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Sökning: WFRF:(Sadrizadeh Sasan)

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1.
  • Alirahmi, Seyed Mojtaba, et al. (författare)
  • An innovative four-objective dragonfly-inspired optimization algorithm for an efficient, green, and cost-effective waste heat recovery from SOFC
  • 2023
  • Ingår i: Energy. - : Elsevier BV. - 0360-5442 .- 1873-6785. ; 263
  • Tidskriftsartikel (refereegranskat)abstract
    • This work proposes a novel yet practical dragonfly optimization algorithm that addresses four competing ob-jectives simultaneously. The proposed algorithm is applied to a hybrid system driven by the solid oxide fuel cell (SOFC) integrated with waste heat recovery units. A function-fitting neural network is developed to combine the thermodynamic model of the system with the dragonfly algorithm to mitigate the calculation time. According to the optimization outcomes, the optimum parameters create significantly more power and have a greater exergy efficiency and reduced product costs and CO2 emissions compared to the design condition. The sensitivity analysis reveals that while the turbine inlet temperatures of power cycles are ineffective, the fuel utilization factor and the current density significantly impact performance indicators. The scatter distribution indicates that the fuel cell temperature and steam-to-carbon ratio should be kept at their lowest bound. The Sankey graph shows that the fuel cell and afterburner are the main sources of irreversibility. According to the chord diagram, the SOFC unit with a cost rate of 13.2 $/h accounts for more than 29% of the overall cost. Finally, under ideal conditions, the flue gas condensation process produces an additional 94.22 kW of power and 760,056 L/day of drinkable water.
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3.
  • Alsved, Malin, et al. (författare)
  • Airborne bacteria in hospital operating rooms during ongoing surgery
  • 2018
  • Konferensbidrag (refereegranskat)abstract
    • IntroductionPost-operative infections obtained from open-wound surgeries constitute an unnecessary load on both healthcare and affected patients. It is well established that increased air cleanliness reduces the number of post-operative infections. Therefore, the ventilation system is important in order to reduce the number of infectious particles in the air during surgery. Ventilation with high airflow, as in operating rooms, consumes a high amount of energy and it is thus desirable to find energy efficient solutions. ObjectivesThe purpose of this work was to evaluate air quality, energy efficiency and working environment comfort for three different ventilation techniques in operating rooms. MethodThe newly developed ventilation system temperature controlled airflow (TcAF) was compared with the conventionally used turbulent mixed airflow (TMA) and laminar airflow (LAF). In total, 750 air sample measurements were performed during 45 orthopaedic operations: 15 for each type of ventilation system [1]. The concentration of colony forming units (CFU)/m3 was measured at three locations in the rooms: close to the wound (<0.5 m), at the instrument table and peripherally in the room. The working environment comfort was evaluated in a questionnaire.ResultsOur study shows that both LAF and TcAF maintains CFU concentrations in the air during ongoing surgery significantly below 10 CFU/m3 at the wound and at the instrument table, and for TcAF also in the periphery of the room, see Figure 1. The median CFU concentration in TMA was at or above 10 CFU/m3 at all locations. TcAF used less than half the airflow to that of LAF, resulting in a 28% reduction in energy consumption. The working environment comfort was perceived less noisy and having less draft in the TcAF than the LAF ventilation.SummaryBoth the LAF and TcAF ventilation maintain high air cleanliness with low CFU concentrations throughout the operation. TMA is less efficient in removing bacteria from the air close to the patient.
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4.
  • Alsved, Malin, et al. (författare)
  • Experimental and computational evaluation of airborne bacteria in hospital operating rooms with high airflows
  • 2018
  • Ingår i: Proceedings of The 5<sup>th</sup> Working &amp; Indoor Aerosols Conference 18-20 April 2018; Cassino, Italy.
  • Konferensbidrag (refereegranskat)abstract
    • Post-operative infections after surgery can be decreased by the use of efficient ventilation with clean air. In this study, we investigated three types of operating room ventilation: turbulent mixed airflow(TMA), laminar airflow (LAF) and a new type of ventilation named temperature controlled airflow(TcAF). Measurements of airborne bacteria were made during surgery and compared with values calculated by computational fluid dynamics (CFD). The results show that LAF and TcAF are most efficient in removing bacteria around the patient. With LAF, there are large differences in bacterial loads, depending on location in the room.
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5.
  • Alsved, M., et al. (författare)
  • Temperature-controlled airflow ventilation in operating rooms compared with laminar airflow and turbulent mixed airflow
  • 2018
  • Ingår i: Journal of Hospital Infection. - : W B SAUNDERS CO LTD. - 0195-6701 .- 1532-2939. ; 98:2, s. 181-190
  • Tidskriftsartikel (refereegranskat)abstract
    • Aim: To evaluate three types of ventilation systems for operating rooms with respect to air cleanliness [in colony-forming units (cfu/m(3))], energy consumption and comfort of working environment (noise and draught) as reported by surgical team members. Methods: Two commonly used ventilation systems, vertical laminar airflow (LAF) and turbulent mixed airflow (TMA), were compared with a newly developed ventilation technique, temperature-controlled airflow (T(c)AF). The cfu concentrations were measured at three locations in an operating room during 45 orthopaedic procedures: close to the wound (<40 cm), at the instrument table and peripherally in the room. The operating team evaluated the comfort of the working environment by answering a questionnaire. Findings: LAF and T(c)AF, but not TMA, resulted in less than 10 cfu/m(3) at all measurement locations in the room during surgery. Median values of cfu/m(3) close to the wound (250 samples) were 0 for LAF, 1 for T(c)AF and 10 for TMA. Peripherally in the room, the cfu concentrations were lowest for T(c)AF. The cfu concentrations did not scale proportionally with airflow rates. Compared with LAF, the power consumption of T(c)AF was 28% lower and there was significantly less disturbance from noise and draught. Conclusion: T(c)AF and LAF remove bacteria more efficiently from the air than TMA, especially close to the wound and at the instrument table. Like LAF, the new T(c)AF ventilation system maintained very low levels of cfu in the air, but T(c)AF used substantially less energy and provided a more comfortable working environment than LAF. This enables energy savings with preserved air quality.
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6.
  • Amjadimanesh, Hossein, et al. (författare)
  • Micro-particle deposition in maxillary sinus for various sizes of opening in a virtual endoscopic surgery
  • 2023
  • Ingår i: Experimental and Computational Multiphase Flow. - : Springer Nature. - 2661-8869 .- 2661-8877. ; 5:3, s. 262-271
  • Tidskriftsartikel (refereegranskat)abstract
    • Treatment of sinusitis by surgical procedures is recommended only when medication therapies fail to relieve sinusitis symptoms. In this study, a realistic 3D model of the human upper airway system was constructed based on CT images of an adult male and three different virtual functional endoscopic sinus surgeries (FESS), including only uncinectomy and uncinectomy with two different sizes of Middle Meatal Antrostomy (MMA) performed on that model. Airflow and deposition of micro-particles in the range of 1–30 µm were numerically simulated in the postoperative cases for rest and moderate activity breathing conditions. The results showed that the uncinate process alone protects the maxillary sinus well against the entry of micro-particles, and its removal by uncinectomy allows particles to deposit on the sinus wall easily. Generally, uncinectomy with a degree of MMA increases the number of deposited particles in the maxillary sinuses compared to uncinectomy surgery alone. In the studied models, the highest particle deposition in the maxillary sinuses occurred among particles with a diameter of 10–20 µm. Also, if a person inhales particles during rest breathing conditions at a low respiratory rate, the number of particles deposited in the sinuses increases. [Figure not available: see fulltext.]
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7.
