| 1. |
- Cholewa, Tomasz, et al.
(författare)
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Heat cost allocation in buildings : Possibilities, problems and solutions
- 2020
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Ingår i: Journal of Building Engineering. - : Elsevier. - 2352-7102. ; 31, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- The individual heat cost allocation is one of the recent topics which is well-known not only for the possibility of increasing the energy efficiency but also for the related problems. However, there is no comprehensive work where the main problems are shown and adequate solutions are proposed. This article presents the main aspects which are important in the area of heat cost allocation. Firstly, the policy issues were underlined and the recommendations for the introduction of general rules for heating costs allocation at the level of a given country were provided. Secondly, the main possibilities, problems and solutions connected to the devices and methods for heat cost allocation were introduced. Then, the energy savings obtained using heat cost allocation were shown on the example of long term field research (8 heating seasons) carried out for six residential buildings, where heat cost allocators were uninstalled. Lastly, comprehensive recommendations were provided, the introduction of which will allow to minimizing the problems connected with heat cost allocation and maximizing the energy savings while maintaining the thermal comfort in the heated rooms.
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| 2. |
- Das, Atanu Kumar
(författare)
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Influence of chemical additive on the physical and mechanical properties of cement-bonded composite panels made from jute stick
- 2020
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Ingår i: Journal of Building Engineering. - : Elsevier BV. - 2352-7102. ; 31
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the study was to observe the effects of chemical additives (calcium chloride (CaCl2) and magnesium chloride (MgCl2)) on the setting time of jute stick cement-bonded composites (CBCs). The setting time was judged based on the measured physical and mechanical properties of the composites as function of the press time. The mixing ratio of jute stick particles, cement and water was set at 2:1:1 for chemical additive (CaCl2/MgCl2) incorporated composites, and a controlled one without additive was manufactured based on jute particles and cement mixing ratio of 2:1. Three concentration levels of 6, 8 and 10% of CaCl2 and MgCl2 were used separately to produce the composite boards. In this study, the composite mixtures were cold-pressed at a pressure of 5 MPa and different pressing duration of 4, 6, 8, 12 and 16 h. Incorporation of the additives reduced the press time, and higher percentage of additives increased the physical and mechanical properties of the composite panels produced. Composite panels made with MgCl2 exhibited better performance compared with those made with CaCl2. The highest modulus of elasticity (MOE) and modulus of rupture (MOR) of the manufactured samples were 10.5 and 4595 MPa, respectively for the maximum percentage of MgCl2 addition with 6 h press time. It appears that these additives especially MgCl2 decreased the setting time of the CBCs, which can be considered as an alternative approach for the industry to produce CBCs in shorter time.
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| 3. |
- Dodoo, Ambrose, 1979-
(författare)
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Primary energy and economic implications of ventilation heat recovery for a multi-family building in a Nordic climate
- 2020
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Ingår i: Journal of Building Engineering. - : Elsevier. - 2352-7102 .- 2352-7102. ; 31:101391, s. 1-14
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Tidskriftsartikel (refereegranskat)abstract
- In this study the primary energy and economic implications of exhaust ventilation air heat recovery are analysed for an existing multi-family building, considering alternative air handling units (AHUs) encompassing centralised and semi-centralised units with counter-flow plate or rotary heat exchangers. The performance of the heat recovery AHUs are analysed considering different economic scenarios, frost conditions, building energy efficiency levels, energy tariffs and heat supply options including electric heat pump and district heating based on cogeneration or heat-only boiler production. Focus has been on understanding the impacts of key economic and technical parameters on the financial viability of the heat recovery AHUs, which seem lacking in current literature. The primary energy is modelled based on hourly energy balance calculations and analysis of entire natural resources chains. The economic performance is analysed considering investment costs as well as net present values of energy cost savings of the AHUs. The results show that the heat recovery AHUs are less cost-effective when using electric heat pump compared to when using district heating in the studied context. The semi-centralised AHUs with rotary heat exchanger seem slightly more cost-effective among the analysed alternatives. Frosting and defrosting need significantly influence the peak heating load and have noticeable impact on the energy and economic performance of the heat recovery AHUs. This study highlights the need for careful design and analysis of AHUs for ventilation heat recovery in buildings, for improved primary energy and cost efficiency.
