The modelling activity presented in this work aims at the assessment of a simplified model, named BS model, which was specifically developed for integration of DSF in Building Simulation. The BS model is based on a pressure loop and on an integral approach to the heat transfer along the vertical channel. It considers buoyancy as a function of the average temperature in the channel. The wind action is taken into account by means of wind pressure coefficients (Cp) on the façade openings.The focus of this study is the experimental validation of the modelling "core": the natural ventilation through the DSF. The validation is based on the dataset of the experimental campaign conducted on a DSF test facility, the "Cube", in Denmark, under IEA ECBCS ANNEX 43/SHC Task 34. Hourly simulations were performed with the BS model for the 15 days of the experimental campaign.A CFD modelling activity was also carried out on a selection of four cases, extracted from the experimental benchmark and representative of different temperature and pressure boundary conditions. The results show that the BS model presents a good level of agreement with the experimental data in predicting the mass flow rate and the heat removed by ventilation. Although the two experimental methods used to determine the airflow rate in the DSF cavity produce in many cases divergent results, it was possible to distinguish valid experimental results for comparison with the BS model. This was possible thanks to a *Manuscript Click here to view linked References 2 thorough analysis of the experimental procedure together with the insight provided by the model into the determination of the driving wind and thermal differential pressures. In particular, by selecting only the measurements associated to sufficiently low wind fluctuations in the hourly averaged data, a good degree of correlation was found between the predicted total driving pressure and the flow measurements.Concerning the four cases investigated also by means of CFD, the agreement between the BS and CFD models is remarkable in terms of outlet temperatures and in the prediction of flow reversal.
In research and assessment of indoor environmental quality (IEQ), the terms ‘Comfort’, ‘Health’ and ‘Well-being’ are often used interchangeably without a clear definition of terms or effects on conditions for occupants. This calls for a systematic restructuring of the ontological approach to IEQ and, based on a meta-analysis of recent IEQ literature, the authors suggest three substantial contributions: 1) A framework consisting of comfort, health and well-being as three equal branches of IEQ to increase focus on previously neglected aspects and make inter-domain relations more transparent. 2) The identification of key IEQ trends and by extension suggestions for formal definitions of three main domains as part of a multidisciplinary conceptual framework for working holistically with IEQ. 3) The introduction of positive stimuli to IEQ assessment as opposed to the predominance of focus on the absence of negative parameters of current practice. Through including this positive stimuli dimension, the field of IEQ shifts from ‘not bad’ to ‘truly good’, encouraging the design of enriched environments to further positive experiences improving occupant well-being.
Research and practice agree that decisions taken early in a project have a higher impact and are less costly. Current building performance assessment methods are not suited to accommodate the responsiveness required for early design processes and are often used for validation in the later stages where the feedback has little design impact. Tools developed specifically for early stage Design Decision Support (DDS) are either too simplistic, provide no solution to addressing combined indoor environmental quality (IEQ), or risk worsening the overall IEQ by optimizing performance indicators in isolation. Most comprehensive building assessment methods evaluate several topics but follow a linear approach which fails to support holistic performance feedback and fails to meet the demand for assessment speed.This paper presents application examples of a holistic IEQ assessment tool (IEQCompass) in design processes. Design experiments demonstrate that the applied approach can meet the challenges of early stage DDS pointed out in existing literature. Findings from the experiments indicate that the IEQCompass can provide: (1) seamless early-stage assessments through rapid-feedback on changing designs, (2) timely decision support by guiding design teams with criteria overviews, design comparisons and holistic assessment results, and (3) dialogue and communication support between architects, engineers and clients.
The CFD simulation accuracy mostly depends on the appropriate setting of boundary conditions and numerical simulation parameters. This study shows the influence of two types of boundary condition settings on the CFD simulation results of Double-Skin Façade (DSF) for a specific problem. These two boundary settings are the constant temperature on the DSF surfaces called Boundary A, and Boundary B is defined via solar radiation using the Discrete Ordinate radiation Model (DOM). The paper verified both the numerical simulations using the experimental data. Comparing the numerical results of two types of boundaries with experimental data shows that both cases underestimated the values lower than 5.2 K and 0.1 m/s for the temperature and velocity respectively at the regarded measured points. Boundary A gives more accurate temperature prediction results while Boundary B shows velocity magnitude closer to the measurements in the middle height of the cavity; the average temperature and velocity differences between the two boundary types are 0.6 K and, 0.003 m/s respectively which are negligible. Finally, the selection of boundary conditions depends on study purposes, however, when the DSF is equipped with blinds and if there is not enough data in hand but the exact value of solar irradiation, using the Boundary B approach is suggested; it can provide reasonable results associated with multi-type of thermal boundary conditions at the same time. Furthermore, if the goal is to investigate the flow pattern in the DSF, Boundary B is argued to perform better than the constant temperature boundary condition.
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