Search

Urban Climate, 21, ISSN:2212-0955

Rural electrification projects are mostly listed as a priority in developing countries due to the numerous benefits it brings to improve people’s quality of life. The starting point for these projects is the accurate estimation of the households’ energy demand, but the large amount of resources that requires the on-site data collection makes this process unattractive to investors. This paper brings a potential solution to that matter, presenting a methodology for modelling the appliances saturation of rural households in developing countries to project their electricity demand. Based on a statistical approach, and including training data from more than 1,100 household samples from Nigeria and Ethiopia, the correlation between household survey data of saturation rates of the most common electricity-consuming appliances in developing countries and different socio-economic, demographic and geographic variables are investigated. Its accuracy is tested using other sets of validation data at a household, state, and national level. Finally, the results are projected using a Geographic Information Systems approach for identifying possible sites to be electrified. The high potential of using this approach for projecting the appliances saturation rates for rural areas was proven by obtaining a good overall accuracy in the results. As expected, the errors obtained at a household level were bigger than at a state or national level, these deviations are attributed to the presence of outliers due to the human behaviour incidence at household scale; which also affects the correlation patterns between the appliances ownership and evident socioeconomic factors., International Journal of Sustainable Energy Planning and Management, Vol 22 (2019)

A macroscopic framework to model heat transfer in materials and composites, subjected to physical degradation, is proposed. The framework employs the partition of unity concept and captures the change from conduction-dominated transfer in the initial continuum state to convection and radiation-dominated transfer in the damaged state. The underlying model can be directly linked to a mechanical cohesive zone model, governing the initiation and subsequent growth and coalescence of micro-cracks. The methodology proved to be applicable for quasi-static, periodic, and transient problems

Proceedings 18th International Symposium on Flow Visualization

This contribution discusses requirements, challenges and solutions for simulation-based design optimization of climate adaptive building shells. We compare the different needs of this approach with design optimization of conventional, static facades, and do this with a focus on achieving energy savings while improving indoor environmental quality in terms of thermal comfort and dynamic daylight performance. The solution we propose couples ESP-r with Radiance through the Building Controls Virtual Test Bed, and employs a receding horizon model-based control approach with evolutionary optimization algorithms to ensure high-performance operational façade adaptation.

We present a model coupling heat, moisture and salt transport, salt crystallization, deformation and damage in porous building materials with the aim of predicting crystallization-induced damage. The model performance is illustrated by simulating the damage caused by sodium chloride crystallization in a porous limestone. The results are compared with experimental observations based on neutron and X-ray imaging, showing a good agreement. The effective stresses that can cause damage are the result of the crystallization pressure combined with a sufficient amount of precipitating salt crystals in a localized zone. 49-59pp Seminário / SWBSS 2014 - 3rd International Conference on Salt Weathering of Buildings and Stone Sculptures DM/NBPC

The article describes a combined damage and permeability 3D model for concrete. The model aims at predicting the permeability of damaged concrete. For the mechanical model a lattice of beam elements was used in which the damage was simulated by a stepwise removal of beams. For the computation of the permeability, the beams removed were connected by transport elements with an aperture proportional to the relative displacement between the nodes previously connected by the beams. The numerical simulations were then compared with experimental results from a diffuse tensile cracking and permeability test. The results of two lattice models were compared with experimental results: i) one where the concrete was considered as a homogenous material; and ii) one where the aggregates were individually modeled. The results show that when the aggregates are included, the simulation agrees better with the test results for low strain values, while for higher strains the homogeneous model is in better agreement. 20 0 10 DM/NPC 2010 15 a 18 de Março

Three different calculation models for wind-driven rain (WDR) are compared: the semi-empirical model in the ISO standard for WDR (ISO), the semi-empirical model by Straube and Burnett (SB) and the CFD model by Choi, extended by Blocken and Carmeliet. This paper builds further on the comparison of these models for idealized building configurations and fixed wind and rain conditions in [Blocken et al., 2010. Comparison of calculation models for winddriven rain deposition on building facades, Atmospheric Environment 44(14): 1714-1725]. In the present paper, these models are applied to a high-rise monumental tower building, for a transient rain event, and the model results are compared with full-scale measurements. The agreement between the CFD results and the measurements is quite good at the upper part of the facade, while the ISO and SB model show large discrepancies at these facade positions.