  • Amjadimanesh, Hossein, et al. (författare)
  • The effect of body position while coughing on the airborne transmission of pathogens
  • 2022
  • Ingår i: Physics of fluids. - : AIP Publishing. - 1070-6631 .- 1089-7666. ; 34:4, s. 041902-
  • Tidskriftsartikel (refereegranskat)abstract
    • Given the recent acceptance of the central role of airborne transmission for SARS-CoV-2, increased attention has been paid to the dispersion of respiratory droplets in different scenarios. Studies including numerical simulations have been conducted on methods for breaking the chains of transmission. Here, we present the first such study on the impact of body position while coughing on the dispersion of respiratory droplets. Four scenarios are examined, including normal standing, bending the head at different angles, coughing into the elbow in still air, and a gentle breeze from the front and behind. The model showed that an uncovered cough is dangerous and causes many droplets to enter the environment, posing a cross-contamination threat to the others. Droplets with an initial diameter smaller than 62.5 mu m remain suspended in windless air for more than 3 min. In the presence of wind, these droplets move with the wind flow and may travel long distances greater than 3.5 m. The model showed that covering the mouth with the elbow while coughing is clearly the best strategy for reducing airborne transmission of exhaled pathogens. About 62% of the initial number of droplets deposit on the cougher's elbow immediately after the cough and have no chance of spreading through the air in both windless and windy conditions. Covering the cough in windless or light breeze conditions also causes the upward thermal plume around the body to expel many small droplets.
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8.
  • Anund Vogel, Jonas, et al. (författare)
  • Buildings post corona
  • 2023
  • Ingår i: The REHVA European HVAC Journal. - 1307-3729. ; 59:2, s. 19-21
  • Tidskriftsartikel (populärvet., debatt m.m.)abstract
    • Buildings Post Corona is a Swedish collaborative research project between Chalmers, KTH Royal Institute of Technology, Lund, and Umeå Universities. The project supports the building sector in designing and maintaining sustainable buildings with a healthy and good indoor environment. The COVID-19 crisis has stressed the importance and urge of this research.The scope of the project is to develop a methodology for the operation and design of buildings with an indoor environment that meets future health and climate challenges. The project’s overall goal is to establish an interdisciplinary platform to document existing experiences and knowledge and to gain new knowledge required for good building design and operation.
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9.
  • Anund Vogel, Jonas, et al. (författare)
  • Enbart avstånd och handhygien räcker inte
  • 2023
  • Ingår i: Fastighetstidningen. - 0348-5552.
  • Tidskriftsartikel (populärvet., debatt m.m.)abstract
    • I denna debattartikel lyfter sex forskare frågan att myndigheter och branschorganisationer delvis gav olika råd kring åtgärder för att begränsa risken för smittspridning inomhus. För att klara nästa pandemi krävs bättre samordning av riktlinjer kring ventilation och luftkvalitet.
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10.
  • Behzadi, Amirmohammad, et al. (författare)
  • A comparative evaluation of alternative optimization strategies for a novel heliostat-driven hydrogen production/injection system coupled with a vanadium chlorine cycle
  • 2022
  • Ingår i: Energy Conversion and Management. - : Elsevier BV. - 0196-8904 .- 1879-2227. ; 267, s. 115878-
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper introduces an innovative and cost-effective multi-generation plant, driven by the central receiverbased concentrated solar systems, to facilitate the desired global green-transition process. The vanadium chlorine thermochemical cycle, which uses hydrogen instead of natural gas in the combustion chamber, is used as an innovative approach for reducing greenhouse gas emissions. The proposed system also includes a thermoelectric generator (TEG) for excess power generation and a multi-effect desalination (MED) unit to reduce exergy loss. The suggested system's technological, economic, and environmental metrics are analyzed and compared to a similar system that stores the created hydrogen rather than burning it in the combustion chamber. Furthermore, the viability of the studied model is investigated under the optimal operating condition, using the example of Sevilla in order to make the conclusions more reliable. According to the findings, the suggested novel configuration is a better alternative in terms of cost and environmental impact owing to decreased product energy costs and CO2 emissions. The outcomes further indicate that the substitution of the condenser with TEG leads to considerably higher power production. According to the optimization findings, the multi-objective grey wolf algorithm is the best optimization strategy compared to the non-dominated genetic and particle swarm approaches. At the best optimization point, 2.5% higher exergy efficiency, 1 $/GJ cheaper product energy cost, and 0.12 kg/kWh lower levelized CO2 emission are achieved compared to the operating condition. The Sankey diagram indicates that the solar heliostat system has the highest irreversibility. The exergy analysis results further reveal that the flue gas condensation process through the Rankine cycle and MED unit lead to a 53.2% reduction in exergy loss. Finally, considerable CO2 emission reductions show that the suggested new method is an effective solution for cleaner energy production in warmer climate countries.
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11.
  • Behzadi, Amirmohammad, et al. (författare)
  • A Green and Energy-Efficient Smart Building Driven by Photovoltaic Thermal Panels Connected to the Grid
  • 2023
  • Ingår i: International Conference on Smart Cities and Green ICT Systems, SMARTGREENS - Proceedings. - : Science and Technology Publications, Lda. - 9789897586514 ; , s. 106-112
  • Konferensbidrag (refereegranskat)abstract
    • The present paper introduces a new smart building system driven by photovoltaic thermal panels. The concept is to improve the contribution of renewable energy in the local matrix for peak load shaving by having a two-way connection with the local electricity network via a rule-based energy monitoring control design. Besides, the feasibility of removing the electrical storage unit with high investment cost is studied by establishing a dynamic interaction between the energy production and usage components to reduce the energy costs over the year. The system has intelligent thermal energy storage integrated with an electrically-driven coil, heat exchanger, pumps, and several smart valves and control units. The transient system simulation (TRNSYS) package is implemented to assess the practicality of the suggested intelligent model for a building complex in Malmo, Sweden. According to the parametric outcomes, by raising the panel area, while the generated electricity increases, the solar utilization factor falls, indicating conflictive changes among performance metrics. The results also show that the renewable resource covers the building's heating and electricity demands for the majority of the year and that a significant amount of energy is sold to the neighbourhood electricity grid, demonstrating the viability of the introduced intelligent model.
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12.
  • Behzadi, Amirmohammad, et al. (författare)
  • A hybrid machine learning-assisted optimization and rule-based energy monitoring of a green concept based on low-temperature heating and high-temperature cooling system
  • 2023
  • Ingår i: Journal of Cleaner Production. - : Elsevier Ltd. - 0959-6526 .- 1879-1786. ; 384
  • Tidskriftsartikel (refereegranskat)abstract
    • This article aims to support the targeted worldwide green transition process by introducing and thoroughly analyzing a low-temperature heating and high-temperature cooling, smart building system. This concept allows for greater use of renewable energy while utilizing less input energy than conventional heating and cooling techniques. The proposed system consists of a reversible water-to-water heat pump driven by low-temperature geothermal energy. A rule-based control strategy is developed to establish an intelligent connection with the regional energy grids for peak shaving and compensating for the building's energy costs over the year. The dynamic simulation is carried out for a multi-family building complex in Stockholm, Sweden, using TRNSYS. The most favorable operating condition is determined via an artificial neural network-assisted tri-objective optimizer based on the grey wolf algorithm in MATLAB. The comparison of the proposed smart model with the conventional system in Sweden results in 332%, 203%, and 190% primary energy reduction, cost saving, and carbon dioxide emission mitigation, respectively. As indicated by the parametric results, the conflicting fluctuation between desirable and unfavorable indicators highlights the importance of multi-objective optimization. The grey wolf optimizer obtains 12% higher efficiency, 1.2 MWh lower annual bought energy, 24 $/MWh lower unit cost, and 5.1 MWh more yearly sold energy than the design condition. The scattered distribution reveals that tank volume and subcooling degree are sensitive parameters. According to the transient results, the suggested smart system can independently satisfy the building's heating, cooling, and electricity demands for more than 81% of the year, thanks to the two-way connection with the electricity and heating networks via the rule-based controller. 
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13.
