挂壁式变频空调器热舒适性的数值模拟及实验研究

结合挂壁式房间空调器的使用特点,运用CFD方法模拟室内空调热环境,对空调送风温度的影响进行了分析.利用房间环境热舒适实验结果,对模拟结果进行对比和分析,验证数值计算模型的准确性.     

大型冷却塔风荷载的数值模拟研究

针对单体和双塔情况下冷却塔的风荷载进行CFD数值模拟计算,获得冷却塔表面的压力系数。单个冷却塔CFD模拟的结果与规范数据比较接近,说明CFD方法的准确性,同时也发现一些偏差,并对偏差产生的原因进行分析。研究了因雷诺数不同而导致的单塔缩尺效应,发现实尺和缩尺模型的计算结果在最大正压和平台区有差别。分析双塔之间的干扰作用,针对不同风向角可分为尾流直接作用、尾流和临近干扰共同作用、临近干扰作用三个区域。     

热声斯特林发动机热动力学特性的CFD研究——第一部分:热声自激振荡演化过程

采用商业计算流体动力学(CFD)软件Fluent6.0对热声斯特林发动机热动力学特性进行了热声自激振荡演化过程的数值模拟研究.主要研究了边界条件、初始条件和数值离散方法对模拟瞬态、可压缩、非线性的热声系统的重要影响,同时给出了两种在回热器内部建立温度梯度的方法,比较了它们对应的不同自激振荡演化过程.模拟结果表明,在高于功产生的临界温度梯度时,波动压力振幅被显著放大.本研究初步验证了该CFD研究的有效性.     

缩尺模型实验在交通噪声影响评价中的应用

本文综述了缩尺模型实验在交通噪声对环境的影响评价的应用，模型实验的基本原理，及实现交通噪声的模拟方法。计算机模拟也是一种预报交通噪声传播特性的方法，它和模型实验相辅相成，在实验中二者应紧密结合。最后指出缩尺模型实验中应注意的问题。     

计算流体力学在真空技术中的应用

计算流体力学与理论流体力学、实验流体力学共同构成流体力学研究体系。随着计算机科学与技术的发展,以及数值求解理论与方法的进步,计算流体力学(CFD)越来越受到研究人员和工程技术人员的重视。CFD理论模型的预测精度获得广泛认可,已经成为复杂流动和传热问题数值分析的研究工具、工程技术领域中的重要设计工具以及基础热流体力学的教学工具,在真空工程领域中也有应用,可作为理解真空设备工作机理的重要研究手段。以水蒸气喷射泵内部流动为例,介绍CFD数值模拟方法。通过数值模拟结果的分析,揭示水蒸气喷射泵抽气效率的内在影响规律,为真空设备的结构优化、性能改进提供依据。     

CFD及ASM-CFD在MBR研究中的应用进展

综述了国内外计算流体力学(Computational Fluid Dynamics,CFD)在膜生物反应器(Membrane Bioreactor,MBR)研究中的应用进展,介绍了与活性污泥模型(Activated sludgemodel,ASM)相结合的ASM-CFD模型在MBR研究中的应用状况.曝气优化,膜组件、膜单元及生物单元结构的优化是目前基于CFD的MBR模拟研究重点.国外CFD模拟研究较早,模拟规模已高达4800m~3/d.与之相比,我国开展MBR的CFD模拟研究起步较晚,目前仍处在小试规模的模拟阶段.ASM-CFD模拟已在常规活性污泥法污水处理研究中得到了成功应用,预期其在MBR的研究、设计与应用中有望成为一个新热点和方向.     

指数脉冲强迫激励CFD模型运动的气动参数识别法

计算流体动力学（CFD）模拟是获得桥梁断面颤振导数的主要方法之一。提出了一种基于CFD计算气动力，建立气动模型并经模型仿真快速识别颤振导数的新方法。该方法采用具有连续频谱分布且位移光滑的指数脉冲序列为CFD模型运动的输入，通过数值模拟得到作用在模型上的气动力。利用已知的输入和气动力建立起反映系统气动力特征的离散时间气动模型。然后利用该模型仿真系统在简谐位移输入的气动力响应，再基于该输入和模型仿真输出识别颤振导数。该方法在竖弯和扭转方向各自仅需一次CFD模拟，无需重复进行CFD计算，能显著减小CFD计算颤振导数的工作量。进行了薄平板颤振导数的识别，研究结果与Theodorsen平板理论解、薄平板风洞试验值的一致性，证明了研究方法的可靠性和有效性。     

