基于红外热成像技术的软包锂电池热特性分析

Based on infrared thermal imaging technology and visual testing methods, the surface temperature variation characteristics and heat generation law of ternary soft-pack lithium battery under different working conditions were investigated. The ambient temperature, the discharge rate, and the ear clamping method are three variable conditions. The two are coupled to the control variable experiment to monitor the temperature rise of the battery surface. The results show that the optimal working temperature of the battery is 25 °C, to ensure that the different rate of discharge experiments at the most suitable working temperature, found that with the increase of the discharge rate, the heat generation increased, the surface temperature of the battery increased, the conductive clip clamping tab is compared with the copper clip holding tab This method will lead to insufficient overcurrent at the ear, a sharp increase in heat generation, and a significant temperature rise on the surface of the battery. This type of clamping is not conducive to heat dissipation of the battery, which provides a parameter basis for thermal battery design optimization and experimental operation. The test results have guiding significance for the optimization of the heat dissipation scheme.     

Investigation into the energy consumption of a data center with a thermosyphon heat exchanger

A data center test model was used to analyze the energy dissipation characteristics and energy consumption of a data center.The results indicate that adequate heat dissipation from a data center cannot be achieved only from heat dissipation through the building envelope during Beijing winter conditions.This is because heat dissipation through the building envelope covers about 19.5% of the total data center heat load.The average energy consumption for an air conditioner is 4 to 5 kW over a 24-h period.The temperature difference between the indoor and outdoor air for the data center with a thermosyphon heat exchanger is less than 20°C.The energy consumption of the thermosyphon heat exchanger is only 41% of that of an air conditioner.The annual energy consumption can be reduced by 35.4% with a thermosyphon system.In addition,the effect of the outdoor temperature on the en-ergy consumption of an air conditioner is greater than the indoor room temperature.The energy consumption of an air conditioner system increases by 5%to 6%for every 1°C rise in the outdoor temperature.     

Heat driven refrigeration cycle at low temperatures

Absorption refrigeration cycle can be driven by low-grade thermal energy, such as solar energy, geothermal energy and waste heat. It is beneficial to save energy and protect environment. However, the applications of traditional absorption refrigeration cycle are greatly restricted because they cannot achieve low refrigeration temperature. A new absorption refrigeration cycle is investigated in this paper, which is driven by low-grade energy and can get deep low refrigeration temperature. The mixture refrigerant R23 R134a and an absorbent DMF are used as its working fluid. The theoretical results indicate that the new cyde can achieve -62℃ refrigeration temperature when the generation temperature is only 160℃. This refrigeration temperature is much lower than that obtained by traditional absorption refrigeration cycle. Refrigeration temperature of -47.3℃ has been successfully achieved by experiment for this new cycle at the generation temperature of 157~C, which is the lowest temperature obtained by absorption refrigeration system reported in the literature up to now. The theoretical and experimental results prove that new cycle can achieve rather low refrigeration temperature.     

Transportation of low-grade thermal energy over long distance by ammonia-water absorption

This paper presents the importance and the cycle choice for long-distance transportation of low-grade thermal energy, and the thermodynamic and hydrodynamic feasibility of single-effect ammonia-water absorption system for heat or cold transportation over long distance are also involved. A model of a long-distance thermal energy transportation system is built and analyzed, which shows satisfactory and attractive results. When a steam heat source at 120℃ is available, the user site can get hot water output at about 55℃ with the thermal COP of about 0.6 and the electric COP of about 100 in winter, and cold water output at about 10℃ with the thermal COP of about 0.5 and the electric COP of 50 in summer. A small-size prototype is built to verify the performance analysis. Basically the experimental data show good accordance with the analysis results. The ammonia-water absorption system is a potential pro-spective solution for the heat or cold transportation over long distance.     

