岩土热物性集总热阻计量模型及其求解体系

由于地埋管周围岩土体状况的复杂性及由此导致的回归分析时统计性误差影响等原因,根据现有岩土热物性传热模型及热响应试验不能精确求解岩土热物性。探讨了消除解释变量性质影响的岩土集总热阻分析方法,并通过计量学误差分析体系进一步建立了岩土集总热阻计量模型,摆脱了相关不确定扰动的复杂影响,将这一传热问题转变为热工计量分析问题,根据逐时集总热阻即可计算出在各种进出口温度及初始土壤温度条件下的逐时单位管长换热量。以多个工程实测结果验证了该模型及其求解体系的有效性。     

气泡混凝土降温性能的试验研究及数值模拟

在解决夏季城市热岛效应和楼顶层高温的方法中,屋顶绿化和含水砂层等都有较好的降温效果,但是分别存在着价格昂贵、维护不便等缺点,因此在工程推广中受到限制.气泡混凝土具有价格便宜且维护简单的优点,并且之前的研究已经体现出了它具有良好蒸发降温性能的潜质.通过对不同吸水性能的气泡混凝土降温性能的试验研究,找出气泡混凝土降温与吸水性能之间的关系,为不同的工程需求提供一定的参考建议;并运用多孔介质热湿迁移模型对其蒸发降温过程进行数值模拟,在用部分试验数据验证数值模型的正确性后,使用此模型对剩余试验数据进行预测,并达到了良好的预测效果.     

A relation between calculated human body exergy consumption rate and subjectively assessed thermal sensation

Application of the exergy concept to research on the built environment is a relatively new approach. It helps to optimize climate conditioning systems so that they meet the requirements of sustainable building design. As the building should provide a healthy and comfortable environment for its occupants, it is reasonable to consider both the exergy flows in building and those within the human body.Until now, no data have been available on the relation between human-body exergy consumption rates and subjectively assessed thermal sensation. The objective of the present work was to relate thermal sensation data, from earlier thermal comfort studies, to calculated human-body exergy consumption rates.The results show that the minimum human body exergy consumption rate is associated with thermal sensation votes close to thermal neutrality, tending to the slightly cool side of thermal sensation.Generally, the relationship between air temperature and the exergy consumption rate, as a first approximation, shows an increasing trend. Taking account of both convective and radiative heat exchange between the human body and the surrounding environment by using the calculated operative temperature, exergy consumption rates increase as the operative temperature increases above 24 °C or decreases below 22 °C. With the data available so far, a second-order polynomial relationship between thermal sensation and the exergy consumption rate was established.     

Year-round numerical simulation of a parabolic solar collector under Lebanese conditions: Beirut case study

A detailed thermal and optical numerical model is developed to simulate the performance of a small-scale parabolic collector having an evacuated receiver line with selective coating, taking into account different energy balances and interactions with the surrounding. An analytical model is developed to estimate the direct, diffuse and global solar radiation intensities on inclined surfaces. The collector performance model was validated using published experimental data. A year-round dynamic simulation for the collector performance under Beirut climatic conditions was carried out with an economic and environmental analysis. The outlet water temperature could reach a maximum of 114°C in July and 52°C in December by employing a collector of about 6 m² aperture area with 0.01 kg/s water flow rate. The maximum daily thermal energy production is attained in July with 22.267 kWh while January exhibits the lowest thermal energy production with 6.704 kWh per day with a maximum thermal efficiency of 72%.     

一种新型墙体热工测试系统的研究

通过对现有建筑维护结构的传热系数现场检测技术的分析与研究,提出了一种新型的墙体传热系数现场检测系统.采用此新型系统对不同厚度的XPS保温板和墙体进行现场测试,将测试结果与理论值进行对比,检验了此系统的可行性以及准确性.并且在检测XPS保温板传热系数时进行了温度修正,提高测试系统的精确度.     

A new simplified thermoregulatory bioheat model for evaluating thermal response of the human body to transient environments

Thermal response of the human cutaneous thermoreceptors depends statically upon temperature and dynamically on the temperature change rate at the depth of the thermoreceptors. Therefore, it is very important to estimate the time-dependent thermoreceptors temperature with a good accuracy. On the other hand, the temperature distribution in skin tissue may be significantly affected by thermoregulatory mechanisms such as shivering, regulatory sweating and vasomotion. In the present study, a new simplified thermoregulatory bioheat model is proposed to describe heat transfer in skin tissue. The new model is constructed by combining the well-known Pennes equations with Gagge’s two-node model. In this model, the human skin is subdivided into three layers (epidermis, dermis and subcutaneous) and the time-dependent temperature of skin tissue is obtained by solving the bioheat equations taking into account thermoregulatory mechanisms. The model has been verified by extensive comparisons with the published analytical and experimental results where a good agreement was found. Therefore, the present model can estimate the skin temperature under transient environments with a very good accuracy.     

