大容量主变压器冷却方式选择

对500KV,1000MVA大容量主变压器冷却方式进行技术经济比较。从设备制造水平、运行情况、生产业绩、占地面积、技术经济等方面分析和探讨主变压器采用自然油循环风冷(ONAF)及强迫油循环油风冷(OFAF/ODAF)冷却方式。     

汽油机活塞冷却喷射两相流及传热分析

为了深入研究活塞冷却喷射的油束运动发展规律及不同活塞冷却方式对传热的影响,对比研究了3种活塞冷却方案.首先,在稳定的流场环境里对油束进行了验证,保证了后续瞬态强气流条件下喷射计算的准确度.通过曲轴箱内的仿真计算,得到了活塞冷却喷射图像、内冷油道与活塞底面的平均传热系数分布、活塞的温度分布.针对模型A(内冷油道强制冷却+...     

大型电力变压器的非电量保护

压力释放阀 　　部颁电力变压器运行规程规定:发生以下任一现象,变压器应立即停用.①变压器内部响声很大、且伴有爆炸声;②在正常负荷及冷却条件下,变压器的油温不正常地不断升高;③变压器油枕和安全气道(防爆管)喷油喷烟;④变压器油色化过甚、油内出现碳质等;⑤变压器套管有严重破损以及放电现象;⑥变压器着火.……     

35kV油漫式电力变压器线圈油道的探讨

35kV油浸式电力变压器线圈3mm和2mm油道的设计比较,通过线圈温升对比,说明2mm油道的技术优势。     

铝活塞用盐芯的制作

盐芯铝活塞即在铝活塞铸造过程中用盐芯形成其内冷却油道的活塞。因内冷却油道内腔较大而油道出口小且数量少，所以一般选用易脱芯的水溶性盐芯。水溶性盐芯指的是以水溶性盐为基体制作的盐芯。其特点是遇水溶解，主要优点就是便于脱芯。正是基于这个优点，使其在带内冷却油道活塞中得到广泛地应用。     

农用配变线圈设计及半油道阻抗电压计算

介绍了我国农用配电变压器的发展过程及在农网中的应用 ,对农用配电变压器在生产及应用方面进行了分析 ,并通过阻抗电压的计算 ,展示出农用配电变压器在生产工艺中既保持了原有的设计技术数据 ,并采用了半油道线圈 ,以满足阻抗电压及机械性能 ,使农用配电变压器在生产加工中达到节电、降低损耗 ,节约能源。     

欧-Ⅲ排放柴油机缸盖冷却水腔流动与传热的数值解析

本文利用CFD和FEM耦合计算的方法,较准确的确定缸盖冷却水腔的热边界条件,对普及型欧-Ⅲ排放柴油机的冷却水腔和缸盖温度场进行了模拟。文章对冷却水腔的整体流动均匀性和整机压力损失进行了分析评估,并对缸盖火力面、喷油器安装孔和排气道周围冷却水腔的冷却情况进行了详细分析。模拟计算结果表明:冷却水腔的流动均匀性和压力损失可以满足使用要求;流经火力面和排气道周围水腔的冷却液流量分配合理;缸盖火力面、喷油器安装孔和排气道周围水腔冷却良好。     

整体锻钢活塞内冷油道设计研究

本论文主要针对整体焊接成型锻钢活塞的内冷油道设计,根据发动机强化指标及性能要求,从活塞整体结构强度、工艺难度、冷却效果等因素考虑,提出可行性设计意见,并借助CFD流体软件分析钢活塞内冷油道的换热系数和填充率,使用有限元法分析钢活塞温度分布、应力分布、疲劳分布,通过数值模拟辅助钢活塞内冷油道设计,并结合试验后活塞外观及检...     

