Pub Date : 2014-01-01DOI: 10.1080/10789669.2013.840523
Shih-cheng Hu, Y. Shiue, A. Shiue, Ming-Heng Tsai
In a conventional arrangement of the airflow pathway in nonunidirectional airflow cleanrooms with wall return schemes, the supply air is introduced from ceiling air grills and the return air, close and vertical to the floor, is extracted from the wall air grills. However, such a wall return ventilation system is theoretically not an optimal design for removing heat and particles released from processing machinery. The conventional wall return system currently used in cleanrooms aims to create an environment with diluted particle concentration in which downward cold supply air from ceiling filters encounters upward air currents generated by drifted particles from processing machinery. To solve the problem, we introduced a new design called fan dry coil units (FDCUs). In this article, we compare the performances of both innovative and traditional ventilation systems in a full-scale cleanroom. For each return air ventilation system, we investigated the effects of air change rates on the removal of 0.1∼5 μm particles. Based on the results, it is noted that the FDCU-return system eliminates about 60% more particles from the cleanrooms, compared with conventional wall-return system.
{"title":"Removal characteristics of particulate matter with different return air system designs in a nonunidirectional cleanroom for integrated circuit (Ic) testing processes","authors":"Shih-cheng Hu, Y. Shiue, A. Shiue, Ming-Heng Tsai","doi":"10.1080/10789669.2013.840523","DOIUrl":"https://doi.org/10.1080/10789669.2013.840523","url":null,"abstract":"In a conventional arrangement of the airflow pathway in nonunidirectional airflow cleanrooms with wall return schemes, the supply air is introduced from ceiling air grills and the return air, close and vertical to the floor, is extracted from the wall air grills. However, such a wall return ventilation system is theoretically not an optimal design for removing heat and particles released from processing machinery. The conventional wall return system currently used in cleanrooms aims to create an environment with diluted particle concentration in which downward cold supply air from ceiling filters encounters upward air currents generated by drifted particles from processing machinery. To solve the problem, we introduced a new design called fan dry coil units (FDCUs). In this article, we compare the performances of both innovative and traditional ventilation systems in a full-scale cleanroom. For each return air ventilation system, we investigated the effects of air change rates on the removal of 0.1∼5 μm particles. Based on the results, it is noted that the FDCU-return system eliminates about 60% more particles from the cleanrooms, compared with conventional wall-return system.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"1 4","pages":"162 - 166"},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72600294","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-01-01DOI: 10.1080/10789669.2013.834780
Yoonkyung Kang, S. Kato
In this study, microwave irradiation was tested as a possible means to disinfect evaporative humidifiers in air-conditioning systems. A mock-up of a humidifier was prepared to identify the applicability of the microwave irradiation system. To characterize the heating properties of this system under optimum operating conditions, the temperature distribution of the humidifier element was measured as a function of various parameters. Variables included the use of ventilation and water spraying during microwave irradiation, the level of radiation output power and whether the element was dry or wet. The results showed that microwave irradiation can heat the evaporative humidifier element about 60°C at 1200 W for exposure times greater than 3 min under nonoperating conditions (without air blower and water spraying). However, the temperature distribution of the element was nonuniform, regardless of whether the conditions were dry or wet. The effectiveness of microwave heating is limited due to nonuniform distribution of temperature. To achieve a uniform surface temperature on the element, further studies are necessary.