  • Behzadi, Amirmohammad, et al. (författare)
  • A rule-based energy management strategy for a low-temperature solar/ wind-driven heating system optimized by the machine learning-assisted grey wolf approach
  • 2023
  • Ingår i: Energy Conversion and Management. - : Elsevier BV. - 0196-8904 .- 1879-2227. ; 277, s. 116590-
  • Tidskriftsartikel (refereegranskat)abstract
    • This work presents an innovative, practical, and cost-effective solution for advancing state-of-the-art intelligent building energy systems and aiding the intended worldwide green transition with maximum renewable inte-gration. The vanadium chloride cycle, electrolyzer unit, and Alkaline fuel cell are powered by the sun's and wind's energy to produce/store/use hydrogen. A rule-based control scheme is designed to provide a sophisticated interplay between the demand/supply sides, components, and local energy networks to reduce peak capacity, lower emissions, and save energy costs. TRNSYS is used to analyze and compare the techno-economic-environmental indicators of the conventional system and the suggested smart model for a multi-family build-ing in Sweden. A grey wolf method is built in MATLAB with the help of machine learning to determine the optimum operating state with the maximum accuracy and the least amount of computational time. The results reveal that the suggested smart model considerably saves energy and money compared to the conventional system in Sweden while lowering CO2 emissions. According to the optimization results, the grey wolf optimizer and machine learning techniques enable greater total efficiency of 13 %, higher CO2 mitigation of 8 %, a larger cost saving of 38 %, and a reduced levelized energy cost of 41 $/MWh. The scatter distribution of important design parameters shows that altering the fuel cell current and electrode area considerably impacts the system's performance from all angles. The bidirectional connection of the proposed smart system with the heating and electrical networks through the rule-based controller demonstrates that it can supply the building's energy re-quirements for more than 300 days of the year. Eventually, the major contribution of the vanadium chloride cycle in the summer and the electrolyzer in the winter to the creation of hydrogen highlights the significance of renewable hybridization in reducing the dependence of buildings on energy networks.
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14.
  • Behzadi, Amirmohammad, et al. (författare)
  • A smart zero-energy building having bidirectional interaction with electricity/heating networks : An attempt to achieve a higher renewable penetration
  • 2023
  • Ingår i: 11th International Conference on Indoor Air Quality, Ventilation and Energy Conservation in Buildings, IAQVE C2023. - : EDP Sciences.
  • Konferensbidrag (refereegranskat)abstract
    • The present research introduces an innovative zero-energy building complex equipped with a rule-based control approach for higher integration of renewable resources in the local energy network while bringing down energy costs. The idea centers on establishing several smart controllers to achieve a bidirectional interaction with the heating/electricity network for peak demand shaving and mitigate energy costs. The proposed system comprises Alkaline fuel cells integrated with a hydrogen storage tank driven by either a vanadium chloride cycle or an electrolyzer unit. The system also has an absorption chiller and smart thermal energy storage to supply the heating and cooling demands. TRNSYS-MATLAB developed code is applied to assess the system's indicators from techno-economic standpoints for a residential building complex in the Scandinavian climate. Also, the parametric investigation and time-dependent analysis are carried out to examine the impact of decision parameters and the ambient condition. According to the results, the solar system's physical appearance is very important since it significantly affects performance efficiency and total cost. The results further reveal that picking up the cells' current from 300 A to 500 A improves the performance efficiency by around 12% while lowering the total cost, illustrating the importance of optimization. The results highlight the importance of smart controllers by showing that over 70% of the year's net energy values are positive, indicating that the proposed system may meet demand and sell excess electricity+heating productions to regional networks. The results further demonstrate that since the net energy values are positive for the majority of days in the spring and summer, the system might operate more independently from the local energy networks on warmer days. Eventually, the higher share of solar in summer and wind energy in colder days for hydrogen production shows that the renewable resources combination results in a secure energy supply to obtain the highest independence from the local grid throughout the year.
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15.
  • Behzadi, Amirmohammad, et al. (författare)
  • An efficient renewable hybridization based on hydrogen storage for peak demand reduction : A rule-based energy control and optimization using machine learning techniques
  • 2023
  • Ingår i: Journal of Energy Storage. - : Elsevier Ltd. - 2352-152X .- 2352-1538. ; 57
  • Tidskriftsartikel (refereegranskat)abstract
    • The present study proposes and thoroughly examines a novel approach for the effective hybridization of solar and wind sources based on hydrogen storage to increase grid stability and lower peak load. The parabolic trough collector, vanadium chloride thermochemical cycle, hydrogen storage tank, alkaline fuel cells, thermal energy storage, and absorption chiller make up the suggested smart system. Additionally, the proposed system includes a wind turbine to power the electrolyzer unit and minimize the size of the solar system. A rule-based control technique establishes an intelligent two-way connection with energy networks to compensate for the energy expenses throughout the year. The transient system simulation (TRNSYS) tool and the engineering equation solver program are used to conduct a comprehensive techno-economic-environmental assessment of a Swedish residential building. A four-objective optimization utilizing MATLAB based on the grey wolf algorithm coupled with an artificial neural network is used to determine the best trade-off between the indicators. According to the results, the primary energy saving, carbon dioxide reduction rate, overall cost, and purchased energy are 80.6 %, 219 %, 14.8 $/h, and 24.9 MWh at optimal conditions. From the scatter distribution, it can be concluded that fuel cell voltage and collector length should be maintained at their lowest domain and the electrode area is an ineffective parameter. The suggested renewable-driven smart system can provide for the building's needs for 70 % of the year and sell excess production to the local energy network, making it a feasible alternative. Solar energy is far less effective in storing hydrogen over the winter than wind energy, demonstrating the benefits of combining renewable energy sources to fulfill demand. By lowering CO2 emissions by 61,758 kg, it is predicted that the recommended smart renewable system might save 7719 $ in environmental costs, equivalent to 6.9 ha of new reforestation. 
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16.
  • Behzadi, Amirmohammad, et al. (författare)
  • An intelligent solar-driven multi-generation energy production/storage system
  • 2022
  • Ingår i: International Conference on Electrical, Computer, Communications and Mechatronics Engineering, ICECCME 2022. - : Institute of Electrical and Electronics Engineers (IEEE).
  • Konferensbidrag (refereegranskat)abstract
    • This work presents an efficient, clean, and cutting-edge building cooling, heating, and power system driven by high-temperature trough collectors and a reseidential wind turbine. The proposed smart system comprises a vanadium chloride hydrogen cycle and electrolyzer unit using the collectors' absorbed heat and turbine's generated wind to produce hydrogen to run alkaline fuel cells. In addition to electricity production, the waste heat of fuel cells is exploited through absorption chiller and heat exchangers for cooling and heating generations. Besides, several controllers are implemented to establish a smart interaction between the system and local energy grids. Transient simulation is performed via TRNSYS-MATLAB developed code for Lund city in southwest Sweden. Moreover, the effect of significant parameters on main performance indicators is studied via parametric study. According to the results, by increasing the solar radiation from summer to winter, solar collectors' contribution to producing the hydrogen is reduced, which signifies the role of wind energy as a secondary source to compensate for the building's demand. The results further reveal that not only the entire building demand is supplied with renewable resources for most of the year but also a considerable energy value is sold to the local energy network, indicating the effectiveness of the suggested system. According to the parametric investigation, while the increase in fuel cell current density has a major positive effect on the performance indicators, the electrode area is recommended to be kept at the lowest bound.
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17.
  • Behzadi, Amirmohammad, et al. (författare)
  • Grid-tied solar and biomass hybridization for multi-family houses in Sweden : An optimal rule-based control framework through machine learning approach
  • 2023
  • Ingår i: Renewable energy. - : Elsevier BV. - 0960-1481 .- 1879-0682. ; 218
  • Tidskriftsartikel (refereegranskat)abstract
    • This article proposes a cutting-edge smart building design that contributes to sustainable development objectives by fostering clean energy, facilitating sustainable cities and communities, and promoting responsible consumption and production. The main goal is to create a clever rule-based framework that will boost the penetration of renewable energy in local grids, reduce the size of the components and, consequently, investment costs, and promote the shift towards a more environmentally friendly future. The system is driven by photovoltaic thermal panels, a novel biomass heater scheme, and a scaled-down heat pump to supply the entire energy demands of multi-family houses. The grey wolf optimizer and a cascade forward neural network model achieve the most optimal condition. According to the results, the suggested smart model outperforms the conventional Swedish system, with an energy cost of 121.2 €/MWh and a low emission index of 11.2 kg/MWh. The results show that knowing how biomass price changes affect the heat pump's operational mode is crucial to ensuring the system's economic viability. In comparison to the design condition, the optimized model increased efficiency by 3.8% while decreasing overall cost (2.1 €/h), emission index (4.4 kg/MWh), and energy costs (29.9 $/MWh). The results further demonstrate that the heat pump meets the vast majority of the year's heating needs, but as electricity prices rise in December, the biomass heater becomes the principal energy provider. May is the month with the lowest average monthly cost, while December and July stand out as the most expensive months of the year due to a dramatic increase in demand. Eventually, the results show that the system runs without external energy sources through the designed optimal control framework and generates excess electricity for around half the year.
