Preliminary investigation of a vapor-open envelope tailored for subtropical climate

Concerning global warming and resource depletion, the impact of buildings in subtropical regions is becoming even greater due to a high growth rate of urbanized areas. From the viewpoint of building physics, the main problem concerning subtropical climate is the high level of humidity in combination with high temperature. In this study, a flexible building envelope consisting of wood and clay components was developed so that the materials and the assemblies can be easily tailored to comply with local climatic conditions. The movement and accumulation of moisture in the wall was of prime concern. This has been investigated by means of testing full scale walls in a climate chamber and the corresponding one dimensional transient heat and transfer simulation. In order to achieve a consistency between calculation and measurement, the individual materials were tested for their hygric and thermal properties. Based on these findings attempts were made to calculate the behavior of an optimized wall assembly under real climatic conditions of central Japan. As a result, it was shown that the hygrothermal behavior of the envelope is predictable by means of the models and the simulation program used, and that no risk of interstitial condensation and mold growth was predicted under the real climatic conditions of Kyoto.     

建筑围护结构热湿性能模拟软件开发

建筑围护结构内的季节性湿传递是围护结构湿损坏的重要影响因素,为简单快速地评估建筑围护结构的热湿性能,基于瞬态耦合传热传湿理论开发了围护结构热湿性能模拟软件.该软件可以进行动态室内外环境参数下的围护结构热、湿特性分析,为结构工程师提供了方便快捷的判断多层墙体内可能出现冷凝的方法,从而选择合适的防护措施.并结合工程实例说明了其应用.     

Simultaneous heat and moisture transfer in soils combined with building simulation

In order to precisely predict ground heat transfer, room air temperature and humidity, a combined model has been developed and conceived to calculate both the coupled heat and moisture transfer in soil and floor and the psychrometrics condition of indoor air. The present methodology for the soil is based on the theory of Philip and De Vries, using variable thermophysical properties for different materials. The governing equations were discretized using the finite-volume method and a three-dimensional model for describing the physical phenomena of heat and mass transfer in unsaturated moist porous soils and floor. Additionally, a lumped transient approach for a building room and a finite-volume multi-layer model for the building envelope have been developed to integrate with the soil model. Results are presented in terms of temperature, humidity and heat flux at the interface between room air and the floor, showing the importance of the approach presented and the model robustness for long-term simulations with a high time step.     

生土建筑围护结构表面吸放湿过程实验研究

陕南地区的生土建筑是一种独特的民居建筑 .为了定量地研究生土建筑室内热湿环境 ,确定生土建筑围护结构表面吸放湿过程质交换系数是一项基础工作 .建筑围护结构表面的热湿迁移过程是一个典型的边界层内的流动、传热和传质过程 ,该过程的微分控制方程比较复杂 ,求解困难 .首次实验研究了生土建筑材料的等温吸放湿过程 ,提出了生土建筑围护结构表面质交换系数实验测试方法 ,实测分析计算结果与利用对流质交换相似关系计算得到的表面质交换系数比较吻合 .本研究为定量地分析生土建筑室内热湿环境奠定了科学基础     

围护结构风致连续破坏数值模拟

基于CFX5.7软件平台,对一典型大跨度空间结构进行风荷载数值模拟,研究结构模型各墙面及屋盖等围护结构存在开孔时内外压联合作用的情况。并将模拟结果与依据《建筑结构荷载规范》（GB50009—2001）中关于内部压力修正的规定得出的结果进行对比,指出规范中存在的一些不足之处。归纳出建筑物围护结构风致连续破坏的一些规律。     

Impact of climate change on residential building envelope cooling loads in subtropical climates

Future trends of cooling load due to heat gain through the building envelopes in the residential sector in subtropical Hong Kong under different emissions scenarios in the 21st century were investigated. Predicted monthly weather data from five general circulation models were gathered and analysed. An increasing trend of building envelope cooling load was observed. The average annual cooling load during the 2009-2100 period would be 6.1% and 9.8% more than that during 1979-2008 for low and medium forcing, respectively. If only the last 30 years (2071-2100) were considered, the percentage increase would be much larger at 12.3% and 21.6%. Four mitigation or energy conservation measures - raising the indoor temperature, thermal insulation, double glazing and tinted glass - were considered. Among them, raising the indoor temperature has the best mitigation potential because there is a growing awareness and recognition of adaptive thermal comfort and it can be readily applied to both existing and new buildings at no extra cost.     

