41 research outputs found
CFD Simulation of Inter-flat Air Cross-contamination - a possible transmission path of infection diseases
No full textThe objective of this study is to investigate the possible transmission mechanism of inter-flat air cross-contamination under the condition of singlesidednatural ventilation. In high-rise residential building with flush windows on the same side, the air pollutants can diffuse from lower flat to adjacent upper flat in the vertical direction related to the interflat air flow through open windows caused by the temperature difference between the indoor air and the air outside of the windows. Based on the validation of CFD models with experimental data given by Heiselberg, the renormalization group (RNG) based k − ε model, together with Carbon dioxide (CO2) used as a tracer, is chosen to reveal this air crosscontamination. Different effects of contamination spread into upper room were evaluated through kinds of cases performed in various conditions. The numerical results demonstrate this possible transmission path
Ventileret vindue med solafskærmning / nat persienne
No full textThe main purpose of this report isinvestigations on ventilated windows.The article primarily dealing with analysisof window energy efficient designand its performance in cold and warmperiod of year. Analysis on seven differentcases has been carried out to identifythe important contributors to the totalenergy gains and losses. These arethen optimised with best solutions toget as good results as possible in energybalance calculations. Energy balancecalculations are second part of investigations.By implementation of thismethod and simulation programs, resultsobtained later can be compared.Problems, concerning panes configuration,location of low-E coating and positionand type of shading device, canbe solved afterwards. The last part ofthe project includes Simple calculationmethod applied to a real building in orderto find most suitable option in aspectof energy balance during year
Improving the Energy Performance in Existing Non-residential Buildings in Denmark Using the Total Concept Method
No full textThis project is a part of a joint European research project, “Total Concept”, which is a method for improving the energy performance in existing non-Residential buildings. The method focuses on achieving maximum energy savings in a Building within the profitability frames set by a building owner, who plans to invest. The method differentiates from other refurbishment approaches by using a comprehensive energy audit plan, advanced energy simulation methods, a complex economic model and analysis of measures that may have a reasonable energysaving potential. The aim of the demonstration project was to form a package of measures for an energy performance improvement in the building based on the Total Concept method. This paper presents results from recently analyzed data on two renovated Danish buildings according to the rules of “Total Concept” method. According to the estimation done based on available information the identified measures in total lead to at least 22% and 37% energy saving, respectively for the building 1 and Building 2
House Owners’ Interests and Actions in Relation to Indoor Temperature, Air Quality and Energy Consumption
No full textIn order to make better and more realistic predictions of energy consumption in dwellings, more knowledge about how individuals and households control the indoor environment is needed. A questionnaire survey was conducted with the objective to study the interest and actions taken in relation to indoor temperature, air quality and energy use by Danish house owners living in single-family detached dwellings with district heating. The house owners express that they are interested in and concerned about the indoor temperature and air quality and that it is an important element in caring for each other in the family. Actions are taken in relation to the temperature in the way that house owners are trying to keep different temperatures in different heated rooms, e.g. to sleep cool or to save heat. Besides they wear warmer clothing, slippers or thick socks during the winter indoors compared to the rest of the year. Actions are taken in relation to improve the air quality by the majority of the house owners by opening windows. The most frequent reasons for opening windows once or several times a day was “to get fresh air” and “in relation to showering”. House owners are interested in saving energy for the sake of the environment and for their own economy, and quite many households indicate that they know their own energy consumption though only few follows it closely. Thus being concerned about energy is not necessarily related to interest in detailed feedback on consumption. Results show that well planned communication about feedback possibilities is important. Women and men answer slightly different to some of the questions, e.g. women are more active in airing, and they wear warmer clothing, whereas men are more active when it comes to following their energy consumption.In order to make better and more realistic predictions of energy consumption in dwellings, more knowledge is needed about how individuals and households control the indoor environment. A questionnaire survey was conducted with the objective of studying the interest and actions taken in relation to indoor temperature, air quality and energy consumption by Danish house owners living in single-family detached houses with district heating. The