Pub Date : 2014-01-01DOI: 10.1080/10789669.2013.813802
A. Nguyen, Young-Il Kim
Thermostatic expansion valves are widely used in heat pump systems to control the liquid refrigerant supply to the evaporator based on the degree of superheat at its exit. In a typical thermostatic expansion valve, the degree of superheat at the exit of an evaporator is measured by a temperature bulb sensor that is in contact with the evaporator outlet tube. In this work, a method to experimentally determine the transient behavior of a temperature bulb sensor of a thermostatic expansion valve is presented. From the experimental data, three parameters were extracted and then used in a mathematical model to reproduce the transient behavior of the temperature bulb sensor. In addition, four methods of installing the temperature bulb sensor to the evaporator outlet tube were experimentally studied. The tube–bulb system with the installation band and the insulation showed the best accuracy.
{"title":"Transient behavior of temperature sensor of expansion valve with various installation","authors":"A. Nguyen, Young-Il Kim","doi":"10.1080/10789669.2013.813802","DOIUrl":"https://doi.org/10.1080/10789669.2013.813802","url":null,"abstract":"Thermostatic expansion valves are widely used in heat pump systems to control the liquid refrigerant supply to the evaporator based on the degree of superheat at its exit. In a typical thermostatic expansion valve, the degree of superheat at the exit of an evaporator is measured by a temperature bulb sensor that is in contact with the evaporator outlet tube. In this work, a method to experimentally determine the transient behavior of a temperature bulb sensor of a thermostatic expansion valve is presented. From the experimental data, three parameters were extracted and then used in a mathematical model to reproduce the transient behavior of the temperature bulb sensor. In addition, four methods of installing the temperature bulb sensor to the evaporator outlet tube were experimentally studied. The tube–bulb system with the installation band and the insulation showed the best accuracy.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"43 1","pages":"36 - 41"},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1080/10789669.2013.813802","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72510702","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: 10.1080/10789669.2013.826982
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}
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}
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: 10.1080/10789669.2013.822252
Ali Moghaddas, Casey Bennett, Emad Rokni, H. Metghalchi
Laminar burning speeds and flame structures of difluoromethane (HFC-32)/air and 1,1-difluoroethane (HFC-152a)/air mixtures have been studied. Experiments have been carried out in constant-volume spherical and cylindrical vessels coupled with a schlieren/shadowgraph system and high-speed complementary metal-oxide-semiconductor (CMOS) camera. Laminar burning speed was determined using a thermodynamic model that employs the pressure rise history of the combustion process. Experiments were conducted for different initial conditions over a wide range of equivalence ratios. Laminar burning speeds of HFC-152a/air mixtures have been measured over the temperature range of 298 K to 580 K and pressure range of 1 to 8 bar. Laminar burning speeds of HFC-32/air mixtures have been measured for the temperature range of 350 K to 475 K and pressure range of 2 to 6.8 bar. Correlations have been developed for laminar burning speeds of HFC-32 and HFC-152a to demonstrate the temperature and pressure dependency of laminar burning speeds of these two refrigerants.
{"title":"Laminar burning speeds and flame structures of mixtures of difluoromethane (HFC-32) and 1,1-difluoroethane (HFC-152a) with air at elevated temperatures and pressures","authors":"Ali Moghaddas, Casey Bennett, Emad Rokni, H. Metghalchi","doi":"10.1080/10789669.2013.822252","DOIUrl":"https://doi.org/10.1080/10789669.2013.822252","url":null,"abstract":"Laminar burning speeds and flame structures of difluoromethane (HFC-32)/air and 1,1-difluoroethane (HFC-152a)/air mixtures have been studied. Experiments have been carried out in constant-volume spherical and cylindrical vessels coupled with a schlieren/shadowgraph system and high-speed complementary metal-oxide-semiconductor (CMOS) camera. Laminar burning speed was determined using a thermodynamic model that employs the pressure rise history of the combustion process. Experiments were conducted for different initial conditions over a wide range of equivalence ratios. Laminar burning speeds of HFC-152a/air mixtures have been measured over the temperature range of 298 K to 580 K and pressure range of 1 to 8 bar. Laminar burning speeds of HFC-32/air mixtures have been measured for the temperature range of 350 K to 475 K and pressure range of 2 to 6.8 bar. Correlations have been developed for laminar burning speeds of HFC-32 and HFC-152a to demonstrate the temperature and pressure dependency of laminar burning speeds of these two refrigerants.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"10 1","pages":"42 - 50"},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78921033","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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