Research

13 pages, 3377 KiB

Open AccessArticle

Intelligent Anti-Seismic Foundation: The Role of Fractal Geometry

by Ahmad Saoud, Diogo Queiros-Conde, Ahmad Omar and Thomas Michelitsch

Buildings 2023, 13(8), 1891; https://doi.org/10.3390/buildings13081891 - 25 Jul 2023

Viewed by 902

Safe and resistant infrastructure is an essential component of public safety. However, existing structures are vulnerable to damage resulting from excessive ground movement due to seismic activity or underground explosions. The aim of this paper, which is part of an extensive study, is [...] Read more.

Safe and resistant infrastructure is an essential component of public safety. However, existing structures are vulnerable to damage resulting from excessive ground movement due to seismic activity or underground explosions. The aim of this paper, which is part of an extensive study, is to develop an isolation system based on periodic materials with H-fractal geometry in order to obstruct, absorb or completely modify the pattern of seismic energy before it reaches the foundations of structures. Fractal metamaterial structures have shown promise for increasing the frequency range prohibited for seismic protection. We report the anti-seismic properties of a seismic metamaterial model based on an H-shaped quasi-fractal cell. The fractal design, also known as seismic metamaterials, has an important impact on the band structures of seismic crystals. Using the fractal as a base unit, anti-seismic phononic crystals were developed, and their band-gap characteristics were shown to display unique features due to the increasing wave propagation path and hybridization between local resonances and Bragg scattering. The seismic–mechanical duality is supposed to provide flexible solutions capable of increasing/widening the band-gaps to improve the level of seismic protection. Full article

(This article belongs to the Special Issue Computational Fluid Dynamics Modeling for Smart Buildings Design)

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16 pages, 4577 KiB

Open AccessArticle

Indoor Airflow Dynamics in Compartmentalized Pneumology Units Equipped with Variable-Thickness MERV-13 Filters

by Camilo Gustavo Araújo Alves, José Tadeu C. Junior, Francisco Bernardino Da Silva Neto, Gustavo R. Anjos, Moisés Dantas Dos Santos and Gustavo Peixoto de Oliveira

Buildings 2023, 13(4), 1072; https://doi.org/10.3390/buildings13041072 - 19 Apr 2023

Viewed by 1040

Abstract

Infection containment in the post-pandemic scenario became a top priority for healthcare engineering control staffers, especially in pneumology sectors, where the treatment of airborne infectious diseases is frequent. In Brazil, where COVID-19 left a long record of casualties, there is a lack of [...] Read more.

Infection containment in the post-pandemic scenario became a top priority for healthcare engineering control staffers, especially in pneumology sectors, where the treatment of airborne infectious diseases is frequent. In Brazil, where COVID-19 left a long record of casualties, there is a lack of information on the influence of filtration systems on the maintenance of regulated operational conditions for indoor comfort in hospital environments. This paper has the following objectives: to study arrangements of filtering systems in hospital acclimatization ducts; to verify how filtering characteristics could compromise safety regulations for airflow in hospital environments; and to identify airflow stagnation points that might favor suspended viral concentrations and increase contamination risks. We used the computational fluid dynamics STAR-CCM+© software to perform numerical simulations of different cases of indoor airflow in a model corresponding to a sector of the Lauro Wanderley University Hospital (João Pessoa city, Brazil). We concluded that standards for maximum velocity are reachable despite thinner or thicker filters affecting the spread of the air. In this way, acclimatization systems are limited by a tradeoff between regulation and protection. Our findings are relevant to future technological development, interventions, safety strategies amidst contamination scenarios, and new filtration arrangements in hospital environments. Full article

(This article belongs to the Special Issue Computational Fluid Dynamics Modeling for Smart Buildings Design)

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38 pages, 12189 KiB

Open AccessArticle

Thermophysical Characterization of Paraffins versus Temperature for Thermal Energy Storage

by Manel Kraiem, Mustapha Karkri, Magali Fois and Patrik Sobolciak

Buildings 2023, 13(4), 877; https://doi.org/10.3390/buildings13040877 - 27 Mar 2023

Cited by 2 | Viewed by 1979

Abstract

Latent heat storage systems (LHSS), using solid–liquid phase change materials (PCMs), are attracting growing interest in many applications. The determination of the thermophysical properties of PCMs is crucial for selecting the appropriate material for an LHSS and for predicting the thermal behavior of [...] Read more.