Radiative and convective heat transfer coefficients of the human body in natural convection

The purpose of this study was to investigate the convective and radiative heat transfer coefficients of the human body, while focusing on the convective heat transfer area of the human body. Thermal sensors directly measuring the total heat flux and radiative heat flux were employed. The mannequin was placed in seven postures as follows: standing (exposed to the atmosphere, floor contact); chair sitting (exposed to the atmosphere, contact with seat, chair back, and floor); cross-legged sitting (floor contact); legs-out sitting (floor contact); and supine (floor contact). The radiative heat transfer coefficient was determined for each posture, and empirical formulas were proposed for the convective heat transfer coefficient of the entire human body under natural convection, driven by the difference between the air temperature and mean skin temperature corrected using the convective heat transfer area.     

A simple method for estimating transient heat transfer in slab-on-ground floors

The problem of calculating transient heat transfer in concrete floor slabs is complicated due to ground coupling, which can require the numerical solution of two or three-dimensional transient conduction equations. This paper presents a simplified method for calculating transient slab-on-ground heat transfer that can be incorporated within hourly simulation programs. The method assumes that there are two primary one-dimensional paths for heat transfer from a ground-coupled floor slab: (1) one-dimensional heat transfer from the perimeter of the slab to the ambient and (2) one-dimensional heat transfer between the slab interior surface and a portion of the soil beneath the slab. The perimeter heat transfer is assumed to occur at quasi-steady state and is characterized in terms of a perimeter heat loss factor (F_p). Transient heat transfer within the slab and ground are modeled using a simple thermal circuit employing three nodes with an adiabatic boundary condition at a specified depth within the soil underneath the slab. Although some simulation models consider this type of two-path model, there appears to be no validation of this approach and there is no guidance for specifying perimeter heat loss factors and underfloor soil depths and node locations for the thermal circuit. In the current paper, results from detailed two-dimensional finite-element models for typical floor constructions and soil properties were used to identify (1) locations for nodes within the slab and soil, (2) correlations for soil depth as a function of soil properties associated with the underfloor adiabatic boundary condition, and (3) correlations for perimeter heat loss factor as a function of soil properties and edge insulation levels for different constructions. Transient heat transfer results from the simple model compared well with results from the finite-element program for different floor constructions, edge insulation, soil properties, locations, and times of year.     

平翅片表面流动和换热的数值模拟研究

利用Fluent软件,采用加密的六面体和四面体网格,建立了翅片管式换热器用矩形平翅片的三维物理模型,对空气内掠翅片表面的流动与换热进行数值模拟求解,得到其在不同风速下的速度场、温度场和努谢尔特数分布,模拟结果与实验数据进行了比较,模拟值偏大,但最大相对误差不超过10．8％。     

陶粒泡沫混凝土热工性能试验研究

采用对比试验的方法对填筑陶粒泡沫混凝土的砌块和填筑普通混凝土的砌块的热工性能进行同条件的室内试验。对比试验结果得到,填筑陶粒泡沫混凝土的砌块传热系数平均值为0.922 W/(m²·K),满足相应规范要求,与填筑普通混凝土的砌块相比,传热系数降低了19.5%,改善砌体结构的保温性能。另外,陶粒泡沫混凝土和普通混凝土填筑的砌体均存在热桥效应,且热桥效应相近,增加了砌体的热阻,而填筑陶粒泡沫混凝土的砌块热桥效应并没有比填筑普通混凝土的砌块热桥效应更显著。     

A design supporting simulation system for predicting and evaluating the cool microclimate creating effect of passive evaporative cooling walls

As a passive cooling strategy to control increased surface temperatures and create cooler urban environments, we have developed a passive evaporative cooling wall (PECW) constructed of pipe-shaped ceramics that possess a capillary force to absorb water up to a level higher than 130 cm. The current paper presents a simulation system to predict and evaluate microclimatic modifying effects of PECWs in urban locations where PECW installation is under consideration at the design stage. This simulation system is composed of a CFD simulation tool and a 3D-CAD-based thermal simulation tool. Simulation methodology of coupling the two simulation tools was developed and described in this paper. Numerical models for simulating surface temperatures and evaporation of PECWs were proposed based on analysis results of experimental data. Validation of the proposed numerical models was confirmed by comparing simulated results with measured data. In order to demonstrate the applicability of the proposed simulation system, a case study was then performed to predict and evaluate the microclimate in a rest station where PECWs were assumed to be installed. Spatial distributions of air temperature, airflow, moisture and surface temperature in the rest station were simulated under a sunny weather condition in the summer of Tokyo. Furthermore, thermal comfort indexes (mean radiant temperature and new standard effective temperature) were used to evaluate thermal comfort in the human activity spaces of the rest station. Simulation results show that this simulation system can provide quantitative predictions and evaluations of microclimatic modifying effects resulting from the application of PECWs.     

