| 1. |
- Cehlin, Mathias, Doktor, 1974-, et al.
(författare)
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Towards benchmarking of urban air quality based on homogenous surface emission
- 2023
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Ingår i: Results in Engineering (RINENG). - : Elsevier. - 2590-1230. ; 20
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Tidskriftsartikel (refereegranskat)abstract
- Here, it is presented a possible methodology and experimental model for benchmarking of air quality in cities. The concept behind the methodology is that a city’s inherent structure affects the potential for contaminant removal due to the resistance it poses to inflow. The approach is based on homogenous emission across the street surface network, representing a worst-case situation. Different levels of complexity can be used for benchmarking, making it valuable for evaluating different layouts. Additionally, an urban ventilation index suitable for these kinds of experimental studies has been suggested.
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| 2. |
- Darbandi, Tayebeh
(författare)
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Fine Particle Collection in Small-Scale Biofuel Boilers Using Packed-Bed Wet Scrubbers
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Small-scale biofuel boilers are one source of particulate matter (PM) emissions, advertently discharging PM into the air and affecting both human health and the environment. According to the World Health Organization, PM was the fifth leading factor of premature death in 2015. To address this issue, the European Commission’s Clean Air Policy Package was established in 2013, aiming to reduce emissions from energy sources by half by 2030. In Europe, small-scale biofuel boilers and domestic heating systems significantly contribute to the total PM emissions. Therefore, it is imperative to find an economical method for cleaning the flue gas expelled from small-scale boilers.The primary aim of this thesis is to investigate the mechanics of PM cleaning and identify the major parameters that influence cleaning efficiency in the case of flue gas in small-scale biomass boilers. To achieve this goal, an experimental setup has been constructed at Luleå University, comprising a 20kW boiler, three heat exchangers, a generator, and a packed-bed wet scrubber. The flue gas generated during combustion heats the water in the boiler, and heats the absorption solution in the generator, then the total flue gas flow through the absorber (packed bed wet scrubber). A packed-bed wet scrubber is used to bring the flue gas into contact with the absorption solution, thereby removing PM from the gas. The solution is then passed through a filter for purification. A portion of the solution is directed to the generator, where absorbed water in the scrubber is evaporated, and the concentrated solution is returned to the absorber. During an extensive 8-month study, the stability of the solution in collecting PM was tested and showed no signs of deterioration. The system’s average efficiency in collecting PM with a size range of D50 (0.8–10 µm) was found to be 60%. Additionally, the heat recovery of the system was improved by 18%.To elucidate the forces acting on PM within the wet scrubber, CFD simulations of various operational conditions were conducted using Ansys Fluent 19.2. These simulations revealed that the concentration gradient had the most significant impact on PM collection, which is explained by the diffusiophoresis phenomenon. However, the temperature gradient (thermophoresis) did not significantly affect PM collection. The influence of diffusiophoresis and thermophoresis on different PM sizes was also examined for varying flue gas velocities, temperatures, and water vapour mass fractions. The results showed that higher flue gas velocities and larger particle sizes decreased the particle collection efficiency. The simulation results were validated through comparisons with established empirical models.Next, the impact of the operational conditions on PM collection efficiency was investigated. Based on the simulations, experiments were conducted to analyse the effects of the water vapour concentration gradient, temperature gradient, and different heights of the packed-bed material in the absorber. The measurements indicated that higher water vapour concentrations increased the PM collection efficiency. To enhance the system’s efficiency, it is recommended to minimise the solution temperature and maximise the concentration of the absorption solution. Furthermore, a fully packed bed in the absorber provided higher particle collection performance than the half- and quarter-filled packed bed.Additional measurements were conducted to evaluate the influence of several other parameters on system efficiency: gas velocity, bed material, humidity, solution flow rate, and using water as a cleaning liquid.Higher flue gas velocities were observed to diminish the contact time between the flue gas and the absorption solution, increasing the effect of the drag force on PM, resulting in reduced collection efficiency. Moreover, an increased flue gas humidity had a positive impact on collection efficiency, primarily owing to its favourable effect on the diffusiophoresis force. A half-filled packed bed of steel pall rings showed higher performance compared with a half-filled packed bed of ceramic Berl saddles. The analysis also revealed no significant difference in efficiency between the wet scrubber column with a half-filled packed bed of steel pall rings and one with a half-filled packed bed of ceramic Berl saddles. A quarter-filled absorber of steel pall rings showed similar results to an empty absorber, indicating an inadequate pressure drop. Additionally, water was less effective than salt solutions, providing force in the opposite direction of the wet surface within the absorber and decreasing the particle collection efficiency.In the subsequent phase, the system’s ability to remove PM from various pelletised fuels was assessed. Each fuel type, including stem wood pellets, mine waste pellets, municipal solid waste pellets, and poplar pellets, exhibited different levels of PM emissions. In the case of stem wood pellet combustion, fine particles with diameters of less than 1 μm were predominant, and the trend was consistent for the other tested fuels. Notably, the system demonstrated 50% efficacy in reducing PM emissions from poplar pellets, which exhibited the highest levels of released PM, and the efficiency may be increased further by increasing the absorber height. The findings from this research may help in developing more efficient systems for cleaning the flue gas in small-scale boilers.
