Heat flux from flames to vertical surfaces

Dimensional analysis is used to examine heat transfer from flames to vertical surfaces. Configurations include a line fire against a wall, a square burner flame against a wall and in a corner, and window flames impinging on a wall. Dimensionless parameters that affect flame heat flux include/l _f ,y/D,l _f /D andkD where is vertical distance,y is horizontal distance,l _f is flame length,D is burner dimension, andk is the flame absorption coefficient. Only the effect of these variables is shown. No general correlation is developed, and more data are needed before these results can be applied with confidence.This paper is a contribution of the National Institute of Standards and Technology and is not subject to copyright.     

Heat and moisture transfer through cold-store walls

The building of an experimental cold-store at a commercial growers' premises in the UK provided an opportunity to measure the behaviour of vapour barrier and insulation in a working setting. The bitumastic vapour barrier was found not to prevent migration of water vapour ; it is therefore suggested that a practical solution would be to design for the eventual escape of most of the resulting moisture.     

Burning rates and heat transfer from wind-blown flames

In the first of this two-part series, the authors discussed the effects of wind on flame bending and trailing. This paper describes investigations of liquid fuel burning rates, flame lengths, wake gas temperatures, and flame radiation. Data are taken from the liquid pool fires described in the earlier article. Note: This is the second of two papers reporting work that was supported in part by the Office of Civil Defense, Department of the Army throgh a contract with the National Bureau of Standards.     

Analysis of convective heat and mass transfer at the vertical walls of a street canyon

The combined effects of urbanization and global climate warming give rise to increased temperatures in urbanized areas, a phenomenon called the urban heat island effect. The higher air temperatures have a negative impact on the energy demand for cooling and on the comfort and health of the people residing in urban areas. One way to mitigate the excess heat in urban areas is to make use of evaporative cooling, for example from ponds, from surfaces wetted by wind-driven rain, or from vegetated surfaces. Therefore understanding the interaction between the urban microclimate and evaporation processes is of interest. In the current paper, a two-step methodology for the simulation of drying processes is proposed and subsequently applied to study the drying behavior of both vertical walls of a square-shaped street canyon. Simulation results reveal the importance of using location-dependent convective heat and mass transfer coefficients (CHTC and CMTC) to capture the spatially non-uniform drying behavior of the wall. Whether the CMTC is obtained via Computational Fluid Dynamics simulations or via a simplified method based on the Chilton-Colburn analogy only slightly affects the drying behavior. The potential for evaporative cooling of wet walls in a hot climate is demonstrated in a final example.     

有翼缘和竖向荷载的带洞口木框架剪力墙的试验研究

轻型木结构房屋在我国尚处于发展阶段,木框架剪力墙试验的目的是为我国轻型木结构房屋的推广和规范的修订提供理论和试验依据。木框架剪力墙是轻型木结构房屋中的主要抗侧力构件,研究木剪力墙的力学性能和黏滞阻尼特性是木结构房屋整体分析的基础。通过6片2.4m高6.0m长的无墙角锚栓的传统木框架剪力墙的单向和反复荷载试验,研究了竖向荷载、翼缘墙体和洞口尺寸对剪力墙的抗剪强度、弹性抗侧刚度、极限位移、墙骨柱上拔和耗能等的影响。结果表明,作用于横墙上的竖向荷载可以显著地提高剪力墙的各项性能,作用于翼缘墙体上的竖向荷载可以降低端部墙骨柱的上拔和部分提高剪力墙的抗剪强度和耗能,洞口尺寸的变化主要影响到墙体的极限位移。试件的破坏形态主要是钉节点的破坏和端部墙骨柱的上拔。     

对集中供暖系统户间传热量问题的分析

分析了户间传热量与建筑物内外围护结构保温隔热性能之间的关系。提出为了减少户间传热量,以利实施分户热计量和分户热收费,应进一步提高建筑物外围护结构的保温水平,对内围护结构采取必要隔热措施也是势在必行,并就此提出具体建议。     