极端热湿地区围护结构热湿耦合传递模型

极端热湿地区常年高温多雨,为了准确预测围护结构内的温度和湿度分布,模拟高温、高湿和高太阳辐射对围护结构的影响,建立了适用于极端热湿地区的围护结构热湿耦合传递模型,在边界条件中加入太阳辐射和雨水负荷对传热传湿的影响,考虑了随材料含湿量不断变化的材料物性参数。为了求解模型,提出了基于计算机软件COMSOL的模型求解方法,利用MATLAB计算方程组不断变化的系数,并确定了软件容差和网格的设置条件:相对容差推荐设定在0.001,绝对容差设定为0.000 1,网格按极细化划分。通过对比HAMSTAD标准实例验证了模型的准确性。     

Thermal performance evaluation of a prefabricated fiber-reinforced plastic building envelope system

Fiber-reinforced plastic (FRP) materials are extensively used in building construction, primarily due to their superior structural performance characteristics. Recently, a newly-developed concept consisting of a prefabricated, interlocking fiberglass composite panel system has been adopted for use in the construction of building envelope systems. The structural characteristics of these panels allow, among other things, expeditious construction. Other performance advantages include corrosion resistance, reduced maintenance, electric insulation characteristics, and electromagnetic transparency. Since little information is available on the thermal performance characteristics of such a panel system, a testing program was developed to investigate the thermal insulation characteristics of FRP panels that are commercially available at the present. Two full-scale 1.2 m by 1.2 m (4 ft by 4 ft) FRP panels were tested. Two panel thicknesses were considered: 25 mm (1 in.) and 75 mm (3 in.). The thermal characteristics of the panels were measured including the effects of the presence of the joints between the panels. A temperature-controlled test plate, calibrated with fibrous glass board material of known thermal conductivity, was used with heat flow sensors to determine the thermal resistance of the FRP panels at the mid-sections of panels and at the interfaces (i.e. joints) between two adjoining panels. Two conditions were simulated; ‘dry joint’ which includes only mechanical interlocking at the joints, and ‘sealed joint’ in which the joints were sealed with a commercially available sealant. The R values of the tested panels were approximately 5% to 46% higher in the sealed-joint condition. Sealed joints decrease heat exchange across the envelope system, thereby increasing the thermal resistance values of the panel system. The relatively high R value of the 75 mm panel system (2.0 (m² K)/W (11.36 (h ft² °F)/Btu)) is encouraging, and makes this envelope system a potential candidate for wider use in energy-conscious commercial buildings.     

光热建筑一体化Trombe墙体系统传热性能

为了改善建筑围护结构的保温隔热性能和利用太阳能,提出了一种光热建筑一体化Trombe墙体系统,建立了实验墙体和模拟计算模型,并对墙体系统的热传递性能进行了实验测试和模拟分析。研究结果表明:实验工况下集热板、主墙层外侧和内侧最高温度测量值分别为91.3、57.9、23.4℃,模拟值为88.4、58.3、17.2℃,墙体系统在冬季具有较好的保温性能;太阳辐射作用下,墙体系统的各材料层均产生竖向温度差,实验工况下竖向温度差为集热板17.9℃、主墙层外侧31.7℃、主墙层内侧2.2℃,模拟值为集热板17.2℃、主墙层外侧21.9℃、主墙层内侧1.2℃;墙体系统各材料表面的竖向温度差随太阳辐射照度增加而增大,随空气夹层厚度增大而减小。     

Efficient solution strategies for building energy system simulation

The efficiencies of methods employed in solution of building simulation models are considered and compared by means of benchmark testing. Direct comparisons between the Simulation Problem Analysis and Research Kernel (SPARK) and the HVACSIM+ programs are presented, as are results for SPARK versus conventional and sparse matrix methods. An indirect comparison between SPARK and the IDA program is carried out by solving one of the benchmark test suite problems using the sparse methods employed in that program. The test suite consisted of two problems chosen to span the range of expected performance advantage. SPARK execution times versus problem size are compared to those obtained with conventional and sparse matrix implementations of these problems. Then, to see if the results of these limiting cases extend to actual problems in building simulation, a detailed control system for a heating, ventilating and air conditioning (HVAC) system is simulated with and without the use of SPARK cut set reduction. Execution times for the reduced and non-reduced SPARK models are compared with those for an HVACSIM+ model of the same system. Results show that the graph-theoretic techniques employed in SPARK offer significant speed advantages over the other methods for significantly reducible problems and that by using sparse methods in combination with graph-theoretic methods even problem portions with little reduction potential can be solved efficiently.     

