The Experts below are selected from a list of 93942 Experts worldwide ranked by ideXlab platform
Fariborz Haghighat - One of the best experts on this subject based on the ideXlab platform.
-
optimization of ventilation systems in Office Environment part ii results and discussions
Building and Environment, 2009Co-Authors: Liang Zhou, Fariborz HaghighatAbstract:Whether one considers the issues related to Office workers' well-being and productivity or the issues from an energy and Environmental perspective, there are clear evidences in favor of improving the quality of Office Environment. Part I of this paper proposed a simulation-based optimization approach by using computational fluid dynamics (CFD) techniques in conjunction with genetic algorithm (GA), with the integration of an artificial neural network (ANN) for response surface approximation (RSA) and for speeding up fitness evaluations inside GA loop. In this part, the results from data preparation for ANN model construction, ANN training and testing, and sensitivity analysis (regarding the impact of weighting factors in the objective function on the optimization results) are presented. Final optimization results indicate that the present choices of objective function and optimization approach are able to result in great improvement in the design and operation of ventilation systems in an Office Environment, with the goal of enhancing the thermal comfort and indoor air quality (IAQ) without sacrificing the energy costs of ventilation.
-
optimization of ventilation system design and operation in Office Environment part i methodology
Building and Environment, 2009Co-Authors: Liang Zhou, Fariborz HaghighatAbstract:Ventilation principles that integrate flexible and responsive elements have grown in popularity in Office buildings due to increasing concerns about the impact of indoor Environment quality on Office workers' well-being and productivity, as well as concerns over the rising energy costs for space heating and cooling in the Office building sector. Such advanced elements as underfloor air distribution (UFAD), passive swirl diffusers, and demand controlled ventilation have posed challenges to system design and operation. This paper is concerned with the development and implementation of a practical and robust optimization scheme, aiming to assist Office building designers and operators to enhance thermal comfort and indoor air quality (IAQ) without sacrificing energy costs of ventilation. The objective function was constructed in a way attempting to aggregate and weight indices (for thermal comfort, IAQ, and ventilation energy usage assessment) into one indicator. The path taken was a simulation-based optimization approach by using computational fluid dynamics (CFD) techniques in conjunction with genetic algorithm (GA), with the integration of an artificial neural network (ANN) for response surface approximation (RSA) and for speeding up fitness evaluations inside GA loop.
R. J. Davies - One of the best experts on this subject based on the ideXlab platform.
-
Spatial correlation and capacity measurements for wideband MIMO channels in indoor Office Environment
IEEE Transactions on Wireless Communications, 2008Co-Authors: Padam L. Kafle, John Mcrory, Apichart Intarapanich, Abu B. Sesay, R. J. DaviesAbstract:This paper describes a broadband multiple input, multiple output (MIMO) channel characterization platform and capacity measurement results in indoor Office Environment. The MIMO testbed has been designed for broadband MIMO channel sounding, capacity measurements and for characterizing the directional-multipaths of the radio propagation channel. The MIMO channel data have been collected in 5 GHz band inside a modern Office Environment. Capacity results from these experiments are discussed for different propagation conditions, including non line-of-sight (NLOS) and LOS propagations with various spacings between array elements. Spatial correlations are analyzed from the measured data and a frequency selective MIMO channel model based on the correlation statistics is validated. Post-processing of the measured data with a sequential ESPRIT (Estimation of Signal Parameters via Rotational Invariance Techniques) algorithm is utilized to extract the directions of departures and arrivals of multipath components at the transmitting and receiving arrays, respectively. A method of obtaining broadband MIMO capacity, indirectly, from a single directional measurement of MIMO propagation channel is also proposed and verified from the measurement results.
Liang Zhou - One of the best experts on this subject based on the ideXlab platform.
-
optimization of ventilation systems in Office Environment part ii results and discussions
Building and Environment, 2009Co-Authors: Liang Zhou, Fariborz HaghighatAbstract:Whether one considers the issues related to Office workers' well-being and productivity or the issues from an energy and Environmental perspective, there are clear evidences in favor of improving the quality of Office Environment. Part I of this paper proposed a simulation-based optimization approach by using computational fluid dynamics (CFD) techniques in conjunction with genetic algorithm (GA), with the integration of an artificial neural network (ANN) for response surface approximation (RSA) and for speeding up fitness evaluations inside GA loop. In this part, the results from data preparation for ANN model construction, ANN training and testing, and sensitivity analysis (regarding the impact of weighting factors in the objective function on the optimization results) are presented. Final optimization results indicate that the present choices of objective function and optimization approach are able to result in great improvement in the design and operation of ventilation systems in an Office Environment, with the goal of enhancing the thermal comfort and indoor air quality (IAQ) without sacrificing the energy costs of ventilation.