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18.
  • Behzadi, Amirmohammad, et al. (författare)
  • Smart design and control of thermal energy storage in low-temperature heating and high-temperature cooling systems : A comprehensive review
  • 2022
  • Ingår i: Renewable & sustainable energy reviews. - : Elsevier BV. - 1364-0321 .- 1879-0690. ; 166, s. 112625-
  • Forskningsöversikt (refereegranskat)abstract
    • Thermal energy storage (TES) is recognized as a well-established technology added to the smart energy systems to support the immediate increase in energy demand, flatten the rapid supply-side changes, and reduce energy costs through an efficient and sustainable integration. On the utilization side, low-temperature heating (LTH) and high-temperature cooling (HTC) systems have grown popular because of their excellent performance in terms of energy efficiency, cost-effectiveness, and ease of integration with renewable resources. This article presents the current state-of-the-art regarding the smart design of TES integrated with LTH and HTC systems. TES is first explained in basic concepts, classification, and design possibilities. Secondly, the literature on well-known existing control approaches, strategies, and optimization methods applied to thermal energy storage is reviewed. Thirdly, the specifications, types, benefits, and drawbacks of the LTH and HTC systems from the viewpoints of supply and demand sides are discussed. Fourthly, the smart design of TES integrated with the LTH and HTC systems based on the control approach/strategy, optimization method, building type, and energy supplier is investigated to find the newest technology, ideas, and features and detect the existing gaps. The present article will provide a realistically feasible solution for having a smart storage configuration with the maximum possible energy efficiency, reliability, and cost-effectiveness for the building owners and the energy suppliers.
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19.
  • Behzadi, Amirmohammad, et al. (författare)
  • Supply-demand side management of a building energy system driven by solar and biomass in Stockholm : A smart integration with minimal cost and emission
  • 2023
  • Ingår i: Energy Conversion and Management. - : Elsevier Ltd. - 0196-8904 .- 1879-2227. ; 292
  • Tidskriftsartikel (refereegranskat)abstract
    • As part of the transition to a sustainable future, energy-efficient buildings are needed to secure users' comfort and lower the built environment's energy footprint and associated emissions. This article presents a novel, realistic and affordable solution to minimize the footprint of smart building energy systems and enable higher renewable energy use in the building sector. For this, an intelligent system is being developed using a rule-based automation approach that considers thermal comfort, energy prices, meteorological data, and primary energy use. In order to lower the installation cost and part of the environmental footprint, batteries are not used, and the heat pump's size is decreased via component integration. Also, different renewable resources are effectively hybridized using photovoltaic thermal panels and an innovative biomass heater to increase the share of renewable energy, enhance reliability, and shave peak load. In order to secure feasibility, the suggested framework is assessed from the techno-economic and environmental standpoints for 100 residential apartments in Stockholm, Sweden. Our results show that 70.8 MWh of renewable electricity is transferred to the local grid, and the remaining 111.5 MWh is used to supply the building's needs and power the electrically-driven components. The biomass heater meets more than 65% of the space heating demand, mainly at low solar power and high electricity prices, illustrating the value of integration strategies to reduce the system's dependability on the local grid. The results further reveal that most energy purchases during the cloudy days and nights are repaid through the sale of excess renewable production during the warmer hours, with a bidirectional connection with the grid. The monthly energy cost is less than 140 $/MWh for most of the years. The cost can be held low due to the exclusion of batteries and minimizing the heat pump size. The proposed system has a low emission index of 11.9 kgCO2/MWh and can reduce carbon dioxide emissions by 70 TCO2/year compared to using the supply from the Swedish energy mix. 
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20.
  • Behzadi, Amirmohammad, et al. (författare)
  • Techno-Environmental Assessment of a Green and Efficient Concept Based on Smart Thermal Storage Interacted with Low-Temperature Heating and High-Temperature Cooling System
  • 2023
  • Ingår i: Proceedings of the 5th International Conference on Building Energy and Environment. - : Springer Nature. ; , s. 1099-1107
  • Konferensbidrag (refereegranskat)abstract
    • Low-temperature heating (LTH) and high-temperature cooling (HTC) systems that use less energy than traditional systems are viable alternatives for dealing with rising energy demand and increasing renewable energy’s share in the global energy matrix. The present work proposes an innovative LTH-HTC system comprising photovoltaic thermal cooling panels, heat pump, and smart thermal energy storage (TES). MATLAB software evaluates the hourly variation of techno-environmental metrics to investigate the proposed system’s feasibility for a case study building in Stockholm. Moreover, the impact of key operational factors on system performance is evaluated by looking at their impact on the performance and environmental facets. According to the results, the primary energy saving and emission mitigation ratios of 54.8 and 57.2% are obtained by applying an intelligent control strategy to the TES. The parametric study results indicate that while the increase of panel area is techno-environmentally suitable, a lower heat pump capacity should be selected.
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21.
  • Chen, Shih-Ying, et al. (författare)
  • Transport of Contaminated Agents in Hospital Wards - Exposure Control with a Personalized Healthcare Ventilation System: Numerical Study
  • 2021
  • Konferensbidrag (refereegranskat)abstract
    • Contaminated agents in hospital wards are the source of nosocomial infections known as hospital-acquired infection (HAI) or healthcare-associated infections (HAIs). Ventilation plays an essential role in the spreading and minimizing the transport of airborne infectious diseases such as Covid-19 and SARS in the hospital ward. The goal of this study is to explore elimination strategies for an efficient removal of contaminated agents, targeting the influence of using local air diffuser and exhaust. Computational Fluid Dynamics (CFD) technique was used to model the airflow field and contamination distribution in the ward environment. Simulated results showed that the bacteria spread from a patient confined to his bed was limited and under certain conditions significantly eliminated. Consequently, a relatively high efficiency of particle removal and a moderated transmission were obtained. Thus, this strategy is able to shorten the exposure time of patient and healthcare staff, as a result, mitigating cross-infection risk at the hospital.
  •  
22.
  • Dastan, Alireza, et al. (författare)
  • CFD simulations of a semi-transverse ventilation system in a long tunnel
  • 2023
  • Ingår i: UNDERGROUND SPACE. - : Elsevier BV. - 2096-2754. ; 11, s. 153-170
  • Tidskriftsartikel (refereegranskat)abstract
    • In the present work, a semi-transverse ventilation system in a long tunnel with a length of 4.9 km, as a complex case study, is numerically studied by performing a set of three-dimensional steady incompressible computational fluid dynamics (CFD) simulations. The ventilation system consisted of a ceiling duct connected to two axial fans at the ending portals, and a series of jet fans in the main tunnel for supporting airflow in the desired direction. To focus on what can and cannot be achieved in commissioning tests, the ventilation system's performance in various scenarios is numerically evaluated with two different tunnel states; empty tunnel and complete traffic congestion with 1176 stationary vehicles - which is almost impossible to evaluate during a commissioning test. By considering two hypothetical locations for the extraction zone from the main tunnel (in a distance of 450 and 1000 m from one portal), it is shown that the required number of jet fans in a traffic condition drops from 57 for the first extraction location to 43 (25% decrease) when the ventilation system extracts from the second zone. We show that if only the close axial fan to the extraction zone is activated, the required number of jet fans reduces by 56% and 72% for the first and second extraction locations, respectively. This finding can provide a cheaper and easier controlling scenario for emergency ventilation.
  •  
23.
  • Du, Chenqiu, et al. (författare)
  • Grey image recognition-based mold growth assessment on the surface of typical building materials responding to dynamic thermal conditions
  • 2023
  • Ingår i: Building and Environment. - : Elsevier BV. - 0360-1323 .- 1873-684X. ; 243
  • Tidskriftsartikel (refereegranskat)abstract
    • Mold growth on building materials poses a threat to both the building structural integrity and occupants' well-being. However, it is generally studied under suitable conditions in laboratory; the assessment is based on visual inspection but lacks an objective criterion. This research explored the effects of simulated dynamic thermal conditions on mold growth on three typical building materials artificially contaminated with Aspergillus niger spores. Test specimens were assessed based on a developed digital image-based method, where image seg-mentation, processing, and greyscale recognition via the OpenCV visual library were introduced. The results showed that the high temperature-high humidity condition in a 24-h cyclic change facilitated mold growth on the surfaces of three materials, especially for gypsum board, with an identified area proportion of 1.13% on the 80th day. This was consistent with the changes of the counted number of mold colonies, and no significant differences were found among the gypsum board, latex paint, and wallpaper. The growth extents of mold spores were objectively evaluated by the mean greyscale values; the values decreased gradually with time, and the decrements were different compared high-temperature to low-temperature conditions. The mold growth models were developed, where the area proportion of mold growth was linearly related to the counted colonies and greyscale values under different material surfaces. This novel grey image recognition-based method provides an accurate means of evaluating mold growth abilities and extents, overcoming the inaccuracy of visual observa-tion. The findings have significant implications for visual inspection, mold prediction, and building management.
