Pub Date : 2014-07-16DOI: 10.1080/10789669.2014.938006
Yang Zhao, F. Xiao, Jin Wen, Yuehong Lu, Shengwei Wang
A new chiller fault detection and diagnosis (FDD) method is proposed in this article. Different from conventional chiller FDD methods, this article considers the FDD problem as a typical one-class classification problem. The fault-free data are classified as the fault-free class. Data of a fault type are regarded as a fault class. The task of fault detection is to detect whether the process data are outliers of the fault-free class. The task of fault diagnosis is to find to which fault class does the process data belong. In this study, support vector data description (SVDD) algorithm is introduced for the one-class classification. The basic idea of the SVDD-based method is to find a minimum-volume hypersphere in a high dimensional feature space to enclose most of the data of an individual class. The proposed method is validated using the ASHRAE RP-1043 (Comstock and Braun 1999) experimental data. It shows more powerful FDD capacity than multi-class SVM-based FDD methods and PCA-based fault detection methods. Four potential applications of the proposed method are also discussed.
提出了一种新的冷水机组故障检测与诊断方法。与传统的冷水机组FDD方法不同，本文将FDD问题视为一个典型的一类分类问题。将无故障数据归为无故障类。一种故障类型的数据被视为一个故障类别。故障检测的任务是检测过程数据是否为无故障类的离群值。故障诊断的任务是找出过程数据属于哪一类故障。本研究引入支持向量数据描述(SVDD)算法进行单类分类。基于svdd的方法的基本思想是在高维特征空间中找到一个最小体积超球，以封闭单个类的大部分数据。采用ASHRAE RP-1043 (Comstock and Braun 1999)实验数据验证了所提出的方法。它比基于svm的多类FDD方法和基于pca的故障检测方法显示出更强大的FDD能力。本文还讨论了该方法的四种潜在应用。
{"title":"A robust pattern recognition-based fault detection and diagnosis (FDD) method for chillers","authors":"Yang Zhao, F. Xiao, Jin Wen, Yuehong Lu, Shengwei Wang","doi":"10.1080/10789669.2014.938006","DOIUrl":"https://doi.org/10.1080/10789669.2014.938006","url":null,"abstract":"A new chiller fault detection and diagnosis (FDD) method is proposed in this article. Different from conventional chiller FDD methods, this article considers the FDD problem as a typical one-class classification problem. The fault-free data are classified as the fault-free class. Data of a fault type are regarded as a fault class. The task of fault detection is to detect whether the process data are outliers of the fault-free class. The task of fault diagnosis is to find to which fault class does the process data belong. In this study, support vector data description (SVDD) algorithm is introduced for the one-class classification. The basic idea of the SVDD-based method is to find a minimum-volume hypersphere in a high dimensional feature space to enclose most of the data of an individual class. The proposed method is validated using the ASHRAE RP-1043 (Comstock and Braun 1999) experimental data. It shows more powerful FDD capacity than multi-class SVM-based FDD methods and PCA-based fault detection methods. Four potential applications of the proposed method are also discussed.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"82 1","pages":"798 - 809"},"PeriodicalIF":0.0,"publicationDate":"2014-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80557147","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 : 2014-07-01DOI: 10.1080/10789669.2014.907096
Chuan He, W. Chen, K. Han, B. Guo, J. Pei, J. Zhang
To guide the selection of gas phase filtration media in the air cleaning devices, it is important to understand and estimate the media performance under usage concentrations. Filters for improving indoor air quality are typically subject to low volatile organic compounds (VOCs) concentration levels (e.g., ∼50 ppb), while the current standard tests per ASHRAE 145.1 (ANSI/ASHRAE 2008). are performed at relatively high challenge concentrations (∼1–100 ppm level). The primary objective of this study was to determine if media that perform well at the high concentration test condition would also perform well under the low concentration. The secondary objective was to investigate if and how existing models of filtration by media bed can be applied to extrapolate the results from the high concentration tests to the low concentration condition. Experiments and simulations were carried out at both high concentrations (100 ppm for toluene and 1 ppm for formaldehyde) and low concentrations (0.05 ppm for toluene and formaldehyde) for six selected filtration media. The results show that (1) the high concentration test data were able to differentiate the relative performance among the media at the low concentration properly, confirming the validity of using ASHRAE 145.1 (ANSI/ASHRAE 2008) for relative performance comparison; (2) significant initial breakthrough observed at high concentration tests of large pellet media was not present at the low concentration tests, indicating the dependency of the adsorption capability of the sorbent media on the concentration level as well as the possible “by-pass” effects (i.e., not all the VOC molecules in the air stream had the same chance to contact with the sorbent media); and (3) existing models need to be improved by incorporating the concentration dependency of the partition coefficient and the by-pass effect in order to predict the breakthrough curve at low concentrations properly. Such an improved model was proposed, evaluated with the measured data, and was found to be promising for physical sorbent, but requires further development for chemical, catalytic sorbent and large pellet sorbent. The study provides previously unavailable experimental data and new insight into the behavior of the filtration media for volatile organic compounds as well as evidence in support of the application of ASHRAE Standard 145.1 (ANSI/ASHRAE 2008) for media performance evaluation.