The service life of building components and building materials strongly depends on their hygrothermal conditions. In this perspective, ventilated facades are employed in which a – sometimes very narrow – air gap or cavity between the rain screen and the back wall is introduced. Hygrothermal modelling of such facades requires knowledge of the air flow patterns, velocity magnitudes and ventilation rates in these cavities. These variables are determined by the complex interaction of several parameters. The following influencing parameters are distinguished: building and cavity geometry, environment topography, position of the cavity inlet and outlet openings, reference wind speed and wind direction. In the past, information on air flow in such cavities for hygrothermal modelling has been mainly obtained by simplified theoretical and/or semi-empirical expressions, which provide an estimate of the air flow rate as a function of the surfaces pressures at the inlet and outlet opening. Usually, a uniform velocity pattern is assumed in the entire cavity volume. Little is known about the actual mean air speed and turbulence intensity inside the cavity. To the knowledge of the authors, no detailed study of the relationship between these variables and the influencing parameters has yet been performed. Such detailed study would require either detailed full-scale measurements or numerical simulation with Computational Fluid Dynamics (CFD). Wind tunnel tests are considered inappropriate due to Reynolds similarity problems for the narrow cavities and the small inlet and outlet openings. This extended abstract presents preliminary results of a comprehensive CFD study on wind-induced air flow through the cavities of an exposed low-rise test house. The house exhibits different cavity assemblies for typical Scandinavian wooden claddings. A specific feature of these simulations is the full numerical simulation of both the air flow pattern around the building and the resulting flow patterns inside the cavities. The simulation results provide the relationship between cavity air change rate and cavity design, facade position, wind velocity and wind direction, and this information will be made available as input for future hygrothermal modelling efforts.

The control of the indoor relative humidity is important with respect of its influence on comfort, indoor air quality, mould growth, durability and energy consumption. One of the measures to passively control or regulate the indoor relative humidity is using the moisture buffering capacity of finishing materials. Building materials such as hygroscopic stuccos and untreated wood can be used for this purpose. In practice these materials often are treated with a paint limiting their buffer capacity. As a consequence, not only the finishing building materials, but also furnishing materials, books and magazines, cloths of curtains, pillows, blankets, etc. may contribute to the moisture buffering capacity of rooms. Recent research shows that those materials may have an important impact on the moisture buffering performance of a room and also may create stable microclimates. In this paper we focus on the role of books and textiles in order to regulate the indoor relative humidity. Measurements show that moisture buffering of books normal to the fore-edge is higher than for the paper alone, because moisture can penetrate deeply into books due to the presence of the thin air layers between the paper sheets. The vapour transport mechanism through the air layer towards the paper is found to increase substantially the possible active area for moisture buffering. In the same way, textiles have to be considered as a bunch of moisture buffering fibres in a loose air environment showing a huge active area but with limited buffering due to the small thickness. In this paper, we present an approach to describe the dynamic sorption behaviour of book and textiles using effective moisture transport properties. Experimental work includes scanning electronic microscopy (SEM) analysis of paper and textile, water vapour permeability measurements and sorption curves. Dynamic tests are also used to determine the moisture transport properties of book and textile. Using a modelling approach, the effective moisture capacity, permeability and effusivity of book and textile is determined. Finally, the effect of the presence of books and textiles in a reference room on the indoor relative humidity is examined though simulation. ispartof: Proceedings of Performance of the Exterior Envelopes of Whole Buildings X International Conference (CD-rom) ispartof: Performance of the Exterior Envelopes of Whole Buildings location:Clearwater Beach, Florida, USA date:2 Dec - 7 Dec 2007 status: published

La dynamique de fluide computationnelle (CFD) est souvent utilisée pour étudier le transfert de chaleur entre un matériau et une lame d’air puisque la CFD peut calculer avec précision le profil de vitesse dans la couche limite. Cependant, les logiciels commerciaux de CFD comportent plusieurs limites pour modéliser l’humidité dans les matériaux poreux. Conséquemment, un modèle a été développé par les auteurs pour simuler le transfert d’humidité entre une lame d’air et un matériau poreux en utilisant la CFD intégrée à un modèle de transfert de diffusion de l’humidité. Dans cet article, la CFD est utilisée pour modéliser la chaleur, le mouvement d’air et le transfert d’humidité dans l’air incluant l’échange radiatif et le transfert convectif de chaleur ainsi que la conduction de chaleur dans le matériau. Le transfert d’humidité dans le matériau est calculé en relais, à chaque pas de temps, avec un modèle complémentaire. Une étude de cas est réalisée pour un écoulement d’air laminaire au-dessus d’une éprouvette de bois.

Despite the establishment of CFD as a tool for calculating the amount of wind-driven rain (WDR) falling onto building facades, very few efforts have been made towards the validation of CFD for this purpose. This paper presents part of a detailed CFD validation study that was conducted at the Laboratory of Building Physics, supported by a new experimental wind, rain and WDR database for a low-rise building. It will be shown that numerical simulation, if conducted with care, can provide quite accurate predictions of the amount of WDR impinging on the building facade and that the main discrepancies in this case were due to a simplification of the upstream wind conditions in the numerical model.

In a PhD study on the heating of monumental churches one of the problems, which was encountered, was the damage to wooden interior parts due to the changing of the indoor climate. Particularly warm air heating frequently leads to sudden changes in relative humidity, which turned out to be dramatically hard for monumental organs during wintertime. The warm air inlet conditions and their result on the airflow and air conditions were examined experimentally and by CFD-simulation. These results provided boundary temperature and humidity conditions, to which the monumental organ was exposed. In an experimental study the response of wooden parts to changing indoor conditions was tested. In a Nuclear Magnetic Resonance (NMR) test setup the moisture content of samples was measured as a function of time and place. These moisture content changes were related to the free mechanical deformation of samples. Together with the measurement of typical material properties of wood, a two-dimensional model was developed in FlexPDE: a finite element program to solve partial differential equations simultaneously.