工质热管比普通DW重力热管易于达到传热极限;试验中纳米悬浮液重力热管的传热强化率为16.19%～146.27%。     

农业机械发动机冷却系统柔性导风罩的试验研究

对传统发动机冷却系统导风罩进行了改进,对其在发动机室内的布局进行了设计。对柔性导风罩的冷却性能进行了理论分析,并在498柴油机上进行了试验研究。分析了传统导风罩与柔性导风罩的径向间隙对发动机冷却风扇容积效率的影响,散热器进出口处的冷却水温度变化情况等。试验表明：这种柔性导风罩可提高风扇的容积效率,减少风扇的驱动功率,降低燃油消耗。     

Optimal Ground Tube Length for Cooling of Electronics Shelters

This paper presents a theoretical, numerical, and experimental study to investigate the possibility of optimizing the configuration (geometry) of underground heat exchangers for maximum heat transfer. The first part of the study identifies a novel fundamental optimization principle for maximizing heat transfer between a tube and its surroundings, which is expected to be present in any buried tube heat exchanger design. The second part presents a practical application of the fundamental principle: a simplified physical model to determine the temperature field inside an electronics shelter that uses an earth-air heat exchanger and the soil as a heat sink. A volume elements methodology is employed to obtain a system of ordinary differential equations with time as the independent variable that combines principles of classical thermodynamics and heat transfer. This allows the computation of the temperature and relative humidity fields at every instant inside the shelter. The numerical results obtained with the proposed model are validated by means of direct comparison with experimental temperature and relative humidity measurements. It is shown that the tube length can be optimized such that the maximum temperature reached inside the shelter is minimal. The results also demonstrate the potential of the utilization of buried tubes for cooling electronic packages. Since accuracy and low computational time are combined, the model is shown to be efficient and could be used as a tool for simulation, design, and optimization of electronic packages cooled by underground heat exchangers.     

椭圆形突片气膜冷却效率的试验研究

为研究突片对气膜冷却效率的影响,设计了3种不同堵塞比的椭圆形突片,采用红外摄像仪对不同形状突片冷却壁面的温度场进行了测试,并分析了气膜冷却效率随吹风比、堵塞比的变化规律.结果表明:突片的存在大大提高了气膜冷却效果;冷却效率随吹风比的增加而增大;且当x/D<7时,存在一个最佳吹风比值;冷却效率随堵塞比的增加而增加;椭圆形突片的气膜冷却效率要高于三角形突片的气膜冷却效率.     

通信基站通风冷却节能系统的研究

绝大部分通信基站设备需一年四季运行空调,耗能巨大。为了减少基站能耗,可采用通风冷却节能系统部分替代空调系统。通风冷却系统对温湿度环境、露点温度、空气洁净度等方面具有特定要求。案例模拟分析结果表明:哈尔滨和北京地区尘降量过大,不适合使用通风冷却节能系统。而在未考虑尘降量的影响时,上海、广州和昆明的可使用时间分别为3949h、4089h、6082h,且该系统在昆明(温和区)的节电率最高,为65.56%。     

A Proper Orthogonal Decomposition Based System-Level Thermal Modeling Methodology for Shipboard Power Electronics Cabinets

A system-level thermal modeling methodology for shipboard power-electronics cabinets is presented and demonstrated for a PCM-1 cabinet, a complex air-to-water-cooled cabinet design of interest to naval applications. The cabinet is completely sealed and the heat dissipation in the power electronics bays is removed from the cabinet by re-circulating the hot air through an air-to-water-cooled packaged heat exchanger that is served by an external fresh water loop. A detailed unit-wise analytical model is developed for the packaged heat exchanger used in the cabinet. Under the prescribed design parameters, the PCM-1 cabinet operating-point air circulation rate was established to be 0.434 m³/s (920 CFM). A compact model is developed for the air convection within the cabinet using 3-D Computational Fluid Dynamics/Heat Transfer (CFD/HT) simulations in conjunction with Proper Orthogonal Decomposition (POD)-based reduced order modeling techniques. The compact model runs about 350 times faster with a mean prediction error within 3.6% for the velocity field, 0.04% for the temperature field, and 0.15% for the pressure field. The resulting overall cabinet model can be integrated into a system-level modeling platform to simulate the thermal response of multiple cabinets. The CFD/HT simulations of the PCM-1 cabinet architecture suggest that its two uppermost bays would experience high air temperatures due to insufficient local air flow.     

地板辐射与下送风复合式供冷系统运行特性实验研究

测量地板辐射与下送风复合式供冷系统运行过程中的室内空气温湿度、围护结构表面温度等室内环境参数,分析室内温湿度、热舒适性、系统换热量的变化规律,并对室内空气环境进行影响因素分析。实验结果表明:室内空气绝对湿度较室内空气温度达到稳定需要的时间更短;MRT(mean radian temperature)、OT(operation temperature)和PMV-PPD值在系统开启后第1.0 h减小速率最大,1.5 h后逐渐趋于稳定,此时,PMV约为0.49,PPD约为10%,在热舒适范围内;地板净辐射换热量、对流换热量和总换热量在系统开启后的1.5 h内递增,然后趋于稳定,此时,地板辐射换热量约为37 W/m~2,占总换热量的47%;室内空气温度和作用温度均随室外综合温度、室内发热量、供回水平均温度和送风温度的增加而增加,当室外综合温度较低或较高,或室内发热量较低,或供回水平均温度较低时,室内空气温度和作用温度变化梯度较小,室内空气温度和作用温度随送风温度增加而增加的速率近似呈线性。     

计算机测控的风冷发动机风扇试验系统的研制

本文介绍的计算机测控的风冷发动机风扇试验系统，采用传感器和计算机技术实现风冷发动机风扇性能试验的数据自动采集、数据自动处理与数据库管理功能，还可配合流场测量装置测量冷却风流场。该系统实现了测试自动化，精度高，应用效果好。     

Thermomagnetic Convection in Square and Shallow Enclosures for Electronics Cooling

Combined temperature and magnetic field gradients established in ferrofluids induce thermomagnetic convection. We report a comparative numerical analysis of steady-state convection carried out for a square and a shallow enclosure under zero-gravity conditions. Two symmetrically placed, discrete, constant-flux flush-mounted heaters on the bottom wall of the cavities represent power-dissipating devices in electronics/MEMS applications. The sidewalls serve as heat sinks. A line dipole placed below the bottom wall is the field-source. The role of the magnetic field, the thermal boundary conditions, and the enclosure dimensions in influencing heat transfer are revealed through a comparative thermal-fluidic analysis in different convection-dominated operational regimes.     

密封对柴油机冷却模块性能影响的试验研究

针对某款载重车用柴油机冷却模块,将换热器间的密封条拆除,使空气自由流通,与原密封方案进行风洞试验对比。结果表明:在风速4～10m/s范围内,中冷器散热量降低0.75%～1.82%,水散热器传热性能提高0.41%～1.36%,模块总散热量提高0.16%～0.48%,阻力下降约10%。在实车上相同的风扇吸风条件下,系统的有效进风量将会增加,模块散热效率进一步提高。紧凑式冷却模块适当减少密封时,其换热量呈现出前排换热器有所减弱后排增强的特性,模块总换热量得到改善,可在匹配设计中灵活调整其密封性能以达到优化柴油机工作条件和节能的目的。