研制高层建筑结构多媒体仿真系统的关键技术

介绍了高层建筑结构多媒体仿真的基本思路,探讨了仿真分析的数学物理模型、开发工具和关键技术,并简述了高层建筑结构多媒体仿真系统MSTB的设计特点.     

Advancement of solar desiccant cooling system for building use in subtropical Hong Kong

The solar desiccant cooling system (SDCS) had a saving potential of the year-round primary energy consumption as compared to the conventional air-conditioning system for full fresh air application in the subtropical Hong Kong. In order to further enhance its energy efficiency, advancement of the basic SDCS was carried out through a strategy of hybrid design. Six hybrid system alternatives of SDCS were therefore proposed, three for full fresh air design while another three for return air design for the building zone. Year-round performance evaluation of each solar hybrid desiccant cooling system was conducted for typical office application under different climatic and loading conditions. All the six hybrid system alternatives were found technically feasible, with up to 35.2% saving of year-round primary energy consumption against the conventional air-conditioning systems. Among the hybrid alternatives, recommendations were made on the SDCS hybridized with vapour compression refrigeration for full fresh air design; and the SDCS hybridized with vapour absorption refrigeration for return air design, since they had the saving potentials of both primary energy and initial cost. These two hybrid system alternatives used evacuated tubes, a more economical type of solar collectors compared to the PV or PVT panels.     

泥水平衡式盾构模拟试验系统的研制与应用

为了探究泥水盾构水下掘进控制和泥水平衡机理等问题,在调研国内外模型盾构设备的基础上确定泥水盾构的基本参数和工作模式,研制出泥水平衡盾构模拟试验系统,包括模型箱、盾构机总成、推进机构、液压动力系统、操作系统、深冷装置等主要部分。该系统可对最高100 m水头条件下泥水平衡盾构施工的主要过程进行模拟,可较真实地再现泥水平衡盾构掘进过程中泥膜的动态形成过程,从而阐明水土压力平衡的机理等关键技术问题,并可为泥水平衡盾构的设计和控制提供重要参数。以砂卵石地层为例配制相似地层和泥浆,并进行盾构试掘进,对设备的功能性进行验证,并初步研究了泥水盾构掘进过程中地表位移的时空变化规律和地层中泥膜的形态。结果表明,由于刀盘无超挖且地层开挖后直接由盾壳支撑,土体移动受到限制,地层变形主要由开挖导致的应力释放产生。排渣装置长度较长,可暂存的渣土量多,使得盾构通过前地表沉降随顶推力和刀盘、排渣装置转速的增大而增大;盾构通过后的地表沉降则由于盾壳与土体的摩擦作用有所减小。在盾构刀盘前方,泥浆渗入地层的范围大致关于盾构轴线对称,泥膜形态呈倒扣的"锅底"形分布,其范围约占刀盘外径的20%~43%。     

Impact of combined moisture buffering capacity of a hemp concrete building envelope and interior objects on the hygrothermal performance in a room

In this article, a hygrothermal building model, taking into account the building envelope, indoor heat and moisture sources, indoor environment and moisture buffering capacity of interior objects, is presented and validated with the test cases found in the literature. The model is used to study the impact of hemp concrete and the moisture buffer capacity of the interior elements on the prediction of the hygrothermal comfort in the building. The numerical results show that the use of hemp concrete in buildings can ensure good hygrothermal comfort. Besides, taking into account the effect of moisture buffering of indoor objects increases the building performance. Our results also suggest that neglecting moisture transfer through the envelope increases significantly the predicted percentage of dissatisfied indices and reduces the acceptability of indoor air quality during the occupied period. This study also confirmed that the combined relative humidity-sensitive ventilation system and moisture buffering capacity of building envelope and of interior objects is a very efficient way to reduce the heating energy consumption.     