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| 3. |
- Honghao, Ren, et al.
(författare)
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Literature Review on Development and Implementation of Cross-Laminated Timber
- 2023
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Ingår i: Proceedings of the 5th International Conference on Building Energy and Environment. - Singapore : Springer. - 9789811998218 - 9789811998225
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Konferensbidrag (refereegranskat)abstract
- Achieving the targets of the Paris Agreement as an international treaty on climate change requires global climate actions by all sectors, including ensuring that buildings are more energy efficient. Today’s modern buildings employ a worldwide well-known and versatile usable building material which is a new type of green low-carbon engineered wood product, cross-laminated timber (CLT), for their structural frames. CLT as an innovative plate-shaped product provides a laminated structure and great physicomechanical characteristics. This article studies the development status and implementation of CLT in Europe, emphasizing its material properties and load-bearing characteristics. The newest findings related to CLT are reported. Also, the environmental benefits of using CLT in the construction industry are discussed. Moreover, the energy performance and performance of the utilized CLT elements are highlighted. According to our findings, the embodied energy and embodied carbon are significantly lower in CLT constructions compared with reinforced concrete and steel structures. Finally, the prospects of CLT are presented.
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| 4. |
- Honghao, Ren, et al.
(författare)
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Proposing new adhesive-free timber edge connections for cross-laminated timber panels: A step toward sustainable construction
- 2024
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Ingår i: Case Studies in Construction Materials. - : Elsevier. - 2214-5095. ; 20
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Tidskriftsartikel (refereegranskat)abstract
- The use of timber as a building material is becoming increasingly popular thanks to its superior environmental performance compared with concrete and steel. However, timber structures rely on solid connections to improve their weak expansibility. Steel connections can be prone to corrosion over time, leading to the decreased structural integrity. Additionally, steel connections require more material and energy to manufacture and install compared with timber connections. This article focuses on the flexural performance of cross-laminated timber (CLT) panels with adhesive-free edge connections under four-point bending tests. First, numerical models of experimentally tested CLT panels were constructed using the finite element (FE) software ABAQUS. Then, these FE models were validated with the comparisons of their results with those of the experimental tests. Afterward, four new adhesive-free edge connections using timber for the CLT panels were developed in this study, helping sustainable construction. Utilizing the designed edge connections of the current study, forty-one parametric studies were numerically conducted on the connected CLT panels to investigate their ultimate loads, strains, displacements, moment capacities, failure modes, and effective stiffness. The factors affecting the edge connections’ load-bearing capacity were also examined and discussed. The study provides helpful insights into the development of CLT as a sustainable construction material with improved adhesive-free edge connections.
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| 5. |
- Johansson, Lisen, et al.
(författare)
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A comprehensive review on properties of tailings-based low-carbon concrete: Mechanical, environmental, and toxicological performances
- 2024
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Ingår i: Developments in the Built Environment. - : Elsevier. - 2666-1659. ; 18
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Tidskriftsartikel (refereegranskat)abstract
- With concrete’s key role in construction and infrastructure, the reduction of its carbon footprint is critical for addressing global carbon emissions. One strategy to reduce environmental impact from concrete production is to replace cement clinker or fine aggregates in concrete with industrial wastes. Mine tailings, being a high-volume under-utilized resource, possess properties making it suitable for use as a partial substitute for cement or fine aggregates. This review article provides an overview of the recent findings within the topic of tailings-based concrete (TBC). Many of the identified publications aimed to describe the mechanical performance of TBC, and to optimize the concrete mix with respect to the strength and durability. The recommended cement replacement ranged from 5 to 25% and the recommended fine aggregate replacement ranged from 20 to 60%. In general, the compressive strength was decreased with increasing use of tailings as a replacement of cement. For the use of tailings as replacement for fine aggregates, the correlation was more complex, normally the mechanical performance enhanced at low replacement levels, until it reached an optimum after which it decreased. CO2 savings for replacing fine aggregate with tailings were up to 12% and for the cement replacement up to 30%. When assessing the environmental performance, most of the publications did not account for the loss of its mechanical performance, which could lead to the risk of underestimating the environmental impact. This review not only provides a basis for understanding the mechanical, toxicological, and environmental performances of TBCs, but also links the perspectives together, unveiling the connections between them. Moreover, this review presents an organized overview of the topic of TBC and points out topics for future research.
