The Experts below are selected from a list of 1731 Experts worldwide ranked by ideXlab platform
Thomas Fend - One of the best experts on this subject based on the ideXlab platform.
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experimental performance of an advanced metal volumetric Air receiver for solar towers
Renewable Energy, 2017Co-Authors: Christoph Pabst, Gereon Feckler, Stefan Schmitz, Olena Smirnova, Raffaele Capuano, Peter Hirth, Thomas FendAbstract:Solar Tower Technology is a promising way to generate sustainable electricity from concentrated solar radiation. In one of the most effective variants of this technology, a so called volumetric Air receiver is used to convert concentrated radiation into heat. This component consists of a high temperature resistant cellular material which absorbs radiation and transfers the heat to an Air flow which is fed from the ambient and from Recirculated Air. It is called volumetric, because the radiation may penetrate into the “volume” of the receiver through the open, permeable cells of the material. In this way a larger amount of heat transfer surface supports the solid to gaseous heat transfer in comparison to a tubular closed receiver. Finally the heated Air is directed to the steam generator of a conventional steam turbine system. In this study an advanced cellular metal honeycomb structure has been designed, manufactured and tested for use as an open volumetric receiver. It consists of winded pAirs of flat and corrugated metal foils. The technology is based on a one which has been primarily developed for the treatment of combustion engine exhaust gases. A number of variations of the pure linear honeycomb structure have been introduced to increase local turbulence and radial flow. Firstly, a set of samples has been tested in laboratory scale experiments to determine effective properties and the solar-to-thermal efficiency. After that, results have been compared with theoretical predictions. Finally, the three most promising materials have been used for a 500 kW test on the research platform of the Solar Tower Julich. Air outlet temperatures of more than 800 °C have been achieved with efficiencies of about 80%, which is about 5% more than the state-of-the-art technology, which is currently used at the main receiver of the Solar Tower. Next to this, lifetime models will be developed to increase the overall reliability of the technology.
Christoph Pabst - One of the best experts on this subject based on the ideXlab platform.
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experimental performance of an advanced metal volumetric Air receiver for solar towers
Renewable Energy, 2017Co-Authors: Christoph Pabst, Gereon Feckler, Stefan Schmitz, Olena Smirnova, Raffaele Capuano, Peter Hirth, Thomas FendAbstract:Solar Tower Technology is a promising way to generate sustainable electricity from concentrated solar radiation. In one of the most effective variants of this technology, a so called volumetric Air receiver is used to convert concentrated radiation into heat. This component consists of a high temperature resistant cellular material which absorbs radiation and transfers the heat to an Air flow which is fed from the ambient and from Recirculated Air. It is called volumetric, because the radiation may penetrate into the “volume” of the receiver through the open, permeable cells of the material. In this way a larger amount of heat transfer surface supports the solid to gaseous heat transfer in comparison to a tubular closed receiver. Finally the heated Air is directed to the steam generator of a conventional steam turbine system. In this study an advanced cellular metal honeycomb structure has been designed, manufactured and tested for use as an open volumetric receiver. It consists of winded pAirs of flat and corrugated metal foils. The technology is based on a one which has been primarily developed for the treatment of combustion engine exhaust gases. A number of variations of the pure linear honeycomb structure have been introduced to increase local turbulence and radial flow. Firstly, a set of samples has been tested in laboratory scale experiments to determine effective properties and the solar-to-thermal efficiency. After that, results have been compared with theoretical predictions. Finally, the three most promising materials have been used for a 500 kW test on the research platform of the Solar Tower Julich. Air outlet temperatures of more than 800 °C have been achieved with efficiencies of about 80%, which is about 5% more than the state-of-the-art technology, which is currently used at the main receiver of the Solar Tower. Next to this, lifetime models will be developed to increase the overall reliability of the technology.
Ali Khaleel Kareem - One of the best experts on this subject based on the ideXlab platform.
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Energy saving and indoor thermal comfort evaluation using a novel local exhaust ventilation system for office rooms.