{"title":"Evaluation of filter media performance: Correlation between high and low challenge concentration tests for toluene and formaldehyde (ASHRAE RP-1557)","authors":"Chuan He, W. Chen, K. Han, B. Guo, J. Pei, J. Zhang","doi":"10.1080/10789669.2014.907096","DOIUrl":"https://doi.org/10.1080/10789669.2014.907096","url":null,"abstract":"To guide the selection of gas phase filtration media in the air cleaning devices, it is important to understand and estimate the media performance under usage concentrations. Filters for improving indoor air quality are typically subject to low volatile organic compounds (VOCs) concentration levels (e.g., ∼50 ppb), while the current standard tests per ASHRAE 145.1 (ANSI/ASHRAE 2008). are performed at relatively high challenge concentrations (∼1–100 ppm level). The primary objective of this study was to determine if media that perform well at the high concentration test condition would also perform well under the low concentration. The secondary objective was to investigate if and how existing models of filtration by media bed can be applied to extrapolate the results from the high concentration tests to the low concentration condition. Experiments and simulations were carried out at both high concentrations (100 ppm for toluene and 1 ppm for formaldehyde) and low concentrations (0.05 ppm for toluene and formaldehyde) for six selected filtration media. The results show that (1) the high concentration test data were able to differentiate the relative performance among the media at the low concentration properly, confirming the validity of using ASHRAE 145.1 (ANSI/ASHRAE 2008) for relative performance comparison; (2) significant initial breakthrough observed at high concentration tests of large pellet media was not present at the low concentration tests, indicating the dependency of the adsorption capability of the sorbent media on the concentration level as well as the possible “by-pass” effects (i.e., not all the VOC molecules in the air stream had the same chance to contact with the sorbent media); and (3) existing models need to be improved by incorporating the concentration dependency of the partition coefficient and the by-pass effect in order to predict the breakthrough curve at low concentrations properly. Such an improved model was proposed, evaluated with the measured data, and was found to be promising for physical sorbent, but requires further development for chemical, catalytic sorbent and large pellet sorbent. The study provides previously unavailable experimental data and new insight into the behavior of the filtration media for volatile organic compounds as well as evidence in support of the application of ASHRAE Standard 145.1 (ANSI/ASHRAE 2008) for media performance evaluation.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"18 1","pages":"508 - 521"},"PeriodicalIF":0.0,"publicationDate":"2014-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91073890","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 : 2014-07-01DOI: 10.1080/10789669.2014.913959
S. Deng, Ruzhu Wang, Yanjun Dai
A performance comparison of experimental results for CO2 trans-critical cycle is presented for an overview of the current level of technology. The published performance data were collected as research objects through comprehensive literature review on experimental research. The methods for data processing, error analysis, and performance evaluation are introduced in the research methodology section. Through the proposed research method, 28 groups of performance results from developed prototypes or test rigs are compared and analyzed using the coefficient of performance and the second law efficiency of thermodynamics. A discussion of the performance comparison between developed CO2 devices and commercial products of synthetic working fluid is also presented based on China's national standards (General Administration of Quality Supervision, Insection and Quarantine of the People's Republic of China 2001, 2003). Based on the comparison results, the state-of-art and possible research directions for CO2 trans-critical cycle technology are summarized and presented.
