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Now showing items 1 - 16 of 18

  • Fast POD method to evaluate infiltration heat recovery in building walls

    Tallet, Alexandra   Liberge, Erwan   Inard, Christian  

    Air infiltration of buildings has a considerable impact on the energy performance of buildings. Permeability or airflow leakage can be evaluated by introducing the Infiltration Heat Recovery (IHR) factor in the energy balance equation. Conventionally, this factor is computed using a Computational Fluid Dynamics (CFD) software, that is time consuming and not very useful for a fast evaluation of balance energy of a building. This article proposes a Reduced-Order model (ROM) approach to evaluate the effect of the permeability of the energy balance for a building. The ROM, based on the well-known Proper Orthogonal Decomposition (POD) method, is developed in the Modelica modeling language. It is successfully applied to the case study of the air infiltration in the low energy consumption building.
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  • A metamodeling method to study the nonlinearity of building thermal behavior

    Jaffal, Issa   Inard, Christian  

    Understanding the nonlinearity of the thermal behavior of buildings is important for their design and energy analysis. This paper presents a method for the study of the nonlinearity of building thermal behavior based on a metamodel for cooling energy needs. Four measures were introduced to assess nonlinearities using the metamodel coefficients. We studied the nonlinearity of the thermal behavior of an office. A higher metamodeling accuracy was generally obtained for hot climates, high internal heat gains and lightweight thermal mass. Conversely, the nonlinearity of thermal behavior was accentuated in cold climates and with low internal heat gains. The nonlinearity measures were strongly associated to the mean outdoor air temperature in fifteen typical European climates using power laws, with R-2 ranging from 0.75 to 0.96. They were also strongly associated to internal heat gains (R-2 > 0.96) in the coldest climate, but low and almost stable in the hottest climate. Moreover, the interactions between the building components were more influential on cooling energy needs than quadratic behavior. A metamodel giving energy needs as a function of the physical and geometric parameters was derived. Its extrapolation with various window-wall ratios generally gave an acceptable accuracy, with quadratic variation of the errors. We propose a classification of building thermal behavior into three regimes: highly nonlinear when the energy needs are close to zero; intermediate with decreasing nonlinearities that can be expressed by power functions; and finally, a quasi-linear regime with almost-steady nonlinearities.
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  • Data mining of building performance simulations comprising occupant behaviour modelling

    Darakdjian, Quentin   Bille, Sylvain   Inard, Christian  

    Occupant behaviour is now widely recognized as a major factor in the disparity between predicted and measured building performance. Stochastic models are a convenient way to model the rational, diverse and complex nature of occupant behaviour, including presence and adaptive behaviour. The FMI standard was used to co-simulate the building energy modelling program EnergyPlus and a multi-agent platform that contains stochastic models in an integrated environment. Using an office building as a case study, we show that data mining, through a correlation matrix and a principal component analysis, was an efficient way of investigating the cumulated influence of occupant behaviour on energy performance. The organisation of simulations was achieved using design of experiments in order to take into consideration multiple building configurations. This paper demonstrates how data mining of stochastic simulations can be used to identify the determinants that have the greatest influence on building energy needs.
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  • A new methodology for the design of low energy buildings

    Chlela, Fadi   Husaunndee, Ahmad   Inard, Christian   RiedeFer, Peter  

    The Kyoto protocol binded the developed countries to reduce the greenhouse gas emissions at least by 5% by 2008-2012 in order to tackle global warming and climate change. Some of the measures of the governments to achieve this goal are to promote new buildings construction and to retrofit existing buildings while satisfying low energy criteria. This means improving energy efficiency of buildings and energy systems, developing sustainable building concepts and promoting renewable energy sources. The design of a low energy building requires parametric studies via simulation tools in order to optimize the design of the building envelope and HVAC systems. These studies are often complex and time consuming due to a large number of parameters to consider. Hence, this paper aims to set up a methodology that simplifies parametrical studies during the design process of a low energy building. The methodology is based on the Design of Experiments (DOE) method which is a statistical method widely used in industry to perform parametric studies that reduces the required number of experiments. (C) 2009 Elsevier B.V. All rights reserved.
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  • Toward integrated building design: A parametric method for evaluating heating demand