  •  
24.
  • Ekberg, Lars, 1962, et al. (författare)
  • Buildings Post Corona
  • 2022
  • Ingår i: The REHVA European HVAC Journal. - 1307-3729. ; 59:2, s. 19-21
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • Buildings Post Corona is a Swedish collaborative research project between Chalmers, KTH Royal Institute of Technology, Lund, and Umeå Universities. The project supports the building sector in designing and maintaining sustainable buildings with a healthy and good indoor environment. The COVID-19 crisis has stressed the importance and urge of this research, which is financially supported by FORMAS (a governmental research council for sustainable development https://formas.se)
  •  
25.
  • Ekberg, Lars, et al. (författare)
  • Covid 19 guidance for the Swedish construction and real estate sectors : results from a survey study
  • 2023
  • Ingår i: The REHVA European HVAC Journal. - 1307-3729. ; 60:2, s. 18-20
  • Tidskriftsartikel (populärvet., debatt m.m.)abstract
    • Buildings Post Corona is a Swedish collaborative research project between Chalmers, KTH Royal Institute of Technology, Lund, and Umeå Universities. The project intends to provide knowledge related to designing, maintaining and operating sustainable buildings with a healthy and good indoor environment.The project aims to contribute to the knowledge and processes needed for the construction and real-estate sectors to meet the needs of the post-pandemic era.In this article, the authors describe the approach in the study and its results.
  •  
26.
  • Enze, Tian, et al. (författare)
  • Airborne Particles removal by Negative Ions Generated in Ambient Air and Inert Gas
  • 2017
  • Ingår i: In: Proceedings of the 10<sup>th</sup> International Symposium on Heating, Ventilation and Air Conditioning – ISHVAC 2017. 19-22 2017; Jinan, China.
  • Konferensbidrag (refereegranskat)abstract
    • Airborne particles can be removed by air ions in enclosed environment, but the main drawback of this method is the formation of harmful by-products such as ozone (O3). In this study, we use ambient air and inert gas, including argon (Ar) and Nitrogen (N2) to generate negative ions respectively, and then release those ions into an enclosed chamber with ambient air. We then investigated the particle concentration decay rates and O3 concentration increase in the chamber. We found that the particle concentration decay rates were 0.343 min-1, 0.209 min-1 and 0.274 min-1 when ions were generated in ambient air, Ar and N2 respectively. The ozone concentration does not show a marked increase when using either ambient air or inert gas (Ar and N2) to generate ions. Since the temperature and humidity of ambient air may influence the ozone generation during ionizing, further study should be investigated.
  •  
27.
  • Eriksson, Martin (författare)
  • A Statistical Approach to Estimate Thermal Performance and Energy Renovation of Multifamily Buildings : Case study on a Swedish city district
  • 2022
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • Several climate and energy goals have been set in the European Union, one of them being to increase energy efficiency. In Sweden, a large potential for increased energy efficiency lies in the residential and service sectors, which account for about 40% of total energy use. A large share of buildings in Sweden were built in the Million Homes Program in the 1960s and ’70s. These buildings are now in need of renovation, which enables renovation with the ambition of reducing energy use. In this thesis, the purpose is to develop an energy signature method, a bottom-up statistical method. This method has been validated using a building energy simulation software called IDA ICE, for two kinds of multifamily buildings from the Million Homes Program. The energy signature method has then been applied to a district located in Gävle, Sweden, containing more than 90 multifamily buildings with similar construction. In addition to characterizing current thermal performance of the buildings, the energy signature method is further developed so that potential for energy renovation of the district can be simulated. Simulated energy renovation is developed to comply with building energy use requirements, according to the most recent Swedish building regulations. Both on building and district level, sensitivity analysis is performed. In both cases the energy signature method is insensitive to changes in internal heat gains and indoor temperature. To investigate the effects of simulated renovation on a local district heating system, results are visualized in a duration diagram, where energy use reduction in different load periods is displayed. Thus, it is demonstrated how the energy signature method can be used as a rapid way of simulating energy renovation on district level and with readily available data. 
  •  
28.
  • Guo, Yong, et al. (författare)
  • Deposition of droplets from the trachea or bronchus in the respiratory tract during exhalation : A steady-state numerical investigation
  • 2020
  • Ingår i: Aerosol Science and Technology. - : Informa UK Limited. - 0278-6826 .- 1521-7388. ; 54:8, s. 869-879
  • Tidskriftsartikel (refereegranskat)abstract
    • Respiratory droplets are bioaerosols that originate from the respiratory tract. Knowing their deposition characteristics during exhalation would facilitate the understanding of the source of large respiratory droplets and their importance in the spread of respiratory infectious diseases. In this study, computational fluid dynamics is used to simulate the motion and deposition of droplets released from either trachea or bronchi in a realistic reconstruction of the human respiratory tract. Influences of airflow structures and locations of droplet generation on droplet deposition are studied, and droplets with diameters between 1 and 50 mu m are examined. The deposition of droplets is found to be influenced mainly by the droplet diameter and the flow rate of exhalation. The number of droplets released from the trachea or bronchi that can escape into the environment decreases as the flow rate increases. When the flow rate is low (10 L/min), the critical diameter of droplets generated in the lower respiratory system that can escape into the air is approximately 12 mu m, but this diameter is approximately 5 mu m when the flow rate is medium (30 to 60 L/min) or large (90 L/min). The larynx is the dominant site of deposition for droplets smaller than the critical diameter, while trachea and bronchus are more important locations that account for the deposition of larger droplets. This study indicates that the lower respiratory tract is an important source of fine droplets (<5 mu m) in indoor environments, and larger droplets probably originate from the upper respiratory tract, which needs further investigation. Copyright
  •  
29.
  • Harsem, Trond Thorgeir, et al. (författare)
  • Design and Parametric Investigation of an Efficient Heating System, an Effort to Obtain a Higher Seasonal Performance Factor
  • 2021
  • Ingår i: Energies. - : MDPI AG. - 1996-1073. ; 14:24
  • Tidskriftsartikel (refereegranskat)abstract
    • The present work introduces an innovative yet feasible heating system consisting of a ground source heat pump, borehole thermal energy storage, an auxiliary heater, radiators, and ventilation coils. The concept is developed by designing a new piping configuration monitored by a smart control system to reduce the return flow temperature and increase the temperature differential between the supply and return flows. The radiators and ventilation heating circuits are connected in series to provide the heat loads with the same demand. The investigation of the proposed model is performed through developed Python code considering a case study hospital located in Norway. The article presents, after validation of the primary heating system installed in the hospital, a parametric investigation to evaluate the effect of main operational parameters on the performance metrics of both the heat pump and the total system. According to the results, the evaporator temperature is a significant parameter that considerably impacts the system performance. The parametric study findings show that the heat pumps with a thermal capacity of 400 kW and 600 kW lead to the highest heat pump and total seasonal performance factors, respectively. It is also observed that increasing the heat pump capacity does not affect the performance indicators when the condensation temperature is 40 degrees C and the heat recovery is 50%. Moreover, choosing a heat pump with a smaller capacity at the heat recovery of 75% (or higher) would be an appropriate option because the seasonal performance values are not varied by changing the heat pump capacity. The results reveal that reducing return temperature under a proper parameters selection results in substantially higher seasonal performance factors of the heat pump and total system. These outcomes are in-line with the United Nations sustainable development goals including Sustainable Cities and Communities.
  •  
30.
  •  
31.