{"title":"A comparative analysis on experimental performance of CO2 trans-critical cycle","authors":"S. Deng, Ruzhu Wang, Yanjun Dai","doi":"10.1080/10789669.2014.913959","DOIUrl":"https://doi.org/10.1080/10789669.2014.913959","url":null,"abstract":"A performance comparison of experimental results for CO2 trans-critical cycle is presented for an overview of the current level of technology. The published performance data were collected as research objects through comprehensive literature review on experimental research. The methods for data processing, error analysis, and performance evaluation are introduced in the research methodology section. Through the proposed research method, 28 groups of performance results from developed prototypes or test rigs are compared and analyzed using the coefficient of performance and the second law efficiency of thermodynamics. A discussion of the performance comparison between developed CO2 devices and commercial products of synthetic working fluid is also presented based on China's national standards (General Administration of Quality Supervision, Insection and Quarantine of the People's Republic of China 2001, 2003). Based on the comparison results, the state-of-art and possible research directions for CO2 trans-critical cycle technology are summarized and presented.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"17 1","pages":"532 - 544"},"PeriodicalIF":0.0,"publicationDate":"2014-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89433954","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 : 2014-07-01DOI: 10.1080/10789669.2014.908691
K. Han, Jensen S. Zhang, B. Guo, Chuan He
To guide the selection and design of air filter/cleaning devices for improving indoor air quality (IAQ), it is important to be able to assess the performance and characteristics of filter media within a reasonable/practical testing period for low concentration conditions (∼50 ppb) under which they are applied. Our study objectives were to investigate whether filter media showing good performance at high concentrations per ASHRAE Standard 145.1 (ASHRAE 2008) would also perform well at low concentrations, typically indoors, and to explore whether and how existing models for filtration media beds can be applied to predict and extrapolate the experimental performance results obtained under high concentrations. Six filter media having different filtration properties, pellet shape and size, and target compound were selected for this investigation. Experiments were performed at both high (∼1 ppm/100 ppm) and low (∼50 ppb) levels of O3/NO2 concentration for all media selected. Existing models were evaluated for the feasibility of data extrapolation from high to low concentration conditions. The results showed that (1) the relative performance of filter media at high concentration was qualitatively indicative of that from the low concentration results and (2) no existing models were suitable for any media having major catalytic removal characteristics for the cases studied, and an improved mechanistic model needs to be developed.
{"title":"Laboratory comparison of relative performance of gas phase filtration media at high and low O3/NO2 challenge concentrations (ASHRAE RP-1557)","authors":"K. Han, Jensen S. Zhang, B. Guo, Chuan He","doi":"10.1080/10789669.2014.908691","DOIUrl":"https://doi.org/10.1080/10789669.2014.908691","url":null,"abstract":"To guide the selection and design of air filter/cleaning devices for improving indoor air quality (IAQ), it is important to be able to assess the performance and characteristics of filter media within a reasonable/practical testing period for low concentration conditions (∼50 ppb) under which they are applied. Our study objectives were to investigate whether filter media showing good performance at high concentrations per ASHRAE Standard 145.1 (ASHRAE 2008) would also perform well at low concentrations, typically indoors, and to explore whether and how existing models for filtration media beds can be applied to predict and extrapolate the experimental performance results obtained under high concentrations. Six filter media having different filtration properties, pellet shape and size, and target compound were selected for this investigation. Experiments were performed at both high (∼1 ppm/100 ppm) and low (∼50 ppb) levels of O3/NO2 concentration for all media selected. Existing models were evaluated for the feasibility of data extrapolation from high to low concentration conditions. The results showed that (1) the relative performance of filter media at high concentration was qualitatively indicative of that from the low concentration results and (2) no existing models were suitable for any media having major catalytic removal characteristics for the cases studied, and an improved mechanistic model needs to be developed.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"1 1","pages":"522 - 531"},"PeriodicalIF":0.0,"publicationDate":"2014-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73909696","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 : 2014-07-01DOI: 10.1080/10789669.2014.920224
A. Behfar, Ziqi Shen, Josephine Lau, Yuebin Yu
Significant process intensification (PI) of heat and mass transfer is indispensable in building compact and energy efficient absorption refrigeration systems. High potentials exist to achieve the required PI through (1) development of active heat and mass transfer enhancement techniques and (2) combining the active enhancement mechanism with proven and widely used passive enhancement techniques in transport processes. There is limited research on the effect of active mechanisms, such as vibration, on heat and mass transfer coefficients in absorption systems with falling film horizontal-tube absorbers. In this general survey, with the aim to enlighten the path for active mechanisms development, recorded heat and mass transfer enhancements via active mechanisms were extracted from pertinent research works, and were summarized in tables suitable for evaluation and comparison. The potential for future research on enhancing heat and mass transfer in absorption chillers was identified.