Latent heat storage systems (LHSS), using solid–liquid phase change materials (PCMs), are attracting growing interest in many applications. The determination of the thermophysical properties of PCMs is crucial for selecting the appropriate material for an LHSS and for predicting the thermal behavior of the PCM. In this context, the thermophysical characterization of four paraffins (RT21, RT27, RT35HC, RT50) at different temperatures, including the solid and liquid phases, is conducted in this investigation. This work is part of a strategic technological brick in the CERTES laboratory of the Paris Est University to build a database for phase change material properties. It contains the measurements of the thermophysical, optical and mechanical properties. It will serve as input for the numerical simulations to study the behavior of PCMs in LHSS. The temperatures and the latent heats of the phase transitions as well as the thermal dependence of the specific heat of the paraffins were evaluated by differential scanning calorimetry (DSC). In addition, the DSC measurements under successive thermal cycles revealed good reliability of the paraffins. Thermogravimetric analysis (TGA) was performed, and the results highlighted the thermal stability of the paraffins. Moreover, the evolutions of the thermal conductivities and diffusivities with temperature were measured simultaneously using the hot disk method. A discontinuity of the thermal conductivities was observed near the melting temperatures. Furthermore, the measurements of the densities of the paraffins at different temperatures were carried out. The volume changes and the coefficients of thermal expansion were assessed. The obtained outcomes of this study were compared with the available bibliographical data. Full article

(This article belongs to the Special Issue Computational Fluid Dynamics Modeling for Smart Buildings Design)

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27 pages, 6669 KiB

Open AccessArticle

Experimental Performance and Cost-Effectiveness of a Combined Heating System under Saharan Climate

by Sidi Mohammed El Amine Bekkouche, Rachid Djeffal, Mohamed Kamal Cherier, Maamar Hamdani, Zohir Younsi, Saleh Al-Saadi and Mohamed Zaiani

Buildings 2023, 13(3), 635; https://doi.org/10.3390/buildings13030635 - 27 Feb 2023

Cited by 1 | Viewed by 1557

Abstract

The solar water heater can be integrated into future residential buildings as the main energy source, which will subsequently reduce the energy cost of water heating. An original configuration for an efficient Domestic Hot Water (DHW) storage tank is developed and experimentally evaluated [...] Read more.

The solar water heater can be integrated into future residential buildings as the main energy source, which will subsequently reduce the energy cost of water heating. An original configuration for an efficient Domestic Hot Water (DHW) storage tank is developed and experimentally evaluated under Saharan climate. This novel DHW configuration includes a hybrid (solar and electric) energy system with a flat plate solar collector coupled with an electric heater. Additionally, a phase change material (PCM) mixture that is composed of paraffin wax and animal fat with a melting temperature between 35.58 °C and 62.58 °C and latent heat between 180 and 210 kJ/kg is integrated into this novel tank configuration. The experimental results indicated that hot water production by using latent heat storage could be economically attractive. By evaluating the cost of water heating expressed in Algerian dinar per liter (DZD/L), it was found that one liter of hot water may cost around 0.1362 DZD/L (i.e., 0.00096 USD/L) compared to 0.4431 DZD/L for the conventional water heater, an average energy cost savings of 69.26%. On a yearly basis, the average energy cost savings may reach up to 80.25% if optimal tilt for the solar collector is adopted on a monthly basis. The flat plate collector may be vulnerable to convective heat transfer; therefore, other solar collectors, such as vacuum tube collectors, may provide enhanced energy performance. Full article

(This article belongs to the Special Issue Computational Fluid Dynamics Modeling for Smart Buildings Design)

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21 pages, 8378 KiB

Open AccessArticle

New Method for Solving the Inverse Thermal Conduction Problem (θ-Scheme Combined with CG Method under Strong Wolfe Line Search)

by Rachid Djeffal, Djemoui Lalmi, Sidi Mohammed El Amine Bekkouche, Tahar Bechouat and Zohir Younsi

Buildings 2023, 13(1), 243; https://doi.org/10.3390/buildings13010243 - 15 Jan 2023

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Abstract

Most thermal researchers have solved thermal conduction problems (inverse or direct) using several different methods. These include the usual discretization methods, conventional and special estimation methods, in addition to simple synchronous gradient methods such as finite elements, including finite and special quantitative methods. [...] Read more.