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| 6. |
- Johansson, Lisen, et al.
(författare)
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Study on Properties and Performance of Green Concrete
- 2023
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Ingår i: SynerCrete'23: International RILEM Conference on Synergising Expertise towards Sustainability and Robustness of Cement-based Materials and Concrete Structures. - : Springer. - 9783031332104 ; , s. 23-35
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Konferensbidrag (refereegranskat)abstract
- Conventional concrete (CC) is for decades the most used construction material worldwide thanks to its good properties such as high strength, high thermal mass, low noise transmission, and high fire resistance. Cement is an important component of CC. The cement industry is a significant source of emissions and accounts for roughly 8% of the world’s CO2 emissions today, which means all improvements that can be made within this single industry benefit the emissions reduction goals. Green concrete (GC) is the development in the field of construction technology, which offers a more sustainable and eco-friendly solution as a building material. GC deals with the mentioned negative issue of cement, since it offers new cementitious matrices where some part of the Portland cement of CC is being replaced by some supplementary cementitious materials, such as industrial by-products, agricultural wastes, or municipal wastes. This paper studies the properties, structural performance, and environmental benefits of GCs. The investigation is done through a literature review, identifying the knowledge gaps, and providing suggestions for further research. The results indicate that there is a good potential to significantly reduce the climate impact of CC by using alternative binder materials in GC.
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| 7. |
- Joudi, Ali, 1980-
(författare)
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Radiation properties of coil-coated steel in building envelope surfaces and the influence on building thermal performance
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Recent studies have shown that the optical properties of building exterior surfaces are important in terms of energy use and thermal comfort. While the majority of the studies are related to exterior surfaces, the radiation properties of interior surfaces are less thoroughly investigated. Development in the coil-coating industries has now made it possible to allocate different optical properties for both exterior and interior surfaces of steel-clad buildings. The aim of this thesis is to investigate the influence of surface radiation properties with the focus on the thermal emittance of the interior surfaces, the modeling approaches and their consequences in the context of the building energy performance and indoor thermal environment.The study consists of both numerical and experimental investigations. The experimental investigations include parallel field measurements on three similar test cabins with different interior and exterior surface radiation properties in Borlänge, Sweden, and two ice rink arenas with normal and low emissive ceiling in Luleå, Sweden. The numerical methods include comparative simulations by the use of dynamic heat flux models, Building Energy Simulation (BES), Computational Fluid Dynamics (CFD) and a coupled model for BES and CFD. Several parametric studies and thermal performance analyses were carried out in combination with the different numerical methods.The parallel field measurements on the test cabins include the air, surface and radiation temperatures and energy use during passive and active (heating and cooling) measurements. Both measurement and comparative simulation results indicate an improvement in the indoor thermal environment when the interior surfaces have low emittance. In the ice rink arenas, surface and radiation temperature measurements indicate a considerable reduction in the ceiling-to-ice radiation by the use of low emittance surfaces, in agreement with a ceiling-toice radiation model using schematic dynamic heat flux calculations.The measurements in the test cabins indicate that the use of low emittance surfaces can increase the vertical indoor air temperature gradients depending on the time of day and outdoor conditions. This is in agreement with the transient CFD simulations having the boundary condition assigned on the exterior surfaces. The sensitivity analyses have been performed under different outdoor conditions and surface thermal radiation properties. The spatially resolved simulations indicate an increase in the air and surface temperature gradients by the use of low emittance coatings. This can allow for lower air temperature at the occupied zone during the summer.The combined effect of interior and exterior reflective coatings in terms of energy use has been investigated by the use of building energy simulation for different climates and internal heat loads. The results indicate possible energy savings by the smart choice of optical properties on interior and exterior surfaces of the building.Overall, it is concluded that the interior reflective coatings can contribute to building energy savings and improvement of the indoor thermal environment. This can be numerically investigated by the choice of appropriate models with respect to the level of detail and computational load. This thesis includes comparative simulations at different levels of detail.
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| 8. |
- Ren, Honghao, et al.
