基于危害性分析的冷却系统可靠性改进技术

应用模糊综合评判方法对加工中心冷却系统的故障模式进行危害性分析,综合考虑了故障发生频率、故障严重程度、测试难易程度和维修难易程度4个影响因素,计算出冷却系统各故障模式的危害度,以确定冷却系统改进设计的重点.针对危害度等级较大的故障模式,提出一种利用热管技术改进现有冷却系统结构的新方法.该方法能够增强冷却系统的冷却效率,减少冷却系统故障,提高冷却系统的可靠性.     

Development of an evaporative cooling system for small four-stroke engines

A new evaporative cooling system for small four-stroke engines has been developed. Performance tests of a four-stoke single cylinder engine equipped with this evaporative cooling system have been carried out in the laboratory. Air removal rates from the closed coolant loop during the starting stage of the engine have been monitored for various engine operating conditions. In addition, data of the brake horsepower, the specific fuel consumption, heat loss to the coolant, cylinder-liner wall temperature and the wall heat flux have been obtained and were compared to those of the identical engine equipped with a conventional liquid cooling system. At a fixed air fuel ratio and under the MBT condition, the brake horsepower of the engine for the evaporative cooling system is enhanced compared to that for the liquid cooling system. The heat loss through the cylinder liner is decreased when the evaporative cooling system is adopted. The test result indicates several benefits of the evaporative cooling system such as faster warm up, better fuel economy and greater engine durability.     

Flow analysis of engine cooling system for a passenger vehicle

A numerical simulation is carried out to analyze the flow field of cooling air through the radiator and engine compartment. In order to consider the strong effect of the suction-type flow by the cooling fan at engine idling condition, a potential flow analysis is attempted by the assumption of a line sink located at the position of the cooling fan. The governing equations for steady two-dimensional, incompressible, turbulent flow are solved with the two-equationk-ε model for turbulence. The velocity profiles in the underhood engine compartment and around the front-end of a real vehicle are measured to compare with the numerical results. The agreement between the numerical and experimental results is fairly good. It is concluded that a two-dimensional computation is a fast and efficient tool for predicting the effect of front-end design on the cooling air flow through the radiator.     

内燃机冷却风扇流固耦合分析

随着内燃机动办性能和转速的不断提高,冷却散热问题越来越受到重视,因而对冷却风扇的研究有重要意义.高速旋转的冷却风扇,叶片受风力反作用后的变形对风扇的性能有很大的影响.利用商业软件SC/Tetra和ANSYS,把流场计算得到的叶片表面压力映射到结构分析中去,考虑流场与结构的相互作用,以流固耦合理论来分析叶片变形前后冷却风扇性能的改变.     

A cooling system using wickless heat pipes for multichip modules: Experiment and analysis

The present study is concerned with a cooling package system for electronic components such as multichip modules (MCM) which are used in many electronic system. The im of the cooling capacity up to heat flux of 4 W/cm² was achieved. A heat flux of 4 W/cm² is about two to three times of the value generally accepted as the limit by forced air cooling together with heat pipes (Kishimoto et al., 1994). The data obtained from the experimental program was used to manifest the deficiency and inaccuracies of multitude of the empirical correlations for various heat transfer modes involved in the computer simulation of the proposed system. The dominant role of the temperature distributions in the system and the related two-phase flow heat transfer have been quantitatively identified and the limit of the computer simulation for such system as proposed in the present study has been advanced.     

加工中心机械主轴冷却系统的创新设计

对AP1540加工中心机械主轴做了简要介绍,对加工中心机械主轴传统的冷却技术进行了研究,并设计了一种新型的加工中心主轴冷却系统,应用于AP15.540加工中心主轴.经主轴温升试验测定,采用该新型冷却系统的加工中心机械主轴温升降低11℃.该新型冷却系统能很好地解决加工中心主轴的内部散热问题和主轴刀具的散热问题.     