建筑供暖系统的水力平衡与节能

本文对供暖系统导致能耗增加的原因进行了分析，并说明降低水力失调度能有效减少供暖系统的能耗。对静态流量平衡阀与动态流量平衡阀的原理、特性，以及各自的作用进行了分析。对供暖系统不同类型的水力调节特点进行了分析。     

Evaluation of a prototype active building envelope window-system

Active building envelope systems represent a new enclosure technology that uses solar energy to compensate for passive heat losses or gains through building envelopes. In ABE systems, energy obtained from solar radiation is converted into electrical energy by using photovoltaic cells. This electrical energy is subsequently used to power a series of solid-state thermoelectric modules, which can control the flow of heat through the enclosure. In order to assess the practical feasibility of ABE systems, we have developed a prototype ABE window-system and an outdoor testing room. A testing system was developed to measure the ABE system's temperatures, solar radiation, current and voltage. Theoretical and experimental results are presented and compared. Finally, the performance of the ABE window-system was evaluated.     

某公共建筑外围护结构节能潜力分析

以夏热冬冷地区某酒店为例,对建筑全年的空调动态负荷及能耗进行了计算分析。给出了采用几种不同方案时建筑及房间的负荷和能耗计算结果,分析了夏热冬冷地区宾馆类公共建筑外围护结构的节能潜力。     

Fast simulation of dynamic heat transfer through building envelope via model order reduction

In this paper, a fast and accurate numerical simulation method on dynamic heat transfer through building envelopes has been developed by using the Krylov subspace and the balanced truncation model order reduction (MOR) algorithms. The computational accuracy and efficiency of the two MOR algorithms are discussed through the numerical simulation on a roof heat transfer in a one-day period, and then the two verified algorithms are applied to simulate the heat transfer through a multilayer wall for a week and the two-dimensional heat transfer through an L-shape thermal bridge. The results show that the relative errors of the two algorithms to the harmonic response method or to the direct solution method are all less than 1%, and the solving time with the two MOR algorithms decreases greatly. In addition, the Krylov subspace MOR algorithm has a faster solving speed and is more suitable for solving the heat transfer through a building envelope than the balanced truncation MOR algorithm.     

Proposed approach for defining climate regions for Turkey based on annual driving rain index and heating degree-days for building envelope design

Field surveys in Turkey indicate that a significant number of exterior wall assemblies in various regions of the country suffer from moisture degradation. These cases reveal that designers are in need for a climate scheme of Turkey, which indicates regions that require special provisions to prevent moisture degradation. Hence, this paper presents an approach for defining climate regions for Turkey. Initially, annual driving rain index (aDRI) based on monthly data is calculated and a driving rain map of Turkey is produced. Then, population-weighted heating degree-days (PW HDD) zones of Turkey are presented. Based on the aDRI and PW HDD zones, three climate regions of Turkey are established. Region 1 represents sheltered locations, i.e. locations which have aDRI less than 3. Region 2 represents locations (aDRI between 3 and 6 and PW HDD<1600), which are exposed to moderate driving rain between September and the end of May when the mean temperatures are above zero. Region 3 includes locations (aDRI between 3 and 6 and PW HDD between 1601 and 2500) which are moderately exposed to driving rain all throughout the year when the mean temperature is well above zero. As a conclusion, the proposed climate regions suggest that the design of wall assemblies located at Regions 2 and 3 must incorporate special provisions to prevent moisture degradation.     

Development of HAM tool for building envelope analysis

Moisture-related building envelope failures have resulted in costly rehabilitation in various regions of North America. To advance building envelope design towards an engineering approach and reduce the occurrence of future failures, an advanced numerical tool was developed, in conjunction with an extensive full-scale experiment, to investigate hygrothermal performance of various wood-frame wall assemblies. Major features of the tool are multi-dimensional and transient coupling of heat and moisture transport; natural air convection integrated in hygrothermal simulation through Darcy–Boussinesq approximation; heat transfer by conduction and convection of sensible and latent heat; moisture transport by vapor diffusion, capillary suction and convection; material database of common building materials in North America; experimental settings or weather data as boundary conditions; and moisture added in the building envelope to simulate the wetting process. The numerical tool achieves good compliances to the benchmarking cases of the HAMSTAD project, and its predictions have shown good agreement with data from the full-scale wall experiment. The numerical tool employs the commercial finite-element software to solve the governing equations. This approach provides building science researchers the flexibility to modify, maintain and share their modeling work efficiently.