The Experts below are selected from a list of 10449 Experts worldwide ranked by ideXlab platform
Hua Wang - One of the best experts on this subject based on the ideXlab platform.
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low grade heat utilization by supercritical carbon dioxide rankine cycle analysis on the performance of Gas Heater subjected to heat flux and convective boundary conditions
Energy Conversion and Management, 2018Co-Authors: Yiqiang Zhang, Yecheng Yao, Guoli Tang, Hua WangAbstract:Abstract The design and optimization of Gas Heater in supercritical carbon dioxide Rankine cycles faces some challenges, among which an urgent one is the effect of thermal boundary condition on the performance of Gas Heater. This work focused on performance comparison and effects of major operating parameters under two most common thermal boundary conditions regarding to low-grade heat sources, by employing a modified Shear-Stress Transport model where a variable turbulent Prandtl formulation was incorporated. Results show that in the pseudo-critical region thermal boundary condition obviously affected the performance of supercritical carbon dioxide Gas Heater. Compared with the uniform heat flux condition, at convective boundary condition impairment occurred in both the local enhancement at high mass flux and local deterioration at low mass flux, due to the self-regulation in local heat input. A nearly uniform thermal field under convective boundary condition was achieved by increasing the mass flux of heat source fluid, while increasing the inlet temperature of source fluid was ineffective to that end. Opposite to constant-property fluid Heater, flow arrangement dramatically affected axial profiles of local heat transfer coefficient while had a much weaker effect on local heat flux in supercritical Gas Heater. Temperature distribution of supercritical carbon dioxide along the Heater was insensitive to the flow arrangement. Further studies reveal that thermal boundary effect was closely related to the buoyancy effect. Thermal boundary condition has a minimal effect on heat transfer of supercritical carbon dioxide when buoyancy effect is negligible. Under heavy influence of buoyancy, thermal boundary effect was obvious in the form of much weaker local deterioration under convective boundary. Finally, the Jackson Nusselt correlation was found applicable to the prediction of overall heat transfer rate under convective boundary condition, with relative deviations within ±15%.
W Oneill - One of the best experts on this subject based on the ideXlab platform.
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the laser assisted cold spray process and deposit characterisation
Surface & Coatings Technology, 2009Co-Authors: M Bray, Andrew Cockburn, W OneillAbstract:Abstract Laser-assisted Cold Spray (LCS) is a new coating and fabrication process which combines the supersonic powder beam found in Cold Spray (CS) with laser heating of the deposition zone. LCS combines some advantages of CS: solid-state deposition, high build rate and the ability to deposit metals onto a range of substrates, with reduced operating costs which arise from not using a Gas Heater and replacing helium with nitrogen as the process Gas. A system has been developed to impact metallic powder particles onto a substrate which is locally heated using a diode laser. A pyrometer and control system are used to record and maintain impact site temperature. In this study, 50 µm powder particles are measured to be traveling at around 400 ms − 1 , and heated to temperatures between 450 °C and 900 °C when they impact the substrates. Build rates of up to 45 g min − 1 were achieved for deposits with less than 1% porosity. Oxygen and nitrogen content in the deposits were measured to be less than 0.6 wt.% and 0.03 wt.% respectively.
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the laser assisted cold spray process and deposit characterisation
Surface & Coatings Technology, 2009Co-Authors: M Bray, Andrew Cockburn, W OneillAbstract:Abstract Laser-assisted Cold Spray (LCS) is a new coating and fabrication process which combines the supersonic powder beam found in Cold Spray (CS) with laser heating of the deposition zone. LCS combines some advantages of CS: solid-state deposition, high build rate and the ability to deposit metals onto a range of substrates, with reduced operating costs which arise from not using a Gas Heater and replacing helium with nitrogen as the process Gas. A system has been developed to impact metallic powder particles onto a substrate which is locally heated using a diode laser. A pyrometer and control system are used to record and maintain impact site temperature. In this study,
Yiqiang Zhang - One of the best experts on this subject based on the ideXlab platform.
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low grade heat utilization by supercritical carbon dioxide rankine cycle analysis on the performance of Gas Heater subjected to heat flux and convective boundary conditions
Energy Conversion and Management, 2018Co-Authors: Yiqiang Zhang, Yecheng Yao, Guoli Tang, Hua WangAbstract:Abstract The design and optimization of Gas Heater in supercritical carbon dioxide Rankine cycles faces some challenges, among which an urgent one is the effect of thermal boundary condition on the performance of Gas Heater. This work focused on performance comparison and effects of major operating parameters under two most common thermal boundary conditions regarding to low-grade heat sources, by employing a modified Shear-Stress Transport model where a variable turbulent Prandtl formulation was incorporated. Results show that in the pseudo-critical region thermal boundary condition obviously affected the performance of supercritical carbon dioxide Gas Heater. Compared with the uniform heat flux condition, at convective boundary condition impairment occurred in both the local enhancement at high mass flux and local deterioration at low mass flux, due to the self-regulation in local heat input. A nearly uniform thermal field under convective boundary condition was achieved by increasing the mass flux of heat source fluid, while increasing the inlet temperature of source fluid was ineffective to that end. Opposite to constant-property fluid Heater, flow arrangement dramatically affected axial profiles of local heat transfer coefficient while had a much weaker effect on local heat flux in supercritical Gas Heater. Temperature distribution of supercritical carbon dioxide along the Heater was insensitive to the flow arrangement. Further studies reveal that thermal boundary effect was closely related to the buoyancy effect. Thermal boundary condition has a minimal effect on heat transfer of supercritical carbon dioxide when buoyancy effect is negligible. Under heavy influence of buoyancy, thermal boundary effect was obvious in the form of much weaker local deterioration under convective boundary. Finally, the Jackson Nusselt correlation was found applicable to the prediction of overall heat transfer rate under convective boundary condition, with relative deviations within ±15%.