人字板型钎焊板式换热器对比分析

为提高人字板型钎焊板式换热器的换热性能,以同一组板片尺寸参数建立了三种不同设计参数的人字板型的换热器流道模型,在相同的边界条件下,使用流体分析软件FLUENT对这三个模型的流动传热进行了仿真分析,得到了这三种不同板型的换热器的速度场、流线图和温度场的分布。通过对比分析,得到以下结论:单向人字板型换热器的温度场分布更为均匀且流体速度较高,而且单向人字板型换热器的温差与换热量较高;双向人字板型换热器与多波纹人字板型换热器的温度等值线起伏较大。     

高炉冷却系统热负荷在线监测系统

本文详细地叙述了系统的组成、工作原理和功能。温度、流量检测采用自行设计的采集装置,成本低,安装简便,可靠性高,满足了测量要求。采用该监测系统可实时地监测高炉冷却系统的水温差、流量及热负荷,为高炉安全生产提供依据。     

Thermal characteristics of graphite foam thermosyphon for electronics cooling

Graphite foams consist of a network of interconnected graphite ligaments and are beginning to be applied to thermal management of electronics. The thermal conductivity of the bulk graphite foam is similar to aluminum, but graphite foam has one-fifth the density of aluminum. This combination of high thermal conductivity and low density results in a specific thermal conductivity about five times higher than that of aluminum, allowing heat to rapidly propagate into the foam. This heat is spread out over the very large surface area within the foam, enabling large amounts of energy to be transferred with relatively low temperature difference. For the purpose of graphite foam thermosyphon design in electronics cooling, various effects such as graphite foam geometry, sub-cooling, working fluid effect, and liquid level were investigated in this study. The best thermal performance was achieved with the large graphite foam, working fluid with the lowest boiling point, a liquid level with the exact height of the graphite foam, and at the lowest sub-cooling temperature.     

倾斜折流栅式换热器壳程热力特性研究

为提升常规斜向流换热器的壳程传热性能,提出了一种倾斜折流栅式换热器。采用CFD分析软件FLUENT,标准k-ε模型方程对两种斜向流换热器的壳程热力特性进行了数值研究,并运用场协同原理分析了斜向流换热器的强化传热机理。结果表明:随着折流栅倾斜角的降低,壳程传热系数、压降、综合性能升高,但随着倾斜角的继续降低,如在(60~70)°范围内,壳程传热系数和综合性能基本保持不变;倾斜折流栅式换热器能够提高壳程局部纵向流场的流速,增加壳程流体整体的斜向流程度和速度场与温度场的协同性,强化换热。倾斜角为70°时,倾斜折流栅式换热器较常规斜向流换热器壳程传热系数和综合性能分别提高(7.54~7.66)%和(6.29~6.45)%。研究结果为斜向流换热器的结构优化和推广应用提供了理论依据。     

Measurements of air temperature distribution and optimum cooling condition inside the computer system

Measurements of the temperature distributions of the cooling air flow inside a computer system have been made. An investigation of the optimum cooling condition for the computer system has also been made. Seventy-one K-type (Chromega-Alumega) thermocouples were used to measure distributions of the air flow temperature inside the computer system. They were calibrated against the standard platinum resistance thermometer (PRT) in a constant water circulating bath within an accuracy of ± 0.15 °C. It was found that the number and position of cooling fans as well as their operating condition, whether air intake or air discharge, can greatly influence the cooling effectiveness in the computer system. The results show that the flow rate of intake air should not be higher than that of the discharge air for the most effective cooling. It follows that the optimum cooling has been achieved inside the computer when the three fans are positioned in the inlet front, outlet back, and outlet top in the computer, respectively. Under these conditions, not only is the average temperature inside the computer system maintained at an appropriate level, but the most effective cooling around the central processor (CPU) and graphic card which are responsible for the largest amount of heat dissipation can be accomplished. This paper was recommended for publication in revised form by Associate Editor Man-Yeong Ha Dae Hee Lee received a B.S. degree in Mechanical Engineering from Hanyang University in 1984. He then went on to receive his M.S. and Ph.D. degrees from University of California at Davis in 1984 and 1987, respectively. Dr. Lee is currently a Professor at the School of Mechanical Engineering and a Dean of Academic Affairs at Inje University in Korea. Dr. Lee’s research interests are in the area of Convection Heat Transfer, Liquid Crystal Thermography, Co-generation, and Renewable Energy.     

