浅埋工程围护结构全年动态传热计算

浅埋地下工程围护结构三维非稳态传热由于受到工程埋深、几何型式、室外气象参数、室内周期性变化空气以及围护结构热特性参数等的影响而显得尤为复杂。将室内空气对围护结构传热的影响综合考虑，基于FLUENT商业软件采用耦合传热计算方法对三维非稳态传热进行数值求解。通过这一方法可以得到围护结构全年动态传热量，并可反求室内空气与围护结构的对流换热系数。     

吐鲁番地区居住建筑围护结构隔热设计研究

合理利用自然气候资源进行围护结构隔热设计可有效提高室内热舒适的同时降低建筑能耗。通过理论计算得到围护结构蓄热性能对室内热环境的作用规律,选取吐鲁番典型多层居住建筑,对比验证室内空气温度实测与模拟结果,采用IES软件模拟分析3种不同蓄热级别建筑的室内空气温度和体感温度,对夏季室内热环境进行评价,结果表明:实测结果与模拟结果吻合较好;轻质围护结构夜间时段热环境质量I级时长增加5%,Ⅱ级时长增加12%;重质围护结构白天时段度时数减少496(℃·h)。研究提出差异性围护结构隔热设计方法,为吐鲁番居住建筑热工设计提供参考。     

室内自然对流数值模拟分析

研究建筑围护结构传热与流体流动综合作用下室内自然对流数值模拟,建立了一套同时在固体-流体区域整体求解连续性方程、动量方程和能量方程的数值模拟方法。具体分析了瑞利数变化范围为104到106时建筑围护结构传热对室内自然对流的影响。数值预测结果表明:该方法能够真实反映室内自然对流问题。为室内自然对流问题数值模拟找到了一种实用有效的方法。     

长江中下游地区梅雨季节的室内热湿环境

经过调研得到长江中下游地区(以南京为例)梅雨季节住宅建筑室内热湿状况,并分析3种不同建筑能耗计算模型(整体建筑热湿空气流动耦合模型HAM,传递函数模型CTF,有效湿渗透深度模型EMPD)的准确性。数值模型基于Matlab-Simulink编写,使用调研数据进行验证,进而使用梅雨季节典型气象参数模拟分析。调研结果显示在2013年梅雨季节,多数时间内建筑室内温度高于28℃,相对湿度高于70%。数值模拟结果显示3种能耗模型对室内温度模拟的差异较小,而对室内湿度的模拟存在较大差异,特别是CTF模型误差最大。结果显示在长江中下游地区梅雨季节,当房间换气次数小于2ACH时,围护结构对于室内环境湿缓冲的作用明显,选择合适的吸放湿材料可有效降低建筑能耗30%以上。     

某火车站房的自然通风效果模拟分析

本文采用稳态自然通风-热耦合模拟的方法分析了某火车站房候车大厅在夏季采用自然通风方案时的降温效果,为该火车站房的通风空调系统设计提供指导意见,对于类似项目的设计具有参考价值.本文采用DeST软件计算建筑得热量,全面考虑了太阳辐射得热、人员设备发热、围护结构传热;利用多区域流体网络通风计算软件CONTAMW和热耦合模拟程...     

极端热湿地区湿驱动势的选择对热湿耦合模型计算的影响

极端热湿地区常年高温高湿,为了研究围护结构的热湿迁移情况,在同时考虑水蒸气和液态水传输的状况下,导出了3种不同湿驱动势的热湿耦合模型:空气含湿量模型、相对湿度模型和毛细压力模型。利用COMSOL进行了数值求解,并将结果与HAMSTAD基准进行了对比分析。结果发现在围护结构内部未出现结露时,3种模型都可以准确地描述围护结构的传热传湿过程。然而围护结构内部出现结露时,只有毛细压力模型适用。因此极端热湿地区进行传热传湿计算时应以毛细压力模型为主,并用其他两种模型进行内部结露验证和结果校对。     

建筑热桥三维传热的影响区域数值模拟分析

本文建立整个房间的三维围护结构模型,利用数值计算分析软件模拟墙体在典型夏季和冬季工况下的温度分布,根据计算结果分析三维传热方法和一维传热方法计算建筑物负荷的差别以及热桥的部位和热桥的影响区域.     