移动热湿源廊道热环境的改善及送风参数优化

为有效改善具有移动热湿源的高温高湿廊道热环境,给工人提供舒适的工作环境。以邯郸市某铁渣转运廊道为依托,建立廊道空气与皮带表面热湿耦合传热物理模型,定性分析不同送风温度、送风风速、铁渣温度、皮带运行速度条件下廊道热环境的改善效果,定量探究其对廊道热环境的影响程度,并拟合各影响因素与廊道温度的相关经验关联式。结果表明：对廊道热环境影响程度由大到小依次为：送风温度、送风风速、铁渣温度、皮带运行速度。送风温度越低,送风风速越高,铁渣温度越低,皮带运行速度越小,越能有效改善廊道热环境。送风温度为22°C,送风风速为2m/s,铁渣温度为65°C,皮带速度为3.0m/s为廊道热环境改善的最优组合方式。文章研究成果将为类似廊道内选择合适的通风方式、设备调控及系统优化提供指导。     

混合动力汽车用DC-DC和IPU散热结构优化

针对混合动力汽车用DC-DC和IPU的已有散热结构散热效果差,导致DC-DC和IPU在使用过程中温升高,从而影响混合动力系统的稳定性和可靠性的问题,根据传热学的质量、动量和能量守恒方程,建立DC-DC和IPU散热结构的三维非稳态散热模型,采用计算流体力学(CFD)方法,对DC-DC和IPU散热系统的流场和温度场进行数值模拟仿真分析。在此基础上,根据传热学理论设计了DC-DC和IPU散热结构的优化方案,并对优化方案的散热效果和温升进行了仿真分析与实验研究,结果表明该优化方案实现了DC-DC和IPU的良好散热,有效降低了温升,满足了混合动力汽车对DC-DC和IPU的使用要求。     

针翅式散热器模块流动传热特性数值优化

为提升中高温电子器件的散热性能,以针翅式散热器模块为研究对象,研究了热管长度、散热器宽度、针翅直径、针翅间距和针翅高度5个结构参数对翅片散热性能的影响,对正交实验设计的16个组合方案下翅片的流动换热性能进行模拟。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)和全因子评价Y作为评价指标,在每个评价指标下利用极差分析主要影响因素和挑选出优化组合。结果表明：影响Nu、f、PEC和Y的最主要因素是针翅间距;最佳优化组合为：针翅间距为2.5 mm,散热器宽度为80 mm,针翅直径为1.5 mm,针翅高度为20 mm,热管长度为25 mm,模块温降为16.28℃,热阻为0.265℃/W。     

冬季温度漂移下心率变异性对人体热舒适的影响

研究显示，环境温度的变化对人体心脏活动的影响显著，寒冷或极端温度会给人们带来心血管疾病。本文基于人体心率变异性指标，探讨了温度漂移热环境在室内热舒适方面的优势，并分析了人体主观热评价、皮肤温度与心率变异性之间的关系。本文设置16名受试者从初始稳定温度（24℃或18℃）经历半小时的温降漂移，最后再经历升温回到初始温度。实验收集了受试者的主观热评价与皮肤温度，并全程监测了其心电信号。通过频域分析法，得到了心率变异性的低频功率/高频功率比值（LF/HF）。结果表明：在冬季，适当的温度漂移可以改善受试者对相同温度热环境的热舒适评价；温度漂移对人体热舒适的影响可以通过LF/HF值表征出来；冬季温度漂移热环境下，人体的LF/HF值与平均皮肤温度、热感觉显著相关。     

低温供暖系统中散热器与风机盘管的供暖效果

本文利用Airpak软件对北京地区煤改电中某农机站小型食堂进行室内热环境的数值模拟,对采用散热器和立式风机盘管两种不同散热末端的房间进行流场模拟,分析人员静坐状态下（1.2 m高度水平面）的温度场、速度场、预计平均热感觉指数（PMV）和预期不满意率（PPD）,通过流场模拟与实测结果的分析说明了在低温供暖系统中采用散热器和风机盘管两种不同的散热末端的特性以及对室内热环境的影响。结果表明,在同一个热源下,使用风机盘管进行供暖的房间在温度和PMV-PPD指数上优于散热器房间,人们的不满意度较小;使用散热器进行供暖的房间温度稳定性较好,适合需要连续供暖的房间;采用数值模拟得到的房间温度略低于实测温度,在一定程度上可以为北京地区煤改电中低温供暖系统合理选择散热末端提供参考。     

