•CFD simulation of an opaque ventilated façade.•Different wind scenario were investigated.•The energy saving obtainable in comparison with unventilated façade were calculated.•The ventilated façade ...reduces the peak load and shifts the thermal wave.
The main benefit attributed to opaque ventilated facades (OVF) is the reduction of cooling load for the building Heating Ventilation and Cooling (HVAC) achieved through ventilation led by natural convection in the ventilated chamber and the protection from solar radiation given by the outer layer of the façade.
This research investigates the thermal behavior of an opaque naturally ventilated façade through Computation Fluid Dynamics (CFD) simulations during summer days. The CFD simulations have been performed in order to analyze the behavior of DSF components under different wind conditions in the summer period, utilizing the weather data of Catania city (Italy).
For the different investigated scenarios, the authors have calculated the temperature and air velocity profiles inside the air gap of the façade, highlighting the different effects of buoyancy and wind forces.
The results show that the wind forces in conjunction with the buoyancy forces affect significantly the performance of OVF components.
Further, the reduction of the heat flux during the summer period has been evaluated by comparing the thermodynamic performance of a naturally ventilated and an unventilated façade with the same geometry and thermo-physical characteristics.
The behavior of the naturally ventilated façade is an improvement in terms of passive cooling of the building compared to the non-ventilated façade since it allows the peak load to be shifted whilst offering energy savings in the range of 47% to 51% depending on climate.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Agricultural and forestry residues are usually processed as wastes; otherwise, they can be recovered to produce electrical and thermal energy through processes of thermochemical conversion, such us ...torrefaction, pyrolysis and gasification.
Currently, the gasification of residual biomass for producing neutral CO2 fuel for energy production is in development stage. In this context, this study proposes anequilibrium-based model, developed by the commercial software Aspen Plus, of a co-current gasifier fueled with agriculture residual, which allows estimating the chemical composition and theheating value of the syngas produced. The prediction of such model includes the main gaseous species, the yields of char and tar and describes the gasification process through the mass and energy balances, the water-gas shift (WGS) and the methanation reaction.
The model validation was carried out through the comparison with experimental data, concerning two biomass with different moisture content and different gasification conditions, for sixteen cases compared.
Overall, the comparison between the results of the simulations and the experimental data have shown a good agreement.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•The work points out the dynamic thermal behavior of massive building.•Experimental measurements have been carried out to evaluate thermal inertia factor.•Assessment of cooling effect of nocturnal ...ventilation.
The aim of this paper is the evaluation of the thermal behavior of a massive building under the synergic combination of natural ventilation and thermal inertia. In particular, an experimental study has been carried out on Villa San Saverio, which is a massive historical building located in Catania (Italy), in order to characterize its thermal performance under dynamic conditions, and to evaluate the potential decrease of the indoor overheating by exploiting natural ventilation and limiting both internal and solar gains.
The analysis of the transient behavior of this building permits to highlight the possibility of diversifying the time lag in relation to the wall orientation. A time lag of 12.00–14.00h can be suggested for the walls due East. On the other hand, a time lag of around 8.00h can be suggested to achieve the same result for the walls due West.
Time lags higher than the values suggested above could be not fully functional, since delaying further the heat transfer from the wall to its inner surface, reduces the useful time for exploiting the cooling effect of the nocturnal ventilation.
The results of both measurements and simulations indicate that high thermal inertia mass combined with natural ventilation prevents phenomena of overheating and ensures good comfort levels in occupied buildings, reducing the needs of cooling systems during summer period.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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•DAYKE-Italy is a project that investigated daylighting in 5 Italian universities.•A survey was distributed to students (N = 542) on perception of daylight in classrooms.•DIVA+ALFA ...simulations were run to calculate daylight, circadian and energy metrics.•Most metrics have significant statistical correlation with subjective responses.•Highest correlation was found for DFm, ALE, and circadian EML.
Results from the DAYKE-Italy project are presented. An investigation on daylighting in eight classrooms in five Italian universities was carried out through a combined approach: an ad-hoc survey administered to students to investigate how they perceive daylight in classroom, and numerical simulations (DIVA + ALFA) to calculate a set of objective metrics (daylight, circadian, and energy-related). A sample of 542 questionnaires was collected through two sessions and the subjective judgments were correlated to objective metrics. Results from descriptive and statistical analyses showed: (i) the correlation was significant for all daylight metrics: among them, average daylight factor and annual light exposure performed higher correlations compared to daylight autonomy, spatial daylight autonomy and useful daylight illuminance; (ii) rooms with a scarce or an optimal daylight provision (according to standards) were rated with comparable subjective score; (iii) the equivalent melanopic lux showed a higher correlation than daylight metrics based on the horizontal workplane; (iv) energy saving up to 50% can be achieved in the presence of high daylight provision and through daylight responsive controls; however, a relamping of fluorescent systems with LED system is recommended to optimize the consumption; furthermore, estimated saving correlated significantly with objective metrics.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
► Computational fluid dynamics analysis of ventilated roofs. ► Three ventilated roofs characterized by equal thermal resistance have been studied. ► Summer performances of ventilated roofs have been ...analyzed. ► The effects of the position of the thermal insulating layer have been evaluated. ► The reduction of heat fluxes through ventilated roof have been calculated.
The European Directive 2002/91/EC about the energy performance of buildings aims to achieve minimum standards on the energy performance both of new and existing buildings that are subject to major renovation.
The improvement of “building performance requirements” and the development of new strategies for “very low energy buildings” represent one of the European Directive priority. In fact, an effective saving potential may be obtained reducing the energy consumptions due to the heat flux transmitted through the envelope of residential and commercial buildings.