{"title":"Heat and mass transfer enhancement potential on falling film absorbers for water-LiBr mixtures via a literature review (RP-1462)","authors":"A. Behfar, Ziqi Shen, Josephine Lau, Yuebin Yu","doi":"10.1080/10789669.2014.920224","DOIUrl":"https://doi.org/10.1080/10789669.2014.920224","url":null,"abstract":"Significant process intensification (PI) of heat and mass transfer is indispensable in building compact and energy efficient absorption refrigeration systems. High potentials exist to achieve the required PI through (1) development of active heat and mass transfer enhancement techniques and (2) combining the active enhancement mechanism with proven and widely used passive enhancement techniques in transport processes. There is limited research on the effect of active mechanisms, such as vibration, on heat and mass transfer coefficients in absorption systems with falling film horizontal-tube absorbers. In this general survey, with the aim to enlighten the path for active mechanisms development, recorded heat and mass transfer enhancements via active mechanisms were extracted from pertinent research works, and were summarized in tables suitable for evaluation and comparison. The potential for future research on enhancing heat and mass transfer in absorption chillers was identified.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"33 1","pages":"570 - 580"},"PeriodicalIF":0.0,"publicationDate":"2014-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77668080","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 : 2014-07-01DOI: 10.1080/10789669.2014.923666
M. C. Baugher
I do not believe I have met a scientist or engineer yet who thinks his or her research is insignificant. However, as much as you may be attached to your project idea, and think that your paper is riveting reading, you may be surprised to find that your idea of significance and that of the editors of journals you submit papers to may not agree. The goal of the HVAC&R Research is to publish original research of lasting significance, which is usable by the research community and is relevant to the HVAC&R field (see Taylor & Francis Author Services 2014 and the journal’s Web site for details about submissions: http://www. tandfonline.com/action/authorSubmission?journalCode= uhvc&page=instructions#.UbYb8ZwRHYY. Clearly, the work should not be identical or substantially the same as work that has been previously published, either by yourself or someone else. Use the lists below as a quick reference guide in determining if the topic of your paper meet’s our standard for significance (Mitchell 2007).
