CPCM/液冷复合电池热管理方式优化设计

目的为了解决锂电池组在放电倍率为2.5 C,环境温度为308.15 K下工作时,其最高温度、最大温差可能超过适宜温度的情况。方法建立基于复合相变材料(CPCM)/液冷复合的电池组散热模型,首先通过实验测得锂电池单体相关性能参数,然后利用数值模拟方法讨论CPCM厚度对电池组散热性能的影响。分析得出当CPCM厚度在一定范围内变化时,单一的相变材料冷却方式不能将电池组最高温度控制在适宜的温度范围内,因此提出CPCM/液冷复合散热方式,以复合相变材料厚度、液冷通道间距、液体流速为设计变量,电池组最高温度和最大温差为优化目标进行多目标优化设计。结果结果表明,优化后的电池组最高温度和最大温差分别为316.88K和0.30K,满足设计要求,但相变材料在相变过程中存在泄露的风险。结论相较于单一的相变材料冷却方式,优化后的复合冷却模型能够大幅度降低电池组的最高温度,同时将最大温差控制在安全范围内;在保证散热模型最外层包装结构具有较高导热性的同时也要加强其结构设计,防止相变材料泄露。     

高热流密度元器件冷却用液冷板的研究及优化

微通道液冷板在高功率密度元器件散热上广泛使用,对板面温度均匀性提出了更加严格的要求.本文以提升液冷板板面温度均匀性为目的,设计了一个同侧单进口、出口的全铝材质的微通道液冷板,在热流密度为300 W的情况下,测试其使用单相水和相变工质冷却的板面温度最大温差分别为2℃以内和2.6℃(R236fa).为了进一步提升温度均匀性...     

某新能源商用车电池组液冷板热管理方案研究

针对某新能源商用车电池组液冷板系统,采用商用CFD软件进行流场分析,并对其进行散热降温计算和试验验证,最后对液冷板进行设计方案优化。结果表明:采用优化方案后,液冷板电芯最高温度低于温度限值(50℃),电芯之间的温差小于4℃,能够满足电池组的热管理要求,保证电池组工作处在合理温度范围内。     

树型微通道换热特性数值研究

建立了三维树型微通道换热器模型,模拟并分析了其热流耦合场。对比了单、双层微通道换热器的最高温度及双层树型微通道在顺流、逆流、交叉流三种情况下的冷却效果。底部热流密度qw=50W·cm-2时,单层微通道底面最高温度为102.5℃,双层微通道底面最高温度均低于63.38℃,且底面低于60℃部分所占比例均高于60%。双层微通道冷却效果明显优于单层微通道,且在逆流方式下,双层微通道底面温度分布均匀,中心部分具有较低温度,有效改善了一般换热器散热不均而造成的中心部分温度过高的问题。     

不同冷却策略下动力电池模块的热性能比较研究

随着新能源汽车技术的快速发展,快充快放正逐渐成为动力电池的主流工作模式,产热功率增加,热性能对动力电池的影响也随之增大。采用数值模拟研究了快充快放条件下动力电池组在不同倍率充放电下的传热特性,比较了纯相变冷却和液冷与相变材料耦合的冷却对电池模块散热效果,分析了上述两种散热方式对电池模块温差和最高温度的控制作用。数值模拟结果表明,当5C快充,立即5C快放条件下,选择最佳流速0.05m/s,电池模块温度最高温度控制在47.33℃,温差为3.39℃,与采用纯相变冷却方式相比,电池最高温度降低34.57℃,温差降低1.14℃。结果表明快充快放条件下液冷与相变材料耦合系统具有良好的动力电池热管理效果。     

双层树型微通道热流耦合场数值研究

建立了双层树型微通道换热器三维模型,模拟分析了其热流耦合场。对比单、双层树型微通道换热器的最高温度及双层树型微通道在顺流、逆流、交叉流三种情况下的冷却效果及底面温度分布所占比例。底部热流密度qw=50 W·cm-2时,单层树型微通道底面最高温度为102.5℃,双层树型微通道底面最高温度低于63.38℃,底面温度低于60℃部分所占比例均高于60%。双层树型微通道冷却效果明显优于单层,在逆流方式下,双层树型微通道底面温度分布均匀,中心部分具有较低温度,有效改善了一般换热器散热不均而造成的中心部分温度过高的问题。     

