新型余热控冷用旋流式冷却器的设计与应用

设计了一种新型旋流式冷却器并介绍了其在某钢厂螺纹钢控轧、控冷加工工艺中的应用情况,探讨了各工艺条件对螺纹钢最终组织、性能的影响。试验表明,该冷却器冷却能力约为常规直喷式冷却器的1．5倍,较常用湍流式冷却器冷却均匀,通过调节水流、水压等参数控冷,可改善螺纹钢的性能。     

Simulation, experimentation, and collaborative analysis of adjacent heat exchange modules in a vehicular cooling system

A cooling system consisting of several heat exchange modules is a necessary part of an automobile, and its performance has a direct effect on a vehicle’s energy consumption. Heat exchangers, such as a charged air cooler (CAC), radiator, oil cooler, or condenser have different structures and can be arranged in various orders, and each combination may produce different effects because of interactions among them. In this study, we aimed to explore the principles governing interactions among adjacent heat exchangers in a cooling system, using numerical simulation and experimental technology. 3D models with different combinations were developed, compared, and analyzed comprehensively. A wind tunnel test platform was constructed to validate the computational results. We found that the heat dissipation of the modules was affected slightly by their relative position (the rules basically comply with the field synergy principle), but was independent of the modules’ spacing within a certain distance range. The heat dissipation of one module could be effectively improved by restructuring, but with a penalty of higher resistance. However, the negative effect on the downstream module was much less than expected. The results indicated that the intensity of heat transfer depends not only on the average temperature difference between cold and hot mediums, but also on the temperature distribution.     

减摇实验装置冷却系统设计

该文针对实验室中各液压实验装置进行冷却系统设计,包括液压系统的发热计算、冷却器的选型、泵的选型和管径计算等.在设计中按3台设备同时使用进行计算,同时兼顾其它设备,使其在任何一种工作情况下都达到所要求的冷却效果.     

空调表冷器热工性能测试的实现及分析

介绍了一种自行研制的空调表冷器热工性能测试系统,该系统是通过对实验室现有空气调节处理过程实验台进行改造制得。在压缩机和节流阀之间装设套管式蒸发器,制得冷冻水,经水泵送入表冷器中,与空气进行换热后重新返回套管式蒸发器中。通过温控器实现表冷器入口冷冻水温度的控制,表冷器进出口冷冻水温通过布置热电偶进行测量,冷冻水流量通过转子流量计进行测量,利用原有干湿球温度计测量空气进出口干湿球温度,进而在不同工况下实现表冷器析湿系数、热交换效率、接触系数和换热量的测试。依据测试结果分析风量、风速、冷冻水流量对表冷器热工性能的影响。     

Computational fluid dynamic simulation of an inter-phasing pulse tube cooler

An inter-phasing pulse tube cooler （IPPTC） consists of two pulse tube units, which are connected to each other at hot ends of the pulse tubes through a needle valve. This paper presents the computational fluid dynamic （CFD） results of an IPPTC using a 2D axis-symmetrical model. General results such as the phase difference between pressure and velocity at cold end and hot end, the temperature profiles along the wall, the available lowest temperature as well as its oscillations and the coefficient of performance （COP） for IPPTC are presented. The formation of DC flow and its effects on the performance of the cooler are investigated and analyzed in detail. Turbulence, which is partially responsible for the poor overall performance of a single orifice pulse tube cooler （OPTC）, is found to be much reduced in IPPTC and its performance is improved significantly compared with the single OPTC.     

Coupled models of heat transfer and phase transformation for the run-out table in hot rolling

Mathematical models are been proposed to simulate the thermal and metallurgical behaviors of the strip occtLrring on the run-out table （ROT） in a hot strip mill. A variational method is utilized for the discretization of the governing transient conduction-convection equation, with heat transfer coefficients adaptively determined by the actual mill data. To consider the thermal effect of phase transformation during cooling, a constitutive equation for describing austenite decomposition kinetics of steel in air and water cooling zones is coupled with the heat transfer model. As the basic required inputs in the numerical simulations, thermal material properties are experimentally measured for three carbon steels and the least squares method is used to statistically derive regression models for the properties, including specific heat and thermal conductivity. The numerical simulation and experimental results show that the setup accuracy of the temperature prediction system of ROT is effectively improved.     

