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Multi-criteria Performance Dynamic Optimization for Heating Operation of Stratum Ventilation Considering Different Metabolic Rates. ARABIAN JOURNAL FOR SCIENCE AND ENGINEERING 2022. [DOI: 10.1007/s13369-022-07119-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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Li H, Fu Z, Xi C, Li N, Li W, Kong X. Study on the impact of parallel jet spacing on the performance of multi-jet stratum ventilation. APPLIED ENERGY 2022; 306:118135. [PMID: 34776588 PMCID: PMC8577804 DOI: 10.1016/j.apenergy.2021.118135] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Revised: 10/18/2021] [Accepted: 10/22/2021] [Indexed: 06/13/2023]
Abstract
With the wide spread of novel coronavirus SARS-CoV-2 pandemic around the word, high quality indoor environment and more efficient mechanical ventilation become the new focus of scholars' attention. Stratum ventilation refers to the ventilation mode that the air supply port on the side wall slightly higher than the height of the working area directly sends fresh air into the working breathing area. As an efficient mechanical ventilation mode, it can create a more healthy and comfortable indoor environment. However, the impact caused by airflow characteristic under stratum ventilation on the thermal performance and indoor comfort is noteworthy due to its supply air outlets are close to the occupied zone. It is widely known that parallel turbulent jets are important for the flow structure and air distribution. Hence, an optimum parallel jet spacing (PJS) between two jet centerlines can obviously enhance the fluid interaction and indoor thermal comfort with low energy consumption. Therefore, this study aims to investigate the impact of the PJS on the performance of multi-jet stratum ventilation. A validated Computational Fluid Dynamics (CFD) model was used to conduct the year-round multivariate analysis. A total of eight PJSs, four inlet locations and five climate zones were discussed synthetically. Air distribution performance index (ADPI), ventilation effectiveness (Et ) and economic comfort coefficient were employed as the evaluation indicators to assess the thermal comfort and energy efficiency in various scenarios. Research results indicated that the PJS showed different influences on the indoor thermal comfort and energy utilization efficiency as a result of cooperative effect including energy dissipation, air short-circuit probability, air distribution uniformity and airflow path. Combining with building energy simulation method, the optimum PJSs of stratum ventilation with different air inlet positions in five climate zones were obtained, which can help provide a comfortable indoor thermal environment and improve energy efficiency in a low-cost way. The data and conclusions presented in this study can supplement the theoretical basis for the actual applications of multiple-jet stratum ventilation used in an office.
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Affiliation(s)
- Han Li
- School of Energy and Environmental Engineering, Hebei University of Technology, China
| | - Zheng Fu
- School of Energy and Environmental Engineering, Hebei University of Technology, China
| | - Chang Xi
- School of Energy and Environmental Engineering, Hebei University of Technology, China
| | - Nana Li
- School of Energy and Environmental Engineering, Hebei University of Technology, China
| | - Wei Li
- North China Municipal Engineering Design & Research Institute Co, Ltd, China
| | - Xiangfei Kong
- School of Energy and Environmental Engineering, Hebei University of Technology, China
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Kong X, Guo C, Lin Z, Duan S, He J, Ren Y, Ren J. Experimental study on the control effect of different ventilation systems on fine particles in a simulated hospital ward. SUSTAINABLE CITIES AND SOCIETY 2021; 73:103102. [PMID: 34189016 PMCID: PMC8222082 DOI: 10.1016/j.scs.2021.103102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Revised: 06/12/2021] [Accepted: 06/14/2021] [Indexed: 05/03/2023]
Abstract
In recent years, a large number of respiratory infectious diseases (especially COVID-19) have broken out worldwide. Respiratory infectious viruses may be released in the air, resulting in cross-infection between patients and medical workers. Indoor ventilation systems can be adjusted to affect fine particles containing viruses. This study was aimed at performing a series of experiments to evaluate the ventilation performance and assess the exposure of healthcare workers (HW) to virus-laden particles released by patients in a confined experimental chamber. In a typical ward setting, four categories (top supply and exhaust, side supply and exhaust) were evaluated, encompassing 16 different air distribution patterns. The maximum reduction in the cumulative exposure level for HW was 70.8% in ventilation strategy D (upper diffusers on the sidewall supply and lower diffusers on the same sidewall return). The minimum value of the cumulative exposure level for a patient close to the source of the contamination pertained to Strategy E (upper diffusers on the sidewall supply and lower diffusers on the opposite sidewall return). Lateral ventilation strategies can provide significant guidance for ward operation to minimizing the airborne virus contamination. This study can provide a reference for sustainable buildings to construct a healthy indoor environment.