U形地埋管换热器的三维数值模拟及传热分析

利用非稳态流动能量守恒方程得到了U形管内流体温度沿管轴向的变化关系,建立了U形地埋管换热器与土壤耦合换热的三维数值模型.把数值解分别与解析解和TRNSYS中的DST模型进行了对比,得出利用数值模型可以提高瞬时传热模拟结果精确度的结论.分析了在给定外界负荷的情况下U形管进出水温度、释热量和外界负荷之间的相互关系.     

忽略回填料与岩土热物性差异对桩基埋管换热计算的影响

桩基埋管换热器具有桩径大、埋深浅的特点,适用于桩基埋管特点的系列导热解析解模型被不断提出,但是该类模型均忽略了回填料与岩土热物性的差异。对于桩径较大的桩基埋管而言,较大的热物性差异将引起较大的计算误差。建立了区别回填料与岩土热物性差异的导热数值解模型,对比分析忽略热物性差异对桩基埋管换热计算的影响,研究表明:导热系数差异对桩基埋管长时间运行的换热热阻计算影响甚小;容积比热差异将引起桩基埋管较大的设计容量误差;桩径越大,热物性差异引起的计算误差越显著。     

土体一维传热方程解析解及热扩散系数测定

传热方程是一类常见的基本数学物理方程,热导率是土体重要的热物理参数。从基本传热方程出发,详细地推导了利用傅立叶级数求解一维传热方程的方法,以地面温度随时间变化的波动方程得到地下不同深度处土体温度分布的解析解。在此基础上,讨论了利用热导率进行土体含水率测量的基本原理,详细地推导了根据地下不同深度的温度计算土体热扩散系数的振幅法、相位法及其应用,介绍了利用传热方程进行数值模拟的计算原理。最后结合实例介绍了该方法的应用效果。     

三种复合墙体构造的热工性能分析

鉴于夏热冬冷地区的气候特点．针对外保温、内保温和复合墙板的保温三种不同的保温形式,计算墙体构造特性,建立ANSYS有限元模型对比分析不同构造墙体的热工性能。模拟结果表明：外保温墙体的温度波衰减度大,延迟时间更长,抵抗室外温度波变化能力强,热稳定性更好。     

Cool roofs impact on building thermal response: A French case study

The refurbishment of building roofs with cool selective coatings is already defined by some standards. Impacts on urban heat island (UHI) and thermal performance of buildings are well identified. In France, most of the developments on building thermal performances are focused on the building envelope insulation, especially for the winter energy performance, and the cool roof technique as a part of the solution for summer conditions is not well established. This passive technique for cooling the cities and indoor environments has a performance depending on the climatic location and constructions morphology. In this paper, we focus on a case study in Poitiers (France): a cool roof for a low-rise building (public housing), without any cooling active system.The performance of the cool coating is detailed through experimental results, completed by a dynamic simulation work on the studied building. In a first part, the case study is presented; the surface temperatures and the climatic conditions were monitored indoor and outdoor. Then, a dynamic simulation for the summer period is compared to the experimental results. This audit study of the actual case study permits the analysis extension of thermal condition in order to compare the performance of the envelope toward the cool roof. This first case study analysis will help understanding the cool roof potential and limitations in a French context. These results will have to be projected for various construction typologies in order to help its development in the different climatic regions. It will be also a part of different European climate first comparison through the work of the EU cool roof project.     

双流体模型气液传质数值模拟初探

以实验测量和数值模拟相结合的方式对气液传质的流体力学行为进行了系统的研究,从更深层次上揭示了气液体系的流动机制,得出了气含率径向分布规律,对气液传质研究具有重要意义。     

建筑物排热对城市区域热气候影响的长期动态模拟及分析

探讨了城市特定区域内热气候的形成机理,特别是建筑物排热在热气候形成中所起的作用,对于从建筑角度减缓城市高温化进程和热岛效应、有针对性地提出改善室外热舒适环境、降低建筑能耗的方法具有重要意义。以南方某典型城市实际大型CBD规划改造项目为研究对象,利用已建立的城市区域热气候预测模型,通过长期动态模拟,分析了城市化后室外热气候特征及室外热平衡规律。结果表明,夏季下垫面传热和空调冷源系统排热分别是城市气候逐渐向高温高湿化发展的主要成因。     

建筑环境设计模拟分析软件DeST第2讲建筑动态热过程模型

介绍了DeST中基于状态空间法建立的建筑动态热过程模型。首先介绍了建立建筑热过程模型中的主要问题和基本方程，指出建立建筑热动态模型必须求解壁体传热的偏微分方程，必须同时考虑构成房间的各个部件的影响以及房间之间的相互影响。以此为前提，详细介绍了DeST对这些问题的处理方法和具体算法，并以实例阐明DeST对建筑热环境的模拟分析。最后为了突出状态空间法的特点，从算法和建立动态热过程模型的方式上对该方法与其他几种方法进行了比较。