{"title":"A study on the effectiveness of microwave heating for disinfection of humidifier elements","authors":"Yoonkyung Kang, S. Kato","doi":"10.1080/10789669.2013.834780","DOIUrl":"https://doi.org/10.1080/10789669.2013.834780","url":null,"abstract":"In this study, microwave irradiation was tested as a possible means to disinfect evaporative humidifiers in air-conditioning systems. A mock-up of a humidifier was prepared to identify the applicability of the microwave irradiation system. To characterize the heating properties of this system under optimum operating conditions, the temperature distribution of the humidifier element was measured as a function of various parameters. Variables included the use of ventilation and water spraying during microwave irradiation, the level of radiation output power and whether the element was dry or wet. The results showed that microwave irradiation can heat the evaporative humidifier element about 60°C at 1200 W for exposure times greater than 3 min under nonoperating conditions (without air blower and water spraying). However, the temperature distribution of the element was nonuniform, regardless of whether the conditions were dry or wet. The effectiveness of microwave heating is limited due to nonuniform distribution of temperature. To achieve a uniform surface temperature on the element, further studies are necessary.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"1 1","pages":"113 - 120"},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73520437","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-01-01DOI: 10.1080/10789669.2013.836876
Pengfei Li, Yaoyu Li, J. Seem, Hongtao Qiao, Xiao Li, J. Winkler
This article is the second in the two-part series examining recent advances in the dynamic modeling of HVAC systems, which can be challenging due to the multi-physical and multi-scale processes of such systems. Part I reviewed the progress in dynamic modeling of major types of HVAC equipment. Part II presents a detailed review of dynamic modeling of HVAC equipment using Modelica, an object oriented modeling platform that has demonstrated potential in addressing HVAC equipment challenges. The Modelica-based modeling platform offers some desirable features, such as object-oriented and acausal modeling, that could significantly facilitate modeling efforts and reduce the time of model development. Currently, there are many numerically robust and efficient integrated simulation environments that support the Modelica-based modeling platform, such as Dymola, SimulationX, and MapleSim. This article reviews historical and recent modeling and simulation tools, and later examines previous work on the Modelica-based dynamic modeling of HVAC equipment. It also presents current issues and possible future directions of dynamic modeling for HVAC equipment.
{"title":"Recent advances in dynamic modeling of HVAC equipment. Part 2: Modelica-based modeling","authors":"Pengfei Li, Yaoyu Li, J. Seem, Hongtao Qiao, Xiao Li, J. Winkler","doi":"10.1080/10789669.2013.836876","DOIUrl":"https://doi.org/10.1080/10789669.2013.836876","url":null,"abstract":"This article is the second in the two-part series examining recent advances in the dynamic modeling of HVAC systems, which can be challenging due to the multi-physical and multi-scale processes of such systems. Part I reviewed the progress in dynamic modeling of major types of HVAC equipment. Part II presents a detailed review of dynamic modeling of HVAC equipment using Modelica, an object oriented modeling platform that has demonstrated potential in addressing HVAC equipment challenges. The Modelica-based modeling platform offers some desirable features, such as object-oriented and acausal modeling, that could significantly facilitate modeling efforts and reduce the time of model development. Currently, there are many numerically robust and efficient integrated simulation environments that support the Modelica-based modeling platform, such as Dymola, SimulationX, and MapleSim. This article reviews historical and recent modeling and simulation tools, and later examines previous work on the Modelica-based dynamic modeling of HVAC equipment. It also presents current issues and possible future directions of dynamic modeling for HVAC equipment.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"32 1","pages":"150 - 161"},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84083535","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-01-01DOI: 10.1080/10789669.2013.826981
H. Moon, Soo Hyeun Yang
Interest in energy and environmental problems is increasing worldwide, and efforts are being made to reduce the environmental burden of the world's energy needs. Simultaneously, the demand for precise comfort control in buildings has increased as people have acquired a better quality of life. In most cases in residential or small commercial buildings, the desired indoor environment is achieved by set temperature controls for cooling, especially with Variable Refrigerant Flow (VRF) or Variable Refrigerant Volume (VRV) systems. However, this set-temperature control method may not guarantee thermal comfort for occupants in energy efficient operation. In this study, a new comfort control algorithm is suggested to ensure better thermal comfort of residents, taking into consideration indoor humidity and initial status of indoor air to run the air conditioner. Furthermore, the performance of the algorithm in terms of energy consumption and the thermal comfort ratio is examined and compared with that of the set-temperature control method.