Xiangjun Liu - One of the best experts on this subject based on the ideXlab platform.
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a potential source for pm2 5 analysis of fine particle generation mechanism in wet flue Gas desulfurization system by modeling drying and breakage of slurry droplet
Environmental Pollution, 2019Co-Authors: Binfan Jiang, Yulei Xie, Dehong Xia, Xiangjun LiuAbstract:Abstract Aerosol particulate matter with dynamic diameter smaller than 2.5 μm (PM2.5) is the main cause for haze pollution in China. As a dominant precursor of PM2.5, SO2 emitted from industrial process is now strictly controlled by using limestone/gypsum Wet Flue Gas Desulfurization (WFGD) system in China. However, a phenomenon that fine particle derived from WFGD is recently addressed, and is suggested to be a potential source of primary PM2.5. Herein, a first investigation into the particle generation mechanism in WFGD system is conducted with a novel droplet (containing particles) drying and breakage model. The proposed model considers a random and porous crust instead of the previous regular crust assumption, and is verified by comparing the modeling results with measurements. An orthogonal test with four factors and three levels is carried out through modeling calculation, and flue Gas temperature (Tg) in the inlet is found to be a governing parameter for PM2.5 yields in WFGD. With Tg in range of 120–160 °C, PM2.5 yields in desulfurizing tower can reach a maximum value at ∼2 × 108 cm−3 under typical WFGD condition. To avoid this situation and reduce the PM2.5 generation, Tg is suggested to be lower than 120 °C. Additionally, a new insight of the elimination effect of Gas-Gas Heater (GGH) on “gypsum rain” in WFGD system is provided.
De Carli Michele - One of the best experts on this subject based on the ideXlab platform.
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Comfort and Perceived Air Quality in Refurbished Social Houses with Mechanical Ventialtion System: The Impact of Occupants Behaviour
The Authors. Published by Elsevier Ltd., 2015Co-Authors: Peretti Clara, Pasut Wilmer, Emmi Giuseppe, De Carli MicheleAbstract:AbstractThe ever-growing demand for a better indoor air quality in residential buildings is increasing the number of whole-house ventilation system installations in new constructions and renovation. In Italy, for residential sector, the national code does not prescribe the use of mechanical ventilation (MV) systems, so their installation is left to the choice of house owners.Two three-storey social housing apartment blocks in Northern Italy were studied. To reduce energy consumption, building envelopes as well as heating systems were refurbished. The thermal insulation was increased and the existing Gas Heater units were replaced with more efficient radiant ceiling systems. The refurbishment measures were the same for both constructions beside the MV system, which was installed in only one building.Indoor temperature and relative humidity were monitored for several apartments during the heating season. The occupants were surveyed to investigate their thermal comfort and perceived air quality. The occupants were interviewed to better understand their responses, and to know how they operate the heating system and the mechanical ventilation system (when present).Survey results show that there are no differences in terms of thermal comfort and perceived air quality between the occupants of the buildings with and without MV systems. The findings may be related to occupants’ behaviour
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COMFORT AND PERCEIVED AIR QUALITY IN REFURBISHED SOCIAL HOUSES WITH MECHANICAL VENTIALTION SYSTEM: THE IMPACT OF OCCUPANTS BEHAVIOUR
ELSEVIER SCIENCE BV, 2015Co-Authors: Peretti Clara, Pasut Wilmer, Emmi Giuseppe, De Carli MicheleAbstract:The ever-growing demand for a better indoor air quality in residential buildings is increasing the number of whole-house ventilation system installations in new constructions and renovation. In Italy, for residential sector, the national code does not prescribe the use of mechanical ventilation (MV) systems, so their installation is left to the choice of house owners.Two three-storey social housing apartment blocks in Northern Italy were studied. To reduce energy consumption, building envelopes as well as heating systems were refurbished. The thermal insulation was increased and the existing Gas Heater units were replaced with more efficient radiant ceiling systems. The refurbishment measures were the same for both constructions beside the MV system, which was installed in only one building.Indoor temperature and relative humidity were monitored for several apartments during the heating season. The occupants were surveyed to investigate their thermal comfort and perceived air quality. The occupants were interviewed to better understand their responses, and to know how they operate the heating system and the mechanical ventilation system (when present).Survey results show that there are no differences in terms of thermal comfort and perceived air quality between the occupants of the buildings with and without MV systems. The findings may be related to occupants' behaviour. (C) 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)