Applied Thermal Engineering, 2017Co-Authors: Ahmed Qasim Ahmed, Shian Gao, Ali Khaleel KareemAbstract:Energy saving, indoor thermal comfort and inhaled Air quality in an office are strongly affected by the flow interaction in the micro-environment around the occupants. The local exhaust ventilation system, which aims to control the transmission of contaminant and extract contaminant Air locally, is widely used in industrial applications. In this study, the concept of the local exhaust ventilation system is developed for use in office applications. Consequently, a novel local exhaust ventilation system for offices was combined with an office work station in one unit. Energy saving, thermal comfort and inhaled Air quality were used to evaluate the performance of the new system. Experimental data from published work are used to validate the computational fluid dynamic model of this study. The performance of the new system for three different amounts of Recirculated Air (35%, 50%, and 65% of the total mass flow rate) was investigated numerically in an office room with and without using the new system to show its impact on energy saving, thermal comfort and inhaled Air quality. The result shows that the new local exhaust ventilation system can reduce the energy consumption by up to 30%, compared with an office not using this system. Furthermore, this system was able to reduce the contaminant concentration in a micro-environment area by up to 61% and improve the human thermal comfort in the occupied zone. It can be concluded that using the local exhaust ventilation concept can make significant improvements to the quality of inhaled Air and produce extra energy saving with an acceptable thermal comfort.
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a numerical study on the effects of exhaust locations on energy consumption and thermal environment in an office room served by displacement ventilation
Energy Conversion and Management, 2016Co-Authors: Ahmed Qasim Ahmed, Shian Gao, Ali Khaleel KareemAbstract:Abstract In an office room, many factors affect the pattern of Airflow, thermal comfort, indoor Air quality and energy saving. In this study, the effects of the location of exhaust diffusers where the warm and contaminant Air is extracted and their relation to room heat sources on thermal comfort and energy saving were investigated numerically for an office served by a displacement ventilation system. The indoor Air quality in the breathing level and the inhaled zone were also evaluated. The contaminants were released from window and door frames in order to simulate the contaminants coming from outside. The amount of energy consumption and the indoor thermal environment for various exhaust locations were investigated numerically using the computational fluid dynamics techniques. The results showed that the thermal indoor environment, thermal comfort, quality of indoor Air and energy saving were greatly improved by combining the exhaust outlets with some of the room’s heat sources such as ceiling lamps and external walls. In particular, a 25.0% of energy saving was achieved by combining the exhaust diffuser with room’s ceiling lamps. In addition, locating the exhaust diffuser near the heat sources also reduced the cooling coil load by 13.8%. The risk of a large difference in temperature between the head and foot levels, increased particle concentration in the occupied zone, as well as increased energy consumption was also clearly demonstrated when the exhaust and Recirculated Air outlet (return opening) were combined in one unit in the occupied boundary area that is located at 2 m away from the occupants. Thus, for the optimum energy saving and better indoor environment, the combination of the indoor heat sources with the exhaust outlet is necessary.
S.c. Sekhar - One of the best experts on this subject based on the ideXlab platform.
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thermal comfort and iaq assessment of under floor Air distribution system integrated with personalized ventilation in hot and humid climate
Building and Environment, 2010Co-Authors: S.c. Sekhar, Arsen Krikor MelikovAbstract:Abstract The potential for improving occupants’ thermal comfort with personalized ventilation (PV) system combined with under-floor Air distribution (UFAD) system was explored through human response study. The hypothesis was that cold draught at feet can be reduced when relatively warm Air is supplied by UFAD system and uncomfortable sensation as “warm head” can be reduced by the PV system providing cool and fresh outdoor Air at the facial level. A study with 30 human subjects was conducted in a Field Environmental Chamber. The chamber was served by two dedicated systems – a primary Air handling unit (AHU) for 100% outdoor Air that is supplied through the PV Air terminal devices and a secondary AHU for 100% Recirculated Air that is supplied through UFAD outlets. Responses of the subjects to the PV-UFAD system were collected at various room Air and PV Air temperature combinations. The analyses of the results obtained reveal improved acceptability of perceived Air quality and improved thermal sensation with PV-UFAD in comparison with the reference case of UFAD alone or mixing ventilation with ceiling supply diffuser. The local thermal sensation at the feet was also improved when warmer UFAD supply Air temperature was adopted in the PV-UFAD system.
