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| 2. |
- Hou, Jing, et al.
(författare)
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Associations of indoor carbon dioxide concentrations, air temperature, and humidity with perceived air quality and sick building syndrome symptoms in Chinese homes
- 2021
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Ingår i: Indoor Air. - : John Wiley & Sons. - 0905-6947 .- 1600-0668. ; 31:4, s. 1018-1028
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Tidskriftsartikel (refereegranskat)abstract
- The indoor environment influences occupants' health. From March 1, 2018, to February 28, 2019, we continuously monitored indoor temperature (T), relative humidity (RH), and CO2 concentration in bedrooms via an online system in 165 residences that covered all five climate zones of China. Meanwhile, we asked one specific occupant in each home to complete questionnaires about perceived air quality and sick building syndrome (SBS) symptoms at the end of each month. Higher CO2 concentration was significantly associated with a higher percentage of perceived stuffy odor and skin SBS symptoms. Higher relative humidity was associated with higher percentage of perceived moldy odor and humid air, while lower RH was associated with a higher percentage of perceived dry air. Occupants who lived in residences with high RH were less likely to have mucosal and skin SBS symptoms (adjusted odds ratio (AOR): 0.73-0.78). However, the benefit of high humidity for perceived dry air and skin dryness symptoms is weaker if there is a high CO2 concentration level.
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| 3. |
- Lai, Dayi, et al.
(författare)
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A comprehensive review of thermal comfort studies in urban open spaces
- 2020
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 742
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Forskningsöversikt (refereegranskat)abstract
- Urban open spaces provide various benefits to large populations in cities. Since thermally comfortable urban open spaces improve the quality of urban living, an increasing number of studies have been conducted to extend the existing knowledge of outdoor thermal comfort. This paper comprehensively reviews current outdoor thermal comfort studies, including benchmarks, data collection methods, and models of outdoor thermal comfort. Because outdoor thermal comfort is a complex issue influenced by various factors, a conceptual framework is proposed which includes physical, physiological and psychological factors as direct influences: and behavioral, personal, social, cultural factors, as well as thermal history, site, and alliesthesia, as indirect influences. These direct and indirect factors are further decomposed and reviewed, and the interactions among various factors are discussed. This review provides researchers with a systematic and comprehensive understanding of outdoor thermal comfort, and can also guide designers and planners in creating thermally comfortable urban open spaces.
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| 4. |
- Lai, Dayi, et al.
(författare)
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An ordered probability model for predicting outdoor thermal comfort
- 2018
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Ingår i: Energy and Buildings. - : ELSEVIER SCIENCE SA. - 0378-7788 .- 1872-6178. ; 168, s. 261-271
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Tidskriftsartikel (refereegranskat)abstract
- Outdoor thermal comfort in urban spaces is gaining increasing research attention because it is associated with the quality of life in cities. This paper presents an ordered probability model for predicting the probability distribution of thermal sensation votes (TSVs) based on 1549 observations obtained from a large-scale field survey conducted at a park in Tianjin, China. With a given set of inputs, the developed model can predict the probability that people will feel cold, cool, slightly cool, neutral, slightly warm, warm, or hot. The predictive capability of the ordered probability model was systematically assessed by comparing it with the survey data and a traditional multivariate linear model. Both models had a similar accuracy in predicting single-value TSVs. However, the ordered probability model performed much better than the multivariate linear model in predicting the probability distribution of TSVs. A sensitivity analysis of the ordered probability model revealed that outdoor air temperature was the most important influencing factor. The impacts of global radiation, relative humidity, and activity level on predicted thermal sensation depended on the outdoor air temperature. The developed ordered probability model was used to predict suitable time periods for holding outdoor activities in Tianjin across a whole year. This new model is a more informative tool for predicting outdoor thermal comfort. (C) 2018 Elsevier B.V. All rights reserved.
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| 5. |
- Liu, Wei, Assistant Professor, 1987-, et al.