    Jaffal, Issa   Inard, Christian   Bozonnet, Emmanuel  

    In this study, we describe a novel method for evaluating building heating demand based on a statistical approach. Our aim is to support integrated building design by providing fast modeling with accuracy close to that of dynamic simulations. A general parametric model encompassing overall building design is proposed based on the analysis of heat transfer. The method is subsequently applied to evaluate the heating demand of a single-family house in a cold French climate. Several polynomial functions are derived from the general model as functions of the amounts of heat transferred by different mechanisms and the physical and geometric building parameters. The model is identified with a small number of dynamic simulations using the design of experiments. The model illustrates how the weighting factors for the various amounts of heat are much higher in cold climates than in hot ones. We demonstrate that building heating demand can be accurately analyzed using the design parameters of the developed model. This analysis highlights the potential of this approach for supporting building energy designers in the choice of energy-efficient solutions. (C) 2012 Elsevier Ltd. All rights reserved.
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  • Free-running temperature and potential for free cooling by ventilation: A case study

    Inard, Christian   Pfafferott, Jens   Ghiaus, Christian  

    Free-cooling by ventilation is one of the most energy efficient techniques for cooling. When ventilation is used for cooling, variable airflow rates should to be used in order to achieve comfortable room temperatures and to minimize the energy demand for mechanical ventilation. Thus, free-cooling, requires, obviously, the existence of a potential for cooling and needs control mechanisms for the airflow. In this study, the free cooling potential by ventilation for office buildings is evaluated by the free-running temperature. The free-running temperature approach is based on the energy balance of heat gains and losses. It is adapted to evaluate the potential for free cooling by ventilation of office buildings for which the gains through the walls are negligible as compared to the internal and solar gains. The free-running temperature of each office room considers solar and internal heat gains, outdoor temperature, indoor temperatures and ventilation air flow rates. The approach is applied to 14 office rooms in a passively cooled office building in Germany and is used to estimate the potential and to evaluate the total energy saving by free cooling by ventilation. The good fit between monitoring data and calculation procedure proves that the free cooling potential can be accurately estimated by using the difference between the comfort limits, i.e. the target value of the indoor temperature, and the free-running temperature. (C) 2011 Elsevier B.V. All rights reserved.
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  • Grey-box identification of air-handling unit elements

    Ghiaus, Christian   Chicinas, Adriana   Inard, Christian  

    The air-handling units (AHUs) provide complete control of temperature and humidity in air-conditioned spaces. The models of the AHU elements are nonlinear and the controlled variables, temperature and relative humidity, coupled. This paper demonstrates that in the case of sensible heat exchange without moisture removal if the outputs of the electric coils, fluid-filled coils and steam humidifiers of an AHU are considered to be the differences between the air temperature and the humidity ratio of the outlet and the inlet, then the models may be written as the product of a static and a dynamic gain. The parameters of the discrete form of these models are experimentally identified. The dynamics of the elements and of their sensors are very similar. Therefore, the parameter identification of the elements takes into account the model of the sensor, previously identified. This grey-box approach combines theoretical modelling, parameter identification of discrete models and parameter identification of partially known models by using optimization techniques. (c) 2006 Elsevier Ltd. All rights reserved.
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  • Numerical study of a hybrid ventilation system for single family houses

    Jreijiry, David   Husaunndee, Ahmad   Inard, Christian  

    The main objective of this study is to develop and test hybrid ventilation systems and control strategies that are suitable for residential buildings. Two ventilation systems were modelled: a mechanical extract ventilation system (called the reference system) and a hybrid low pressure ventilation system that can support two different types of demand control strategies (occupancy detection and CO2 concentration). The newly developed models were assembled with the existing thermal models of the SIMBAD Building and HVAC Toolbox developed by the CSTB. A single family house located in Athens (Greece), Nice (France), Trappes (France) and finally Stockholm (Sweden) was considered as the case study. Yearly simulations were performed to assess the performance of the hybrid ventilation control strategies. The assessment criteria used are related to indoor air quality, thermal comfort, energy consumption and stability of control strategies. The results show that the low pressure ventilation system can improve the indoor air quality and reduce the fan energy consumption compared to the reference system while maintaining the same building energy consumption for heating. (c) 2006 Elsevier Ltd. All rights reserved.
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  • Development of a multiobjective optimization procedure dedicated to the design of district energy concept