密封条对六分螺旋折流板换热器壳程侧换热影响

针对两种不同剪裁方式(60°、90°)布置的六分螺旋折流板,建立无密封条和存在密封条的换热器壳程侧模型;采用CFD分析软件借助数值模拟的方法,研究密封条及密封条结构改变对换热器壳程侧流动和传热的影响。结果表明:密封条的存在能够有效的提高壳程侧的换热系数,对90°扇形剪裁方式布置的六分螺旋折流板换热器壳程的影响较60°明显;在壳程侧换热系数增加的同时,壳程压降也随之增大。密封条宽度与间隙比值越大,壳程侧的换热系数越高;当比值为94.1%时,壳程单位压降换热系数较无密封条时增加(8.05~17.8)%。     

基于ANSYS的固定管板式换热器的热应力分析及评定

应用ANSYS有限元分析软件对固定管板式换热器进行热应力分析及评定。由应力强度云图可知最大应力强度发生在管板锻件的管程侧过渡圆角处。设定3条应力评定路径,进行线性化处理,在内压与热载荷作用下,对各路径上的一次加二次应力进行评定,得到应力评定结果。     

热电制冷冰箱散热器热分析及其结构尺寸研究

利用FLUENT软件对热电制冷不等间距的型材散热器进行了三维数值热流耦合模拟分析,得到了其流场及温度场分布,研究了在室温、强迫对流的条件下散热器尺寸、入口风速角度对其传热性能的影响,对散热器进行了结构尺寸选择,不仅使材料节省了22%,而且使散热器热阻降低了3.6%,为热电制冷冰箱用散热器的设计提供了有效的方法。     

数控机床模块设计中建模及运动仿真

按照模块化设计思想,利用图形技术和仿真技术,遵循工业设计原则,在数控机床模块划分的基础上,进行了三维参数化建模、单机拼装、单机空运动仿真的研究。     

发电机定子冷却系统故障处理

本文介绍了发电机定子冷却系统中由测量和调节仪表引起的故障及解决方法,为类似的故障提供了解决思路。     

Thermal analysis of casting dies with local temperature controller

In high pressure die casting processes, a die plays a critical role in removing heat from the molten metal during the cavity filling and solidification stages. Proper control of die temperature is essential for producing superior quality components and yielding high production rates. In this paper, a computerized intelligent real-time monitoring and control system (IRMCS) is developed for die casting processes involving cooling of a die with multiple channels. A local temperature controller is designed to monitor temperature signals from the die insert and flow rate signals from the cooling lines. The performance of the controller is evaluated, and the effect of the controller on local temperature and heat transfer of casting dies is analyzed. The experimental results obtained from a laboratory die casting process simulator indicate that the developed control system is capable of adjusting the desired supply of cooling water into multiple cooling lines, which effectively controls the local temperature of the die insert within a given range. Hence, the desired thermal pattern of the die becomes achievable.     

气动发动机排气冷量在内燃机冷却系统中的回收利用研究

针对气动发动机排气的低温特性,提出了利用气动发动机排气冷却内燃机散热器的技术方案。通过初步试验,获得了气动发动机在不同转速下的排气流量和温度特性。基于初步试验结果,建立了气动发动机排气与内燃机冷却水的热交换模型,并进行了仿真计算,得到了不同水泵流量下,热水流经换热器的进出口温差以及换热量。研究结果表明,换热器进出口热水温差、换热量随着气动发动机转速的升高而增大;随水泵流量的增加,热水流经换热器进出口的温差逐渐减小,换热量增大,但各个水泵流量下的换热量相差较小,当发动机转速为700r／min时,温差增加值及换热量的增加值均为最小;随着气动发动机转速增加,气动发动机排气的冷量炯变化范围很小,回收指数逐渐上升,冷量回收效果变好。     