{"title":"Evaluation of the energy performance and thermal comfort of an air conditioner with temperature and humidity controls in a cooling season","authors":"H. Moon, Soo Hyeun Yang","doi":"10.1080/10789669.2013.826981","DOIUrl":"https://doi.org/10.1080/10789669.2013.826981","url":null,"abstract":"Interest in energy and environmental problems is increasing worldwide, and efforts are being made to reduce the environmental burden of the world's energy needs. Simultaneously, the demand for precise comfort control in buildings has increased as people have acquired a better quality of life. In most cases in residential or small commercial buildings, the desired indoor environment is achieved by set temperature controls for cooling, especially with Variable Refrigerant Flow (VRF) or Variable Refrigerant Volume (VRV) systems. However, this set-temperature control method may not guarantee thermal comfort for occupants in energy efficient operation. In this study, a new comfort control algorithm is suggested to ensure better thermal comfort of residents, taking into consideration indoor humidity and initial status of indoor air to run the air conditioner. Furthermore, the performance of the algorithm in terms of energy consumption and the thermal comfort ratio is examined and compared with that of the set-temperature control method.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"1 1","pages":"61 - 71"},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74867721","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-01-01DOI: 10.1080/10789669.2013.840524
Andrew J. Hoisington, J. P. Maestre, J. Siegel, K. Kinney
Building professionals are increasingly being called upon to conduct indoor microbial investigations as they remediate moisture-damaged buildings and design new, healthy, sustainable buildings. Characterizing the indoor microbial community present in the built environment is challenging and complicated by the vast array of biological methods available to building professionals. Furthermore, the particular biological technique employed to study an indoor environment can have a significant impact on the results obtained. This study evaluates the advantages and disadvantages of four biological methods suitable for indoor microbial investigations: culturing, quantitative polymerase chain reaction (qPCR), Sanger sequencing, and pyrosequencing. The results obtained from a study of four buildings are used to evaluate the merits of each bioanalytical approach. In each of the four study sites, the microbial-laden dust recovered on HVAC filters was used to provide a passive, long-term sample of the indoor air. Culturing of the microorganisms recovered from the dust was the least expensive method tested but provided a limited characterization of the microbial community present. qPCR provided the most specific information about the presence and quantity of target microorganisms but this method requires a priori knowledge of the species of interest and specifically designed primers that may not enumerate unanticipated species. Sanger sequencing provided microbial identification at the species level but lacked coverage to fully describe the microbial community present. Pyrosequencing provided in-depth sequence coverage of the microbial community present (to the genus level) but the vast dataset generated required increased computational analysis and data storage. Nevertheless, pyrosequencing when coupled with qPCR for target species quantification represents a viable approach that should become more accessible to building professionals as user-friendly software for analyzing sequencing results becomes available and more commercial laboratories offer these services.
{"title":"Exploring the microbiome of the built environment: A primer on four biological methods available to building professionals","authors":"Andrew J. Hoisington, J. P. Maestre, J. Siegel, K. Kinney","doi":"10.1080/10789669.2013.840524","DOIUrl":"https://doi.org/10.1080/10789669.2013.840524","url":null,"abstract":"Building professionals are increasingly being called upon to conduct indoor microbial investigations as they remediate moisture-damaged buildings and design new, healthy, sustainable buildings. Characterizing the indoor microbial community present in the built environment is challenging and complicated by the vast array of biological methods available to building professionals. Furthermore, the particular biological technique employed to study an indoor environment can have a significant impact on the results obtained. This study evaluates the advantages and disadvantages of four biological methods suitable for indoor microbial investigations: culturing, quantitative polymerase chain reaction (qPCR), Sanger sequencing, and pyrosequencing. The results obtained from a study of four buildings are used to evaluate the merits of each bioanalytical approach. In each of the four study sites, the microbial-laden dust recovered on HVAC filters was used to provide a passive, long-term sample of the indoor air. Culturing of the microorganisms recovered from the dust was the least expensive method tested but provided a limited characterization of the microbial community present. qPCR provided the most specific information about the presence and quantity of target microorganisms but this method requires a priori knowledge of the species of interest and specifically designed primers that may not enumerate unanticipated species. Sanger sequencing provided microbial identification at the species level but lacked coverage to fully describe the microbial community present. Pyrosequencing provided in-depth sequence coverage of the microbial community present (to the genus level) but the vast dataset generated required increased computational analysis and data storage. Nevertheless, pyrosequencing when coupled with qPCR for target species quantification represents a viable approach that should become more accessible to building professionals as user-friendly software for analyzing sequencing results becomes available and more commercial laboratories offer these services.