(författare)
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Flexural Behavior of Cross-Laminated Timber Panels with Environmentally Friendly Timber Edge Connections
- 2024
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Ingår i: Buildings. - : MDPI. - 2075-5309. ; 14:5
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Tidskriftsartikel (refereegranskat)abstract
- As a sustainable construction material, timber is more promoted than steel, concrete, and aluminum nowadays. The building industry benefits from using timber based on several perspectives, including decarbonization, improved energy efficiency, and easier recycling and disposal processes. The cross-laminated timber (CLT) panel is one of the widely utilized engineered wood products in construction for floors, which is an ideal alternative option for replacing reinforced concrete. One single CLT panel has an outstanding flexural behavior. However, CLT cannot be extended independently without external connections, which are normally made of steel. This article proposes two innovative adhesive-free edge connections made of timber, the double surface (DS) and half-lapped (HL) connections. These connections were designed to connect two CLT panels along their weak direction. Parametric studies consisting of twenty models were conducted on the proposed edge connections to investigate the effects of different factors and the flexural behavior of CLT panels with these edge connections under a four-point bending test. Numerical simulations of all the models were done in the current study by using ABAQUS 2022. Furthermore, the employed material properties and other relevant inputs (VUSDFLD subroutines, time steps, meshes, etc.) of the numerical models were validated through existing experiments. The results demonstrated that the maximum and minimum load capacities among the studied models were 6.23 kN and 0.35 kN, respectively. The load–displacement responses, strain, stress, and defection distributions were collected and analyzed, as well as their failure modes. It was revealed that the CLT panels’ load capacity was distinctly improved due to the increment of the connectors’ number (55.05%) and horizontal length (80.81%), which also reinforced the stability. Based on the findings, it was indicated that adhesive-free timber connections could be used for CLT panels in buildings and replace traditional construction materials, having profound potential for improving buildings’ sustainability and energy efficiency.
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| 9. |
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Urban Transition - Perspectives on Urban Systems and Environments
- 2023
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Samlingsverk (redaktörskap) (refereegranskat)abstract
- This book assembles the latest knowledge linked to urban environments and urban socio-eco-technological systems including urban, energy, transport, material, and ecosystems. Urban environments and systems affect every person’s life in many ways and can have negative impacts on the local and global environment. They create value but sometimes with a high environmental cost from a lifecycle perspective. Therefore, scientists and global leaders call for an urban transition to create more environmental urban environments and systems that are climate positive, sustainable, and healthy, which is necessary for society to function within the planetary boundaries. This is a great challenge. Huge transformations and new ways of thinking regarding the design and co-existence of technical, social, and ecological systems are necessary to turn the present challenge into opportunities. This book, Urban Transition - Perspectives on Urban Systems and Environments, explores this challenge and several different topics related to possible, probable, or necessary urban transitions in the urban environment. It assembles a variety of authors who present many aspects and the latest knowledge linked to urban transitions of the urban environment and urban socio-eco-technological systems - including urban-, energy-, transport-, building- material- and eco-systems.Furthermore, the importance of the urban systems and urban environments is seldom clearly linked to their impact on the environment and humans. This book examines this gap, the crucial issues relating to how urban systems influence the urban structure, and how they can be formed and designed to become more sustainable. It explores the link between the complex systems in cities, the physicality of the built environment, and the living environments for the people. The book proposes a rich garden of ideas to provoke and develop current research, debate, and new forms of practices.
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| 10. |
- Wallhagen, Marita, tekn dr, docent, 1979-, et al.
(författare)
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Viewpoints on Environmental Assessment of Building Certification Method - Miljöbyggnad
- 2021
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Ingår i: Urban Transition - Perspectives on Urban Systems and Environments. - : IntechOpen.
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Bokkapitel (refereegranskat)abstract
- Production, management, use, and end-of-life of buildings has a large impact on climate change. Therefore, environmental targets are set to lower the greenhouse gas (GHG) emissions from the building sector. To reach these targets building regulation and voluntary environmental assessment methods (EAMs) that evaluate and certify the building's environmental impact are put forward as tools to push the building sector towards lower GHG emissions. In Sweden, building design is governed by building regulations and the dominant EAM is ‘Miljöbyggnad’ (MB) (“Environmental building”). Today, more than 1900 buildings have been certified by MB and it has influenced the building and property sector. In this chapter the potential impact MB and the linked Swedish building regulations have on building performance, energy use and GHG emissions, will be reviewed and discussed. The analysis investigates several of the MB’s indicators, evaluate to what degree EAMs can influence the design of the building and the energy system to lower the energy use and GHG emissions based on material choices. The analysis presents important aspects that may influence the design of the building and its energy system and what challenges and possibilities the indicators, criteria and regulations can have on buildings and climate change. In addition, some modification and suggestion for improvements are presented.
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