A study on cooling efficiency using 1-d analysis code suitable for cooling system of thermoforming

Thermoforming is one of the most versatile and economical processes available for polymer products, but cycle time and production cost must be continuously reduced in order to improve the competitive power of products. In this study, water spray cooling was simulated to apply to a cooling system instead of compressed air cooling in order to shorten the cycle time and reduce the cost of compressed air used in the cooling process. At first, cooling time using compressed air was predicted in order to check the state of mass production. In the following step, the ratio of removed energy by air cooling or water spray cooling among the total removed energy was found by using 1-D analysis code of the cooling system under the condition of checking the possibility of conversion from 2-D to 1-D problem. The analysis results using water spray cooling show that cycle time can be reduced because of high cooling efficiency of water spray, and cost of production caused by using compressed air can be reduced by decreasing the amount of the used compressed air. The 1-D analysis code can be widely used in the design of a thermoforming cooling system, and parameters of the thermoforming process can be modified based on the recommended data suitable for a cooling system of thermoforming. This paper was recommended for publication in revised form by Associate Editor Dongsik Kim Zhen-Zhe Li received his B.S. degree in Mechanical Engineering from Yanbian University, China, in 2002. He then received his M.S. degree in Aerospace Engineering from Konkuk University, South Korea, in 2005. He then received his Ph.D. degree in Mechanical Engineering from Chonnam National University, South Korea, in 2009. Dr. Li is currently a Researcher of the Department of Mechanical Engineering, Chonnam National University, South Korea. Dr. Li’s research interests include applied heat transfer, fluid mechanics and optimal design of thermal and fluid systems. Kwang-Su Heo received his B.S. degree in Mechanical Engineering from Chonnam National University, South Korea, in 1998. He then received his M.S. and Ph.D. degrees in Mechanical Engineering from Chonnam National University, South Korea, in 2003 and 2008, respectively. Dr. Heo is currently a Post-doctorial Researcher of the Department of Mechanical Engineering, KAIST(Korean Advanced Institute of Science and Technology), South Korea. Dr. Heo’s research interests include applied heat transfer, fluid mechanics and thermal analysis of superconductor. Dong-Ji Xuan received his B.S. degree in Mechanical Engineering from Harbin Engineering University, China, in 2000. He then received his M.S. degree in Mechanical Engineering from Chonnam National University, South Korea, in 2006. He is currently a Ph.D. candidate of the Department of Mechanical Engineering, Chonnam National University, South Korea. His research interests include control & optimization of PEM fuel cell system, dynamics & control, mechatronics. Seoung-Yun Seol received his B.S. degree in Mechanical Design from Seoul National University, South Korea, in 1983. He then received his M.S. degree in Mechanical Engineering from KAIST(Korean Advanced Institute of Science and Technology), South Korea, in 1985. He then received his Ph.D. degree in Mechanical Engineering from Texas Tech University, USA, in 1993. Dr. Seol is currently a Professor of the School of Mechanical and Systems Engineering, Chonnam National University, South Korea. Dr. Seol’s research interests include applied heat transfer, fluid mechanics and thermal analysis of superconductor.     

Characteristics of fluid flow and heat transfer in a fluidized heat exchanger with circulating solid particles

The commercial viability of heat exchanger is mainly dependent on its long-term fouling characteristic because the fouling increases the pressure loss and degrades the thermal performance of a heat exchanger. An experimental study was performed to investigate the characteristics of fluid flow and heat transfer in a fluidized bed heat exchanger with circulating various solid particles. The present work showed that the higher densities of particles had higher drag force coefficients, and the increases in heat transfer were in the order of sand, copper, steel, aluminum, and glass below Reynolds number of 5,000.