(författare)
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A combined CFD-based genetic algorithm and human body thermoregulation model for designing the indoor thermal environment
- 2022
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Ingår i: BS 2021. - : International Building Performance Simulation Association. ; , s. 2727-2733
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Konferensbidrag (refereegranskat)abstract
- A thermally comfortable indoor environment is critical for ensuring the health and productivity of the occupants. This study aims to develop a combined CFD-based genetic algorithm and human body thermoregulation model for the inverse design of indoor thermal environment. This investigation developed the CFD solver in OpenFOAM, the genetic algorithm by GenOpt, and the human body thermoregulation model in Matlab. A shell file was used to run those three parts in need automatically. The developed model was validated by the measured human skin temperature from literature. The model was further applied to design the thermal environments in an office with displacement ventilation for demonstration. In the office case with displacement ventilation, the thermal comfort was maximized when the air supply air temperature and velocity was 25 oC, and 0.08 m/s. Coupling thermoregulation model with CFD inverse design provides a more detailed way to optimize the indoor thermal environment, and at the same time, local thermal discomfort can be reduced.
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| 6. |
- Liu, Wei, Assistant Professor, 1987-, et al.
(författare)
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Inverse design of a thermally comfortable indoor environment with a coupled CFD and multi-segment human thermoregulation model
- 2023
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Ingår i: Building and Environment. - : Elsevier BV. - 0360-1323 .- 1873-684X. ; 227
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Tidskriftsartikel (refereegranskat)abstract
- A thermally comfortable indoor environment is critical for ensuring the health and productivity of the occupants. To design a thermally comfortable environment, CFD-based methods assume the occupants' surface temperature to be fixed values for simplicity and use PMV to estimate thermal comfort level. The constant surface temperature assumption would lead to inaccurate prediction of the indoor environment and the use of PMV would lead to a waste of the rich spatial information calculated by CFD. Therefore, this study developed and validated a coupled CFD and multi-node human thermoregulation model (HTM). The CFD and HTM synchronize data during the simulation and the occupant skin temperature could be updated. The final skin temperature could be used to quantify the thermal comfort level. The accuracy of the coupled model in predicting the skin temperature was validated by experimental data from literature. The coupled model was further integrated with genetic algorithm for inverse design. The inverse design of thermal environment in an office with two occupants and displacement ventilation was used for demonstration. With the CFD-HTM model, genetic algorithm was able to identify an optimal condition that leads to the least deviation of skin temperature of local body parts from the neutral values. The developed CFD-HTM coupling scheme can be used to effectively design indoor environment with improved thermal comfort.
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| 7. |
- Liu, Wei, Assistant Professor, 1987-, et al.
(författare)
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Performance of fast fluid dynamics with a semi-Lagrangian scheme and an implicit upwind scheme in simulating indoor/outdoor airflow
- 2022
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Ingår i: Building and Environment. - : Elsevier. - 0360-1323 .- 1873-684X. ; 207:B
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Tidskriftsartikel (refereegranskat)abstract
- Computational fluid dynamics can be time consuming for predicting indoor airflows and pollutant transport in large-scale problems or emergency management. Fast fluid dynamics (FFD) is able to accomplish efficient and accurate simulation of indoor/outdoor airflow. FFD solves the advection term of the Navier–Stokes equations either by a semi-Lagrangian (SL) scheme or an implicit upwind (IU) scheme. The SL scheme can be highly efficient, but its first-order version is not conservative and introduces significant numerical diffusion. To improve its accuracy, a high-order temporal and interpolation scheme that not only reduces dissipation and dispersion errors but also guarantees the convergence speed should be applied. Otherwise, an IU scheme instead could be used to solve the advection term. The IU scheme is conservative and introduces minor numerical diffusion, but it may increase the computation time. Therefore, this study investigated the performance of FFD with SL scheme using high-order temporal and interpolation schemes and that with IU scheme. The comparisons used experimental data of two indoor airflows and one outdoor airflow. The results showed that FFD with IU scheme was overall more accurate than FFD with SL scheme. In simulating indoor airflow, both methods were robust and the predictions were independent of time step sizes if the Courant number was less than or equal to one. In simulating the outdoor airflow, the FFD with SL scheme performed better than the FFD with IU scheme for large time step sizes. The FFD with IU scheme consumed 44%–61% computing time of the FFD with SL scheme.