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"9 1","pages":"167 - 175"},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81006055","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-01-01DOI: 10.1080/10789669.2013.834781
S. Bengea, Anthony Kelman, F. Borrelli, Russell D. Taylor, S. Narayanan
The article presents field experiment results from the implementation of a model predictive controller which optimizes the operation of a variable volume, dual-duct, multi-zone HVAC unit serving an existing mid-size commercial building. This full-scale proof-of-concept study was used to estimate the benefits of implementing advanced building control technologies during a retrofit. The control approach uses dynamic estimates and predictions of zone loads and temperatures, outdoor weather conditions, and HVAC system models to minimize energy consumption while meeting equipment and thermal comfort constraints. The article describes the on-line implementation of the hierarchical control system, including communication of the optimal control scheme with the building automation system, the controlled set-points and the component-level feedback loops, as well as the measured energy and indoor comfort performance benefits from the demonstration. The building-scale experiments and the receding-horizon control algorithm implementation results are described. Site measurements show this algorithm, when implemented in state-of-the-art direct digital control systems, consistently yields energy savings and reduces peak power while improving the indoor thermal comfort. The demonstration results show energy savings of 20% on average during the transition season, 70% on average during heating season, and 10% or more peak power reduction, all relative to pre-configured, rule-based schedules implemented in the retrofitted direct digital control system.
{"title":"Implementation of model predictive control for an HVAC system in a mid-size commercial building","authors":"S. Bengea, Anthony Kelman, F. Borrelli, Russell D. Taylor, S. Narayanan","doi":"10.1080/10789669.2013.834781","DOIUrl":"https://doi.org/10.1080/10789669.2013.834781","url":null,"abstract":"The article presents field experiment results from the implementation of a model predictive controller which optimizes the operation of a variable volume, dual-duct, multi-zone HVAC unit serving an existing mid-size commercial building. This full-scale proof-of-concept study was used to estimate the benefits of implementing advanced building control technologies during a retrofit. The control approach uses dynamic estimates and predictions of zone loads and temperatures, outdoor weather conditions, and HVAC system models to minimize energy consumption while meeting equipment and thermal comfort constraints. The article describes the on-line implementation of the hierarchical control system, including communication of the optimal control scheme with the building automation system, the controlled set-points and the component-level feedback loops, as well as the measured energy and indoor comfort performance benefits from the demonstration. The building-scale experiments and the receding-horizon control algorithm implementation results are described. Site measurements show this algorithm, when implemented in state-of-the-art direct digital control systems, consistently yields energy savings and reduces peak power while improving the indoor thermal comfort. The demonstration results show energy savings of 20% on average during the transition season, 70% on average during heating season, and 10% or more peak power reduction, all relative to pre-configured, rule-based schedules implemented in the retrofitted direct digital control system.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"1 1","pages":"121 - 135"},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89564022","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-01-01DOI: 10.1080/10789669.2013.836877
Pengfei Li, Hongtao Qiao, Yaoyu Li, J. Seem, J. Winkler, Xiao Li
Dynamic modeling of HVAC equipment is a subject of particular importance for control system design and fault detection and diagnosis, while the transient behaviors of the associated processes are, in principle, very complicated and feature strong interactions among multiple physical domains. Part I of this article reviews the research advancement in dynamic modeling of HVAC equipment, focusing on advancement of the past several years, including vapor compression cycles, air-handling units, major types of chillers, cooling tower, heating systems, and renewable-energy driven systems. In Part II, we will present a detailed review of advances in dynamic modeling of HVAC equipment using Modelica, an equation-based multi-physical dynamic simulation platform.