立式陈列柜双层风慕的CFD优化

风幕卷吸渗入的热负荷是超市陈列柜热负荷的主要来源,为减少热空气的吸入量通常设置双层风幕,两层风幕相互影响。本文采用雷诺应力模型对某带双层风幕的立式超市陈列柜的流场和温度场进行了仿真计算和实验验证。并在CFD理论模型基础上,对风幕的影响因数进行了调整和优化,为风幕系统的优化设计提供依据,     

水下爆炸作用下舰船总纵强度模型实验方案研究

考虑了自由场中水下爆炸一次冲击波和气泡脉动相似律,研究了在大缩尺比船模水下爆炸实验中,使用畸变模型实现对原型总纵强度准确预测的方法。考虑模型的制造工艺性,对缩比模型的板架结构进行改造生成畸变模型。通过对四种舰船缩尺实验方案进行水下爆炸数值计算分析,并对实际模型横剖面弯矩预测偏差进行总结,得到当缩尺比为1/4、畸变系数为3时,实验模型能在工程精度范围内实现对原型横剖面弯矩的准确预测,同时满足制造工艺和经济性的最终实验方案。文章的结论可为大缩尺比船模水下爆炸实验的工程应用提供参考。     

酒店中庭热环境系统的设计研究

针对酒店中庭热环境特点,从理论上分析了中庭得热的影响因素和计算方法,同时提出采用能耗模拟软件和CFD软件对中庭的热环境进行联合模拟分析,并在实际的项目中运用该方法进行研究分析,为系统设计提出合理的建议。     

大空间建筑空调稀释型送风方式三维数值模拟

论述了CFD模拟大空间建筑室内空气流动的必要性;对采用稀释型送风方式的大空间建筑空调室内空气流动的速度场和温度场进行了数值模拟并对其结果进行了分析.结果表明:稀释型(上送)方式的分层空调在大空间建筑空调中是较好的送风方式.     

Concept for thermal insulation arrangement within a flexible cryostat for HTS power cables

The successful application of high temperature superconducting power cables requires improved flexible cryostats with respect to their thermal heat load between environment (300 K) and LN₂ (77 K) operating temperature. Heat transfer through the thermal insulation consists of thermal radiation, solid and residual gas conduction. Considering this heat load contributions, a new concept for the thermal insulation arrangement is presented in this paper. The main advantage of this concept consists in a separation of the thermal insulation and the supporting structure. This separation protects the thermal insulation from degradation by mechanical load. The fraction of solid heat conduction through this support structure is minimised by small contact areas and high heat conduction lengths. Heat transfer due to residual gas conduction is reduced by improved evacuation conditions close to the cold wall. Finally the structure allows subdivision of the multilayer insulation ensuring an optimal number of layers with respect to their insulation thickness, i.e. an optimal layer density.     

Air velocity characteristics within vented pallets loaded in a refrigerated vehicle with and without air ducts

During transport using refrigerated vehicles, this being a vital link in the cold chain, the maintaining of even temperature throughout the cargo is essential in order to preserve the quality, safety and shelf life of perishable food. Within the refrigerated container, the temperature level and its homogeneity are directly governed by airflow patterns. The design of the air-distribution system should allow these airflows to compensate heat fluxes exchanged through the insulated walls or generated by the products.In this paper, a reduced-scale model and CFD predictions were used to investigate experimentally and numerically the airflow patterns within a typical refrigerated truck configuration loaded with vented pallets filled with spherical objects. The experiments were carried out using a laser Doppler velocimetry and thermal sphere-shaped probes located inside the pallets. The aim was to investigate air velocity characteristics above and within pallets. The performance of ventilation was characterized with and without supply air duct systems. Both configurations are extensively used in refrigerated transport. Full-scale measurements were also performed within a load of fruit during transport in a refrigerated truck in order to evaluate the temperature distribution under given operating conditions.The numerical modelling of airflow was performed using the computational fluid dynamics (CFD) fluent code and the Reynolds Stress Model (RSM) turbulence model. Numerical and experimental data make it possible to evaluate the air ventilation levels and their heterogeneity between the pallets. The numerical predictions show reasonable agreement with experimental data. The studied supply air duct system improves significantly the homogeneity of ventilation in the vehicle.     