-
optimization of ventilation system design and operation in Office Environment part i methodology
Building and Environment, 2009Co-Authors: Liang Zhou, Fariborz HaghighatAbstract:Ventilation principles that integrate flexible and responsive elements have grown in popularity in Office buildings due to increasing concerns about the impact of indoor Environment quality on Office workers' well-being and productivity, as well as concerns over the rising energy costs for space heating and cooling in the Office building sector. Such advanced elements as underfloor air distribution (UFAD), passive swirl diffusers, and demand controlled ventilation have posed challenges to system design and operation. This paper is concerned with the development and implementation of a practical and robust optimization scheme, aiming to assist Office building designers and operators to enhance thermal comfort and indoor air quality (IAQ) without sacrificing energy costs of ventilation. The objective function was constructed in a way attempting to aggregate and weight indices (for thermal comfort, IAQ, and ventilation energy usage assessment) into one indicator. The path taken was a simulation-based optimization approach by using computational fluid dynamics (CFD) techniques in conjunction with genetic algorithm (GA), with the integration of an artificial neural network (ANN) for response surface approximation (RSA) and for speeding up fitness evaluations inside GA loop.
Padam L. Kafle - One of the best experts on this subject based on the ideXlab platform.
-
Spatial correlation and capacity measurements for wideband MIMO channels in indoor Office Environment
IEEE Transactions on Wireless Communications, 2008Co-Authors: Padam L. Kafle, John Mcrory, Apichart Intarapanich, Abu B. Sesay, R. J. DaviesAbstract:This paper describes a broadband multiple input, multiple output (MIMO) channel characterization platform and capacity measurement results in indoor Office Environment. The MIMO testbed has been designed for broadband MIMO channel sounding, capacity measurements and for characterizing the directional-multipaths of the radio propagation channel. The MIMO channel data have been collected in 5 GHz band inside a modern Office Environment. Capacity results from these experiments are discussed for different propagation conditions, including non line-of-sight (NLOS) and LOS propagations with various spacings between array elements. Spatial correlations are analyzed from the measured data and a frequency selective MIMO channel model based on the correlation statistics is validated. Post-processing of the measured data with a sequential ESPRIT (Estimation of Signal Parameters via Rotational Invariance Techniques) algorithm is utilized to extract the directions of departures and arrivals of multipath components at the transmitting and receiving arrays, respectively. A method of obtaining broadband MIMO capacity, indirectly, from a single directional measurement of MIMO propagation channel is also proposed and verified from the measurement results.
Mika Ruponen - One of the best experts on this subject based on the ideXlab platform.
-
Flow pattern and thermal comfort in Office Environment with active chilled beams
Hvac&r Research, 2012Co-Authors: Hannu Koskela, Risto Kosonen, Henna Häggblom, Mika RuponenAbstract:In modern Offices, the heat load per floor area has increased. With high cooling loads, the possibility of draft problems increases. The purpose of this article was to study the flow patterns and draft risk in an Office Environment where cooling and air distribution is implemented with active chilled beams. The study is based on experiments in a laboratory mock-up room in three load conditions: summer, winter, and midseason (spring/autumn). Thermal plumes from heat sources and warm or cold windows had a notable effect on the flow pattern and velocity distribution in the occupied zone. Areas with increased draft risk were found in locations where the supply jet turns down to the occupied zone. Draft risk can also be high at the floor level as a result of a circulating flow pattern in the room. This article concentrates on measurement and modeling results in a single-person Office room. Comparisons are made with corresponding results in an open-plan Office.
-
air distribution in Office Environment with asymmetric workstation layout using chilled beams
Building and Environment, 2010Co-Authors: Hannu Koskela, Risto Kosonen, Henna Häggblom, Mika RuponenAbstract:Abstract Air flow patterns and mean air speeds were studied under laboratory conditions representing a full scale open-plan Office. Three basic conditions were tested: summer, spring/autumn and winter. Chilled beams were used to provide cooling, outdoor air supply and air distribution in the room. The heat sources had a notable influence on the flow pattern in the room causing large scale circulation and affecting the direction of inlet jets. The maximum air speed in the occupied zone was higher than the recommendations. The mean air speed was also high on at the floor level but low on at the head level. The air speed was highest in the summer case under high cooling load. Results indicate that especially with high heat loads, it is difficult to fulfill the targets of the existing standards in practice. Two main sources of draught risk were found: a) downfall of colliding inlet jets causing local maxima of air speed and b) large scale circulation caused by asymmetric layout of chilled beams and heat sources. The first phenomenon can cause local draught risk when the workstation is located in the downfall area. The flow pattern is not stable and the position of draught risk areas can change in time and also due to changes in room heat sources. The second phenomenon can cause more constant high air speeds on at the floor level. CFD-simulation was able to predict the general flow pattern but somewhat overestimated the air speed compared to measurements.
