Survey of the existing approaches to assess and design natural ventilation and need for further developments

ISBN : 978-0-947649-40-1 Disponible à l'adresse : www.ibpsa.org/proceedings/BS2009/BS09_0220_227.pdfInternational audienceIn the last years many building designers have turned their attention to natural ventilation, due to the potential benefits in terms of energy consumption related to ventilation and air-conditioning, especially in mild and moderate climates. Consequently, several calculation techniques have been developed to design and predict the performance of natural ventilation. This article presents a review of the existing approaches to predict natural ventilation performance, including simple empirical models, nodal models (mono-zone and multi-zones), zonal models and CFD models. For each approach, we analyse the physical basis, the main modelling assumptions, the necessary input data and the area of applicability. Thus, the integration of these methodologies in the available simulation programs is examined, with reference to the different phases of the natural ventilation design process and some examples of application are given. The aim of the review is to identify the main practical limits of existing programs in designing natural ventilation and in predicting its performance and the consequent need for further developments

Influence Of Building Zoning On Annual Energy Demand

Simulation tools are widely used to assess the energy consumption of a building. In the modeling process, some choices should be made by the simulation tool user such as the division of the building into thermal zones. The zoning process is user dependent, which results in some difference in energy consumption results and model set-up and computational times. The aim of this work is to assess the influence of building zoning on the results of the dynamic thermal simulation including airflow and thermal transfers between zones For this purpose, several different building zonings are applied to the same office building, and then the results of the dynamic thermal simulations are compared in terms of energy consumption (heating, cooling, and auxiliaries) and computational and set-up times. To assess the impact of thermal zoning, five cases are studied (from the most to the least complex): - 1) *49-zone model* : each zone gathers the premises with the same air handling system, the same occupancy profile, at each floor and building orientation. - 2) *44-zone model* : the premises containing the same air handling system are gathered at every floor, even though their occupancy profile is different. - 3) *26-zone model*: all floors are merged, except for the first and the top floors (under-roof). - 4) *21-zone model* : the first and the under-roof floors are merged with the others if the premises have the same occupancy profile and handling system. - 5) *11-zone model* : the premises with a different orientation but with the same occupancy profile and handling system are gathered. The importance of airflow coupling is evaluated by using the most detailed model (49 zones) and comparing the cases with or without considering air transfer from offices to corridors and toilets (from which air is extracted). Then, to study the impact of thermally connecting juxtaposed zones, the “21-zone model” with and without thermal transfer are compared. Finally, the impact of merging the floors is analyzed by considering different roof and floor insulations and the impact of merging the orientations is studied by using different glazed surface ratio

A deep phenotyping experience: up to date in management and diagnosis of Malan syndrome in a single center surveillance report

Background Malan syndrome (MALNS) is a recently described ultrarare syndrome lacking guidelines for diagnosis, management and monitoring of evolutive complications. Less than 90 patients are reported in the literature and limited clinical information are available to assure a proper health surveillance. Results A multidisciplinary team with high expertise in MALNS has been launched at the "Ospedale Pediatrico Bambino Gesu", Rome, Italy. Sixteen Italian MALNS individuals with molecular confirmed clinical diagnosis of MALNS were enrolled in the program. For all patients, 1-year surveillance in a dedicated outpatient Clinic was attained. The expert panel group enrolled 16 patients and performed a deep phenotyping analysis directed to clinically profiling the disorder and performing critical revision of previously reported individuals. Some evolutive complications were also assessed. Previously unappreciated features (e.g., high risk of bone fractures in childhood, neurological/neurovegetative symptoms, noise sensitivity and Chiari malformation type 1) requiring active surveillance were identified. A second case of neoplasm was recorded. No major cardiovascular anomalies were noticed. An accurate clinical description of 9 new MALNS cases was provided. Conclusions Deep phenotyping has provided a more accurate characterization of the main clinical features of MALNS and allows broadening the spectrum of disease. A minimal dataset of clinical evaluations and follow-up timeline has been proposed for proper management of patients affected by this ultrarare disorder

Analyse expérimentale et simulation de la ventilation naturelle mono-façade pour le rafraîchissement des immeubles de bureaux