竖直纵向肋片管自然对流传热特性试验研究及结构优化

利用搭建的试验台对竖直放置的纵向肋片管的传热特性进行试验,获得了相同结构参数下肋片形式分别是开放式、平端面封闭式和弧形端面封闭式下的散热量,单位质量散热量和金属热强度。对不同的肋片管,利用正交试验得到了各因素对散热量和单位质量散热量的影响程度,并获得了试验条件下肋片管的最优结构。     

分户热计量户间传热问题的探讨

分析了不同因素对户间传热的影响情况,以及因户间传热负荷给设计采暖负荷、采暖设备设计选型、用户使用、投资增加等带来的问题,并提出解决问题的措施。     

Thermal evaluation of vertical greenery systems for building walls

This research involves the study of 8 different vertical greenery systems (VGSs) installed in HortPark to evaluate the thermal impacts on the performance of buildings and their immediate environment based on the surface and ambient temperatures. VGSs 3 and 4 have the best cooling efficiency according to the maximum temperature reduction of the wall and substrate surfaces. These results point to the potential thermal benefits of vertical greenery systems in reducing the surface temperature of buildings facades in the tropical climate, leading to a reduction in the cooling load and energy cost. In terms of the lowest diurnal range of average wall surface temperature fluctuation, VGSs 4 and 1 show the highest capacities. No vertical greenery system performs well in term of the diurnal range of average substrate temperature fluctuation. By limiting the diurnal fluctuation of wall surface temperatures, the lifespan of building facades is prolonged, slowing down wear and tear as well as savings in maintenance cost and the replacement of façade parts. The effects of vertical greenery systems on ambient temperature are found to depend on specific vertical greenery systems. VGS 2 has hardly any effect on the ambient temperature while the effects of VGS 4 are felt as far as 0.60 m away. Given the preponderance of wall facades in the built environment, the use of vertical greenery systems to cool the ambient temperature in building canyons is promising. Furthermore, air intakes of air-conditioning at a cooler ambient temperature translate into saving in energy cooling load.     

Acoustics evaluation of vertical greenery systems for building walls

After decades of fast growth, the scarcity of land in cities causes many buildings to be constructed very close to expressways, exposing occupants to serious noise pollution. In recent years, sustainable cities have found that greenery is a key element in addressing this noise pollution, giving rise to the popularity of vertical greenery systems (VGS). This research has two objectives. The first involves the study of eight different vertical greenery systems installed in HortPark, Singapore to evaluate their acoustics impacts on the insertion loss of building walls. Experiment shows a stronger attenuation at low to middle frequencies due to the absorbing effect of substrate while a smaller attenuation is observed at high frequencies due to scattering from greenery. Generally, VGS 2, 7 and 8 exhibit relatively better insertion loss. The second objective aims to determine the sound absorption coefficient of the vertical greenery system constructed in the reverberation chamber which is found to have one of the highest values compared with other building materials and furnishings. Furthermore, as frequencies increases, the sound absorption coefficient increases. In addition, it is observed that the sound absorption coefficient increases with greater greenery coverage.     

Heat conduction across double brick walls via BEM

The Boundary Element Method (BEM) is used to compare the steady-state heat and moisture diffusion behaviour across double brick walls provided by two different models: in the first one, the brick wall is assumed to be composed of a set of homogeneous layers bonded together, which is the model frequently used to predict internal condensation; in the second model, the geometrical modelling and hygrothermal properties of the individual bricks are taken into account.The BEM is implemented allowing the use of multi boundaries, which permits the full discretization of the brick cavities.Three different construction solutions are analysed. In the first, the double-brick wall is assumed not to be thermally insulated; in the second, the space between the two layers of bricks is filled with thermal insulation material; in the third solution, both the space between the brick layers and the holes of the inner brick layer are filled with thermal insulating material.     