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Affiliation(s)
- Xiangfei Kong
- School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin, China
| | - Chenli Guo
- School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin, China
| | - Zhang Lin
- City University of Hong Kong Shenzhen Research Institute, Shenzhen, China
| | - Shasha Duan
- School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin, China
| | - Junjie He
- School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin, China
| | - Yue Ren
- School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin, China
| | - Jianlin Ren
- School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin, China
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A Comprehensive Thermal Comfort Analysis of the Cooling Effect of the Stand Fan Using Questionnaires and a Thermal Manikin. SUSTAINABILITY 2019. [DOI: 10.3390/su11185091] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
In this study a quantitative analysis was performed on the effect on thermal comfort of the stand fan, a personal cooling device that creates local air currents. A total of 20 environmental conditions (indoor temperatures: 22, 24, 26, 28, and 30°C; fan modes: off, low (L) mode, medium (M) mode, and high (H) mode) were analyzed using questionnaires on male and female subjects in their 20s and a thermal manikin test. The contents of the questionnaire consisted of items on thermal sensation, thermal comfort, thermal acceptability, and demands on changes to the air velocity. This step was accompanied by the thermal manikin test to analyze the convective heat transfer coefficient and cooling effect quantitatively by replicating the stand fan. Given that this study provides data on the cooling effect of the stand fan in quantitative values, it allows for a comparison of energy use with other cooling systems such as the air conditioner, and may be used as a primary data set for analysis of energy conservation rates.
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Experimental Evaluation of the Ventilation Effectiveness of Corner Stratum Ventilation in an Office Environment. BUILDINGS 2019. [DOI: 10.3390/buildings9070169] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
An experimental study was conducted in a room resembling an office in a laboratory environment. The study involved investigating the ability of corner-placed stratum ventilation in order to evaluate the ventilation’s effectiveness and local thermal comfort. At fixed positions, the air temperature, air velocity, turbulence intensity, and tracer gas decay measurements were carried out. The results show that corner-placed stratum ventilation behaves very similar to a mixing ventilation system when considering air change effectiveness. The performance of the system was better at lower supply air flow rates for heat removal effectiveness. For the heating cases, the draught rates were all very low, with the maximum measured value of 12%. However, for the cooling cases, the maximum draught rate was 20% and occurred at ankle level in the middle of the room.
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Costa ML, Freire MR, Kiperstok A. Strategies for thermal comfort in university buildings - The case of the faculty of architecture at the Federal University of Bahia, Brazil. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2019; 239:114-123. [PMID: 30897477 DOI: 10.1016/j.jenvman.2019.03.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Revised: 02/11/2019] [Accepted: 03/02/2019] [Indexed: 06/09/2023]
Abstract
Buildings constructed according to bioclimatic architectural principles in amenable climates have often experienced posterior interventions that have closed ventilation openings for the installation of air conditioning units. The present work sought to investigate the reasons for installing air conditioning equipment in buildings even under adverse economic conditions and with the awareness of their negative environmental implications. The Faculty of Architecture building at the Federal University of Bahia, located in the city of Salvador, Bahia State, Brazil, was the focus of the present investigation. It was determined that the lack of maintenance of the windows and window frames, and the closing of projected openings compromised natural ventilation. The study confirmed the adequacy of the architectural project in relation to the local climate, and in loco measurements likewise confirmed the efficiency of natural ventilation through the windows and other openings in the faculty room and classrooms examined. The results of the interviews concerning thermal comfort indicated that 53% of the users felt comfortable. Nonetheless, it was found that the building's windows and window frames were poorly maintained, compromising their ability to facilitate efficient natural ventilation and significantly diminishing the capacity for thermal regulation in the building. This study calls attention to the necessity of refining and improving the maintenance of university buildings to reduce the intensive use of artificial air conditioning in detriment to investments in projects that could lend priority to natural ventilation and the maintenance of good window operating conditions.