Natural ventilation can contribute to the reduction of the air conditioning demand and to the improvement of thermal comfort in office buildings. In this thesis, a simple configuration of natural ventilation, namely single-sided ventilation, is studied experimentally and by simulation. The main phenomena contributing to air change, thermal effect and wind effect, are discussed. Thus, the validity and applicability of existing models to calculate the ventilation rate is evaluated, by comparing their results with those of experiments conducted in a room with a single opening. Thus, CFD results are compared with experimental ones in order to validate the use of CFD for the study of single-sided ventilation. Guidance on the performance of different types of turbulence models is provided. Results from a turbulence model, namely RANS RSM, are used to establish a new correlation for calculating the ventilation rate. This new correlation shows better performance than previously existing correlations, in particular in the case of leeward opening. Finally, this new correlation is coupled to a dynamic thermal model to evaluate the cooling potential of single-sided natural ventilation in new low-energy office buildings. In particular, we study the reduction of cooling requirements in air-conditioned buildings and the number of hours of discomfort without any air conditioning system. The influence of several parameters is considered: climate, orientation, thermal inertia, rate of glazed area, internal gains and ventilation strategy (daily, night and both daily and night ventilation). Simulations show a significant reduction of cooling demand, between 30 and 90%. Moreover, it is possible to achieve thermal comfort throughout the whole year without using air conditioning in offices, provided that high thermal inertia is used and internal and solar gains are reduced.L'application de la ventilation naturelle peut contribuer sensiblement à la réduction des besoins de climatisation et à l'amélioration du confort d'été dans les immeubles de bureaux. Dans cette thèse, une configuration simple de ventilation naturelle, c'est-à-dire la ventilation mono-façade, est étudiée expérimentalement et par simulation. Après avoir examiné les phénomènes qui contribuent au renouvellement de l'air, on évalue la validité et l'applicabilité des modèles existants afin de calculer le débit de ventilation, en comparant leurs résultats avec ceux d'une campagne de mesures effectuée dans une pièce expérimentale. Ensuite, on valide l'utilisation de la CFD, avec trois modèles différents de turbulence, pour la simulation de la ventilation naturelle mono-façade, par comparaison avec les essais. Les résultats d'un des modèles de turbulence (RANS RSM) sont utilisés pour l'établissement d'une nouvelle corrélation pour le calcul du débit de ventilation. Celle-ci apporte des améliorations par rapport aux corrélations existantes, en particulier lorsque l'ouverture est située sous le vent. Cette nouvelle corrélation est couplée à un modèle thermique dynamique afin d'évaluer le potentiel de rafraîchissement de la ventilation naturelle mono-façade dans des immeubles de bureaux neufs. En particulier, on étudie la réduction des besoins de climatisation dans des immeubles climatisés et le nombre d'heures d'inconfort en l'absence de climatisation. L'influence de plusieurs paramètres est considérée : climat, orientation, inertie, taux de surface vitrée, apports internes et stratégie de ventilation (diurne, nocturne et diurne + nocturne). Les simulations montrent des réductions importantes des besoins de refroidissement, entre 30 et 90%. Il est possible de se passer de climatisation, sans générer d'inconfort, à condition de privilégier une inertie lourde et de maitriser les apports internes et solaires

Analyse expérimentale et simulation de la ventilation naturelle mono-façade pour le rafraîchissement des immeubles de bureaux

L'application de la ventilation naturelle peut contribuer sensiblement à la réduction des besoins de climatisation et à l'amélioration du confort d'été dans les immeubles de bureaux. Dans cette thèse, une configuration simple de ventilation naturelle, c'est-à-dire la ventilation mono-façade, est étudiée expérimentalement et par simulation. Après avoir examiné les phénomènes qui contribuent au renouvellement de l'air, on évalue la validité et l'applicabilité des modèles existants afin de calculer le débit de ventilation, en comparant leurs résultats avec ceux d'une campagne de mesures effectuée dans une pièce expérimentale. Ensuite, on valide l'utilisation de la CFD, avec trois modèles différents de turbulence, pour la simulation de la ventilation naturelle mono-façade, par comparaison avec les essais. Les résultats d'un des modèles de turbulence (RANS RSM) sont utilisés pour l'établissement d'une nouvelle corrélation pour le calcul du débit de ventilation. Celle-ci apporte des améliorations par rapport aux corrélations existantes, en particulier lorsque l'ouverture est située sous le vent. Cette nouvelle corrélation est couplée à un modèle thermique dynamique afin d'évaluer le potentiel de rafraîchissement de la ventilation naturelle mono-façade dans des immeubles de bureaux neufs. En particulier, on étudie la réduction des besoins de climatisation dans des immeubles climatisés et le nombre d'heures d'inconfort en l'absence de climatisation. L'influence de plusieurs paramètres est considérée : climat, orientation, inertie, taux de surface vitrée, apports internes et stratégie de ventilation (diurne, nocturne et diurne + nocturne). Les simulations montrent des réductions importantes des besoins de refroidissement, entre 30 et 90%. Il est possible de se passer de climatisation, sans générer d'inconfort, à condition de privilégier une inertie lourde et de maitriser les apports internes et solaires.PARIS-MINES ParisTech (751062310) / SudocSudocFranceF

