1,720,995 research outputs found
Urban heat island in Padua, Italy: simulation analysis and mitigation strategies
Full text linkUrban Heat Island effect was widely studied in large cities around the world, more rarely in medium size ones. The paper reports on the study of the UHI phenomenon in Padua, a medium size city of the North-East of Italy, one of the most industrialized and developed parts of the country.
Experimental measurements were carried out during 2012 summer, recording the main thermo-hygrometric variables by mobile surveys along an exact path crossing different zones of the city area (urban, sub-urban and rural). Some measurements in situ in characteristic sites of the city area (like historic centre, high and low density populated residential zones, industrial zone, rural zone) were carried out in order to evaluate thermal comfort indexes. The analysis of the data highlights the presence of UHI effect with different magnitudes in function of the zone of the city. In the city centre, an historical zone, the effect was up to 7 °C.
The ENVImet simulation model was used in order to quantify possible increases in thermal comfort as a consequence of some mitigation strategies. In particular, a very famous square of the city (Prato della Valle) was analysed: it can be considered representative of the phenomenon because of the size and so the very different characteristics from the UHI effect point of view. Two scenarios were analysed besides the actual one (“AsIs” scenario): “Green ground” (halving the asphalt surface and doubling the green and plants surface) and “Cool Pavements” (increasing the albedo of impervious horizontal surfaces).
The simulations results are presented both in terms of UHI intensity (difference in air dry-bulb temperature between Prato della Valle and a reference rural site) and in terms of mean radiant temperature and thermal comfort sensation. The results are presented both in spatial and temporal terms for a typical summer day. The “Green ground” scenario allows till 1.4 °C and 3 °C decrease in air temperature, respectively during the night and the day. The same items for the “Cool Pavements” scenario are, respectively, 1.8 and 4 °C
The importance of software's and weather file's choice in dynamic daylight simulations
No full textThe prediction of daylight availability in indoor
environments is nowadays an extremely relevant topic in
the design practice for many reasons: it affects the design
of the electric lighting system and therefore the
calculation of the related energy consumption; it also has
an impact on evaluation of comfort. Dynamic daylight
simulations are a helpful tool to predict daylight
availability in indoor environments and consequently to
evaluate the possible reduction in energy consumptions.
However, there are different software packages that
perform dynamic daylight simulations and they use
different engines and calculation methods which may be
a source of differences in the results. Moreover this type
of analysis requires a weather data file of the building's
location to be performed. Since there are many of them
available, which are developed from historical sets of
weather measurements using different methods, the use
of one or another can affect the simulations' results.
Therefore in this paper an example of the impact on
dynamic daylight simulations' results of different
weather data files (IWEC, Meteonorm, TRY and Satel-
Light) and different software (Daysim and 3ds Max
Design®) will be reported
A Novel Methodology for Risk Assessment of Airborne Transmission due to Covid-19 in University Classrooms
No full textThe Covid-19 pandemic revolutionized the way of designing buildings, which should be created to improve health conditions and limit the spread of contagion. Among these, schools certainly need special attention. To improve indoor conditions, the first step of this study was conducted by simulating three classrooms having different ventilation strategies, using a CFD analysis. Then the infection probability was calculated using the Gammaitoni-Nucci model to analyse the risk in the classrooms according to different ventilation and building characteristics. The study showed the need for providing adequate ventilation to ensure healthy conditions for the students. Furthermore, the infection probability was calculated considering non-uniform environments, which can result from various air distributions in the classroom due to local non-uniformities. The configuration obtained from the CFD analysis was then compared to the standard condition. which considers the classrooms as uniform environments. This allows an understanding of the effective conditions to which students are exposed and to comprehend whether the classical models do not risk
underestimating the infection probability. This study provides a new methodology for airborne transmission risk assessment in non-homogeneous environments and supports designers with a new tool to evaluate HVAC systems layout and classroom operation
Analisys of energy efficiency measures on envelope and control system: case study for an existing building
No full textComparison of Direct Radiation Split Algorithms for Energy Simulation of Buildings
No full textDirect normal radiation (DNI) has great importance for both
energy building simulations and solar energy systems. The
data is seldom available from measurements but usually is
recovered from global radiation data using split algorithms.
The present paper analyses the performance of 33 different
split radiation models and the error which arises when
applied to building energy simulations using generated
hourly weather files.
The split models have been applied to an observed dataset
composed by 525888 points, which comprises global and
diffuse radiation on the horizontal plane, related to -year
measurements, starting from 2001 with 10-minute time
steps.