{"title":"Editorial: You may feel your research is significant, but is it significant enough for us?","authors":"M. C. Baugher","doi":"10.1080/10789669.2014.923666","DOIUrl":"https://doi.org/10.1080/10789669.2014.923666","url":null,"abstract":"I do not believe I have met a scientist or engineer yet who thinks his or her research is insignificant. However, as much as you may be attached to your project idea, and think that your paper is riveting reading, you may be surprised to find that your idea of significance and that of the editors of journals you submit papers to may not agree. The goal of the HVAC&R Research is to publish original research of lasting significance, which is usable by the research community and is relevant to the HVAC&R field (see Taylor & Francis Author Services 2014 and the journal’s Web site for details about submissions: http://www. tandfonline.com/action/authorSubmission?journalCode= uhvc&page=instructions#.UbYb8ZwRHYY. Clearly, the work should not be identical or substantially the same as work that has been previously published, either by yourself or someone else. Use the lists below as a quick reference guide in determining if the topic of your paper meet’s our standard for significance (Mitchell 2007).","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"410 1","pages":"497 - 497"},"PeriodicalIF":0.0,"publicationDate":"2014-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76470986","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 : 2014-07-01DOI: 10.1080/10789669.2014.920223
Zhengwei Li, G. Huang
Sensors are one of the key components in a modern building energy management system (BEMS). Accurate sensors are the prerequisite for the success of any building energy optimization strategy. As sensors are subject to environment disturbance and performance deterioration, their accuracy tends to decrease during their service lives. Sensor calibration is an efficient way to improve measurement accuracy and reliability. However, due to a large number of sensors installed in modern air conditioning (AC) systems, conventional regular calibration may be laborious while not optimal when the system energy performance are concerned. In order to improve measurement accuracy and reliability, a hybrid sensor management strategy is proposed in this article. This strategy integrates a measured variable importance ranking technique with a data fusion technique. Comparison of this strategy with a conventional regular calibration in case studies shows that this strategy improves both the energy and control performance of AC systems.
{"title":"A hybrid technique to improve measurement accuracy and reliability in AC systems","authors":"Zhengwei Li, G. Huang","doi":"10.1080/10789669.2014.920223","DOIUrl":"https://doi.org/10.1080/10789669.2014.920223","url":null,"abstract":"Sensors are one of the key components in a modern building energy management system (BEMS). Accurate sensors are the prerequisite for the success of any building energy optimization strategy. As sensors are subject to environment disturbance and performance deterioration, their accuracy tends to decrease during their service lives. Sensor calibration is an efficient way to improve measurement accuracy and reliability. However, due to a large number of sensors installed in modern air conditioning (AC) systems, conventional regular calibration may be laborious while not optimal when the system energy performance are concerned. In order to improve measurement accuracy and reliability, a hybrid sensor management strategy is proposed in this article. This strategy integrates a measured variable importance ranking technique with a data fusion technique. Comparison of this strategy with a conventional regular calibration in case studies shows that this strategy improves both the energy and control performance of AC systems.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"21 1","pages":"581 - 591"},"PeriodicalIF":0.0,"publicationDate":"2014-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87773535","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 : 2014-07-01DOI: 10.1080/10789669.2014.920688
M. Modera, C. Wray, D. Dickerhoff
Air-handling system leakage reduces the amount of air delivered to conditioned spaces and in most cases wastes energy and money. Standards exist for where and how to measure system airtightness, but they tend to focus on new construction, and only on the high-pressure (1500–2500 Pa [6–10 in. w.c.])/ medium-pressure [500–1500 Pa (2–6 in. w.c.]) portions of the system. This article investigates air leakage in the low-pressure (≤500 Pa [≤2 in. w.c.]) portions of large commercial-building air-handling systems (i.e., downstream of variable-air-volume box inlet dampers). A simplified diagnostic protocol for measuring low-pressure leakage that can be used during normal system operation in an existing building is presented and utilized for this investigation. A validation of the protocol using a calibrated leak in a field installation is also presented, as are the results of applying this protocol in nine other buildings around the United States. The validation results indicate that normalized leakage can be measured to within 10 L/s at 25 Pa (20 cfm at 0.1 in w.c.), with and without the existence of significant flow through the minimum opening of the box inlet damper. The field test results indicate that low-pressure leakage varied considerably from system to system (standard deviation of 50% of the mean value), and that the average value was approximately 10% of the flow entering the low-pressure system sections. The variability of the measured results, combined with a simplified analysis of the impacts of this leakage, suggest that testing of low-pressure system leakage in commercial buildings should be economically justifiable.