重质糠醛精制装置循环水系统的优化

针对重质糠醛精制装置循环水冷却器的结构特性和生产中环水冷却器管束结垢等问题,依据炼油分部对水冷却器防止管束腐蚀及结垢的最低流速要求,核算出该装置的最小用水量和相应水冷器的阀门开度,对该装置的循环水的使用提出优化措施,在一定的程度上解决循环水引起水冷却器管束结垢等问题。     

Secondary cooling technology for high-efficiency continuous billet-casting

The mathematical model of high-efficiency continuous billet casting was developed, incorporating the effective spraying water coefficient and the effective specific spraying water flowrate of secondary cooling. To realize uniform cooling in secondary cooling zones, the spraying cooling structure and the arrangement of nozzles were redesigned and optimized, and an additional spraying cooling zone was used. A new secondary cooling model of spraying water was built. It was found that the required spraying water flowrate of a cooling zone was related with the casting speed, the casting temperature, the compositions of liquid steel and the cooling water temperature of secondary cooling. The operation of the reformed caster proved that the spraying cooling structure and the new secondary cooling model were suitable, and the casting speed was greatly enhanced. The highest casting speed was (3.8 to 4.0) m/min for billet with a section of 150×150 mm2. The quality and the output of the billet were improved, and the economical benefit was heightened.     

有源液池内自然对流与冷却盘管内强制对流的耦合传热

建立了含内热源的液池内自然对流与冷却盘管内强制对流耦合传热的三维物理、数学模型,进行了相应的数值模拟计算。分别对不同内热源强度,不同冷却流体流量下液池内流体温度场以及液池与盘管内溶液换热系数进行了分析,得出换热系数随内热源强度和冷却流体流量的变化曲线,并与实验值进行了比较。结果表明盘管冷却传热模型能够较好的反映液池内的换热。     

水环多联集成空调系统在北方大型建筑中的应用

首先,设计了一种水环多联式集成空调（WLVRF）系统.该系统节能环保,是多联机、水环路和空气源热泵的集成产物,适用于北方大型建筑中.其中,水环路替代制冷剂管路承担了建筑各区域间能量转移的任务,从而减小了单台多联机的规模,提高了机组效率.然后,应用现有的制冷剂和建筑负荷模型,以DATAFIT和MATLAB软件为工具,建立了该系统中各主要组成设备及其他组件的集总参数法数学模型,并模拟了系统性能.通过市场调查,计算出系统的初始投资和运行费.最后,将WLVRF系统和传统多联机（VRF）系统进行比较,结果显示WLVRF系统具有更优良的运行工况,运行费用更低.     

等离子割炬喷嘴热－流耦合分析及优化设计

等离子割炬工作原理复杂,喷嘴在冷却水温度场和流场耦合作用下工作,实物实验难度较大,文章采用CFD软件针对两种割炬喷嘴进行数值模拟,分析在不同冷却水流速度下的温度云图和温度曲线图,确定喷嘴结构,给出建议冷却水流速度。     

本钢FTSC生产热轧板卷边裂的原因分析及控制

本钢采用FTSC短流程工艺生产热轧卷板时,因钢中[Al]、[N]、[B]控制不当,生成[AlN]及[BN]析出造成晶界脆性,二冷水量冷却不均、钢板在弯曲和矫直时产生边裂。文章通过控制钢中[Al]、[B]的含量,减少中碳钢生产过程中增氮、降低薄板坯二冷水量等措施,减少了边裂缺陷的发生。     

Application of singular perturbation method in analyzing traffic density waves

Car following model is one of microscopic models for describing traffic flow. Through linear stability analysis, the neutral stability lines and the critical points are obtained for the different types of car following models and two modified models. The singular perturbation method has been used to derive various nonlinear wave equations, such as the Korteweg-de-Vries (KdV) equation and the modified Korteweg-de-Vries (mKdV) equation, which could describe different density waves occurring in traffic flows under certain conditions. These density waves are mainly employed to depict the formation of traffic jams in the congested traffic flow. The general soliton solutions are given for the different types of car following models, and the results have been used to the modified models efficiently.     

多孔陶瓷管式露点间接蒸发冷却器的设计计算

为了提高管式间接蒸发冷却器壁面的亲水性,提出了一种采用多孔陶瓷材料的新方法.该方法将多孔陶瓷材料与蒸发冷却技术有机结合,从一次空气风量和二次空气风量、一次空气状态参数和二次空气状态参数、冷却器结构、固体多孔陶瓷管的传热以及冷却器阻力等方面对多孔陶瓷管式露点间接蒸发冷却器进行了设计计算.计算结果表明该设计合理可行.最后,依据设计制作出多孔陶瓷管式露点间接蒸发冷却器.     

