Numerical simulation on the temperature field in an equipment cabin of a high-speed railway train

With train speed increasing, the heat generation from its key equipment is growing as well and the cooling and ventilation of the equipment cabin become more and more important. In this paper, computational fluid dynamics (CFD) method is adopted to simulate the airflow and the temperature field in indoor and outdoor space of the equipment cabin when the train moves at 250 km/h in open space. The simulation results indicate that the surface temperature of the main heat generation equipment is not beyond the limit. When the train moves forward and backward, the maximum average surface temperature of the heat generation equipment is 56.5 °C and 71.7 °C, respectively, and the airflow rates of the fans in the equipment cabin are decreased by 9.1% and 5.2%, if compared to the rated value, respectively. Both forward and backward running conditions should be considered when designing the layout of the equipment and grilles. It is suggested that, the major heat generation equipment should be located in the middle of the cabin; the flow rate decrement of the cooling fan when the train moves at 250 km/h should be taken into account.     

夏季空调房间气流组织的数值模拟

应用计算流体力学方法对夏季空调房间两种送风参数下的室内气流组织进行了数值模拟,给出了速度场和温度场的分布状况,通过对比分析,指出舒适性空调夏季采用较低的送风速度能使室内温度场和速度场分布更均匀。     

暖通空调气流组织数值模拟的特殊性

从计算流体力学CFD应用于暖通空调工程的角度,阐述了通风空调房间内气流组织数值计算的特殊性和难点,对风口模型、湍流模型、辐射模型、热源模型、计算收敛速度以及复杂物理条件的描述等作了分析和介绍,并提出了相应的对策或解决思路。     

空间站座舱工位送风的性能分析

分析了工位送风在空间站的适用性,确定了评价指标.建立了物理模型和数学模型,分析了不同工位送风量和送风速度对舱内乘员工位区空气质量的影响,得到了CO2浓度、空气龄、空气新鲜度比、局部换气效率和工位区风速分布,同时与无工位送风进行了对比.结果表明,工位送风在较小风量时就可以满足空气质量要求,符合航天器轻量化原则;在相同总风量下加大工位送风量后,工位区的性能指标均有所改善;在工位送风量一定情况下,送风速度提高有助于改善舱内的沉闷感.     

铁路客站无组织渗风现状调研及数值模拟研究

通过对全国16个大型铁路客站现场调研,总结了客站主要空间的无组织渗风现状及特点,归纳了目前控制无组织渗风的节能做法。通过调研发现,由于客站建筑及使用特点,大量的无组织渗风量增加了夏季空调和冬季供暖能耗,并且影响室内热舒适。通过数值模拟方法,分析了门斗和空气幕对客站无组织渗风的控制效果,并对各自控制无组织渗风的特性给出了评判和使用建议。     

高速铁路列车检修库热风系统数值模拟与改进

以京沪高速铁路某列车检修库为例,利用CFD技术,对检修库联合供暖设计方案中列车底部热风系统的实施效果进行了模拟。结合8个典型算例,对检修库内空气速度分布、温度分布、热舒适度指标PMV分布及列车表面的热流密度进行了模拟,确定了合理的送风口位置和最佳的送风参数。     

Recent developments of high-speed railway bridges in China

China’s high-speed railway (HSR) construction industry has been experiencing a golden period of opportunities in the recent decades. Due to the necessity of protecting arable lands and the advantage of rapid construction, bridges (elevated structures) are predominantly used in China’s HSRs, which must meet the critical small settlement requirement. This article first reviews the main technical standards of small- to medium-span HSR bridges, where their comparison with the Japanese standard and International Union of Railway standards is highlighted. Then, the long-span HSR steel bridges are described and discussed case by case. Based on the engineering practice of HSRs, the main achievements and key technologies of HSR bridges in China are provided, followed by the opportunities and challenges of the current and future developments of HSR bridges.     

Distribution of exhaled contaminants and personal exposure in a room using three different air distribution strategies

The level of exposure to human exhaled contaminants in a room depends not only on the air distribution system but also on people's different positions, the distance between them, people's activity level and height, direction of exhalation, and the surrounding temperature and temperature gradient. Human exhalation is studied in detail for different distribution systems: displacement and mixing ventilation as well as a system without mechanical ventilation. Two thermal manikins breathing through the mouth are used to simulate the exposure to human exhaled contaminants. The position and distance between the manikins are changed to study the influence on the level of exposure. The results show that the air exhaled by a manikin flows a longer distance with a higher concentration in case of displacement ventilation than in the other two cases, indicating a significant exposure to the contaminants for one person positioned in front of another. However, in all three cases, the exhalation flow of the source penetrates the thermal plume, causing an increase in the concentration of contaminants in front of the target person. The results are significantly dependent on the distance and position between the two manikins in all three cases. PRACTICAL IMPLICATIONS: Indoor environments are susceptible to contaminant exposure, as contaminants can easily spread in the air. Human breathing is one of the most important biological contaminant sources, as the exhaled air can contain different pathogens such as viruses and bacteria. This paper addresses the human exhalation flow and its behavior in connection with different ventilation strategies, as well as the interaction between two people in a room. This is a key factor for studying the airborne infection risk when the room is occupied by several persons. The paper only takes into account the airborne part of the infection risk.     