  • Hazeri, Mohammad, et al. (författare)
  • Details of the physiology of the aerodynamic and heat and moisture transfer in the normal nasal cavity
  • 2020
  • Ingår i: Respiratory Physiology & Neurobiology. - : Elsevier. - 1569-9048 .- 1878-1519. ; 280
  • Tidskriftsartikel (refereegranskat)abstract
    • Anatomically accurate 3D models of 10 healthy nasal cavities are developed from computerized tomography (CT) scan images. Considering anatomical and physiological importance of different parts of the nasal cavity, the surface of each nasal passage is divided to eleven anatomical surfaces. Also the coronal cross sections in the nasal passage are divided to six sub-sections that share the total nasal passage airflow. The details of the flow field, heat transfer and water-vapor transport are numerically investigated for resting and low activity conditions. The mean and standard deviation of the different anatomical and air conditioning parameters such as: surface area, wall shear stress, heat and moisture transfer on different parts of the nasal passage surfaces and volume flow rates through different sections are presented. Results show that the percentages of airflow for inferior, middle and superior meatuses are 11.3 +/- 6.4, 36.5 +/- 9.5, 1.9 +/- 0.81 % respectively and 4.1 +/- 2.1 % of air passes through olfactory area. The inhaled air passing from the remaining surface (main passage) is 46.2 +/- 10 %. Heat and moisture fluxes are highest in the anterior part of the nasal cavity, turbinates and lower part of the septum respectively. The percentage of the heat transfer from turbinates is 25.7 +/- 3.9 % of total nasal heat transfer.
  •  
32.
  • Hazeri, Mohammad, et al. (författare)
  • Regional deposition of the allergens and micro-aerosols in the healthy human nasal airways
  • 2021
  • Ingår i: Journal of Aerosol Science. - : Elsevier BV. - 0021-8502 .- 1879-1964. ; 152
  • Tidskriftsartikel (refereegranskat)abstract
    • The nasal cavity is the inlet to the human respiratory system and is responsible for the olfactory sensation, filtering pollutant particulate matter, and humidifying the air. Many research studies have been performed to numerically predict allergens, contaminants, and/or drug particle deposition in the human nasal cavity; however, the majority of these investigations studied only one or a small number of nasal passages. In the present study, a series of Computed Tomography (CT) scan images of the nasal cavities from ten healthy subjects were collected and used to reconstruct accurate 3D models. All models were divided into twelve anatomical regions in order to study the transport and deposition features of different regions of the nasal cavity with specific functions. The flow field and micro-particle transport equations were solved, and the total and regional particle deposition fractions were evaluated for the rest and low activity breathing conditions. The results show that there are large variations among different subjects. The standard deviation of the total deposition fraction in the nasal cavities was the highest for 5 x 10(4) impaction parameter (IP)<1.125 x 10(5) with a maximum of 20%. The achieved results highlighted the nasal cavity sections that are more involved in the particle deposition. Particles with IP = 30,000 deposit more in the middle turbinate and nasopharynx areas, while for particles with IP = 300,000, deposition is mainly in the anterior parts (kiesselbach and vestibule regions). For small IP values, the amounts of deposition fractions in different regions of the nasal cavity are more uniform.
  •  
33.
  • Hu, Nan, et al. (författare)
  • Review of experimental measurements on particle size distribution and airflow behaviors during human respiration
  • 2024
  • Ingår i: Building and Environment. - : Elsevier. - 0360-1323 .- 1873-684X. ; 247
  • Tidskriftsartikel (refereegranskat)abstract
    • In recent years, pandemic outbreaks have raised concerns about the spread of respiratory infections and their impact on public health. Since the pathogen emission during human respiration is recognized as the primary source, characterizing the physical properties of exhaled particles and airflow has become a crucial focus of attention. This article critically reviews experimental studies in exhaled particles and airflow, examines the uncertainty introduced by different measurement methods, analyzes how it is reflected in measurement outcomes, and provides an in-depth understanding of particle size distribution and airflow behaviors of human respiration. The measurement techniques assessment highlights the variability among particle sizing techniques in detection size range, collection efficiency, hydration status of captured particles, and experimental protocols. A combination of sampling-based instruments and laser imaging systems is recommended for particle sizing to cover a wider detection range, with refined setups in thermal conditions, sampling distance, volume, and duration. Meanwhile, it identifies the complementary nature of qualitative and quantitative measurements of airflow characterization techniques. Image recording systems plus data reconstruction programs are suggested to capture dynamic airflow features while accuracy validation by other techniques is required at the same time. Subsequent analysis of the measurement data showed that the various experimental measurements provided substantial information, but they also revealed disagreements and challenges in quantification. The dominance of submicron aerosols in exhaled particles and jet-like transport in exhaled airflow is obvious. More efforts should be made to measure particles larger than 20 μm, capture airflow dynamics in a high temporal and spatial resolution, and quantify the impact of face coverings to improve the understanding of human respiratory emissions.
  •  
34.
  • Hu, Nan, et al. (författare)
  • Ventilation performance evaluation of an operating room with temperature-controlled airflow system in contaminant control : A numerical study
  • 2024
  • Ingår i: Building and Environment. - : Elsevier Ltd. - 0360-1323 .- 1873-684X. ; 259
  • Tidskriftsartikel (refereegranskat)abstract
    • This article investigates the efficacy of temperature-controlled airflow systems in modern operating rooms for contaminant control, a critical factor in preventing surgical site infections. We have conducted experimental measurements in an operating room equipped with temperature-controlled ventilation to map the airflow field and contaminant dispersion (airborne particles with diameters ranging from 0.5 to 1 μm). The results were used to validate the computational fluid dynamics code, which was then employed to simulate and examine different conditions, including contaminant release locations and air supply rates. Realizable k-epsilon and passive scalar models were utilized to simulate airflow and airborne particle phases. We assessed the airflow distribution and contaminant dispersion, utilizing indices such as ventilation and air change efficiency scales. The analysis provided quantitative insights into the distribution and removal of contaminants, as well as the speed at which the room air was replaced. Contamination was found to be effectively reduced when contaminants were released near exhaust outlets or under central unidirectional inlets. The presence of the operating table caused a big distortion of the central downward airflow, forming a horizontal air barrier at the periphery. Under this unique interior configuration, an appropriate air supply ratio between central and periphery zones was required to achieve optimal overall ventilation performance.
  •  
35.
  • Izadi, T., et al. (författare)
  • The effect of ventilation system with and without under-platform exhaust on the concentration of braking micro-particles inside the subway system
  • 2022
  • Ingår i: Tunnelling and Underground Space Technology. - : Elsevier Ltd. - 0886-7798 .- 1878-4364. ; 128
  • Tidskriftsartikel (refereegranskat)abstract
    • Thermal comfort has been the main target of the ventilation in subway systems. However, pollutant concentration and aerosol dispersion could be the leading health issues in underground metro stations. This study numerically simulated a train movement inside a subway system using the Dynamic Mesh Technique for a 3-D computational domain consisting of four stations and connecting tunnels. The effects of both the ventilation system and the train-induced fluid flow inside the subway system were investigated. Then, the particle generation and dispersion due to train braking are considered, and the impact of the ventilation system on reducing the particle concentration inside the station was investigated. It is shown that the airflow inside the subway system is entirely affected by the piston effect. The airflow generated by the train movement is much higher than that generated by the operation of the ventilation system when only one train passes through the tunnel. The results show that the ventilation system, consisting of the supply and exhaust fans inside the tunnel and supply grilles inside the platform, can reduce the particle concentration by half, except for the platform beside the stopped train when the train enters the station and during half of the train stop time. The other design concept demonstrates that the under-platform exhaust system considerably reduces the concentration of the particles released by the train braking system on the trackside platform.
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36.
  • Khan, Amirul, et al. (författare)
  • WS6 : Challenges in ventilation for the operating theatres of the future: Making the invisible visible
  • 2022
  • Ingår i: 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. - : International Society of Indoor Air Quality and Climate.
  • Konferensbidrag (refereegranskat)abstract
    • This workshop showcased several methods for operating theatre design and operation. The different research projects presented are all ongoing and could contribute to the development and implementation of novel methods, advancing the field of ventilation design and improving IAQ, thermal comfort and infection risk in operating theatres.
  •  
37.