基于脑电的温度阶跃变化环境下的人体热舒适研究

热环境作为评价建筑物理环境的重要部分,影响着人的工作效率和情绪变化。不同环境温度下的脑电信号与人体主观投票相结合是一种评价热舒适的新方法。本研究选取14名身体健康的成年人在人工气候室经历由低温15°C分别突变到18°C、24°C和30°C三个过程,通过快速傅里叶变换,将温度阶跃变化环境下测得的脑电信号转化为脑电频谱功率值,与主观投票和额头温度相结合,进一步探究脑电各分区和各波段与热舒适的相关性。研究表明,额叶区频谱功率值变化可作为人体热舒适的评价指标,频谱功率值与热舒适显著相关,且随着舒适程度的增加而降低,当温度突变到接近人体中性温度24°C时,功率值最低。同时发现与热愉悦情绪和注意力有关的额叶区θ波段功率值随着舒适程度的增加而增加,当温度突变到24°C时,θ波相对脑电功率变化最明显,增加了20%左右。     

Effect of heat treatment on microstructures and properties of a novel Al-Zn-Mg-Cu alloy for oil drilling

In view of the special requirements for strength, heat resistance and corrosion resistance of Al-Zn-Mg-Cu alloy for oil drilling, the Al-6.2 Zn-2.5 Mg-1.6 Cu alloy was prepared by increasing Cu content on basis of Russian Series 1953 alloy. The effect of heat treatment on the microstructures and properties of the alloy was characterized by optical microscope(OM), scanning electron microscope(SEM) and transmission electron microscope(TEM), and investigated by tensile test at room temperature, thermal exposure test and corrosion test. The results show that the strength after T6 aging treatment exhibit a decrease trend as an increase of the solution temperature from465 °C to 480 °C. After the solution treated by the rate of 470 °C/1 h, second phases dissolve into the matrix very well and the strength property reaches optimum. The alloy has better comprehensive properties treated by a solution treatment of 470 °C/1 h and then followed by an aging treatment of 120 °C/24 h + 170 °C/1 h + 120 °C/24 h. Under the aging state, the precipitated phases inside the grains are suitable in size, while on the grain boundary distribute discontinuously and the precipitate-free zone is obvious. Besides, the alloy still maintain high tensile properties. The yield strength, tensile strength and elongation are 650 MPa, 686 MPa,12.0%, respectively. The yield strength retention after heat exposure is 92%. The alloy has good corrosion resistance and the exfoliation corrosion degree. The average corrosion rate in the H_2S and CO_2 environment is 0.0024 mm/a, which is far less than the required 0.12 mm/a. It is insensitive to H_2S and CO_2 environments.     

热辐射在倾斜通道热流场的作用

针对热辐射是通道内热流场的重要影响因素之一,采用实验和数值计算方法对倾斜角度为10°、20°和30°的两端开口通道内热流场进行了研究。使用基于大涡模拟(LES)求解浮力驱动N S方程的数值模拟方法求得的模拟结果和实验值吻合较好。通过使用耦合热辐射模型的数值计算结果和忽略热辐射的数值计算结果分别与实验结果进行对比分析的方法发现,在热源一定的条件下,对于倾斜角度在10°～30°之间的通道,热辐射使通道上部高温区域的温度降低,随着倾斜角度的增大,热辐射对通道低端开口上壁面附近的影响作用减弱,而倾斜角度对于热辐射在通道高端开口上壁面附近的作用则影响不大,同时,在通道倾斜角度为30°时,热辐射使通道内高温区域向高端开口方向倾斜,并使通道高端的下部温度升高。整个实验和计算结果可为倾斜通道内热流场的理论研究提供参考依据。     

二氧化硅气凝胶的性能受热过程的影响

成功地以水玻璃为硅源,经乙醇溶剂替换及六甲基二硅醚和盐酸的混合液对SiO₂湿凝胶表面基团改性后,常压干燥制备出低密度、高比表面积、超疏水、低热导率的高性能SiO₂气凝胶块体.SiO₂气凝胶在室温至400℃附近具有稳定的疏水性能,460℃附近气凝胶由疏水型完全转变成亲水型.重点研究了室温至400℃之间,SiO₂气凝胶的微观结构和物理性能受热处理过程的影响.SiO₂气凝胶即使经过400℃高温热处理后,仍能保持优异的疏水性能、较高的比表面积和较低的热导率等.     