    Perez, Nicolas   Riederer, Peter   Inard, Christian  

    Increasing energy efficiency in the building sector is essential if we are to meet the objectives of sustainable development. The district scale offers significant potential for improving energy efficiency, particularly at the early stages of the design. Thus, a transversal approach to the optimization of the energy concept of districts was adopted. It was undertaken using the DIMOSIM (District MOdeller and SIMulator) simulation platform, which provides a detailed analysis of a configuration. The energy, economic and environmental aspects were combined to obtain the best overall performance. The multiobjective optimization procedure is multi-level and includes direct search and the NSGA-ll evolutionary algorithm to deal with the specificities of this particular problem. Indeed, the search space contains continuous and discrete parameters, it is almost infinite and the objective functions are non-linear. This article describes the complete optimization procedure that was developed to solve this complex problem. A case study on the design of an eco-district illustrates the possibilities offered by this type of approach to obtain the best design solutions. (C) 2018 Elsevier B.V. All rights reserved.
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  • Reduced-scale study of wind influence on mean airflows inside buildings equipped with ventilation systems

    Le Roux, Nicolas   Faure, Xavier   Inard, Christian   Soares, Sandrine   Ricciardi, Laurent  

    To study mass transfers inside buildings equipped with ventilation systems, a methodology has been developed to carry out reduced-scale experiments for studying isothermal flows in a steady or a transient state. This methodology has been numerically and experimentally validated on simple configurations and applied to two reference configurations representative of nuclear facilities. The wind influence on mass transfers inside these configurations, in nominal, damaged (ventilation stopped) or accidental (internal overpressure) situations, has been studied by carrying out wind tunnel experiments. The objectives of this article are to present the scaling-down methodology and the main experimental results concerning the influence of wind on steady-state airflows inside the reduced-scale models. It is notably shown that wind effects can lead to a partial or a total loss of the pollutant containment inside buildings. The reliability of the zonal code SYLVIA, which is used to support safety assessments in nuclear facilities, has then been analysed from these experimental results. (c) 2012 Elsevier Ltd. All rights reserved.
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  • Mean structure and integral analysis of electric convector thermal plumes

    Inard, Christian   Meslem, Amina   Depecker, Patrick   Barles, Pierre  

    In this study, we present an experimental and numerical analysis of thermal plumes issued from electric convectors. The study of the mean velocity and temperature profiles measured within the thermal plume shows that the self-similarity of the profiles is only partly achieved. We developed an integral model that takes into account the settlement flow region by the variations of the entrainment coefficient and the ratio between the temperature and velocity profile widths. A comparison between computed and experimental results proves that the model gives a satisfactory prediction of the physical phenomena. We propose finally a simplified thermal plume model for an integration into a thermal building code.
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  • A simplified model for the prediction of air temperature distribution in buildings

    Inard, Christian   Depecker, Patrick   Roux, Jean-Jacques  

    This study presents a zonal model for predicting the air temperature distribution in buildings. This model is unique in the calculation of mass air flows between two zones. To do so, we distinguish zones where the momentum is small and for which we calculate the flow rates with the aid of a pressure field, and the driving zones described using appropriate specific flow laws. To better understand the consistency of the model, we used experimental results obtained with a one and then a two zone test cell and an experimental atrium with various thermal conditions. A comparison between computed and measured air temperature distributions proves that the model gives a satisfactory prediction of the physical phenomena. This allows us to consider the integration of this type of model into a thermal multizone building code in relation with thermal comfort, energy consumption and indoor air quality.
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  • Simulation tools to assess microclimate and building energy - A case study on the design of a new district