house owners state that they are interested in, and concerned about, the indoor temperature and air quality and that it is an important element in caring for each other in the family. Actions are taken in relation to the temperature in the way that house owners are trying to keep different temperatures in differently heated rooms, e.g. to sleep in a cool bedroom or to save heat. Besides they wear warmer clothing, slippers or thick socks indoors during the winter compared with the rest of the year. Actions are taken to improve the air quality by the majority of the house owners by opening windows. The most frequent reasons for opening windows once or several times a day was “to get fresh air” and “in relation to showering”. House owners are interested in saving energy for the sake of the environment and for their own economy, and quite a lot of households indicate that they know their own energy consumption, though only few follow it closely. Thus being concerned about energy is not necessarily related to an interest in detailed feedback on one’s own energy consumption. Results show that well-planned communication about feedback possibilities is important. Women and men answer slightly differently to some of the questions, e.g. women are more active in airing, and they wear warmer clothing, whereas men are more actively following their energy consumption
Improving the Energy Performance in Existing Non-residential Buildings in Denmark Using the Total Concept Method
No full textThis project is a part of a joint European research project, “Total Concept”, which is a method for improving the energy performance in existing non-Residential buildings. The method focuses on achieving maximum energy savings in a Building within the profitability frames set by a building owner, who plans to invest. The method differentiates from other refurbishment approaches by using a comprehensive energy audit plan, advanced energy simulation methods, a complex economic model and analysis of measures that may have a reasonable energysaving potential. The aim of the demonstration project was to form a package of measures for an energy performance improvement in the building based on the Total Concept method. This paper presents results from recently analyzed data on two renovated Danish buildings according to the rules of “Total Concept” method. According to the estimation done based on available information the identified measures in total lead to at least 22% and 37% energy saving, respectively for the building 1 and Building 2
House Owners’ Interests and Actions in Relation to Indoor Temperature, Air Quality and Energy Use
No full textIn order to make better and more realistic predictions of energy consumption in dwellings, more knowledge is needed about how individuals and households control the indoor environment. A questionnaire survey was conducted with the objective of studying the interest and actions taken in relation to indoor temperature, air quality and energy consumption by Danish house owners living in single-family detached houses with district heating. The house owners state that they are interested in, and concerned about, the indoor temperature and air quality and that it is an important element in caring for each other in the family. Actions are taken in relation to the temperature in the way that house owners are trying to keep different temperatures in differently heated rooms, e.g. to sleep in a cool bedroom or to save heat. Besides they wear warmer clothing, slippers or thick socks indoors during the winter compared with the rest of the year. Actions are taken to improve the air quality by the majority of the house owners by opening windows. The most frequent reasons for opening windows once or several times a day was “to get fresh air” and “in relation to showering”. House owners are interested in saving energy for the sake of the environment and for their own economy, and quite a lot of households indicate that they know their own energy consumption, though only few follow it closely. Thus being concerned about energy is not necessarily related to an interest in detailed feedback on one’s own energy consumption. Results show that well-planned communication about feedback possibilities is important. Women and men answer slightly differently to some of the questions, e.g. women are more active in airing, and they wear warmer clothing, whereas men are more actively following their energy consumption
Investigation of Ventilation Strategies for the Day-Care Institutions
No full textTwo existing nursery buildings, a mechanically and a naturally ventilated one, were chosen for investigations of energy saving potential and IAQ, using the different from present ventilation strategies and their control principles. These investigations are carried out applying a dynamic building simulation tool BSim. Each building is modelled separately and each of these models is “calibrated” using the detailed experimental data. Calibrated models are then used to evaluate different ventilation strategies for these particular buildings. This paper is aimed to illustrate the differences in assumptions for building operation on the design stage and actual building operation. Finally, it is not argued in favour to one or another ventilation principle, but in favour of demand controlled ventilation
Initial Development of a Combined PCM and TABS Solution for Heat Storage and Cooling