Geothermal measurements in the pilot-boreholes of the china continental scientific drilling

The geothermal measurements in the pilot-boreholes of the China Continental Scientific Drilling (CCSD) indicate that the temperature gradients in the target area of the deep drilling range from 19 to 26℃/km, which is lower than that (25—30℃/km) for the global continental area and similar to that for the KTB (21—28℃/km). Thermal conductivity measurements for 44 core samples show that the ultra-high pressure (UHP) metamorphic rocks have 50% higher thermal conductivity (with a mean of 3.94±1.26 W/mK) than that for the average value of the upper crust. The measured heat flow values vary between 76 and 80 mW/m², higher than that for the global continental area (65±1.6 mW/m²) and the continental China (61±15.5 mW/m²) as well as the adjacent North Jiangsu Basin (68 mW/m²), but lower than that below 1000 m in the KTB (85 mW/m²). The elevated heat flow in the pilot-boreholes can be attributed to the lateral heat concentration due to higher rock thermal conductivity of the UHP belt than that of the adjacent rocks. Lower deep temperature in the target area of the deep drilling can be expected due to the lower measured temperature gradient, which means that the Sulu area is geothermally suitable for continental deep drilling.     

Application study of a correction method for a spacecraft thermal model with a Monte-Carlo hybrid algorithm

The correction of a thermal model for a thermally controlled satellite in ground test conditions is studied using a Monte Carlo hybrid algorithm.First,the global and local parameters are summarized according to sensitivity analyses on uncertain parameters,and then the model correction is treated as a parameter optimization problem to be solved with a hybrid algorithm.Finally,the correction of the thermal model is completed using a layered correction method.The sensitivity analysis showed that the effective emissivities across the multi-layer insulation (MLI) and the emissivities of the thermal control coating are global parameters,while the contact heat transfer coefficients are local parameters.After correction,the deviations between the calculated and test values were all within ± 3 ℃.The final results prove that the method in this study is superior to traditional methods and satisfies the requirements for thermal model correction.     

Constructal entransy optimizations for insulation layer of steel rolling reheating furnace wall with convective and radiative boundary conditions

Based on the entransy dissipation extremum principle for thermal insulation process, the constructal optimizations for a plane insulation layer of the steel rolling reheating furnace wall with convective and radiative boundary conditions are carried out by taking the minimization of entransy dissipation rate as optimization objective. The optimal construct of the plane insulation layer is obtained. The results show that for the convective heat transfer boundary condition, the optimal constructs of the insulation layer obtained based on the minimizations of the entransy dissipation rate and heat loss rate are obvi- ously different. Comparing the optimal construct obtained based on the minimization of the entransy dissipation rate with that based on the minimization of the heat loss rate, the entransy dissipation rate is reduced by 5.98 %, which makes the global thermal insulation performance of the insulation layer improve. For the combined convective and radiative heat transfer boundary condition, compared the insulation layer having an increasing thickness with that having constant thickness and a decreasing thickness, the entransy dissipation rates are reduced by 16.59 % and 39.72 %, respectively, and the global thermal insulation performance of the insulation layer is greatly improved.There exits an optimal constant coefficient α2,opt which leads to the minimum dimensionless entransy dissipation rate of the insulation layer. The difference between the optimal constant coefficients α2,opt obtained based on the minimizations of the entransy dissipation rate and the maximum temperature gradient of the insulation layer is small. This makes the corresponding thermal stress obtained based on the minimum dimensionless entransy dissipation rate also be small, and the global thermal insulation performance and thermal safety of the insulation layer are improved simultaneously. The results obtained can provide some guidelines for the optimal designs of the insulation layers.     