利用ANSYS计算异型围护结构中的热桥线传热系数

热桥对于建筑围护结构的整体节能计算、内表面的结露温度评估有着很大的影响。本文首先介绍了目前国内外建筑围护结构中热桥的传热计算方法及其研究现状,阐述了确定结构性热桥线传热系数的一般方法。然后通过对二维稳态传热模拟软件PTDA(Planar Temperature Distribution and Analysis)进行的模拟对比分析,提出了利用ANSYS有限元计算软件计算异型围护结构中热桥线传热系数的方法,该方法对实际工程节能计算起参考作用。     

大气压力变化对建筑冷热负荷的影响

利用De ST-C软件建立围护结构为双面水泥砂浆的砖墙结构的建筑模型。通过计算不同压力下建筑围护结构的热阻,找出不同风速条件下围护结构的压力变化与围护结构传热性能之间的定量关系。进而得出当大气压力从55 k Pa上升到103 k Pa时,模拟建筑的年累积冷负荷指标和热负荷指标都有不同幅度的增大。     

多层墙体内部湿迁移对传热的影响

墙体的传热传质对建筑围护结构的热工性能、建筑能耗和室内环境有着十分重要的影响。本文以相对湿度和温度为驱动势建立多层墙体一维非稳态热湿空气耦合传递模型(HAM模型),并利用有限元法进行了数值求解,重点关注了湿迁移对传热的影响机理。研究结果表明:考虑传湿时墙体内外壁面附近出湿度梯度大,相变速率大,湿流密度大;墙体内部会产生湿积累;墙体内部湿迁移主要受蒸汽扩散主导,墙体交界面处局部Nu数变化受湿迁移的影响大;相变过程对传热的影响不可以忽略。     

Simulation of coupled heat and moisture transfer in air-conditioned buildings

The simultaneous heat and moisture transfer in the building envelope has an important influence on the indoor environment and the overall performance of buildings. In this paper, a model for predicting whole building heat and moisture transfer was presented. Both heat and moisture transfer in the building envelope and indoor air were simultaneously considered; their interactions were modeled. The coupled model takes into account most of the main hygrothermal effects in buildings. The coupled system model was implemented in MATLAB-Simulink, and validated by using a series of published testing tools. The new program was applied to investigate the moisture transfer effect on indoor air humidity and building energy consumption under different climates. The results show that the use of more detailed simulation routines can result in improvements to the building's design for energy optimisation through the choice of proper hygroscopic materials, which would not be indicated by simpler calculation techniques.     

Coupling indoor airflow,HVAC, control and building envelope heat transfer in the Modelica Buildings library

This paper describes a coupled dynamic simulation of an indoor environment with heating, ventilation, and air conditioning (HVAC) systems, controls and building envelope heat transfer. The coupled simulation can be used for the design and control of ventilation systems with stratified air distributions. Those systems are commonly used to reduce building energy consumption while improving the indoor environment quality. The indoor environment was simulated using the fast fluid dynamics (FFD) simulation programme. The building fabric heat transfer, HVAC and control system were modelled using the Modelica Buildings library. After presenting the concept, the mathematical algorithm and the implementation of the coupled simulation were introduced. The coupled FFD–Modelica simulation was then evaluated using three examples of room ventilation with complex flow distributions with and without feedback control. Further research and development needs were also discussed.     

Conjugate conduction convection and radiation heat transfer through hollow autoclaved aerated concrete blocks

A computational fluid dynamics (CFD) model is developed to study thermal performance of hollow autoclaved aerated concrete (AAC) blocks in wall constructions of buildings under hot summer conditions. The goal is to determine size and distribution of cavities (within building blocks) that reduce heat flow through the walls and thereby lead to energy savings in air conditioning. The model couples conjugate, laminar natural convective flow of a viscous fluid (air) in the cavities with long-wave radiation between the cavity sides. Realistic boundary conditions were employed at the outdoor and indoor surfaces of the block. A state-of-the-art building energy simulation programme was used to determine the outdoor thermal environment that included solar radiation, equivalent temperature of the surroundings, and convective heat transfer coefficient. The CFD problem is put into dimensionless formulation and solved numerically by means of the control-volume approach. The study yielded comprehensive, detailed quantitative estimates of temperature, stream function and heat flux throughout the AAC block domain. The results show a complex dependence of heat flux through the blocks on cavity and block sizes. In general, introducing large cavities in AAC blocks, being a construction material of low thermal conductivity, leads to greater heat transfer than the corresponding solid blocks. Several small cavities in a block may lead to small reductions in heat flux, but the best configuration found is a large cavity with a fine divider mesh in which case heat flux reductions of 50% are achievable.     