    Gros, Adrien   Bozonnet, Emmanuel   Inard, Christian   Musy, Marjorie  

    Since some years, dense cities and compact buildings are promoted as sustainable and energy efficient designs. Nevertheless, urban planning strategies should take into account the interactions between buildings and the Microclimate because the Urban Heat Island (UHI) phenomenon can increase the cooling load of buildings and is strongly influenced by urban morphology, urban landscaping and the thermal properties of buildings and soil. The modification of these parameters, such as building density, can mitigate UHI, with direct and indirect improvement of building energy performances. The case study presented in this paper concerns a new district in La Rochelle (France) named Atlantech. Currently at the design stage, the goal is to transform this old military camp into a zero carbon district. This study was performed in parallel with urban planning using EnviBatE and SOLENE-Microclimate simulation. Two building densities are compared through the impacts on solar irradiance, wind airflows, building indoor temperatures and energy demand. Analysis of reference and densified district highlights various impacts such as the wind velocity decrease, up to 80%, and the effect on an existing nearby building solar irradiation, reduced by 7%. These results underline the potential usefulness of these simulation tools for urban planners at the design stage. (C) 2015 Elsevier B.V. All rights reserved.
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  • Experimental and numerical study of thermal stratification in a mantle tank of a solar domestic hot water system

    Kenjo, Lana   Inard, Christian   Caccavelli, Dominique  

    The simulation and the optimisation of the mantle tank of solar domestic hot water systems needs dynamic simulation over long periods of time (e.g. 1 year). A model for such a mantle tank was developed by using the zonal approach. The dimensions of the zones are determined based on physical considerations. A mixing coefficient is identified to model the water flow in the mantle heat exchanger. Comparisons of the results of temperatures distribution of the model and of experiments show a difference <7% for three positions of the inlet water flow in the mantle heat exchanger. (C) 2007 Elsevier Ltd. All rights reserved.
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  • Direct and Indirect Impacts of Vegetation on Building Comfort:A Comparative Study of Lawns,Green Walls and Green Roofs

    Malys, Laurent   Musy, Marjorie   Inard, Christian  

    Following development and validation of the SOLENE-microclimat tool, the underlying model was used to compare the impacts of various greening strategies on buildings' summer energy consumption and indoor comfort. This study distinguishes between direct and indirect impacts by successively implementing the test strategies on both the studied building and surrounding ones; it also considers insulated vs. non-insulated buildings. Findings indicate that green walls have a direct effect on indoor comfort throughout the entire building, whereas the effect of green roofs is apparently primarily confined to the upper floor. Moreover, the indirect effect of a green wall is greater, mainly due to the drop in infrared emissions resulting from a lower surface temperature. It has also been proven that the indirect effects of green walls and surrounding lawns can help reduce the loads acting on a non-insulated building.
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  • Ventilation Heat Recovery from Wood-Burning Domestic Flues. A Theoretical Analysis Based on a Triple Concentric Tube Heat Exchanger

    Peigne, Pierre   Inard, Christian   Druette, Lionel  

    This paper presents a new air-heating system concept for energy-efficient dwellings. It is a system designed to heat a low-energy building by coupling a heat-recovery ventilation system with a three-fluid heat exchanger located on the chimney of a wood-pellet stove. The proposed work focuses on the heat transfer that occurs between flue gases, the ventilation air and the combustion air within a triple concentric tube heat exchanger with no insulation at its outer surface. The main objective is to predict outlet temperature for the specific geometry of the heat exchanger studied here. Thus, the governing differential equations are derived for a counter-co-current flow arrangement of the three fluids. Then analytical solutions for the steady-state temperature distribution are obtained as well as the amount of heat transferred to the outside. An expression for the effectiveness of the heat exchanger is also proposed. Based on these results, calculations are performed on a case study to predict the fluid temperature distribution along the heat exchanger. Finally, a parametric study is carried out on this case study to assess the influence of the relevant parameters on the effectiveness of the heat exchanger. In addition, computation of heat losses to the outside justifies whether insulation is needed.
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