空调表冷器热工性能测试系统的研制

对实验室现有空气调节处理过程实验台进行改造,在压缩机和节流阀之间装设套管式蒸发器,通过其制得冷冻水,将冷冻水经由水泵送入表冷器中,与空气进行换热后重新返回套管式蒸发器中.通过温控器实现表冷器入口冷冻水温度的控制,表冷器进出口冷冻水温通过布置热电偶进行测量,冷冻水流量通过转子流量计进行测量,利用原有干湿球温度计测量空气进出口干湿球温度,进而实现表冷器热交换效率、接触系数、析湿系数和换热量的测定.改造后的实验台还可以作为冷热源,在教学和科研中发挥作用.     

金属比热容测量方法的研究

在传统金属比热容测定方法基础上,经过多方面研究得出两种测量改进方法：选择高温点为水,用混合法测量金属比热容;用比较方法,根据牛顿冷却定律测定金属的比热容．两种方法均具有较高的测量精度,且操作方便．     

EGR在CA498柴油机上的试验研究

本文介绍了80C196单片机驱动比例电磁阀,进而对真空调节的EGR系统进行控制,来降低CA498的排放值,特别是NOX的排放值,并对其进行试验.结果表明:采用EGR系统后CA498的排放量下降明显.     

基于遗传算法的供水管网需求乘数因子校核

水力模型已广泛应用于给水管网设计、分析与运行中。在所有水力模型中,需水量是导致模型输出最不确定的参数之一。因用水情况不确定,使得管网中的节点需水量变得异常复杂。在大多数实际管网中,用于校核节点需水量的监测设备数量有限,且小于未知量个数,使得节点需水量校核作为欠定问题,令节点需水量校准产生较大误差,并且传统遗传算法校核节点需水量的方法是假定所有节点的需求乘数因子一致,这也导致校核后的模型无法接近真实运行情况,因此提出在欠定条件下用遗传算法解决需求乘数因子的校核问题。通过对一个实际案例多次运行并取平均值作为结果进行验证,结果表明,遗传算法的校核结果不仅能够与被测位置的实际值相拟合,而且可以得到非测量位置的管道流量和节点水头,其中校核后的节点水头和管道流量误差较小,平均误差分别为1.78%、4.05%。该方法相比于传统校核方法具有更高精度,且更能反映出管网真实运行情况,同时还避免了传统校核方法中因遗传算法产生局部最优解而导致误差偏大的问题,对于大型管网模型校核也具有一定参考价值。     

Effects of Exhaust Gas Recirculation on the Homogeneous Charge Combustion Process of n-Heptane at Different Load Conditions

Effects of exhaust gas recirculation （ EGR） on homogeneous charge combustion of n-heptane was studied through simulation and experiment. Experiments were carried out in a single cylinder, four-stroke, air cooled engine and a single cylinder, two-stroke, water cooled engine. In the four-stroke engine, experiments of the effects of EGR were examined using heated N2 addition as a surrogate for external EGR and modifying engine to increase internal EGR. The ignition timing was sensitive to EGR due to thermal and chemical effects. EGR or extra air is a key factor in eliminating knock during mid-load conditions. For higher load operation the only way to avoid knock is to control reaction timing through the use of spark ignition. Experimental and modeling results from the twostroke engine show that auto-ignition can be avoided by increasing the engine speed. The twostroke engine experiments indicate that high levels of internal EGR can enable spark ignition at lean conditions. At higher load conditions, increasing the engine speed is an effective method to control transition from homogeneous charge compression ignition （ HCCI） operation to non-HCCI operation and successful spark ignition of a highly dilute mixture can avoid serious knock.     

Numerical investigation on thermal properties of micro-pin-fin cooler

Micro-pin-fin cooler mounted on the power chip enables the heat removal to meet modern microsystem requirement. Carbon nanotubes (CNTs) have been proven as a potential material for micro-coolers due to the superior thermal conductivity, good mechanical property and so forth, and there appear various applications of CNTs in the micro-cooler technology. In the present paper, an analysis of the thermal and hydraulic characteristics of the micro-pin-fin heat sink was conducted, where air was used as the cooling medium and an impinging jet was introduced to enhance the heat transfer. Three-dimension computational fluid dynamics (CFD) simulations were carried out for micro-pin-fin coolers with various parameters, including the pin-fin size and pattern as well as the jet velocity and nozzle diameter. The flow field and thermal properties of the micro-pin-fin heat sink were obtained, and the heat removal efficiency was evaluated.