No full textThis paper investigates heat storage and cooling concept that utilizes both phase change material (PCM) and a thermal active building system (TABS) implemented in a hollow core concrete deck element. PCMs are promising materials for improving the heat storage capacity of a building due to their significant thermal energy storage capabilities. The TABS has a potential for increasing the exploitation of the thermal mass of the building, which is rarely exposed for heat transfer.The main objective of this study is to optimize the location and amount of PCM in a hollow core deck in order to optimize heat storage capacity. A series of simulations were conducted using the COMSOL program to obtain knowledge regarding the dynamic heat storage capacity of the investigated hollow core deck element as a function of the amount and location of PCM. Furthermore, the dynamic heat storage capacity of a passive deck element and the possible cooling power of the thermally activated deck element were predicted and then compared. Finally, results obtained from precise numerical simulations in COMSOL Multiphysics were compared with results calculated in the whole building simulation software BSim. Initial results indicate that the best location of the PCM in the hollow core concrete deck element is close to the surface that is facing to the room. Moreover, the heat transfer coefficient on the surface of the deck has a very significant impact on the heat storage capacity of the concrete deck element
Numerical predictions of the discharge coefficient of a window with moveable flap
No full textDischarge coefficient and wind-pressure coefficient are the key input parameters for estimating the airflow rates in naturally ventilated building designs. This paper focuses on the study of the discharge coefficient (CD) in case of a moveable (bottom-hinged) window flap. Computational fluid dynamics (CFD) techniques are used for estimating the airflow through the window. Focus is given to the window on the windward side of the building. The first objective of this study is to validate the k-ε turbulent model for the estimation of airflow rates through the window. It is done by comparing the numerical results with existing results of full-scale measurements under a laboratory conditions. The second objective is to find an accurate method to estimate the airflow rate (using orifice plate equation) in the case of a window with a moveable flap. It is done by using CFD predictions together with the validated turbulent model. A single value of CD (usually 0.6 to 0.65) is not appropriate for the operable window with moveable flap. The results of the simulation validates that the k-ε turbulent model can predict the airflow rates within an acceptable range, when the pressure difference (across the opening) is higher than 0.5 Pa. This study also confirms that the single value of the CD is not sufficient for a window with moveable flap. At the end, a more accurate method is presented for estimating the airflow through a window with moveable flap
Parameter study on performance of building cooling by night-time ventilation
No full textEspecially for commercial buildings in moderate climates, night-time ventilation seems to be a simple and energy-efficient approach to improve thermal comfort in summer. However, due to uncertainties in the prediction of thermal comfort in buildings with night-time ventilation, architects and engineers are still hesitant to apply this technique. In order to reduce the uncertainties, the most important parameters affecting night ventilation performance need to be identified. A typical office room was therefore modelled using a building energy simulation programme (HELIOS), and the effect of different parameters such as building construction, heat gains, air change rates, heat transfer coefficients and climatic conditions including annual variations on the number of overheating degree hours (operative room temperature >26 °C) was evaluated. Climatic conditions and air flow rate during night-time ventilation were found to have the largest effect. But thermal mass and internal heat gains also have a significant effect on cooling performance and the achievable level of thermal comfort. Using this modelling approach, significant sensitivity to heat transfer was found only for total heat transfer coefficients below about 4 W/m2 K.Especially for commercial buildings in moderate climates, night-time ventilation seems to be a simple and energy-efficient approach to improve thermal comfort in summer. However, due to uncertainties in the prediction of thermal comfort in buildings with night-time ventilation, architects and engineers are still hesitant to apply this technique. In order to reduce the uncertainties, the most important parameters affecting night ventilation performance need to be identified. A typical office room was therefore modelled using a building energy simulation programme (HELIOS), and the effect of different parameters such as building construction, heat gains, air change rates, heat transfer coefficients and climatic conditions including annual variations on the number of overheating degree hours (operative room temperature >26 °C) was evaluated. Climatic conditions and air flow rate during night-time ventilation were found to have the largest effect. But thermal mass and internal heat gains also have a significant effect on cooling performance and the achievable level of thermal comfort. Using this modelling approach, significant sensitivity to heat transfer was found only for total heat transfer coefficients below about 4 W/m2 K