新型活塞冷却油道的设计与成型技术

活塞作为内燃机中承受高温高压的部件,除了常规的冷却方式,不断地追求活塞结构上的改进,在不增加活塞质量和影响内燃机的功率的前提下,加强对活塞的冷却,将是活塞未来的发展方向,我们介绍了一种新型的冷却道活塞的设计技术,以及利用盐芯在铸造过程中形成冷却油道的生产技术。     

装甲车辆发动机冷却系统空气流动的仿真模型

基于一维动态可压缩气体流动方程建立了装甲车辆发动机冷却系统空气流动的仿真模型 ,考虑了车辆动力舱内流道几何尺寸、壁面摩擦、散热器传热、风扇做功以及分支流动对冷却气流的影响。对一台履带式装甲车辆发动机冷却系统的空气流动进行了实例仿真计算 ,为研究装甲车辆发动机冷却系统空气流动的性能提供了一种理论分析手段。     

气膜冷却对高压涡轮叶栅损失特性的影响研究

为获得全气膜气冷涡轮叶栅的损失特性,采用试验及数值仿真方法,研究了不同冷气流量、不同叶栅出口马赫数条件下冷气射流对叶栅损失的影响。通过叶栅槽道静压云图及叶片表面压力分布等试验及数值仿真结果对比,验证了通冷气叶栅性能仿真分析方法的准确性。结果表明：同一冷气流量比下,通冷气叶栅能量损失系数随着马赫数的增大先减小后增大,在设计马赫数附近损失最低;通冷气叶栅能量损失系数随着冷气流量的增大而增大,且前后腔均通冷气时能量损失系数最大,前腔单独通冷气时能量损失系数最小;通冷气叶栅能量损失系数随着冷气与主流温比增大而增大。     

Effect of cooling channel geometry on re-cooled cycle performance for hydrogen fueled scramjet

Developing fuel with higher heat sink is widely carried out to meet the cooling requirement for an airbreathing hypersonic vehicle. However, a Re-Cooled Cycle has been newly proposed for a regeneratively cooled scramjet to reduce the fuel flow for cooling. Fuel heat sink (cooling capacity) is repeatedly used to indirectly increase the fuel heat sink. Parametric sensitivity analysis of Re-Cooled Cycle of a hypersonic aircraft is explored. An analytical fin-type model for incompressible flow in smooth-wall rectangular ducts in terms of hydrodynamic, thermal, power balance and Mach number constraints is proposed. Based on this model, the difference of the cooling channel structure design between Re-Cooled Cycle and regenerative cooling is discussed, and a new optimization index is introduced for Re-Cooled Cycle. The sensitivity of the cycle performance to cooling channel geometry is investigated, and the optimal performance of a Re-Cooled Cycle is obtained by satisfying constraints. The differences of the effect of channel design variables between Re-Cooled Cycle and regenerative cooling are also discussed.     

Optimal mixed convection for maximal energy recovery with vertical porous channel (solar wall)

A vertical open-ended channel filled with a porous medium, with an imposed heat flux and a heat loss coefficient on one of its walls, is studied numerically. A fan can enhance the self-driven flow, and therefore a mixed convection regime is considered. The objective is to maximize the overall energy recovery (heat transfer to the fluid minus fan power). Correlations are developed for optimal pressure drop to be imposed by the fan and maximal energy recovery, as a function of the Rayleigh number, the channel aspect ratio, and the heat loss coefficient. The optimal allocation of the total energy losses (i.e., sum of the heat loss and fan power) is shown. Potential applications include solar wall and solar chimney used for ventilation and preheating of makeup air in buildings.     

A passive solar building for ecological research in Argentina: the first two years experience

An energy-efficient building, featuring energy conservation, passive solar heating, and natural cooling strategies, was designed and built in La Pampa, a province in the temperate semi-arid region of central Argentina. Of compact design, it houses 350 m² of useful floor area in a roughly linear scheme, with the main spaces facing north and ancillary spaces (services) facing south. Solar windows running from above spandrel and up to ceiling height are provided for all the main spaces, and clerestory windows are provided for the solar gain to the south-facing spaces. An integrated sunspace is incorporated into the centre bay of the north facade, providing additional heat to inner spaces as well as functional and visual expansion. In the design stage, a simulation analysis was performed to assess the environmental and energy performance of the alternatives. The main energy features of the resulting building are a volumetric loss coefficient of 1.09 W m⁻³ °C⁻¹, and a predicted solar savings fraction of 70%. The summer cooling strategy includes the passive induction of exterior air into the building through earth-coupled ducts. Cooling by cross-ventilation is made possible during the night, but to preserve the security of the building from sudden storms, this occurs only when the building is occupied. Shading devices protect all windows in summer. Provisional monitoring, started during the 1995 winter period, showed encouraging possibilities of energy savings with adequate comfort conditions, demonstrating the technical feasibility of the scheme.     