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Affiliation(s)
- Maria Lívia Costa
- Universidade Federal da Bahia, Escola Politécnica, Programa de Engenharia Industrial, Salvador, Bahia, Brazil.
| | - Marcia Rebouças Freire
- Universidade Federal da Bahia, Escola Politécnica, Programa de Engenharia Industrial, Salvador, Bahia, Brazil.
| | - Asher Kiperstok
- Universidade Federal da Bahia, Escola Politécnica, Programa de Engenharia Industrial, Salvador, Bahia, Brazil.
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Cheng Y, Lin Z. Experimental investigation into the interaction between the human body and room airflow and its effect on thermal comfort under stratum ventilation. INDOOR AIR 2016; 26:274-285. [PMID: 25857272 DOI: 10.1111/ina.12208] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2014] [Accepted: 03/30/2015] [Indexed: 06/04/2023]
Abstract
Room occupants' comfort and health are affected by the airflow. Nevertheless, they themselves also play an important role in indoor air distribution. This study investigated the interaction between the human body and room airflow under stratum ventilation. Simplified thermal manikin was employed to effectively resemble the human body as a flow obstacle and/or free convective heat source. Unheated and heated manikins were designed to fully evaluate the impact of the manikin at various airflow rates. Additionally, subjective human tests were conducted to evaluate thermal comfort for the occupants in two rows. The findings show that the manikin formed a local blockage effect, but the supply airflow could flow over it. With the body heat from the manikin, the air jet penetrated farther compared with that for the unheated manikin. The temperature downstream of the manikin was also higher because of the convective effect. Elevating the supply airflow rate from 7 to 15 air changes per hour varied the downstream airflow pattern dramatically, from an uprising flow induced by body heat to a jet-dominated flow. Subjective assessments indicated that stratum ventilation provided thermal comfort for the occupants in both rows. Therefore, stratum ventilation could be applied in rooms with occupants in multiple rows.
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Affiliation(s)
- Y Cheng
- Department of Architecture and Civil Engineering, City University of Hong Kong, Kowloon, Hong Kong
| | - Z Lin
- Division of Building Science and Technology, City University of Hong Kong, Kowloon, Hong Kong
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Sekhar SC. Thermal comfort in air-conditioned buildings in hot and humid climates--why are we not getting it right? INDOOR AIR 2016; 26:138-152. [PMID: 25626476 DOI: 10.1111/ina.12184] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Accepted: 12/24/2014] [Indexed: 06/04/2023]
Abstract
While there are plenty of anecdotal experiences of overcooled buildings in summer, evidence from field studies suggests that there is indeed an issue of overcooling in tropical buildings. The findings suggest that overcooled buildings are not a consequence of occupant preference but more like an outcome of the HVAC system design and operation. Occupants' adaptation in overcooled indoor environments through additional clothing cannot be regarded as an effective mitigating strategy for cold thermal discomfort. In the last two decades or so, several field studies and field environmental chamber studies in the tropics provided evidence for occupants' preference for a warmer temperature with adaptation methods such as elevated air speeds. It is important to bear in mind that indoor humidity levels are not compromised as they could have an impact on the inhaled air condition that could eventually affect perceived air quality. This review article has attempted to track significant developments in our understanding of the thermal comfort issues in air-conditioned office and educational buildings in hot and humid climates in the last 25 years, primarily on occupant preference for thermal comfort in such climates. The issue of overcooled buildings, by design intent or otherwise, is discussed in some detail. Finally, the article has explored some viable adaptive thermal comfort options that show considerable promise for not only improving thermal comfort in tropical buildings but are also energy efficient and could be seen as sustainable solutions.