{"title":"Recent advances in dynamic modeling of HVAC equipment. Part 1: Equipment modeling","authors":"Pengfei Li, Hongtao Qiao, Yaoyu Li, J. Seem, J. Winkler, Xiao Li","doi":"10.1080/10789669.2013.836877","DOIUrl":"https://doi.org/10.1080/10789669.2013.836877","url":null,"abstract":"Dynamic modeling of HVAC equipment is a subject of particular importance for control system design and fault detection and diagnosis, while the transient behaviors of the associated processes are, in principle, very complicated and feature strong interactions among multiple physical domains. Part I of this article reviews the research advancement in dynamic modeling of HVAC equipment, focusing on advancement of the past several years, including vapor compression cycles, air-handling units, major types of chillers, cooling tower, heating systems, and renewable-energy driven systems. In Part II, we will present a detailed review of advances in dynamic modeling of HVAC equipment using Modelica, an equation-based multi-physical dynamic simulation platform.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"15 1","pages":"136 - 149"},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84434318","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-01-01DOI: 10.1080/10789669.2013.826982
B. Hajra, T. Stathopoulos, A. Bahloul
The performance of different ASHRAE models besides their general development since 1997 forms the basis of this article. The experimental results of a few recent near-field pollutant dispersion studies are compared to those produced by ASHRAE models. These cases include isolated buildings and adjacent building configurations. In fact, ASHRAE can only be used to estimate rooftop dilutions on an emitting building and does not provide formulations to estimate dilutions on adjacent building surfaces. The results from this study show that ASHRAE models provide reasonable dilution estimates for low exhaust momentum ratios (M), while previous ASHRAE models predict lower dilutions than wind tunnel data for all cases. Furthermore, ASHRAE 2011 predicts reasonable dilutions on the leeward wall of the emitting building, which is an important contribution of the current ASHRAE model. It is suggested that future ASHRAE model versions should be capable of estimating reasonable dilutions on adjacent building surfaces for realistic urban scenarios, by taking into account the spacing between buildings.
{"title":"Performance of ASHRAE models in assessing pollutant dispersion from rooftop emissions","authors":"B. Hajra, T. Stathopoulos, A. Bahloul","doi":"10.1080/10789669.2013.826982","DOIUrl":"https://doi.org/10.1080/10789669.2013.826982","url":null,"abstract":"The performance of different ASHRAE models besides their general development since 1997 forms the basis of this article. The experimental results of a few recent near-field pollutant dispersion studies are compared to those produced by ASHRAE models. These cases include isolated buildings and adjacent building configurations. In fact, ASHRAE can only be used to estimate rooftop dilutions on an emitting building and does not provide formulations to estimate dilutions on adjacent building surfaces. The results from this study show that ASHRAE models provide reasonable dilution estimates for low exhaust momentum ratios (M), while previous ASHRAE models predict lower dilutions than wind tunnel data for all cases. Furthermore, ASHRAE 2011 predicts reasonable dilutions on the leeward wall of the emitting building, which is an important contribution of the current ASHRAE model. It is suggested that future ASHRAE model versions should be capable of estimating reasonable dilutions on adjacent building surfaces for realistic urban scenarios, by taking into account the spacing between buildings.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"124 1","pages":"72 - 79"},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87974863","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
It is essential to investigate person-to-person contaminant transport in mechanically ventilated spaces to improve air distribution design and reduce the infection risk from airborne infectious diseases. This article provides a systematic study of the effects of ventilation mode, ventilation rate, and person-to-person distance on person-to-person contaminant transport. This study first collected available cases of person-to-person contaminant transport from the literature to create a database. Then this investigation identified the limitations of the existing data and added a number of cases to complete the database. The additional cases were generated by using a Reynolds-averaged Navier-Stokes (RANS)-Eulerian model that was validated by experimental data from an occupied office with under-floor air-distribution (UFAD) systems. The database shows that the overall performance of displacement ventilation and the UFAD systems was better than that of mixing ventilation. A higher ventilation rate was beneficial in reducing person-to-person contaminant transport to some extent. Person-to-person contaminant exposure increased rapidly with a decrease in person-to-person distance when the distance was smaller than 1.1 m. Generally speaking, person-to-person distance is an important parameter when compared with ventilation mode and ventilation rate.