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thermal comfort and iaq assessment of under floor Air distribution system integrated with personalized ventilation in hot and humid climate
Building and Environment, 2010Co-Authors: S.c. Sekhar, Ruixin Li, Arsen Krikor MelikovAbstract:Abstract The potential for improving occupants’ thermal comfort with personalized ventilation (PV) system combined with under-floor Air distribution (UFAD) system was explored through human response study. The hypothesis was that cold draught at feet can be reduced when relatively warm Air is supplied by UFAD system and uncomfortable sensation as “warm head” can be reduced by the PV system providing cool and fresh outdoor Air at the facial level. A study with 30 human subjects was conducted in a Field Environmental Chamber. The chamber was served by two dedicated systems – a primary Air handling unit (AHU) for 100% outdoor Air that is supplied through the PV Air terminal devices and a secondary AHU for 100% Recirculated Air that is supplied through UFAD outlets. Responses of the subjects to the PV-UFAD system were collected at various room Air and PV Air temperature combinations. The analyses of the results obtained reveal improved acceptability of perceived Air quality and improved thermal sensation with PV-UFAD in comparison with the reference case of UFAD alone or mixing ventilation with ceiling supply diffuser. The local thermal sensation at the feet was also improved when warmer UFAD supply Air temperature was adopted in the PV-UFAD system.
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three dimensional numerical simulation of a hybrid fresh Air and Recirculated Air diffuser for decoupled ventilation strategy
Building and Environment, 2007Co-Authors: S.c. SekharAbstract:Abstract In conventional mixing ventilation Air conditioning system, fresh Air which has been polluted by Recirculated Air is supplied to occupied zone. Therefore, more fresh Air which results in energy penalty needs to be supplied in order to keep good indoor Air quality (IAQ) and thermal comfort. Some alternatives such as personalized ventilation Air conditioning system can address this problem effectively by supplying fresh Air directly into occupied zone. However, room layouts and visual effects will be influenced deeply because of extended Air ducts. A new approach supplying fresh Air directly by utilizing high velocity circular Air jet without mixing with Recirculated Air is introduced. Objective measurements and computational fluid dynamics (CFD) tool are used to evaluate corresponding indoor parameters to verify that it can both supply fresh Air into occupied zone effectively and avoid draught rating. It is found that the measured Air velocities are within the limits (0.25 m/s) of thermal comfort standards, although they are close to the limits. Higher Air change rate can be obtained in breathing zone than that in ambient Air in the background area. The predicted results show unique distributions of Airflow characteristics and are in fAir agreement with empirical measurements. Different angles of Recirculated Air diffuser blades, different lengths and directions of protruding fresh Air jets and different inlet velocities of fresh Air are adopted for comparing the effectiveness and efficiency of this new ventilation strategy numerically.
Gereon Feckler - One of the best experts on this subject based on the ideXlab platform.
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experimental performance of an advanced metal volumetric Air receiver for solar towers
Renewable Energy, 2017Co-Authors: Christoph Pabst, Gereon Feckler, Stefan Schmitz, Olena Smirnova, Raffaele Capuano, Peter Hirth, Thomas FendAbstract:Solar Tower Technology is a promising way to generate sustainable electricity from concentrated solar radiation. In one of the most effective variants of this technology, a so called volumetric Air receiver is used to convert concentrated radiation into heat. This component consists of a high temperature resistant cellular material which absorbs radiation and transfers the heat to an Air flow which is fed from the ambient and from Recirculated Air. It is called volumetric, because the radiation may penetrate into the “volume” of the receiver through the open, permeable cells of the material. In this way a larger amount of heat transfer surface supports the solid to gaseous heat transfer in comparison to a tubular closed receiver. Finally the heated Air is directed to the steam generator of a conventional steam turbine system. In this study an advanced cellular metal honeycomb structure has been designed, manufactured and tested for use as an open volumetric receiver. It consists of winded pAirs of flat and corrugated metal foils. The technology is based on a one which has been primarily developed for the treatment of combustion engine exhaust gases. A number of variations of the pure linear honeycomb structure have been introduced to increase local turbulence and radial flow. Firstly, a set of samples has been tested in laboratory scale experiments to determine effective properties and the solar-to-thermal efficiency. After that, results have been compared with theoretical predictions. Finally, the three most promising materials have been used for a 500 kW test on the research platform of the Solar Tower Julich. Air outlet temperatures of more than 800 °C have been achieved with efficiencies of about 80%, which is about 5% more than the state-of-the-art technology, which is currently used at the main receiver of the Solar Tower. Next to this, lifetime models will be developed to increase the overall reliability of the technology.