In regions with high level of solar radiation, ventilation of building structures reduces the cooling load during summer period and contributes to the reduction of the energy needs of buildings. During summer period, one of the advantages provided by the ventilation is the reduction of the heat fluxes transmitted by the structures exposed to the solar radiation, thanks to the combined effect of the surfaces shading and of the heat removed by the air flow rate within the ventilated air gap.
The objective of this paper has been the analysis of thermal behavior of ventilated roofs characterized by a different placement of thermal layer insulation respect to the air gap. The “Fluent” software has been used with the aim of acquiring a better knowledge of the thermo-fluid dynamic behavior of the air within the ventilated roof and the heat fluxes through ventilated roofs have been calculated.
The results of the study show that the ventilation of roofs can reduce significantly the heat fluxes (up to 50%) during summer season.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Limited data exist on the occurrence of the dwarf sperm whale Kogia sima in the Mediterranean Sea and its parasite fauna. Here, the occurrence of the anisakid species Anisakis physeteris and A. ...pegreffii in the stomach chambers of an adult female dwarf sperm whale, stranded in southern Italy, is reported. In addition, the occurrence of Phyllobothrium delphini larvae infecting the blubber of the caudal peduncle region was recorded. A. physeteris and A. pegreffii represent the 2 parasite species of the genus, mostly distributed in the Mediterranean Sea in fish and squids. The finding of A. pegreffii and A. physeteris in the dwarf sperm whale represents a new record in this host species for the Mediterranean Sea. The study of gastrointestinal content also revealed a massive presence of cephalopod beaks identified as belonging to pelagic squids including the umbrella squid Histioteuthis bonnellii, the reverse jewel squid H. reversa, the long-armed squid Chiroteuthis veranii, and the comb-finned squid Ctenopteryx sicula. The feeding habits of the dwarf sperm whale, as well as the occurrence of these squid residuals in the cetacean host, suggest that these squid species play a major role in maintaining the life cycle of anisakid parasite species and P. delphini.
Ventilated facades can be used in cases of renovation of existing buildings and new buildings to improve both the thermal performance of building, and external architectural skin. The energy ...advantage provided by the ventilated facades during the summer is the reduction of the heat load due to the combined effect of the shading of the external wall and the air flow caused by natural convection into the heated duct.
The evaluation of ventilated facade performance requires a complete thermofluid-dynamic analysis of a ventilated air duct and an accurate knowledge of heat transfer coefficients, friction factors and thermo-physical properties of the materials.
The Authors have used the computer code “Fluent” to investigate the thermal behaviour of three different typologies of ventilated facades.
The aim of this research is to show an analytical method for design applications able to provide all the useful criteria for choosing the most suitable ventilated facades both in case of forced convection, due to the action of a fan, and natural convection due to stack effect.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The present study reports data on a 20 months campaign monitoring enteric viruses (hepatitis A, norovirus, rotavirus, astrovirus, sapovirus, and aichivirus) and bacteria (Salmonella spp.) in ...seawater. The aim of this work was to assess the potential correlation among the presence of viruses/bacteria and different environmental factors like seasonality, water discharge sources (treated and untreated wastewater, mixed waters and raw water) as well as influence of the Italian lockdown measure against COVID-19 pandemic. Results showed different prevalence of the investigated viruses with values equal to 16 % for norovirus GI, 15.1 % for norovirus GII, followed by 13.8 % for astrovirus, and 13.3 % for sapovirus. Rotavirus was detected in the 8.4 % of samples and aichivirus was detected with the lowest prevalence of 3.5 %. Hepatitis A virus was never identified in the monitoring campaign. Salmonella spp. was detected with a prevalence of 36.6 %. Statistical analysis displayed a high correlation for the two noroviruses simultaneous detection (NGI and NGII) while a lower correlation was found for co-presence of noroviruses with astrovirus, sapovirus or Salmonella spp. A significant decrease of enteric pathogens in seawater was observed during the restrictions period. Results on seasonality highlighted a higher viral prevalence correlated to the wet season for all the pathogens but rotavirus and aichivirus, which instead showed an opposite trend and a higher incidence in the dry season. With respect to discharge typology, some viruses displayed a higher prevalence in treated waters (astrovirus, rotavirus, sapovirus and aichivirus) while the other investigated pathogens (noroviruses and Salmonella spp.) showed a higher prevalence in mixed waters. The main observations of this work were used to define a potential monitoring strategy that could be useful for sanitary Authorities to implement surveillance plans aimed at preventing possible sanitary outbreaks and/or environmental quality deterioration.
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•Enteric pathogens circulation: development of a multi-factor approach.•Reduction of enteric viruses circulation due to the lockdown measure.•Correlation among pathogens circulation with season and discharge typologies.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Abstract
The outdoor radiant field is a key aspect to determine outdoor comfort conditions for humans, especially in urban areas. In order to unveil the dependence of the radiant field on the ...features of the urban fabrics, this study analyses the space distribution of the Mean Radiant Temperature (T
MRT
) and the radiant field in various urban tissues of the city of Catania (Italy) in a typical Mediterranean climate. The study is based on simulations through the Solar and LongWave Environmental Irradiance Geometry model (SOLWEIG) implemented in UMEP. Results show that the worst conditions occur in areas with moderately deep urban canyons, abundant impervious surfaces and lack of vegetation: here, the TMRT can easily reach 78 °C while in more than 80% of the area it exceeds 60 °C. By modelling the time trends of the shortwave and longwave radiant heat fluxes perceived by a pedestrian, it has been possible to observe that the highest contribution to the outdoor radiant field comes from the downward solar irradiance. However, the downward and upward longwave radiant flux closely follows: this suggests the importance of providing shading rather than using highly reflective surfaces that can exacerbate heat stress by means of the increased reflected shortwave radiation.
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