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| 8. |
- Sun, Rui, et al.
(författare)
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A computationally affordable and reasonably accurate approach for annual outdoor thermal comfort assessment on an hourly basis
- 2024
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Ingår i: Energy and Buildings. - : Elsevier Ltd. - 0378-7788 .- 1872-6178. ; 316
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Tidskriftsartikel (refereegranskat)abstract
- The thermal environment and thermal comfort of an outdoor space have large spatial and temporal variations. To provide an overall picture, outdoor thermal comfort (OTC) should be analyzed on a yearly basic with high temporal-spatial resolution. The difficulty of annual OTC evaluation lies in the huge computational cost of wind simulations. Therefore, our study proposed a method to accelerate wind simulations through the use of Fast Fluid Dynamics (FFD), Proper Orthogonal Decomposition (POD) and Reynolds Number Independence (Re-independence). A case study of an actual urban building complex was employed to validate our study by comparing the integrated index Universal Thermal Climate Index (UTCI) results by our method with those by fully-resolved simulations. The average difference of UTCI was just 0.06 ∘C, indicating that the accuracy of our method is guaranteed. Besides, it only took 8 hours to complete the OTC assessment of this site with an area of 125,600 m2. The framework proposed in this study can be used to reveal the complete picture of OTC with affordable computational cost and reasonable accuracy.
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| 9. |
- Sun, Rui, et al.
(författare)
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Building form and outdoor thermal comfort : Inverse design the microclimate of outdoor space for a kindergarten
- 2023
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Ingår i: Energy and Buildings. - : Elsevier BV. - 0378-7788 .- 1872-6178. ; 284
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Tidskriftsartikel (refereegranskat)abstract
- Thermally comfortable mircoclimate is essential for creating high-quality outdoor spaces that attract cit-izens and boost city vitality. Previous design efforts to improve outdoor thermal comfort were usually conducted at large scales, such as city scale, neighborhood scale, urban block scale. Few researchers focused on the building scale. This study proposes an optimization framework based on genetic algorithm to determine the building shape, orientation, and location during early design stage that reduces the overall thermal stress in the target outdoor space. Solar radiation and wind fields were simulated to obtain the outdoor Universal Thermal Climate Index (UTCI) as the performance indicator. The simulations were validated against the experimental data. This investigation applied the proposed optimization framework to design the outdoor space for a kindergarten under the climate of Tianjin and Shanghai, respectively. The results showed that optimization reduced the overall thermal stress. The most favour-able kindergarten forms were suggested through optimization. Moreover, solar radiation has been proved to contribute more to outdoor thermal comfort than wind field and heat stress is more important than cold stress during optimization. This study supplements the inverse design of outdoor thermal comfort at building scale and provides suggestions to create comfortable urban outdoor spaces.
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| 10. |
- Sun, Rui, et al.
(författare)
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Improving outdoor thermal comfort of a kindergarten by optimizing its building shape with genetic algorithm
- 2023
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Ingår i: 11th International Conference on Indoor Air Quality, Ventilation and Energy Conservation in Buildings, IAQVE C2023. - : EDP Sciences.
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Konferensbidrag (refereegranskat)abstract
- Thermally comfortable mircoclimate is essential for creating high-quality outdoor spaces that attract citizens and boost city vitality. Previous design efforts to improve outdoor thermal comfort were usually conducted at large scales, such as city scale, neighborhood scale, urban block scale. Few researchers focused on the building scale. This study proposes an optimization framework based on genetic algorithm to determine the building shape, orientation, and location during early design stage that reduces the overall thermal stress in the target outdoor space. Solar radiation and wind fields were simulated to obtain the outdoor Universal Thermal Climate Index (UTCI) as the performance indicator. The simulations were validated against the experimental data. This investigation applied the proposed optimization framework to design the outdoor space for a kindergarten under the climate of Tianjin and Shanghai, respectively. The results showed that optimization reduced the overall thermal stress. The most favourable kindergarten forms were suggested through optimization. This study supplements the inverse design of outdoor thermal comfort at building scale and provides suggestions to create comfortable urban outdoor spaces.
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