户间传热与面积份摊百分数的取值分析

户间传热是集中供暖热计量中的一个技术难题。目前我国采取的解决办法是将系统总供热量中的一部分按各户建筑面积进行分摊,这部分热量占系统总供热量在百分数称为面积分摊百分数。对面积分摊百分数的影响因素进行了计算分析和灵敏度分析,认为户型、室内平均温度、换气次数对面积分摊百分数的影响较大,较为合理的数值范围是30%～45%。     

CL保温外墙的热传导分析

通过试验,测试分析了CL外墙、粉煤灰外墙、普通外墙的热传导性,并采用有限元分析软件,数值模拟了三种墙体的热流密度及传热后的内壁温度,同时对比了实测值与模拟结果,指出CL墙体具有良好的保温节能性。     

A phoenix from the flames

In this detailed account of an unusual project in Pondicherry, India, the celebrated Dutch ceramic artist and sculptor describes the building of a small, vaulted brick house. The house, however, was built with 'green' bricks; it was used as a kiln for the firing of a pile of other green bricks and tiles so that, after firing, the house itself would be transformed into a structure of hardened fired-clay bricks. The experiment took place at the Golden Bridge Pottery, established by American potters Ray Meeker and Deborah Smith some sixteen years ago. The author's consultancy role in the project was grant-aided by the Dutch government.     

Graybody radiation from conical flames

The spatial dependence of graybody radiation from a cone, the shape representative of small flames, has been computed. A comparison of the radiative heat flux from this model and experimental measurements of the total heat flux from a flame indicate that up to 74 percent of the total emitted intensity is radiative.     

A phoenix from the flames

In this detailed account of an unusual project in Pondicherry, India, the celebrated Dutch ceramic artist and sculptor describes the building of a small, vaulted brick house. The house, however, was built with ‘green’ bricks; it was used as a kiln for the firing of a pile of other green bricks and tiles so that, after firing, the house itself would be transformed into a structure of hardened fired‐clay bricks. The experiment took place at the Golden Bridge Pottery, established by American potters Ray Meeker and Deborah Smith some sixteen years ago. The author's consultancy role in the project was grant‐aided by the Dutch government.     

Damaged masonry walls in two-way bending retrofitted with vertical FRP strips

Unreinforced masonry (hereafter termed ‘masonry’) structures comprise a significant proportion of the building stock in many countries worldwide, however their walls do not behave well under out-of-plane loading, such as that experienced during seismic events. Consequently, many existing masonry structures require some form of retrofit to comply with existing codes. As part of ongoing research at The University of Adelaide on the out-of-plane bending behaviour of masonry walls, eight full-scale walls (with window openings) were tested under reversed-cyclic loading. Four of the severely damaged walls were subsequently retrofitted using externally bonded (EB) (three walls) and near-surface mounted (NSM) (one wall) fibre-reinforced polymer (FRP) strips and tested again to quantify the increase in strength and ductility relative to the original capacities. A debonding mechanism not yet quantified for retrofitted masonry walls was observed and identified as displacement induced (DI) debonding. It is a result of a differential out-of-plane displacement at either side of a crack in the wall. NSM strips are more susceptible due to their orientation. This paper presents the results of the wall tests along with detailed accounts of the wall failure modes.     

Nonlinear behavior of composite shear walls with vertical steel encased profiles

Research on seismic engineering of buildings using composite steel-concrete structural systems has increased in the past decade. One horizontal resisting system for buildings, placed in seismic areas, is the composite steel-concrete structural shear wall with steel encased profiles (CSRCW). The benefits of this structural system, relative to more common systems, include the performance characteristics when subjected to service or ultimate loads. The present paper summarizes the experimental results of recent research made on six experimental steel-concrete composite elements 1:3 scale, tested in laboratory under cyclic lateral loads. The experimental elements differ by the arrangement of the steel shapes embedded in the cross section of the wall and by the cross section type of the steel encased profiles. All specimens were tested under constant vertical load and cyclically increasing horizontal (lateral) loads. The tests were performed until failure. Using the recorded data during the tests, the following parameters are presented and discussed: maximum load capacity, stress and strain distribution in structural components (reinforcements, structural steel and on concrete surface), interstory drifts, cracking patterns, deformation and degradation capacity.