Aplicação de CFD para o cálculo de coeficientes de pressão externos nas aberturas de um edifício = Application of CFD simulations for the calculation of external wind pressure coefficients on openings of a building

Pressure coefficients (Cp) are a key parameter in the study of wind-driven natural ventilation in buildings. This paper reports the results of a research study aimed at evaluating the feasility of using CFD (Computational Fluid Dynamics) to obtain Cp data and also evaluating the importance of some of the aspects of the simulation setup in the results obtained. The following aspects are addressed: mesh independence, sensitivity to the wind profile and to the roughness of the domain floor. Values of y+ are discussed, and surface-averaged Cp values from the literature are compared to local Cp calculated by CFD. The building used in the simulations is a 5 storey, isolated building, typically adopted in social housing projects in Brazil. This paper concludes that CFD simulations are feasible and constitute an important alternative to obtain Cp values when compared to wind tunnel experiments. However, differences in the simulation setup may lead to significant deviations in the results, both in absolute values (up to ± 0.5) and in relative values (up to 50%). The mesh independence test has proven to be fundamental for a reliable simulation. The same applies for the inlet wind profile definition. Future work should focus on the validation of simulations

Simulation support for research and development of advanced building skin concepts

Innovations in high-performance building envelope components are an essential step towards reaching the ambitious targets for a more sustainable built environment. Enhancing product development workflows can turn out to be an invaluable resource in this process. In this paper we illustrate how building performance simulation (BPS) can be used to support research and development activities for innovative building skin concepts. The key opportunity lies in assisting informed decision-making. The increased availability of information on whole-building performance can be used as a resource for communication with internal and external stakeholders. We outline a systematic approach that shows how BPS can be embedded in all phases of the widely used Stage-Gate approach. Experiences from two case studies are discussed to show the potential of this method in practical settings

Seasonal Thermal Sensation Vote - An indicator for long-term energy performance of dwellings with no HVAC systems

Dwellings with no heating, ventilation and air conditioning (HVAC) systems are commonly found in many countries. The long-term thermal performance of these buildings can be assessed based on hourly data of occupant thermal discomfort integrated over the required timespan (e.g. total degree hours of discomfort per year). This approach can be easily applied when simulation is adopted in the assessment, but field studies using this approach are rare as they would require complex, costly and long measurement/survey campaigns. This paper addresses the challenges on conducting field studies on long-term thermal performance of dwellings with no HVAC system by introducing a novel performance indicator: the Seasonal Thermal Sensation Vote (S-TSV). S-TSV adopts the standard 7-point thermal sensation scale and is based on the perceived overall thermal sensation recalled by the user of the building for specific seasons and times of day. The new performance indicator is not intended to replace existing ones, but to complement them in the understanding of the complex thermal performance processes taking place in buildings with no HVAC. S-TSV was applied in a field study targeting a small sample of dwellings in Brazil. Results demonstrate the capabilities of S-TSV to describe trends in buildings performance in this sample. S-TSV also assisted on the identification of relationships between such performance and some independent variables addressed in this field study (e.g. windows operation, footwear and income), considering a threshold of p-values <0.05 on the chi-square statistic test

Assessing the performance potential of climate adaptive greenhouse shells

Agriculture is responsible for 7.2% of the final energy consumption in the Netherlands; most energy is used for heating and lighting in the greenhouse sector. Currently, the greenhouse sector faces major challenges in reducing its energy demand while increasing crop quality and quantity. One route to improve the performance of industrial greenhouses could be based on using climate adaptive shells. These shells are capable of changing their thermal and optical properties on an hourly, daily, or seasonal basis to optimize performance. The climate adaptive shell concept shows considerable potential for performance improvement in the building sector. However, its potential for the greenhouse sector is yet unknown. This paper quantifies this potential by predicting the energy savings and the increase in net profit using a new framework based on numerical simulation and optimization techniques. The simulation results show that climate adaptive greenhouse shells increase net profit between 7% and 20 % for tomato producing Dutch greenhouses. Monthly and hourly adaptation resulted in considerable primary energy savings of 23% and 37%, respectively. It is expected that the predicted net profit increase and energy savings will drive the attention of the greenhouse industry towards the development of climate adaptive greenhouse shells

CFD como ferramenta para simular ventilação natural interna por ação dos ventos: estudos de caso em tipologias verticais do "Programa Minha Casa, Minha Vida"

Resumo A ventilação natural é uma estratégia projetual passiva que deve ser usada sempre que possível em países de clima quente como o Brasil. Entre os vários métodos para predizer o comportamento da ventilação natural está o uso da dinâmica de fluidos computacional. O objetivo deste artigo é analisar a ventilação natural por ação dos ventos no interior de edifícios usando o método de simulação por CFD. A pesquisa toma como estudos de caso três edifícios multifamiliares do Programa Minha Casa, Minha Vida. Analisou-se o desempenho da ventilação para três ângulos de incidência do vento (0º, 90º e 135º). São apresentados resultados quantitativos (velocidade média do vento em cada ambiente interno) e qualitativos (imagens do fluxo de ar externo e interno). Os resultados indicaram melhor desempenho de ventilação na tipologia 1, com planta do tipo "H", na qual a abertura localizada na grande reentrância representou papel determinante. Na tipologia 2, com volumetria próxima ao quadrado, a solução de ventilar banheiro e cozinha através da abertura da área de serviço mostrou-se ineficiente. O pior desempenho foi verificado na tipologia 3, caracterizada por maiores fachadas monolíticas (sem reentrâncias)

Assessing the accuracy of a simplified building energy simulation model using BESTEST : the case study of Brazilian regulation

This paper reports the use of an internationally recognized validation and diagnostics procedure to test the fidelity of a simplified calculation method. The case study is the simplified model for calculation of energy performance of building envelopes, introduced by the Brazilian regulation for energy efficiency in commercial buildings. The first step of the assessment consisted on evaluating the simplified model results using the BESTEST. This paper presents a straightforward approach to apply the BESTEST in other climates than the original one (Denver, USA). The second step of the assessment consisted on applying the simplified model to evaluate four building typologies, and compare the results with those obtained using a state of the art building energy simulation (BES) program. For some BESTEST cases, the simplified model presented results inside of a confidence interval calculated by the authors. However, the simplified model was found to yield significant difference in the four building typologies analysed. Moreover, in all four building typologies analysed, the simplified model led to a lower energy efficiency label when compared to the label obtained using BES. The paper concludes that the simplified model may require improvements to properly indicate the actual energy performance of commercial building envelopes