Most thermal researchers have solved thermal conduction problems (inverse or direct) using several different methods. These include the usual discretization methods, conventional and special estimation methods, in addition to simple synchronous gradient methods such as finite elements, including finite and special quantitative methods. Quantities found through the finite difference methods, i.e., explicit, implicit or Crank–Nicolson scheme method, have also been adopted. These methods offer many disadvantages, depending on the different cases; when the solutions converge, limited range stability conditions. Accordingly, in this paper, a new general outline of the thermal conduction phenomenon, called (θ-scheme), as well as a gradient conjugate method that includes strong Wolfe conditions has been used. This approach is the most useful, both because of its accuracy (16 decimal points of importance) and the speed of its solutions and convergence; by addressing unfavorable adverse problems and stability conditions, it can also have wide applications. In this paper, we applied two approaches for the control of the boundary conditions: constant and variable. The θ-scheme method has rarely been used in the thermal field, though it is unconditionally more stable for θ∈ [0.5, 1]. The simulation was carried out using Matlab software. Full article

(This article belongs to the Special Issue Computational Fluid Dynamics Modeling for Smart Buildings Design)

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23 pages, 5691 KiB

Open AccessArticle

The Potential of Using Passive Cooling Roof Techniques to Improve Thermal Performance and Energy Efficiency of Residential Buildings in Hot Arid Regions

by Wafa Athmani, Leila Sriti, Marwa Dabaieh and Zohir Younsi

Buildings 2023, 13(1), 21; https://doi.org/10.3390/buildings13010021 - 22 Dec 2022

Cited by 4 | Viewed by 3769

Abstract

In hot dry regions, the building envelope receives abundant solar radiation, which contributes to heat stress and indoor thermal discomfort. To mitigate overheating inside spaces, cooling is the main basic requirement during most of the year. However, due to the harsh climatic conditions, [...] Read more.

In hot dry regions, the building envelope receives abundant solar radiation, which contributes to heat stress and indoor thermal discomfort. To mitigate overheating inside spaces, cooling is the main basic requirement during most of the year. However, due to the harsh climatic conditions, buildings fail to provide passively the required comfort conditions. Consequently, they are fully dependent on-air conditioning systems, which are huge energy consumers. As roofs are exposed to the sun throughout the daytime, they are estimated to be the main source of heat stress. In return, they can contribute significantly to achieve optimum comfort and energy savings when efficient design strategies are used in an early design stage. To examine the potential for cooling load reduction and thermal comfort enhancement by using cooling roof techniques in residential buildings, a study was performed in the city of Biskra (southern Algeria). Accordingly, an in-field measurement campaign was carried out on test-cells during five days in summer. Three different cooling roof techniques were addressed: (a) cool reflective white paint (CR), (b) white ceramic tiles (CT) and (c) a cool-ventilated roof (C-VR). These roofing alternatives were investigated by monitoring both roof surface temperatures and indoor temperatures. Comparative analysis showed that a cool-ventilated roof is the most efficient solution, reducing the average indoor temperature by 4.95 °C. A dynamic simulation study was also performed based on TRNSYS software to determine the best roofing system alternatives in terms of thermal comfort and energy consumption, considering the hottest month of the year. Simulation tests were run on a base-case model representing the common individual residential buildings in Biskra. Results showed that a double-skin roof combined with cool-reflective paint is the most efficient roofing solution. By comparison to a conventional flat roof, meaningful improvements have been achieved, including reducing thermal discomfort hours by 45.29% and lowering cooling loads from 1121.91 kWh to 741.09 kWh. Full article

(This article belongs to the Special Issue Computational Fluid Dynamics Modeling for Smart Buildings Design)

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19 pages, 6028 KiB

Open AccessArticle

A Parametric Study on the Effects of Green Roofs, Green Walls and Trees on Air Quality, Temperature and Velocity

by Azin Hosseinzadeh, Andrea Bottacin-Busolin and Amir Keshmiri

Buildings 2022, 12(12), 2159; https://doi.org/10.3390/buildings12122159 - 07 Dec 2022

Cited by 4 | Viewed by 1970

Abstract

The rapid increase in urbanisation and population growth living in urban areas leads to major problems including increased rates of air pollution and global warming. Assessing the impact of buildings on wind flow, air temperature and pollution dispersion on people at the pedestrian [...] Read more.