{"title":"Systematic study of person-to-person contaminant transport in mechanically ventilated spaces (RP-1458)","authors":"Chun Chen, Juncheng Zhu, Zijie Qu, Chao-Hsin Lin, Zheng Jiang, Qingyan Chen","doi":"10.1080/10789669.2013.834778","DOIUrl":"https://doi.org/10.1080/10789669.2013.834778","url":null,"abstract":"It is essential to investigate person-to-person contaminant transport in mechanically ventilated spaces to improve air distribution design and reduce the infection risk from airborne infectious diseases. This article provides a systematic study of the effects of ventilation mode, ventilation rate, and person-to-person distance on person-to-person contaminant transport. This study first collected available cases of person-to-person contaminant transport from the literature to create a database. Then this investigation identified the limitations of the existing data and added a number of cases to complete the database. The additional cases were generated by using a Reynolds-averaged Navier-Stokes (RANS)-Eulerian model that was validated by experimental data from an occupied office with under-floor air-distribution (UFAD) systems. The database shows that the overall performance of displacement ventilation and the UFAD systems was better than that of mixing ventilation. A higher ventilation rate was beneficial in reducing person-to-person contaminant transport to some extent. Person-to-person contaminant exposure increased rapidly with a decrease in person-to-person distance when the distance was smaller than 1.1 m. Generally speaking, person-to-person distance is an important parameter when compared with ventilation mode and ventilation rate.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"20 1","pages":"80 - 91"},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77217997","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-01-01DOI: 10.1080/10789669.2013.834779
H. Saber
The 2009 ASHRAE Handbook—Fundamentals (Chapter 26) provided a table that contains the thermal resistances (R-values) of vertical, horizontal, and high-sloped (45°) enclosed airspaces. This table is extensively used by modelers, architects, and building designers in the design for the R-values of building enclosures. The effect of the airspace aspect ratio and the inclination angle (θ) of 30° on the R-values are not accounted for in the ASHRAE table. However, previous studies showed that the aspect ratio of the airspace can affect its R-value. In this article, the previous studies that focused on determining the R-values for vertical, horizontal, and high-sloped enclosed airspaces are extended to investigate the effect of the aspect ratio on the R-values of low-sloped (θ = 30°) enclosed airspaces under downward heat flow for different airspace thicknesses and having a wide range of values for the effective emittance, mean temperature, and temperature differences across the airspaces. Thereafter, practical correlation is developed for determining the R-values of low-sloped enclosed airspaces for future use by modelers, architects, and building designers.
{"title":"Practical correlation for thermal resistance of low-sloped enclosed airspaces with downward heat flow for building applications","authors":"H. Saber","doi":"10.1080/10789669.2013.834779","DOIUrl":"https://doi.org/10.1080/10789669.2013.834779","url":null,"abstract":"The 2009 ASHRAE Handbook—Fundamentals (Chapter 26) provided a table that contains the thermal resistances (R-values) of vertical, horizontal, and high-sloped (45°) enclosed airspaces. This table is extensively used by modelers, architects, and building designers in the design for the R-values of building enclosures. The effect of the airspace aspect ratio and the inclination angle (θ) of 30° on the R-values are not accounted for in the ASHRAE table. However, previous studies showed that the aspect ratio of the airspace can affect its R-value. In this article, the previous studies that focused on determining the R-values for vertical, horizontal, and high-sloped enclosed airspaces are extended to investigate the effect of the aspect ratio on the R-values of low-sloped (θ = 30°) enclosed airspaces under downward heat flow for different airspace thicknesses and having a wide range of values for the effective emittance, mean temperature, and temperature differences across the airspaces. Thereafter, practical correlation is developed for determining the R-values of low-sloped enclosed airspaces for future use by modelers, architects, and building designers.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"66 1","pages":"112 - 92"},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72793596","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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