TBM隧道在不同围岩条件下的数值模拟分析

通过利用ANSYS有限元分析软件,对TBM法隧道施工的过程进行数值模拟分析,结合隧道的工程地质情况,通过分析其应力应变的状态,提出了ANSYS模拟TBM在不同围岩条件下开挖隧道时围岩应力变化的可行性,得出了TBM隧道在不同围岩条件下的一些基本特征。     

论高铁候车大厅空气调节净化的重要性

针对高铁候车大厅当前的空气环境,尤其是在特定环境下易受到严重污染的区域,结合国家室内环境标准要求,人们对生活环境质量需求日益增高,从空气调节的工作原理、流程及空气净化技术,分析了当前形势下如何提高高大空间空气质量及空气净化的必要性。     

Fast simulation of temperature distribution in air conditioned rooms by using proper orthogonal decomposition

Real-time control of air conditioning needs dynamic models of temperature distribution and air velocity field in rooms. Complete models, based on computational fluid dynamics (CFD), give this information, but they are too time-consuming for real-time applications. Therefore, a reduced model is needed. In mixed convection, when the air temperature has negligible variations, the velocity field may be considered fixed. In this case, the size of a CFD model may be reduced by solving only the energy balance equation, then putting this equation in the form of state-space and finally by reducing its order by proper orthogonal decomposition (POD). This algorithm was applied to a room equipped with a fan coil. Four fixed airflow fields, corresponding to negligible air temperature variation, were considered, resulting in four airflow patterns: the air jet sticks to the ceiling and reaches the opposite wall, the air jet falls before reaching the opposite wall, the air jet reaches the ceiling without extending along it, and the air jet falls before reaching the ceiling. The reduced model obtained from these airflow patterns was validated by comparing with CFD results for step variation of inlet temperature. As the order of the reduced model is always lower than seven, it may be used for real-time control applications.     

工位空调送风气流微环境评价

模拟了三种送风速度下送风气流在人体活动区形成的速度场、温度场及PMV的分布,结果表明人员活动区存在送风不均匀和温度分层现象,有助于解决吹风感;PMV值在 1和-1之间,可以满足人体热舒适要求。     

大型集中空调水系统调试浅析——以京沪高速铁路上海虹桥站为例

总结了大型集中空调水系统调试过程中需要注意和解决的几个问题,对传统大管径空调水系统冲洗方法提出了质疑,对调试过程中的水流量分配提出了自己的观点,希望为大型集中空调水系统的调试提供一种新的思路和方法.     

三种空气源热泵户式集中空调系统的运行分析

详细介绍了变制冷剂流量多联分体式空调系统、空气源热泵水管式空调系统、空气源热泵风管式空调系统3种不同的户式集中空调方式在夏热冬冷地区的运行分析,指出了产品、设计、施工和使用中存在的问题,并提出了改进建议.     

水系统中三例气塞故障的分析

对工程中遇到的三例水系统气塞故障加以总结,分析其原因,认为气塞是建筑水系统常见故障,应从设计、施工、运行管理三方面加以重视。     

隧道火灾临界风速的理论计算与数值模拟

对比分析了国内外的相关文献资料,数值模拟了不同风速下火灾烟气的扩散情况,根据不同风速下烟雾的回流距离确定临界风速,对其取值提出了建议.     

数值模拟用于室内空气质量控制的研究进展

介绍了室内空气模型和污染物模型的建立方法,以及IAQ的影响因素。指出了需要进一步研究的问题。     

人防工程高大空间空调气流组织数值模拟研究

针对某地下人防指挥大厅人员和散热设备分布规律,选取不同的送风口数量、送风口尺寸、送风口布置方式和送风速度,提出了3个设计方案。利用CFD软件对各方案的温度分布、速度分布进行了模拟,确定了合理的送风口位置和最佳的送风参数,得到了满足人体热舒适性要求的设计方案。     

某建筑中庭气流组织的数值模拟

利用Fluent软件分别对冬、夏季工况下的球形喷口侧送风方案、条形风口侧送风方案和冬季工况下的条形风口侧送风+地板辐射供暖方案的气流组织进行了模拟,并对模拟结果进行了评价分析。结果表明条形风口侧送风+地板辐射供暖方案具有更好的舒适效果。     

Experimental and numerical analysis of air and radiant cooling systems in offices

This paper analyses office cooling systems based on all air mixing ventilation systems alone or coupled with radiant ceiling panels. This last solution may be effectively applied to retrofit all air systems that are no longer able to maintain a suitable thermal comfort in the indoor environment, for example in offices with high thermal loads.