空气处理系统泄漏减少了输送到空调空间的空气量，在大多数情况下浪费了能源和金钱。现有标准规定了在哪里以及如何测量系统气密性，但这些标准往往集中在新建筑上，而且只针对高压(1500-2500 Pa[6-10英寸])。)/中压[500-1500 Pa (2-6 in。[c])系统的一部分。本文研究了低压(≤500pa[≤2in。大型商业建筑空气处理系统的一部分(即变风量箱入口阻尼器的下游)。一个简化的诊断方案，用于测量低压泄漏，可以在现有建筑的正常系统运行中使用，并用于本次调查。还介绍了在现场装置中使用校准泄漏对协议进行验证的情况，以及在美国其他九座建筑物中应用该协议的结果。验证结果表明，在25 Pa (20 cfm, 0.1 w / c)条件下，无论箱式进口阻尼器的最小开口是否存在明显的流量，归一化泄漏都可以测量到10 L/s以内。现场测试结果表明，不同系统的低压泄漏量差异很大(标准差为平均值的50%)，平均值约为进入低压系统段流量的10%。测量结果的可变性，结合对这种泄漏影响的简化分析，表明在商业建筑中测试低压系统泄漏在经济上是合理的。
{"title":"Low pressure air-handling system leakage in large commercial buildings: Diagnosis, prevalence, and energy impacts","authors":"M. Modera, C. Wray, D. Dickerhoff","doi":"10.1080/10789669.2014.920688","DOIUrl":"https://doi.org/10.1080/10789669.2014.920688","url":null,"abstract":"Air-handling system leakage reduces the amount of air delivered to conditioned spaces and in most cases wastes energy and money. Standards exist for where and how to measure system airtightness, but they tend to focus on new construction, and only on the high-pressure (1500–2500 Pa [6–10 in. w.c.])/ medium-pressure [500–1500 Pa (2–6 in. w.c.]) portions of the system. This article investigates air leakage in the low-pressure (≤500 Pa [≤2 in. w.c.]) portions of large commercial-building air-handling systems (i.e., downstream of variable-air-volume box inlet dampers). A simplified diagnostic protocol for measuring low-pressure leakage that can be used during normal system operation in an existing building is presented and utilized for this investigation. A validation of the protocol using a calibrated leak in a field installation is also presented, as are the results of applying this protocol in nine other buildings around the United States. The validation results indicate that normalized leakage can be measured to within 10 L/s at 25 Pa (20 cfm at 0.1 in w.c.), with and without the existence of significant flow through the minimum opening of the box inlet damper. The field test results indicate that low-pressure leakage varied considerably from system to system (standard deviation of 50% of the mean value), and that the average value was approximately 10% of the flow entering the low-pressure system sections. The variability of the measured results, combined with a simplified analysis of the impacts of this leakage, suggest that testing of low-pressure system leakage in commercial buildings should be economically justifiable.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"77 1","pages":"559 - 569"},"PeriodicalIF":0.0,"publicationDate":"2014-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74444828","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 : 2014-07-01DOI: 10.1080/10789669.2014.899466
D. Yashar, P. Domanski, Honghyun Cho
One of the most influential factors of the performance of a finned-tube heat exchanger is the distribution of the air passing through it; therefore, it must be known in order to produce a highly efficient design. We examined two different common style air-to-refrigerant, finned-tube heat exchangers: a single-slab coil oriented at an angle of 65° to the duct wall and an A-shaped coil with an apex angle of 34°. We used particle image velocimetry (PIV) to measure their in-situ airflow distributions. The results show that the airflow distributions for both heat exchangers are highly nonuniform with different sections being subject to vastly different air velocities. We also used a momentum resistance-based computational fluid dynamics (CFD) approach to model the airflow distributions through these heat exchangers. The modeled results agreed with the measured values, with most of the simulated velocities falling within +/-10% of the measured velocities. The results of this study show that the velocity profile for any configuration is strongly influenced by the geometry of the heat exchanger and other features in its proximity and, therefore, each installation configuration will have its own unique velocity distribution. The information presented in this paper documents the maldistribution of airflowing through finned-tube heat exchangers and highlights the sources and magnitude of the nonuniformities.