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| 4. |
- Liu, Fangzhou, et al.
(författare)
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Finite element modelling for the dynamic analysis of hollow-core concrete floors in buildings
- 2020
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Ingår i: Journal of Building Engineering. - : Elsevier Ltd. - 2352-7102. ; 32
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Tidskriftsartikel (refereegranskat)abstract
- Precast hollow-core concrete (HC) slabs are widely used in construction, especially in Nordic countries. The combination of prestressing and low self-weight due to the voids makes it possible to build long-span floors. However, this also implies that the floors become more sensitive to vibrations from human activities, and consequently a finite element model of the floor is often necessary in order to perform a dynamic analysis. However, there are no guidelines or recommendations to implement such finite element models for HC floors. In this paper, six in-situ dynamic experiments performed in 4 buildings are presented. For each case, several finite element models have been implemented and tested. These analyses show that the orthotropic shell model for the HC floor proposed by the authors in a previous publication gives good results in all the studies. The results also indicate that the concrete walls or the steel beams and columns surrounding the floor should be incorporated in the finite element model in order to get accurate results. Besides, in some cases, the floors below and above must be modelled in order to catch all the eigenmodes. The influence of the non-bearing internal walls is also discussed.
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| 5. |
- Rana, Md Nasim, et al.
(författare)
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Influence of chemical additive on the physical and mechanical properties of cement-bonded composite panels made from jute stick
- 2020
-
Ingår i: Journal of Building Engineering. - : Elsevier BV. - 2352-7102. ; 31
-
Tidskriftsartikel (refereegranskat)abstract
- The aim of the study was to observe the effects of chemical additives (calcium chloride (CaCl2) and magnesium chloride (MgCl2)) on the setting time of jute stick cement-bonded composites (CBCs). The setting time was judged based on the measured physical and mechanical properties of the composites as function of the press time. The mixing ratio of jute stick particles, cement and water was set at 2:1:1 for chemical additive (CaCl2/MgCl2) incorporated composites, and a controlled one without additive was manufactured based on jute particles and cement mixing ratio of 2:1. Three concentration levels of 6, 8 and 10% of CaCl2 and MgCl2 were used separately to produce the composite boards. In this study, the composite mixtures were cold-pressed at a pressure of 5 MPa and different pressing duration of 4, 6, 8, 12 and 16 h. Incorporation of the additives reduced the press time, and higher percentage of additives increased the physical and mechanical properties of the composite panels produced. Composite panels made with MgCl2 exhibited better performance compared with those made with CaCl2. The highest modulus of elasticity (MOE) and modulus of rupture (MOR) of the manufactured samples were 10.5 and 4595 MPa, respectively for the maximum percentage of MgCl2 addition with 6 h press time. It appears that these additives especially MgCl2 decreased the setting time of the CBCs, which can be considered as an alternative approach for the industry to produce CBCs in shorter time.
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| 6. |
- Sadeghian, Parastoo, et al.
(författare)
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Impact of surgical lamp design on the risk of surgical site infections in operating rooms with mixing and unidirectional airflow ventilation : A numerical study
- 2020
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Ingår i: Journal of Building Engineering. - : Elsevier. - 2352-7102. ; 31
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Tidskriftsartikel (refereegranskat)abstract
- Operating room (OR) ventilation plays an important role in mitigating the spread of bacteria-carrying particles (BCPs) and preventing the incidence of surgical site infections (SSIs). The use of surgical lamps in ORs is critical for patient safety and staff comfort. However, the surgical lamp serves as an obstruction in the ventilation airflow and also as a source of heat generation, which often creates a stagnant area under the lamp. Such a stagnant area is normally poorly ventilated, where a significant amount of BCPs can accumulate. As the lamp is usually positioned above the patient to illuminate the wound, the accumulation of airborne BCPs under the lamp leads to a high risk of infections and constitutes a threat to patient safety. Therefore, we proposed an innovative design of the surgical lamp, that is, the fan-mounted surgical lamp. The performance of this new design of lamp was compared with the conventional closed-shape lamp under two ventilation strategies: mixing and unidirectional airflow (UDF) ventilation. To account for different working conditions, both the horizontal and 45° orientations were applied to the lamps. We employed numerical simulations to predict the BCPs contamination in the proximity of the surgical site, as it is directly related to the risk of SSIs. The results showed that the fan-mounted lamp considerably reduced the level of contamination under both ventilation strategies. Results also suggested that the contamination level cannot be effectively reduced by only adjusting the orientation of the closed-shape lamp under unidirectional airflow ventilation.