Hygrothermal behavior modeling of the hygroscopic envelopes of buildings: A dynamic co-simulation approach

High levels of humidity in buildings lead to building pathologies. Moisture also has an impact on the indoor air quality and the hygrothermal comfort of the building’s occupants. To better assess these pathologies, it is necessary to take into account the heat and moisture transfer between the building envelope and its indoor ambience. In this work, a new methodology was developed to predict the overall behavior of buildings, which combines two simulation tools: COMSOL Multiphysics© and TRNSYS. The first software is used for the modeling of heat, air and moisture transfer in multilayer porous walls (HAM model: Heat, Air and Moisture transfer), and the second is used to simulate the hygrothermal behavior of the building (BES model: Building Energy Simulation). The combined software applications dynamically solve the mass and energy conservation equations of the two physical models. The HAM-BES coupling efficiency was verified. In this paper, the use of a coupled (HAM-BES) co-simulation for the prediction of the hygrothermal behavior of building envelopes is discussed. Furthermore, the effect of the 2D HAM modeling on relative humidity variations within the building ambience is shown. The results confirm the importance of the HAM modeling in the envelope on the hygrothermal behavior and energy demand of buildings.     

Coupling of thermal mass and natural ventilation in buildings

The coupling of thermal mass and natural ventilation is important to passive building design. Thermal mass can be classified as external thermal mass and internal thermal mass. Due to great diurnal variation of ambient air temperature and solar radiation intensity, heat transfer through building envelopes, which is called external thermal mass, is a complex and unsteady process. Indoor furniture are internal thermal mass, affecting the indoor air temperature through the process of absorbing and releasing heat. In this paper, a heat balance model coupling the external and internal thermal mass, natural ventilation rate and indoor air temperature for naturally ventilated building is developed. In this model, the inner surface temperature of building envelopes is obtained based on the harmonic response method. The effect of external and internal thermal mass on indoor air temperature for six external walls is discussed of different configurations including lightweight and heavy structures with and without external/internal insulation. Based on this model, a simple tool is developed to estimate the indoor air temperature for certain external and internal thermal mass and to determine the internal thermal mass needed to maintain required indoor air temperature for certain external wall for naturally ventilated building.     

浅埋地下工程间歇空调最优启停时间的神经网络控制

将影响最优启停时间的四个主要因素作为控制输入,最优启停时间作为系统输出,建立了最优启停时间的神经网络预测模型。分析了考虑岩土蓄热作用下室内热环境的变化,应用CFD模拟软件建立了采用间歇空调时室内空气与周围岩土的耦合传热模型,将模拟所得数据用来训练神经网络模型,得出的最优模型可用于预测各种复杂的非线性条件下的最优启停时间。通过一小型系统模型验证了该神经网络控制的有效性。     

采暖方式对农村住宅室内热环境影响

以农村住宅采暖房间为研究对象,分析火炕和散热器采暖方式对其室内热环境的影响。室内空气自然对流采用Boussinesq假设,辐射传输方程采用净热流法,湍流采用k-ε模型描述,建立采暖房间室内热环境数学模型,利用Fluent对火炕及散热器采暖的室内热环境进行数值模拟。     

基于缩尺模型的下送风分层空调室内热环境实验研究

大空间建筑具有体积大、高度高的特点,采用全室空调将会产生极大的能源浪费,因此,分层空调的应用越来越受到重视。考虑到实际建筑中难以人为控制各种扰量的产生,在下送风分层空调的缩尺模型实验房中进行了室内热环境的实测实验,采用电热膜模拟实际建筑通过围护结构的传热量,室内设置多个温度测点记录热环境的变化。将多个实验工况结果进行对比,分析了变送风温度、送风量以及围护结构得热量3种因素对室内热环境的影响规律,为后续大空间下送风形式分层空调的深入研究奠定基础。     

空调室内氡及粒子污染的传播及其数值模拟

室内氡(含氡子体)污染的传播与粒子(悬浮颗粒)污染在室内的传播过程相关,通风空调气流对氡及粒子污染的传播影响很大。本文详细阐述了室内氡和粒子的来源和特点、氡及其子体在空气中的传播机理以及除去方法,分析了通风空调系统对室内氡及子体传输的影响、以及氡在空气中迁移的动力学模型,分析比较了通风室内氡及粒子污染物迁移沉降过程的数值模拟方法,提出了空调气流环境下氡及粒子污染传播及其数值模拟中的关键问题。