The rapid increase in urbanisation and population growth living in urban areas leads to major problems including increased rates of air pollution and global warming. Assessing the impact of buildings on wind flow, air temperature and pollution dispersion on people at the pedestrian level is, therefore, of crucial importance for urban design. In this study, the effect of different forms of urban vegetation including green roofs, green walls and trees on velocity, air temperature and air quality is assessed using computational fluid dynamics (CFD) for a selected area of the East Village. This study indicates that adding a building increases air temperature, pollution concentration and velocity at the pedestrian level. A parametric analysis is conducted to assess the impact of various key parameters on air temperature, pollution and velocity at the pedestrian level. The variables under consideration include wind speed, ranging from 4–8 m/s at a reference height of 10 m, and vegetation cooling intensity, ranging from 250–500 W·m⁻³. Three scenarios are tested in which the streets have no bottom heating, 2 °C bottom heating and 10 °C bottom heating. Pollution is simulated as a form of passive scalar with an emission rate of 100 ppb s⁻¹, considering NO₂ as the pollutant. In all cases, vegetation is found to reduce air velocity, pollutant concentration and temperature. However, the presence of vegetation in various forms alters the pattern of pollution dispersion differently. More specifically, the results indicate that planting trees (e.g., birch trees) close to the edge of buildings can decrease the air temperature by up to 2–3 °C at the pedestrian level. Increasing the cooling intensity of the vegetation from 250 to 500 W·m⁻³ results in significantly lower air temperature, whereas lower wind speeds result in a higher concentration of pollutants at the pedestrian level. A combination of green walls and trees is found to be the most effective strategy to improve the thermal environment and air quality. Full article

(This article belongs to the Special Issue Computational Fluid Dynamics Modeling for Smart Buildings Design)

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17 pages, 7956 KiB

Open AccessArticle

Numerical Evaluation of the Flow Field of an Isothermal Dual-Corner Impinging Jet for Building Ventilation

by Arman Ameen, Haruna Yamasawa and Tomohiro Kobayashi

Buildings 2022, 12(10), 1767; https://doi.org/10.3390/buildings12101767 - 21 Oct 2022

Cited by 3 | Viewed by 1385

Abstract

The corner impinging jet ventilation is a new air distribution system for use in office environments. This study reports the mean flow field behavior of dual isothermal corner-placed inlets based on an impinging jet in a square-shaped room with the size of 7.2 [...] Read more.

The corner impinging jet ventilation is a new air distribution system for use in office environments. This study reports the mean flow field behavior of dual isothermal corner-placed inlets based on an impinging jet in a square-shaped room with the size of 7.2 m × 7.2 m. A detailed numerical study is carried out to evaluate the influence the different configuration parameters, such as the inlet placement, same side or opposite side, and supply airflow rate, have on the flow field. The results show that the highest velocity peak for all cases is obtained at x = 0.5 m and the lowest at x = 3.5 m. The velocity profiles development remains similar when increasing the flow rate. For the zone evaluation, the results show that Case 1 and 2 (V = 20 L/s) meet the requirement of not exceeding 0.15 m/s during the heating season in the occupied zone according the BBR standard both for same-side and opposite-side configurations. For Case 4, the optimal placement of the inlets is opposite to each other when V = 30 L/s for the BBR requirements. Case 1, 2, 3, 4, 5, and 7 all meet the requirement of not exceeding 0.25 m/s during the cooling season both for the same-side and opposite-side configurations. For Case 8, the optimal placement of the inlets is opposite to each other when V = 50 L/s. Full article

(This article belongs to the Special Issue Computational Fluid Dynamics Modeling for Smart Buildings Design)

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