The generated weather files have been employed as input for
energy simulations with EnergyPlus on a building generated
using DesignBuilder software. We investigated the impact
of the weather files in building energy simulation highlighting
the performances of four models selected among the 33
models by means of statistical indicators, during different
periods of the dataset, since its amplitude allowed us to
decompose and analyse 10 different years
Determining the Energy Benefits from Passive Solar Design Integration through the Sensitivity Analysis of Different Case Studies
No full textThe increasing energy demand of our buildings is putting stress on the building systems and energy grids in terms
of need for efficiency improvements. The maximization of the overall performance requires a multidisciplinary approach towards seeking innovative solutions to help reduce the building loads. In terms of efficient energy planning, the building design phase has often been often disregarded or looked at from a single point of view. In this case, research places its attention either on the performance of the opaque or transparent envelope to define optimization criteria. A comprehensive analysis of the impact of different passive solutions on the energy demand of buildings with different uses is the core of the present paper. The main goal is to define design guidelines for the integration of simple to complex passive configurations into the building design to help reduce the heating demand by better exploiting solar radiation. The paper gathers data from 384 simulations, on different test buildings, with the permutation of various design parameters, including window-to-wall ratio, wall heat transfer coefficient and heat capacity. Simulations were run in two different locations, typical of southern and northern Italian climate conditions, for both residential and office use. After the best solutions according to the heating or total energy performance over a nominal year were highlighted, the guidelines were applied to a case study. The aim is to determine a methodology to properly integrate passive solutions on the basis of energy performance. This performance, indeed, constitutes a tradeoff of the potential of passive systems to understand when it can be profitable to integrate these. The building analyzed, a cohousing project still in the design phase, showed that 10 to 16 % of the total energy demand can be saved. The energy saving is reached by simply integrating and declining the passive configuration suggested with marginal modifications to the initial design
The benchmark of a new SIMULINK library for the thermal dynamic simulation of buildings.
No full textNowadays, for NZEB buildings the complexity of the interactions between thermal plants and buildings is increasing. The reduction of the primary energy consumptions in NZEB is generally pursued by maximizing the use of renewable energy which gives a discontinuous contribution during the season; it becomes important to study in detail the dynamic interactions between the building and the adopted HVAC systems, by taking into account unsteady state behaviour of walls, roofs, windows and so on. This kind of analysis can be obtained by using conventional dynamic simulation software (i.e. TRNSYS, ESP-r, Energy Plus, DesignBuilder). It has been demonstrated that a detailed analysis of controlled HVAC systems can be also obtained by using SIMULINK and in the past open block libraries made in SIMULINK have been proposed for HVAC system analysis, like in the case of the CARNOT blockset. However, a weak point of CARNOT is still considered the building modelling due to its limited flexibility and completeness. For this reason, a new specific library named ALMABuild based on SIMULINK blocks for the dynamic modelling of a building is presented in this paper with the aim to integrate and improve the blocks already available in CARNOT.
In ALMABuild the modelling of a building with SIMULINK is driven by means of a series of Graphical User Interfaces (GUI). In this paper a benchmark of ALMABuild is shown by using TRNSYS as reference. The comparison evidenced a good agreement between the two methods. However, differences are present each time that the procedure indicated by the European Standard EN ISO 13790:2008 (and integrally followed by ALMABuild) is not in agreement with the procedure followed by TRNSYS (based on American standards)
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Dynamic Simulation as a Tool for the Analysis of the Interactions Among the Controllers of HVAC Systems
Full text linkDuring the last decade, the application of electronics to the different components of HVAC systems has offered new and sophisticated control systems able to adapt the behaviour of each single device and of the whole plant to design specifications. These sophisticated finely-tuned control systems are, in principle, able to play an im-portant role in reducing energy consumption and im-proving thermal comfort. At the same time, there has been a marked increase in the complexity of the HVAC plant layout. Combining the complexity of plants with that of the control systems and taking into account the possibility of equipping each component of the plant with its own control system, the result is a new genera-tion of energy systems with many possible interactions between controllers. Hence it becomes impossible for a designer to evaluate, in an easy way, the effects of such interactions. As a consequence, it is difficult to know, at the design-stage, how the overall control system will op-erate. Nowadays, dynamic simulation of the complete HVAC system makes it possible to emulate the system in which the controllers operate. In this paper, the dynamic model of a basic HVAC system involving a condensing boiler, radiators with thermostatic valves and an inverter driven hydraulic pump is presented. Each element of the circuit is equipped with its own control. The model of the system has been built by using a custom-made library of Simulink blocks specifically created for the dynamic sim-ulation of controlled HVAC systems. The dynamic model will be used in order to underline the strong influence of the control system on the HVAC energy efficiency and thermal comfort conditions. Specific design rules limiting the negative interaction among the activated control sys-tems are inferred by the results shown in this paper
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