Theoretical analysis on heat and mass transfer in a direct evaporative cooler

The heat and mass transfer between air and water film in the direct evaporative cooler is theoretically analyzed in present paper. A simplified cooling efficiency correlation is proposed based on the energy balance analysis of air. The correlation may be applied to the water-drip cross-flow direct evaporative cooler, in which the wet special durable papers with different wave angles form the air channel. The Influences of the air frontal velocity and the thickness of pad module on the cooling efficiency of a direct evaporative cooler are discussed. An optimum frontal velocity of 2.5 m/s is recommended to decide the frontal area of pad module in the given air flow. The simplified correlation of cooling efficiency is validated by the test results of a direct evaporative cooler.     

Thermal analysis of a flat-plate boiling collector having sub-cooled inlet and saturated exit states

The analysis of the thermal performance of a boiling flat-plate solar collector is presented. A generalized heat removal factor and a new formulation for the overall thermal loss coefficient are developed. It is demonstrated that the conventional heat removal factor for non-boiling collectors is a limiting case of a more generalized result. The new formulation for the overall thermal loss coefficient is shown to be a function of the fractional non-boiling length of the flow channel. The influence of the inlet sub-cooling is evaluated and the operating limits of solar flat-plate collectors are determined. A comparison is made between the thermal model for boiling collectors having sub-cooled inlet states and experimental results. Favorable agreement is obtained.     

Flow field and heat transfer analysis of local structure for regenerative cooling panel

Local structure of cooling panel has great effects on the heat transfer in the cooling channel for the scramjet. The problems of flow dead area and mass flow rate non-uniform distribution caused by the local structure effect the cooling effectiveness in the channel seriously. Numerical simulation to the flow field of scramjet cold panel with four different fuel injection island structures respectively has been carried out using the CFD commercial software-CFX in this research. The results reveal that flow dead area has been eliminated and flow field has been improved for the optimized structure. Furthermore, local resistance loss has been decreased and the mass flow rate non-uniform distribution in the channel has been reduced. Based on the optimized results, some suggestions about the local design of cooling panel have been proposed in this research.     

Particle swarm optimization for redundant building cooling heating and power system

An optimal and redundant building cooling heating and power (BCHP) system can yield economical savings, but more importantly can save energy as well as reduce the emission of pollutants. This paper presents the energy flow analysis of the conventional separation production (SP) system and the redundant BCHP system. Four decision variables (the capacity of power generation unit (PGU), the capacity of heat storage tank, the on–off coefficient of PGU and the ratio of electric cooling to cool load) to be optimized are selected in consideration of the design and the operation strategy of BCHP system. An objective function to simultaneously measure the energetic, economical and environmental benefits achieved by BCHP system in comparison to SP system is constructed and maximized. Particle swarm optimization algorithm (PSOA) is employed to search the optimal solutions. A case study of BCHP system with thermal storage unit and hybrid cooling system is presented to ascertain the feasibility and validity of the optimization method.     

等效热降法在空冷300MW机组中的应用

以新型300MW空冷机组为例,分别使用正平衡、反平衡及等效热降方法对机组进行分析,这几种方法的特点和计算结果对比表明,等效热降法在机组性能及局部进行能损分析,提供节能改造手段等方面具有明显的优势。     

Thermal investigation of the conjugate heat transfer problem in multi-row circular minichannels

A numerical three-dimensional flow and conjugate heat transfer in circular minichannel-based multi-row heat sink is presented in this article. Effects of geometrical parameters including channel dimensions, channel arrangements (inline or staggered), and the number of channel rows with a single-pass flow on the thermal performance of the heat sink are presented. The determination of the bottom surface temperature, average heat transfer coefficient, thermal resistance as well as the pressure drop was reported. The number of rows and the diameter of the circular channel for a constant Reynolds number were found to have a remarkable cooling effect on the heat sink. It was found out that in the case of using four channel rows with the channel diameter of 1?mm, the cooling capacity is 88.5?W/cm² compared to 28?W/cm² for a single row 1?mm diameter.