  • Lind, M. C., et al. (författare)
  • Minimizing the airborne particle migration to the operating room during door opening
  • 2019
  • Ingår i: Proceedings 10th International Conference on Indoor Air Quality, Ventilation and Energy Conservation in Buildings, IAQVEC. - : Institute of Physics Publishing.
  • Konferensbidrag (refereegranskat)abstract
    • Airborne bacteria that enter an open wound during surgery can result in post-operative infections, commonly referred to as surgical site infections (SSIs). The level of contaminants is usually lower in the operating rooms (ORs) in contrast to adjacent corridors. Penetration of particles carrying bacteria through the doorway during a door opening gives rise to the OR contaminant level as door-opening and passage may occur every 2.5 minutes during a given surgical activity. The authors had previously conducted a successful research study to reduce the contaminant migration from an anteroom, through the doorway, into an Airborne Infection Isolation Room (AIIR). In contrast to the AIIRs, the ORs are usually over-pressured related to the surrounding environments. However, both ORs and AIIRs share the same interest in avoiding air exchange between the room and the adjacent space. This paper, built upon the previous research achievement, proposes an innovative design solution to reduce the bacteria penetration to the ORs during a door opening and staff passage. Previously achieved results from CFD simulation and laboratory measurement confirmed that installing a ventilation unit that supplies a high air volume into the OR through low-velocity wall diffusers, may significantly reduce the contaminant migration to the OR during door-opening activities.
  •  
38.
  • Mahani, Narges Hassani Pour, et al. (författare)
  • Thermal comfort analysis in office rooms served by low temperature heating systems
  • 2022
  • Ingår i: 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. - : International Society of Indoor Air Quality and Climate.
  • Konferensbidrag (refereegranskat)abstract
    • Indoor air quality in office rooms directly influences occupants' comfort and productivity. Higher air change rates in offices compared to residential buildings increase the heating demand considerably in cold climate countries. Reducing the thermal losses from exterior walls and windows provides the possibility of using low-temperature heating systems in order to reduce the required heating and enhance the occupants' perceived thermal comfort. In the present study, the indoor air quality in an office room under Nordic climate has been investigated using computational fluid dynamics method. A well-insulated window (so-called energy-active window) is installed at the exterior wall. The effect of using two heating emission systems, floor heating, and radiator, on the perceived thermal comfort of the occupants has been studied and compared.
  •  
39.
  • Marashian, Shahrzad, 1990-, et al. (författare)
  • Enhancing Indoor Environmental Simulations: A Comprehensive Review of CFD Methods
  • 2023
  • Konferensbidrag (refereegranskat)abstract
    • Computational Fluid Dynamics (CFD) simulations are extensively used to model indoor environments, including airflow patterns, temperature distribution, and contaminant dispersion. These simulations provide valuable insights for improving indoor air quality, enhancing thermal comfort, optimizing energy efficiency, and informing design decisions. The recent global pandemic has emphasized the importance of understanding airflow patterns and particle dispersion in indoor spaces, highlighting the potential of CFD simulations to guide strategies for improving indoor air quality and public health. Consequently, there has been a significant increase in research focused on studying the transport and dispersion of pollutants in indoor environments using CFD techniques. These simulations are vital in advancing engineers' understanding of indoor environments; however, achieving accurate results requires careful method selection and proper implementation of each step. This paper aims to review the state-of-the-art CFD simulations of indoor environments, specifically focusing on strategies employed for three main simulation components: geometry and grid generation, ventilation strategies, and turbulence model selection. Researchers can select suitable techniques for their specific applications by comparing different indoor airflow simulation strategies.
  •  
40.
  • Marashian, Shahrzad, 1990-, et al. (författare)
  • Investigation of two different ventilation designs in a single-bed isolation room
  • 2023
  • Ingår i: The 11th International Conference on Sustainable Development in Building and Environment.
  • Konferensbidrag (populärvet., debatt m.m.)abstract
    • The recent epidemic of the coronavirus disease showed the increased importance of controlling the transmission of contamination in the ward areas more than before. The performance of the ventilation systems in healthcare facilities can significantly impact the overall healthcare quality. This paper aims to compare two ventilation designs in an isolation room of a hospital and study the indoor airflow pattern. Computational fluid dynamics using ANSYS Fluent software was employed for the numerical simulation of the fluid flow. The simulation included the prediction of flow patterns and particle trajectories with the additional investigation into the impact of considering human thermal plume and modeling particle trajectories considering the turbulent fluctuations using the discrete random walk method in the simulation.  
  •  
41.
  • Marashian, S., et al. (författare)
  • Modeling particle distribution in a ventilated room with modified discrete random walk methods
  • 2022
  • Ingår i: The International Journal of Ventilation. - : Informa UK Limited. - 1473-3315 .- 2044-4044. ; , s. 1-18
  • Tidskriftsartikel (refereegranskat)abstract
    • The airflow and micro-particle dispersion in a 3-D ventilated scaled room has been simulated numerically. The flow field was studied by the Eulerian method using a Reynolds Averaged Navier-Stokes model, and we used the Lagrangian approach to solve the equations of particle motion. The purpose is to evaluate and compare various discrete random walk methods (DRW) and continuous random walk methods (CRW) to evaluate particle concentration distribution in indoor environments. The isotropic DRW method’s performance has been compared with models in which anisotropy of turbulence is applied, including CRW and modified DRW models based on near-wall direct numerical simulation results, near-wall kinetic energy, and the helicity of the flow. The results reveal that the isotropic DRW method can predict particle concentration in the indoor environment, and using a modified DRW model is not necessary.
  •  
42.
  • Mattox, Tracy M., et al. (författare)
  • Impact of Source Position and Obstructions on Fume Hood Releases
  • 2019
  • Ingår i: Annals of Work Exposures and Health. - : OXFORD UNIV PRESS. - 2398-7308 .- 2398-7316. ; 63:8, s. 937-949
  • Tidskriftsartikel (refereegranskat)abstract
    • A fume hood is the most central piece of safety equipment available to researchers in a laboratory environment. While it is understood that the face velocity and sash height can drastically influence airflow patterns, few specific recommendations can be given to the researcher to guide them to maximize the safety of their particular hood. This stems from the issue that fundamentally little is known regarding how obstructions within the hood can push potentially harmful particles or chemicals out of the fume hood and into the breathing zone. In this work, we demonstrate how the position of a typical nanoparticle synthesis setup, including a Schlenk line and stir plate on an adjustable stand, influences airflow in a constant velocity fume hood. Using a combination of smoke evolution experiments and the aid of computational fluid dynamics simulations, we show how the location and height of the reaction components impact airflow. This work offers a highly visual display intended especially for new or inexperienced fume hood users. Based upon our studies and simulations, we provide detailed guidance to researchers and lab technicians on how to optimally modify reaction placement in order to protect the breathing zone while working.
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43.
  • Moniripiri, Mohammad, et al. (författare)
  • Numerical simulation of unsteady airflow in a nasal cavity for various sizes of maxillary sinus opening in a virtual endoscopic surgery
  • 2021
  • Ingår i: Respiratory Physiology & Neurobiology. - : Elsevier BV. - 1569-9048 .- 1878-1519. ; 291, s. 103690-
  • Tidskriftsartikel (refereegranskat)abstract
    • Functional endoscopic sinus surgery (FESS) is performed to treat sinusitis when treatment with medication fails. In the present study, three different virtual maxillary sinus endoscopic surgeries were performed on a realistic 3D computational model of the nasal cavity of an adult male under the supervision of a specialist. They included only uncinectomy, uncinectomy + 8mm Middle Meatal Antrostomy (MMA) and uncinectomy + 18 mm MMA. Simulations were performed for two human activity respiratory rates, including rest and moderate activities, and effects of different surgeries and respiratory rates on maxillary sinus were investigated. It was found that after endoscopic sinus surgery, the volume of air entering the maxillary sinus increased significantly, and as the size of the MMA increased, or the breathing condition changed from rest to moderate activity, this volume of air increased. For the rest condition, on average for both nasal passages, for uncinectomy +8 mm MMA, around 15 % of the inhaled flow and 7 % of the exhaled flow enter the maxillary sinuses. For uncinectomy +18 mm MMA, these values are 24 % and 14 %, respectively. As human activity increases, a lower portion of inhaled and exhaled air enters the maxillary sinuses. For the moderate activity condition, on average for both nasal passages, for uncinectomy +8 mm MMA, around 11 % of the inhaled flow and 6 % of the exhaled flow rate enters the maxillary sinus. For uncinectomy +18 mm MMA, these values are 16 % and 8%, respectively. Comparing the steady and unsteady simulation results showed that the quasi-steady flow assumption could predict the flow in the maxillary sinus and the volume of air entering the sinuses, almost at any moment of respiration, with acceptable accuracy.
