1,721,033 research outputs found
Mist cooling in urban spaces: Understanding the key factors behind the mitigation potential
Full text linkMist cooling is a widely known and applied heat mitigation technology, especially in urban settings. Despite this, conceiving the right installation is no trivial matter as scattered and unstandardized is the knowledge on the multiple interrelations with the local microclimate. This paper investigates how the cooling efficiency of a dry mist system depends on the local meteorological trends. An experimental system of 24 overhead nozzles constantly operating at 0.7 MPa, was installed in Italy and monitored for a week in summertime. Temperature and relative humidity underneath the mist were mapped in five locations with a time step of 10 s, together with the main meteorological parameters, measured at an undisturbed location, for reference. Cooling and humidification capacity were characterized as probability density, key summary statistics and relevant confidence intervals with minimal redundancy and minimal distortion. A supervised learning algorithm was used to disclose the sensitivity of the recorded temperature drop to the contextual microclimatic evolution. It was demonstrated that the cooling capacity of the tested system was largely a function of the local wet bulb depression, as instantaneous reading as well as short-term trend. Additionally, solar irradiation and wind speed were found to be negatively and positively correlated, respectively
Evaluation of ISO 52010-1: 2017 and proposal for an alternative calculation procedure
No full textA proper evaluation of the building energy consumption implies an accurate assessment of the solar gains and consequently an exact estimation of the direct and diffuse solar radiation on tilted and oriented surfaces. The new standard EN ISO 52016-1: 2017 introduces a new hourly methodology for the calculation of energy performance of buildings and is complemented by EN ISO 52010-1:2017, which specifies the procedure for the conversion of climate data for energy calculations. These standards represent a good compromise between the old EN ISO 13790:2008 and Trnsys, since they allow for a more accurate evaluation of energy consumption than the former, while being less onerous than the latter. In the present work, EN ISO 52010-1:2017 is analysed for the first time and an alternative calculation procedure is proposed. These two algorithms are then compared with two other irradiance splitting methods implemented in Meteonorm and Trnsys code. In order to test performance and limits of the different calculation algorithms, we make a comparison among such methods on five European cities characterized by different climatic characteristics. Results show that the model implemented in EN ISO 52010-1:2017 overestimates the diffuse solar irradiance on horizontal plane for all the considered locations, while the proposed procedure and those implemented in the Trnsys and Meteonorm softwares show similar results. Using Trnsys algorithm as a baseline, the proposed calculation algorithm gives the best approximation among the considered models for what concerns the direct, diffuse and global irradiance on vertical surfaces exposed to south, east and west
Natural convection in a rectangular enclosure with an array of chips mounted on a vertical wall
No full textExploring the use of immersive virtual reality to assess occupants’ productivity and comfort in workplaces: An experimental study on the role of walls colour
Full text linkVirtual Reality application in holistic investigations for energy and cost-saving building design, aimed at humans’ well-being and performance, is still emerging and needs validation. In this study, tests in real and virtual scenarios of an office room were performed, investigating the impact of three walls colours (red, white, blue) and two indoor air temperatures (17–22 °C) on 23 participants’ work productivity (through a proofreading task) and thermal and visual sensations (through surveys). The first goal was the comparison of the results obtained in the real and virtual settings; the second one the assessment of the effect of walls’ colour and temperature levels on the mentioned variables in each environment. Statistical analyses were then performed “between groups” (Wilcoxon and t-tests, among datasets of the two environments) and “within groups” (ANOVA and Scheirer test, within each environment). The study revealed no statistically significant variations in productivity and sensation votes, thus supporting the suitability of VR as a proper research technology in this domain. The study also demonstrated no statistically significant effects of colour and temperature on productivity and comfort results within the tested settings. Future investigations should involve a wider range of temperatures and colours and address a wider subjects’ sample
SHEAR AND THERMO-HYGROMETRIC PERFORMANCE OF STRUCTURAL INSULATED PANELS COMPRISING EPS CORE AND OSB SKINS
No full textIn the last decades, the need for improved thermal-structural integrated solutions for building construction has prompt towards the development of Structural Insulated Panels (SIPs), a cost-effective wall system capable of transferring shear loads among panel layers and minimizing localized heat loss This study explored both mechanical and thermal behaviour of SIPs, composed by an Expanded Polystyrene (EPS) core within two oriented strand board (OSB) sheets. Six panels (1200x1200x170mm3) were tested under in-plane horizontal load in two configurations: (i) three single SIP wall; (ii) three double SIPs wall, joined together with a block spline and metal connections. Both specimens were anchored to a lower steel metal beam through anchor bolts and hold-downs. Moreover, the panels were characterized as regard the steady-state thermal behaviour. The study demonstrated that this wall system is a viable solution for sustainable buildings since it presents high shear strength, elevated ductility and good thermal-hygrometric performance