锂离子电池仿生树状通道液冷板数值优化

目的 将锂离子电池在5C放电倍率、环境温度298.15 K的工作条件下的最大温度和温差控制在适宜范围内。方法 在锂电池两侧插入带通道的仿生树状液冷板,建立电池模块液冷散热模型。首先验证液冷数值模型的准确性,然后通过正交试验设计研究分支流道角度、入口流速、分支流道宽度和液冷板厚度对冷板散热性能的影响,并通过极差分析对4种影响因素进行重要程度排序,确定最佳的参数组合。结果 经优化后,锂电池的最高温度为302.4 K、温差为3.4 K,满足设计要求,但冷却剂在流动循环过程中存在泄漏风险。结论 提出的树状液冷板满足锂电池热管理性能的要求,优化后电池模块的表面温度在安全范围内,同时电池的温度均匀性显著提高。应选择导热系数高的冷板材料,并注重冷板结构设计,防止冷却剂泄漏。     

电动汽车锂离子电池热管理系统研究进展

目的为保证电动汽车在使用过程中安全可靠,需对车用锂离子电池进行温度控制。方法从电池的最高温度、使用寿命以及最大温差等方面,对空冷、液冷、相变材料冷却、微通道/微热管冷却以及加热方式的研究进行综述分析。结果相对于常规的空冷、液冷、相变材料与热管等冷却方式以及新型的热电制冷等方式,基于微通道、微通道冷板及微通道热管式的电池热管理系统(BTMS)具有更为卓越的换热性能,已成为一种可行且有效的热管理解决方案;BTMS存在整体结构复杂、换热细节研究不深、实用性不强以及针对微通道的相关强化研究不足等问题。结论在微通道液冷式BTMS的研究基础上,对其进行强化换热与强化结构体力学强度等研究,可以显著增强BTMS及整体系统的换热性能与结构强度,以及对锂离子电池产生更好的温控效果,提高了电动汽车的安全性与可靠性。     

射流式水冷散热器关键参数对性能影响的模拟研究

目前传统的风冷散热技术已无法满足高热流密度电子器件的散热需求,液冷散热技术已成为目前的研究热点。射流式水冷散热器作为液冷散热技术的一种,主要通过喷嘴将流体工质喷射到固体表面来达到散热目的。本文研究了射流式水冷散热的主要参数（喷射面积比、喷嘴数量、有无微通道）对散热器性能的影响,模拟结果表明：该散热器的最佳喷射面积比为0.14,此时散热器底板平均温度为55.8 ℃,压力损失为5.35 kPa,努塞尔数和传热系数分别为28.1和3.45 kW/ (m2·K) ;最佳的喷嘴数量为4,此时散热器底板平均温度最低,为51.4 ℃,压力损失为5.52 kPa,努塞尔数和传热系数达到最高值,分别为35.2和4.33 kW/ (m2·K),并有效的消除了局部热点;微通道的增加微通道的增加使散热器整体换热性能显著增强,平均温度降低 3 ~ 6 ℃ ,当喷嘴数量为 4 时,布置微通道可使努塞尔数由 35. 2 升至 43. 3,传热系数由 4. 33 kW/ (m2·K)增至 5. 32 kW/ (m2·K),但压力损失略微上升(约 升高 20~ 60 Pa)。     

绝缘栅双极晶体管表面电沉积镍基石墨烯薄膜的制备及其散热性能研究

将镍基石墨烯薄膜应用在IGBT模块散热方面,提出了镍基石墨烯薄膜的制备工艺,并利用扫描电镜、透射电镜、能谱仪等对镍基石墨烯薄膜进行表征。结果表明,当电流密度为2 A/dm~2时,镍基石墨烯薄膜中的有大量的Ni和C元素,镍基石墨烯薄膜中的石墨烯平均粒径为32.5 nm。当脉冲电流密度为1 A/dm~2时,镍基石墨烯薄转移镍基石墨烯薄膜后的S1芯片的散热效果较好。当脉冲电流密度为2 A/dm~2时,镍基石墨烯薄转移镍基石墨烯薄膜后的S2芯片的散热效果最好,其最大散热量为14.9℃。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.