{"title":"An experimental and computational study of approach air distribution for slanted and A-shaped finned-tube heat exchangers","authors":"D. Yashar, P. Domanski, Honghyun Cho","doi":"10.1080/10789669.2014.899466","DOIUrl":"https://doi.org/10.1080/10789669.2014.899466","url":null,"abstract":"One of the most influential factors of the performance of a finned-tube heat exchanger is the distribution of the air passing through it; therefore, it must be known in order to produce a highly efficient design. We examined two different common style air-to-refrigerant, finned-tube heat exchangers: a single-slab coil oriented at an angle of 65° to the duct wall and an A-shaped coil with an apex angle of 34°. We used particle image velocimetry (PIV) to measure their in-situ airflow distributions. The results show that the airflow distributions for both heat exchangers are highly nonuniform with different sections being subject to vastly different air velocities. We also used a momentum resistance-based computational fluid dynamics (CFD) approach to model the airflow distributions through these heat exchangers. The modeled results agreed with the measured values, with most of the simulated velocities falling within +/-10% of the measured velocities. The results of this study show that the velocity profile for any configuration is strongly influenced by the geometry of the heat exchanger and other features in its proximity and, therefore, each installation configuration will have its own unique velocity distribution. The information presented in this paper documents the maldistribution of airflowing through finned-tube heat exchangers and highlights the sources and magnitude of the nonuniformities.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"17 1","pages":"498 - 507"},"PeriodicalIF":0.0,"publicationDate":"2014-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87855515","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 : 2014-06-06DOI: 10.1080/10789669.2014.929422
Yang He, Jianqiang Deng, Zao-xiao Zhang
By the stability analysis of the basic transcritical CO2 ejector expansion refrigeration cycle (EERC), the paper proposed a new system which introduces another evaporator downstream the ejector to increase the gas quality into the separator and a vapor feedback valve to decrease the exceed gas into the compressor. The two new components stand for two different cycles: two-stage evaporation cycle and vapor feedback cycle. The theoretical analysis of the new system is carried out based on the first and second laws of thermodynamics to show the effect of the parameters on the system performance, such as entrainment ratio, high-side pressure, outlet temperature of gas cooler, etc. The results by the first law show that, compared with basic EERC the new system can be used in wider range of working conditions, and the COP of the two-stage evaporation cycle is 28.6% higher and the vapor feedback cycle is lower slightly. By exergy analysis at optimum high-side pressure, it is found that the exergy destruction of ejector is the greatest part. The simulation results also give the working ranges of the two cycles, which can help to analyze the system control. Hence, the improvement in the system is a promising method to reduce the restrain in basic EERC system but more study is still needed.
{"title":"Thermodynamic study on a new transcritical CO2 ejector expansion refrigeration system with two-stage evaporation and vapor feedback","authors":"Yang He, Jianqiang Deng, Zao-xiao Zhang","doi":"10.1080/10789669.2014.929422","DOIUrl":"https://doi.org/10.1080/10789669.2014.929422","url":null,"abstract":"By the stability analysis of the basic transcritical CO2 ejector expansion refrigeration cycle (EERC), the paper proposed a new system which introduces another evaporator downstream the ejector to increase the gas quality into the separator and a vapor feedback valve to decrease the exceed gas into the compressor. The two new components stand for two different cycles: two-stage evaporation cycle and vapor feedback cycle. The theoretical analysis of the new system is carried out based on the first and second laws of thermodynamics to show the effect of the parameters on the system performance, such as entrainment ratio, high-side pressure, outlet temperature of gas cooler, etc. The results by the first law show that, compared with basic EERC the new system can be used in wider range of working conditions, and the COP of the two-stage evaporation cycle is 28.6% higher and the vapor feedback cycle is lower slightly. By exergy analysis at optimum high-side pressure, it is found that the exergy destruction of ejector is the greatest part. The simulation results also give the working ranges of the two cycles, which can help to analyze the system control. Hence, the improvement in the system is a promising method to reduce the restrain in basic EERC system but more study is still needed.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"10 1","pages":"655 - 664"},"PeriodicalIF":0.0,"publicationDate":"2014-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82018925","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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