甘肃某博物馆中庭热环境数值模拟与分析

以甘肃一拟建博物馆中庭为例，采用CFD数值方法对建筑中庭温度场进行模拟，计算不同负荷下中庭高度方向和人员活动范围内的温度分布，分析各种建筑因素对中庭内温度分布的影响。研究结果表明，良好的中庭建筑和通风设计能有效改善室内热环境，满足人体的热舒适要求。     

精密离心机热变形多物理场耦合数值计算

离心机是惯性导航系统加速度计的标定设备,转盘变形将严重影响标定精度.综合考虑离心机机室内空气流动、流动传热以及机箱和转盘的导热,结合CFD和FEM方法,对精密离心机的热变形进行流-热-固多场耦合计算.分析了多物理场耦合计算原理,采用流固耦合换热整场求解法计算离心机温度场,采用顺序耦合法计算转盘热变形.计算结果表明:在300r/min转速下,转盘最大温升为1.23℃;越远离转盘中心,温升越大;加速度计安装位置的温度计算值与实测值一致,验证了本方法的正确性;转盘安装加速度计位置的径向热变形为7.89μm,热变形是变形累积的结果且随着转盘转速增加而增大.     

Effects of wall conduction on natural convection in a porous triangular enclosure

Conjugate natural convection in a two-dimensional triangular enclosure filled with a porous medium is examined in this article. It is assumed that the solid vertical wall is of finite conductivity and that the temperature of the inclined wall is lower than that of the vertical wall, while the horizontal wall is adiabatic. A finite difference method is used to solve the governing equations of convection and conduction for different parameters as Rayleigh number, width of the vertical solid wall, aspect ratio of the enclosure and thermal conductivity ratio between solid and porous media. It is found that heat transfer increases with increasing Rayleigh number and aspect ratio of the triangle, decreasing wall thickness and with the increase of the wall conductivity.     

LNG储罐主容器泄漏时外罐壁的传热特性

以一种LNG储罐为研究对象,利用有限单元法(FEM)分析了在主容器泄漏时的混凝土外罐壁的传热特性,研究了泄漏发生时外罐壁温度随着时间的变化过程,泄漏发展后的外罐壁的温度分布和热流密度,以及热保护边角(TCP)对于外罐壁传热的影响,指出了外罐壁热传导达到稳定后的传热特性.     

大空间下送风分层空调的同步求解模型的研究

提出了一种大空间下送风分层空调环境下的同步求解模型,用于预测室内空气垂直温度分布和内壁面温度分布以及下送风环境下的空调冷负荷;进行了大空间建筑下送风环境下的夏季热环境实验,实测室内空气垂直温度分布和内壁面温度分布以及夏季冷负荷,并验证对比了实验值和模型计算值,结果表明温度数据吻合良好,冷负荷的相对误差小于10％.     

Thermal-hydraulic CFD study in louvered fin-and-flat-tube heat exchangers

Heat transfer performance prediction by CFD codes is of major interest. Usually air-side heat transfer characteristics of fin-and-tube heat exchangers are determined from limited experimental data. The ability of CFD code to predict flow patterns and thermal fields allows determining the heat transfer characteristics by performing ‘numerical experiments’. CFD calculations of a 1-row automotive condenser are compared to experimental results and correlations of the literature matching the fin design and the flow conditions. Calculations are performed for different air frontal velocities. 2D models, with uniformly constant fin temperature overestimate significantly the heat transfer coefficient. 3D models, taking into account tube effects, conjugate heat transfer and conduction through the fin are in better agreement with the experimental results. However, even if an offset in noticed between CFD calculations and the experimental results, the trends are comparable and CFD study permits to reach local information, leading to better understanding of the physical phenomena involved in compact heat exchangers. An attempt for 2D unsteady flow has also been performed. Results are discussed in terms of flow pattern and heat transfer coefficient behaviour.     

夏季办公室空调房间气流组织的数值模拟

为了描述和分析在夏季使用分体落地式空调器来制冷的办公室室内的气流组织,根据实际情况建立其物理和数学模型,应用CFD方法对办公室空调房间上送下回的送风方式下的气流组织进行三维数值模拟。通过Fluent软件来进行数值解算,给出室内速度场和温度场的分布状况。通过对不同空间位置的速度矢量图和温度等值线图的分析,得到了该室内气流组织的合理性和人员所处不同区域的热舒适性,并以此来指导办公室内空调通风的设计和改进。