  •  
44.
  • Moshksayan, K., et al. (författare)
  • In-silico investigation of airflow and micro-particle deposition in human nasal airway pre- and post-virtual transnasal sphenoidotomy surgery
  • 2022
  • Ingår i: Computer Methods in Biomechanics and Biomedical Engineering. - : Informa UK Limited. - 1025-5842 .- 1476-8259. ; 25:9, s. 1000-1014
  • Tidskriftsartikel (refereegranskat)abstract
    • Sphenoid sinus, located posterior to the nasal cavity, is difficult to reach for a surgery. Several operation procedures are available for sphenoidotomy, including endoscopic surgeries. Although the endoscopic sinus surgery is minimally invasive with low post-operative side effects, further optimization is required. Transnasal sphenoidotomy is a low invasive alternative to transethmoidal sphenoidotomy, but it still needs to be studied to understand its effects on the airflow pattern and the particle deposition. In this work, we simulated airflow and the micro-particle deposition in the nasal airway of a middle-aged man to investigate the change in particle deposition in the sphenoid sinus after virtual transnasal sphenoidotomy surgery. The results demonstrated that after transnasal sphenoidotomy, particle deposition in the targeted sphenoid sinus was an order of magnitude lower than that observed after virtual transethmoidal sphenoidotomy surgery. In addition, the diameter of the particles for the peak deposition fraction in the targeted sinus was shifted to smaller diameters after the transnasal sphenoidotomy surgery compared with that in the post-transethmoidal condition. These results suggest that the endoscopic transnasal sphenoidotomy can be a better procedure for sphenoid surgeries as it decreases the chance of bacterial contaminations and consequently lowers the surgical side effects and recovery time.
  •  
45.
  •  
46.
  • Nasiri, Fuzhan, et al. (författare)
  • Data Analytics and Information Technologies for Smart Energy Storage Systems : A State-of-the-Art Review
  • 2022
  • Ingår i: Sustainable cities and society. - : Elsevier BV. - 2210-6707. ; 84, s. 104004-
  • Forskningsöversikt (refereegranskat)abstract
    • This article provides a state-of-the-art review on emerging applications of smart tools such as data analytics and smart technologies such as internet-of-things in case of design, management and control of energy storage systems. In particular, we have established a classification of the types and targets of various predictive analytics for estimation of load, energy prices, renewable energy inputs, state of the charge, fault diagnosis, etc. In addition, the applications of information technologies, and in particular, use of cloud, internet-of-things, building management systems and building information modeling and their contributions to management of energy storage systems will be reviewed in details. The paper concludes by highlighting the emerging issues in smart energy storage systems and providing directions for future research.
  •  
47.
  • Nejad Ghafar, Ali, 1971-, et al. (författare)
  • Application of Low-Frequency Rectangular Pressure Impulse in Rock Grouting
  • 2017
  • Ingår i: Grouting 2017. - Reston, VA : American Society of Civil Engineers (ASCE). - 9780784480793 ; , s. 104-113
  • Konferensbidrag (refereegranskat)abstract
    • In order to sufficiently seal an underground facility in fractured rock, it is essential to obtain adequate grout spread into the surrounding fractures. The grout spread itself depends on parameters, the most significant of which are the filtration tendency and rheological properties. These properties can be affected by the applied pressure. High-frequency oscillating pressure has been shown to improve grout spread by virtue of reducing the grout viscosity. However, this method has not yet been industrialized due to the quick dissipation of the oscillation along a fracture. In a recent investigation, we examined a low-frequency rectangular pressure-impulse using a short slot. The results showed significant improvements in the injected grout volume in comparison to the static pressure results. In this paper, we examine the method in a considerably longer artificial fracture in order to investigate the dissipation of the pressure impulses. The study indicates the potential of the method to improve the grout spread in rock grouting.
  •  
48.
  • Nejad Ghafar, Ali, 1971-, et al. (författare)
  • Evaluation of the Real Time Grouting Control (RTGC) Theory using an Artificial Fracture with Variable Aperture
  • 2018
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • The real time grouting control (RTGC) theory has been developed to monitor the spread of grout in rock fractures. It predicts the extent of the grout spread over time using the grout properties and the applied pressure. Despite extensive work conducted to verify it in both the lab and the field, it has not yet been sufficiently investigated in the lab under geometry conditions similar to a real fracture in rock. This paper presents a novel effort to examine the performance of the RTGC theory in the presence of constrictions by using an artificial fracture, the so-called varying aperture long slot (VALS). The paper compares the predictions of grout propagation with the experimental results. The predictions obtained using a hydraulic aperture, the way that the theory was previously used in the early stages of development, showed relatively good agreement with the experimental results. In predictions obtained using the mean-physical aperture, the way that the theory is currently used in field applications, the results showed considerably faster spread than the experimental results. This suggests that use of the mean-physical aperture does not always give a good approximation of the apertures to employ in predictions using the RTGC theory. Depending on the geometry conditions, the hydraulic aperture might be more realistic.
  •  
49.
  • Nejad Ghafar, Ali, 1971-, et al. (författare)
  • Varying aperture long slot (VALS), a method for studying grout penetrability into fractured hard rock
  • 2017
  • Ingår i: ASTM geotechnical testing journal. - : ASTM International. - 0149-6115 .- 1945-7545. ; 40:5, s. 871-882
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper presents the design, manufacturing, and assembly of a new laboratory apparatus for investigation of grout filtration tendency and penetrability into rock fractures. The method makes it possible to examine grout samples composed of a wide range of cements and additives/ admixtures with different water-to-solid ratios. The apparatus can be used to investigate the influence of different parameters on grout penetrability. Examples of these parameters include the cement particle size/distribution curves/chemical compositions, and the type and ratio of additives/admixtures that provide a variety of setting/hardening times, and rheological and strength properties. The grouting operation into the rock fractures is replicated using an artificial slot with 4-m-long constrictions varying from 230 to 10 μm, and selective inlet and outlet. The apparatus can also accommodate grouting experiments under both static and dynamic pressure conditions up to 1, 500 kPa to study their influence. Illustrative results are also provided.
  •  
50.
  • Nhien, L. C., et al. (författare)
  • A new approach to wind farm stabilization and peak electricity support using fuel cells : Case study in Swedish cities
  • 2024
  • Ingår i: International journal of hydrogen energy. - : Elsevier Ltd. - 0360-3199 .- 1879-3487. ; 80, s. 22-38
  • Tidskriftsartikel (refereegranskat)abstract
    • The present article introduces and investigates a new approach for shaving the peak electricity demand and mitigating energy instability. At the heart of this concept is a smart integration for efficient hydrogen production/storage/usage to minimize energy costs and maximize the renewable penetration in the local electricity grid. The system is driven by a wind farm integrated with proton exchange membrane (PEM) electrolyzers and reverse osmosis desalination units for efficient electricity, hydrogen, and freshwater production. It also combines with PEM fuel cells equipped with a hydrogen tank to meet the demand constantly when renewable electricity is unavailable or unstable. The system's practicality is assessed and compared for various Swedish cities with high wind potential from thermodynamic, economic, and environmental aspects to see where it works effectively. The comparative results of various scenarios show that integrating 32 wind turbines, 2 electrolyzers, and 2 reverse osmosis units, with 25% of electricity going to electrolyzers, 20% to reverse osmosis, and 55% to the grid, is the most optimal configuration/allocation. Optimal locations for the power plant are identified in Visby, Halmstad, and Lund due to favorable wind conditions. Setting up the system in Visby could prevent 1878.2 tonnes of CO2 emissions, generate 93,910 MWh of electricity annually, and create 213 ha of green space. The proposed system in Visby could boast the biggest electricity generation capacity, reaching 11,263 MWh, sufficient to power 938 households. Scaling this model to 12 cities in Sweden could provide the electricity needs of 4500 households, demonstrating the potential for widespread impact.
  •  
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