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Affiliation(s)
- S C Sekhar
- Department of Building, School of Design and Environment, National University of Singapore, Singapore, Singapore
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Cheng Y, Lin Z. Experimental study of airflow characteristics of stratum ventilation in a multi-occupant room with comparison to mixing ventilation and displacement ventilation. INDOOR AIR 2015; 25:662-671. [PMID: 25626596 DOI: 10.1111/ina.12188] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2014] [Accepted: 01/19/2015] [Indexed: 06/04/2023]
Abstract
UNLABELLED The motivation of this study is stimulated by a lack of knowledge about the difference of airflow characteristics between a novel air distribution method [i.e., stratum ventilation (SV)] and conventional air distribution methods [i.e., mixing ventilation (MV) and displacement ventilation (DV)]. Detailed air velocity and temperature measurements were conducted in the occupied zone of a classroom with dimensions of 8.8 m (L) × 6.1 m (W) × 2.4 m (H). Turbulence intensity and power spectrum of velocity fluctuation were calculated using the measured data. Thermal comfort and cooling efficiency were also compared. The results show that in the occupied zone, the airflow characteristics among MV, DV, and SV are different. The turbulent airflow fluctuation is enhanced in this classroom with multiple thermal manikins due to thermal buoyancy and airflow mixing effect. Thermal comfort evaluations indicate that in comparison with MV and DV, a higher supply air temperature should be adopted for SV to achieve general thermal comfort with low draft risk. Comparison of the mean air temperatures in the occupied zone reveals that SV is of highest cooling efficiency, followed by DV and then MV. PRACTICAL IMPLICATIONS This study reports the unique profiles of flow, temperature, turbulence intensity, and power spectrum of stratum ventilation, which can have a number of implications for both knowledge and understanding of the flow characteristics in a stratum-ventilated room. With respect to the former, it expounds the fundamental characteristics of this air distribution method; and with respect to the latter, it reveals the mechanism of thermal comfort and energy saving under stratum ventilation.
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Affiliation(s)
- Y Cheng
- Department of Architecture and Civil Engineering, City University of Hong Kong, Kowloon, Hong Kong, S.A.R
| | - Z Lin
- Department of Architecture and Civil Engineering, City University of Hong Kong, Kowloon, Hong Kong, S.A.R
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Kalmár F. Innovative method and equipment for personalized ventilation. INDOOR AIR 2015; 25:297-306. [PMID: 24923841 DOI: 10.1111/ina.12138] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Accepted: 06/06/2014] [Indexed: 06/03/2023]
Abstract
At the University of Debrecen, a new method and equipment for personalized ventilation has been developed. This equipment makes it possible to change the airflow direction during operation with a time frequency chosen by the user. The developed office desk with integrated air ducts and control system permits ventilation with 100% outdoor air, 100% recirculated air, or a mix of outdoor and recirculated air in a relative proportion set by the user. It was shown that better comfort can be assured in hot environments if the fresh airflow direction is variable. Analyzing the time step of airflow direction changing, it was found that women prefer smaller time steps and their votes related to thermal comfort sensation are higher than men's votes.
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Affiliation(s)
- F Kalmár
- Department of Building Services and Building Engineering, University of Debrecen, Debrecen, Hungary
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Cheng Y, Fong ML, Yao T, Lin Z, Fong KF. Uniformity of stratum-ventilated thermal environment and thermal sensation. INDOOR AIR 2014; 24:521-532. [PMID: 24438214 DOI: 10.1111/ina.12097] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Accepted: 01/11/2014] [Indexed: 06/03/2023]
Abstract
Three human test series were conducted to evaluate the uniformity of the thermal environments in a stratum-ventilated chamber with dimensions of 8.8 m (L) × 5.1 m (W) × 2.4 m (H). In all, nineteen conditions were generated by adjusting the room temperature, supply airflow rate, and supply terminal type. An air diffuser performance index (ADPI) of at least 80% was achieved for most cases. This result shows that the air velocity and temperature in the occupied zone are reasonably uniform. Subjective assessments using the ASHRAE 7-point scale indicate that the thermal sensations of the subjects in stratum ventilation are also uniform. This study examines the applicability of the predicted mean vote (PMV) model for evaluating stratum ventilation. When compared to the actual mean thermal sensation votes (ATS), the PMV values are acceptable. The PMV results at a height of 1.1 m above the floor show better agreement with the ATS than at a height of 0.1 m.
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Affiliation(s)
- Y Cheng
- Building Energy & Environmental Technology Research Unit, Division of Building Science and Technology, City University of Hong Kong, Kowloon, Hong Kong
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