The influence of the acoustic performance in the certification of a school buildings according to the ITACA protocol
No full textData-driven automation of HVAC systems: An experimental study in a university study room
No full textThis study proposes a framework for controlling HVAC systems for university study rooms that includes a data-driven model capable of identifying the probability of user interaction with air conditioning and ventilation systems, depending on the thermal sensation vote (TSV), perceived air quality (PAQ) and microclimate parameters (air and operative temperature, air velocity, relative humidity and CO2). The experimental setup allowed the participants to carry out their usual study/work activities without the need to be supervised. This allowed the occupants not to be psychologically conditioned and made their experience and interaction with the environment/systems as realistic as possible. The analysis of the experimental data showed that the operative temperature mainly influences the thermal sensation of the occupant inside the room, while the perceived air quality depends not only on the CO2 concentration but also on thermal perception and air velocity. Furthermore, three predictive models (heating, cooling and IAQ) were obtained from the experimental data, indicating the probability of user interaction with the system (R2 between 0.85 and 0.94). The heating phase model was also verified by automatizing the heating system through the developed framework and comparing the user's sensations before and after control (users unaware of the changes). The use of the models increased users' thermal comfort from 39 % to 82 %, confirming the effectiveness of the syste
Prestazione energetica di coperture verdi su strutture fortemente isolate
No full textLa capacità di raffrescamento passivo
delle coperture verdi può essere inibita
dall’elevato isolamento richiesto dal legislatore
che esige un contenimento dei consumi invernali
anche in paesi dal clima più temperato
Impact of climate change on the energy and comfort performance of nzeb: A case study in Italy
Full text linkClimate change is posing a variety of challenges in the built realm. Among them is the change in future energy consumption and the potential decay of current energy efficient paradigms. Indeed, today’s near-zero Energy buildings (nZEBs) may lose their virtuosity in the near future. The objective of this study is to propose a methodology to evaluate the change in yearly performance between the present situation and future scenarios. Hourly dynamic simulations are performed on a residential nZEB located in Rome, built in compliance with the Italian legislation. We compare the current energy consumption with that expected in 2050, according to the two future projections described in the Fifth Assessment Report (AR5) by the Intergovernmental Panel on Climate Change (IPCC). Implications for thermal comfort are further investigated by assuming no heating and cooling system, and by tracking the free-floating operative temperature. Compared to the current weather conditions, the results reveal an average temperature increase of 3.4◦ C and 3.9◦ C under RCP4.5 and RCP8.5 scenarios, estimated through ERA-Interim/UrbClim. This comes at the expense of a 47.8% and 50.3% increase in terms of cooling energy needs, and a 129.5% and 185.8% decrease in terms of heating needs. The annual power consumption experiences an 18% increase under both scenarios due to (i) protracted activation of the air conditioning system and (ii) enhanced peak power requirements. A 6.2% and 5.1% decrease in the hours of adaptive comfort is determined under the RCP4.5 and RCP8.5′ s 2050 scenarios out of the concerted action of temperature and solar gains. The results for a newly proposed combined index for long-term comfort assessments reveal a milder future penalty, owing to less pronounced excursions and milder daily temperature swings
Thermal performance of a massive wall in the Mediterranean climate: Experimental and analytical research
No full textIn the Mediterranean climate, indoor overheating and, thus, excessive use of cooling systems represents one of the main problems both for the occupants' health and energy consumption. In order to limit this problem, an appropriate design or energy retrofitting of the building envelope is of utmost importance. The predominance of massive buildings in the Italian territory and the need to comply with Italian regulations often leads technicians to not optimal energy saving solutions. To this purpose, this experimental research was conducted on a mockup building, located in Fabriano and characterized by high thermal mass walls (W0) and two different external insulating systems: Cork based lightweight plaster (W1) and Extruded polystyrene foam panel (XPS) (W2). Furthermore, a virtual model in TRNSYS, a transient simulation software, was used to compare analytical and simulated values. Results show that W2 undergoes a higher level of thermal stress than W1, due to higher peaks in the external surface temperature and larger fluctuations in daily temperature. Therefore, a high value of thermal resistance of the external insulation and low value of external areal heat capacity on a massive building causes external surface overheating problems, thus, not representing the optimal construction solution
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