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| 7. |
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| 8. |
- Simanic, Branko, et al.
(författare)
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Predicted and measured user-related energy usage in newly built low-energy schools in Sweden
- 2020
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Ingår i: Journal of Building Engineering. - : Elsevier BV. - 2352-7102. ; 29
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Tidskriftsartikel (refereegranskat)abstract
- Literature and experience show that the differences between calculated and measured building energy performance still exist. The literature shows that user-related parameters are significant with regard to energy performance in low-energy buildings and this means that the choice of parameters is one of the main factors leading to this difference. However, the parameters themselves are associated with uncertainty when predicting and calculating their effects. One of the identified research gaps is the lack of data on behavioral energy use and profiles. The aim of this study is to provide relevant feedback, which will help the building industry and research communities to predict more accurately the user-related impacts on energy performance and, subsequently, enable reduction of the differences between calculated and measured energy performance. This article analyses measured user-related parameters and building energy usage in seven recently built low-energy schools in Sweden. Regression analysis is applied when analysing the parameters and their influence on energy usage. With the help of the measurements carried out, all the studied schools were determined to be low-energy schools. The results show differences between calculated and measured building energy performances in the studied schools and these vary from –44 to +28%. At least 33% of measured energy usage depends on the user-related parameters. Ventilation rates and running times as well as space heating set points were found to be the user-related parameters that have the most significant effects on total energy usage. Finally, some important recommendations for good building operation practice and measurement methodology are presented.
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| 9. |
- Younis, Adel, et al.
(författare)
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Cost effectiveness of reinforcement alternatives for a concrete water chlorination tank
- 2020
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Ingår i: Journal of Building Engineering. - : Elsevier. - 2352-7102. ; 27, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- Reinforced concrete tanks in water/wastewater treatment plants are susceptible to severe corrosion due to aggressive exposure conditions resulting from the application of certain treatment chemicals and methods. Non-corrosive materials, such as stainless steel or fiber reinforced polymer (FRP), may be attractive alternative reinforcement options for such concrete structures. However, the high initial cost of such materials imposes constraints on their use, although such thinking ignores improvements in long-term concrete durability. The current paper addresses the use of non-corrosive reinforcement in a concrete water chlorination tank using life-cycle cost analysis (LCCA) that aims to evaluate the cost effectiveness of different reinforcement alternatives. A comparison was established between four concrete reinforcing materials, namely, black steel, epoxy coated steel, stainless steel, and glass-FRP (GFRP) through a 100-year analysis period. The results of this study suggest that the use of non-corrosive reinforcement helps achieve a considerable long-term cost saving. LCCA showed that GFRP becomes more economical than black steel in 35 years following construction. The net present cost (NPC) obtained for the GFRP-reinforced concrete was approximately 43% lower than that of the black steel reinforced concrete. The use of stainless steel also had a potential advantage but was less cost-effective than GFRP, with a 50-year payback period and an NPC 25% lower than that of the conventional design. Epoxy coated steel also showed a long-term cost benefit when compared to black steel, with approximately 11% reduction in NPC and 15-year extension in the service life. Sensitivity analyses were performed to assess the effects of the analysis period, discount rate, construction costs, concrete strength, and the use of supplementary cementitious materials on the LCCA outcomes.
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