某型号汽车起重机发动机高速空载状态热特性分析

为解决某型号汽车起重机散热效果差的问题,研究其液压系统原理,根据主要元件的产热与散热特性,建立了液压系统的热平衡数学模型;基于AMESim软件建立了汽车起重机在发动机高速空载状态下的热液压系统仿真模型,并通过实验对比散热器进出口的温度验证了仿真模型的准确性;分析了发动机高速空载工况下4个泵的压力损失特性.结果表明：2号泵能量损失最大,约38%,由多路阀和中心回转体的能量损失而产生的热量是液压系统的主要产热源;3号泵和4号泵的回油产热也较大,且由于原始设计中回油没有经过冷却处理,导致汽车起重机液压系统整体的散热效果较差.通过将回转系统和控制系统的回油引入散热器,改进后的多路阀各口出口温度降低,油箱的出口温度也明显降低,提高了液压系统的散热效果,改进合理有效,为今后改进汽车起重机液压系统的热管理控制策略提供了指导.     

直线发动机起动及怠速燃烧特性仿真与优化

通过建立GT-Power发动机仿真模型研究直线发动机的起动及怠速过程的燃烧特性,利用发动机台架实验获取的缸压数据和GT-Power仿真结果的对比,验证了仿真模型的准确性,分析不同点火时刻及过量空气系数对直线发动机起动定转速下燃烧特性的影响,并对怠速控制参数进行寻优研究.结果表明:在相同过量空气系数下,推迟点火时刻从-50°(上止点之前,下同)到20°,直线发动机后燃现象逐渐增多,并在点火时刻为-40°时,缸压峰值、瞬时放热率峰值最大以及累积放热总量均达到最大值;在相同的点火时刻下,减小过量空气系数从1.62到0.62,直线发动机缸内压力峰值先增后减,在过量空气系数为0.83时,直线发动机缸压峰值、瞬时放热率峰值最大,累积放热总量较多.     

转折角对Z形通道印刷电路板式换热器中二氧化碳流动与换热特性的影响

针对超临界二氧化碳气冷堆核电系统中Z形通道印刷电路板式换热器的优化设计，通过数值模拟研究转折角对印刷电路板式换热器中二氧化碳流动和换热特性的影响规律，分别拟合出摩擦因子和努塞尔数的计算关联式，分析传热过程的热阻，并讨论换热器的综合性能。结果表明，摩擦因子和对流换热系数均随转折角的增大呈抛物线规律增长，在转折角小于20 °时增长较慢。导热热阻占总传热热阻的4.16%～16.02%，并随二氧化碳质量流率和转折角的增大而升高，在印刷电路板式换热器的传热计算中，不应被忽略。随着转折角的增加，通道中努塞尔数的增长幅度小于摩擦因子的增长幅度，传递相同热量的泵送功率增大，但所需换热面积减小，换热器的制造成本下降，实际应用中需进一步通过技术经济分析以选取最佳转折角。为了控制通道中流动阻力占进口压力的比例，转折角以不超过20 °为宜。     

Constructal optimization on T-shaped cavity based on entransy dissipation minimization

The entransy dissipation extremum principle provides new warranty and criterion for optimization of heat transfer. For a heat transfer model of a rectangular solid wall with an open T-shaped cavity, a dimensionless equivalent thermal resistance based on entransy dissipation is taken as optimization objective, and constructal optimization for the model is carried out when the system volume, the cavity volume and the volume of rectangle occupied by T-shaped cavity are fixed. Numerical results indicate that the optimal geometry construct of cavity can be schemed out based on entransy dissipation extremum principle. The formulation of dimensionless global （maximum） thermal resistance presented in a literature is modified; some new rules which are different from those reported in the literature are obtained based on the minimization of the modified objective. Comparisons of the numerical results show that the optimal system constructs deduced respectively from the two thermal resistance objectives are very different. The optimization by taking equivalent thermal resistance minimization as objective can more effectively reduce mean temperature difference of heat transfer than the optimization by taking maximum thermal resistance minimization as objective, so that the performance of heat transfer for the total system can be improved. The more freedom the cavity has, the better the total system performance is. The correlations of the equivalent thermal resistance and the maximum thermal resistance of the system and three geometric degrees of freedom are found by using function fitting.