Progress on single-sided ventilation techniques for buildings

International audienceSingle-sided natural ventilation is a free cooling solution which accommodates readily to most office building layouts. However, this technique is often ruled out by building designers since its ability to maintain comfort conditions is difficult to assess. Indeed, the cooling effect of this technique driven by wind and stack effects is highly dependent on outdoor conditions. This article intends to review the techniques of single-sided natural ventilation and the tools available to assess the performance of this technique. Then, the performance of single-sided natural ventilation is assessed for low-energy office buildings in two European climates. The methodology is based on the use of a building energy simulation program coupled with a recently developed correlation for single-sided ventilation. Several cases of office buildings are assessed, taking into account the main factors influencing the natural ventilation potential such as building loads, thermal inertia and orientation. For each building case, the energy-saving potential of a mixed-mode cooling system is analysed compared with the same building case with a full air-conditioning system. The comfort level of non-air-conditioned buildings is then studied for each building case. Finally, the impact of the window type on the performance of single-sided natural ventilation is assessed

Reversible air conditioning potential in office buildings in Europe

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Full scale experimental study of single-sided ventilation: Analysis of stack and wind effects

ERRATUM : Caciolo, M., Stabat, P., & Marchio, D. (2011). Erratum: Full scale experimental study of single-sided ventilation: Analysis of stack and wind effects (energy and buildings (2011) 43 (1765-1773)). Energy and Buildings, 43(11), 3295 Erratum available at http://dx.doi.org/10.1016/j.enbuild.2011.08.023Article available online 25 March 2011International audienceNatural ventilation can contribute to the reduction of the air conditioning demand and to the improvement of thermal comfort in buildings. In this paper, the flow field and the air change rate generated by a simple configuration of natural ventilation, namely single-sided ventilation, are examined experimentally. The experiments are realized in a full scale building exposed to outdoor conditions, using several measurement techniques. The main features of the flow generated by stack and wind effect are examined for different outdoor conditions (temperature difference, wind speed and direction). Finally, measured air change rates are compared to those calculated by existing correlations in order to analyze their applicability to the experimental configuration. Results show that the wind generates turbulence diffusion at the opening, counteracting the stack effect. Moreover, in the case of windward opening, there is an additional effect, namely the effect of mixing layer, which tends to increase the airflow rate. Existing correlations give reasonably good results in the case of windward opening, while in the case of leeward opening they overestimate the airflow rate

Numerical simulation of single-sided ventilation using RANS and LES and comparison with full-scale experiments

International audienceSingle-sided natural ventilation is a simple and energy-efficient method to passively cool a building, thus reducing or avoiding air-conditioning use. CFD has the potential to give detailed information about the complex flow generated by the interaction of buoyancy and wind in single-sided ventilation. In this paper, three experiments on single-sided ventilation are reproduced by CFD, using two turbulence models (RANS and LES). A detailed description of the experimental set-up, the numerical methods and the comparison method between experiments and simulations are provided. Results from RANS and LES are compared to experiments in terms of average and turbulent flow field, local airspeed, turbulence and temperature at the opening and airflow rates. The comparison shows that LES has the potential to provide more accurate results than RANS in most of the cases, capturing better the turbulent characteristics of the flow. However, the computational cost of LES is at least an order of magnitude higher than that of RANS

Effet de différentes solutions techniques sur les températures de non-chauffage et de non-refroidissement et sur le potentiel de free cooling dans les bâtiments de bureaux

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