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AIP Conference Proceedings [Author(s) SolarPACES 2017: International Conference on Concentrating Solar Power and Chemical Energy Systems - Santiago, Chile (26–29 September 2017)] - Heat flux and temperature measurements on glass envelope and bellows of parabolic trough receivers
摘要： This paper reports heat flux measurements on parabolic trough receivers, which are integrated to calculate the receiver overall heat loss. Integrated heat fluxes yield an overall heat loss value which agrees with DLR ThermoRec heat loss measurements within ± 5 %, in the simplified case of assuming a homogeneous heat flux distribution around the receiver circumference. Heat flux measurements also allow separating glass envelope and shielded bellow heat loss terms for receiver thermal modelling. Shielded bellows only represent 3 to 4 % of the receiver total length at ambient temperature, however heat flux measurements show that their contribution to the overall receiver heat loss ranges from 5 to 15 %, depending on the shield construction and the absorber temperature. The receiver specific heat loss thus tends to lie above the glass envelope specific heat loss. Almost homogeneous heat flux values are measured along the glass envelope length (variation below 5 %), while more inhomogeneous heat flux values are observed over circumference of the glass envelope (variation between top and side of 17 %). The measurement setup analysis shows a good repeatability, although a proper mounting of heat flux sensors is important in order to avoid systematic biases.
关键词： heat loss,parabolic trough receivers,heat flux measurements,glass envelope,shielded bellows
更新于2025-09-04 15:30:14
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Application of kinetic flux vector splitting scheme for solving viscous quantum hydrodynamical model of semiconductor devices
摘要： In this article, one-dimensional viscous quantum hydrodynamical model of semiconductor devices is numerically investigated. The model treats the propagation of electrons in a semiconductor device as the flow of a charged compressible fluid. It plays an important role in predicting the behavior of electron flow in semiconductor devices. The nonlinear viscous quantum hydrodynamic models contain Euler-type equations for density and current, viscous and quantum correction terms, and a Poisson equation for electrostatic potential. Due to high nonlinearity of model equations, numerical solution techniques are applied to obtain their solutions. The proposed numerical scheme is a splitting scheme based on the kinetic flux-vector splitting (KFVS) method for the hyperbolic step, and a semi-implicit Runge-Kutta method for the relaxation step. The KFVS method is based on the direct splitting of macroscopic flux functions of the system on the cell interfaces. The second order accuracy of the scheme is achieved by using MUSCL-type initial reconstruction and Runge-Kutta time stepping method. Several case studies are considered. For validation, the results of current scheme are compared with those obtained from the splitting scheme based on the NT central scheme. The effects of various parameters such as device length, viscosities, different doping and voltage are analyzed. The accuracy, efficiency and simplicity of the proposed KFVS scheme validates its generic applicability to the given model equations.
关键词： Numerical simulation,Kinetic flux-vector splitting scheme,Semiconductor devices,Viscous quantum hydrodynamic model
更新于2025-09-04 15:30:14
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Effect of supplemental blue light intensity on the growth and quality of Chinese kale
摘要： The influence of blue light on the growth and quality of vegetables is controversial, since both positive and negative effects have been observed on different varieties of vegetables and most research has been conducted with a combination of light spectrums. In this work, we investigated the effects of supplemental blue light intensity on growth, nutritional quality, and health-promoting compounds of Chinese kale (Brassica alboglabra Bailey) using only blue (460 nm) light-emitting diodes 10 days before harvest in a greenhouse under ambient light conditions. Four blue-light treatments were conducted (0, 50, 100, and 150 μmol m?2 s?1, named T0, T50, T100, and T150, respectively) with 12 h (6:00–18:00) of light treatment per day. The growth of Chinese kale plants was improved by supplemental blue light. The fresh and dry weights of Chinese kale plants were significantly higher under T50 and T100 than those in the other treatments. The content of chlorophyll b and total chlorophyll increased significantly under T50, and the content of carotenoids increased significantly under T150. The contents of soluble sugars and free amino acids were significantly increased under the blue light treatments. The nitrate content decreased with increasing blue light intensity, while the anthocyanin content increased. The contents of vitamin C in T50 and total phenolic compounds in T150 were significantly higher than in T0. The flavonoid contents were significant higher in T50 and T150, and significantly lower in T100. Our results show that blue light can influence the growth and quality of Chinese kale and 50 μmol m?2 s?1 of supplemental blue light might be the most feasible light intensity for Chinese kale production.
关键词： Photosynthetic photon flux density,Biomass,Health-promoting compounds,Brassica alboglabra,Nutritional quality
更新于2025-09-04 15:30:14
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[ASME ASME 2017 Power Conference Joint With ICOPE-17 collocated with the ASME 2017 11th International Conference on Energy Sustainability, the ASME 2017 15th International Conference on Fuel Cell Science, Engineering and Technology, and the ASME 2017 Nuclear Forum - Charlotte, North Carolina, USA (Monday 26 June 2017)] Volume 2: I&C, Digital Controls, and Influence of Human Factors; Plant Construction Issues and Supply Chain Management; Plant Operations, Maintenance, Aging Management, Reliability and Performance; Renewable Energy Systems: Solar, Wind, Hydro and Geothermal; Risk Management, Safety and Cyber Security; Steam Turbine-Generators, Electric Generators, Transformers, Switchgear, and Electric BOP and Auxiliaries; Student Competition; Thermal Hydraulics and Computational Fluid Dynamics - Heat Transfer Performance of LiF–NaF–KF Salt in a Corrugated Receiver Tube With Non-Uniform Solar Flux
摘要： The heat flux on the receiver tube is non-uniform because of uneven solar flux and receiver structure, which causes overheating and thermal stress failure of receiver and affected safe operations of the Concentrated Solar Power(CSP) system. In order to reduce the temperature difference in receiver tube wall and improve the efficiency of CSP system, the ternary eutectic salt LiF–NaF–KF (46.5–11.5–42 wt.%, hereafter FLiNaK), which has a better high thermal stability than that of nitrate salts at operating temperature of 900 °C, is selected as HTF, and heat transfer performance of FLiNaK in a corrugated receive tube with non-uniform heat flux is simulated by CFD software in the present work. The numerical results reveal that the non-uniform heat flux has a great influence on the temperature distributions of the receive tube and FLiNaK salt. Compared with the result of bare tube, the corrugated tube can not only significantly reduce the temperature difference in tube wall and salt by improving the uniformity of temperature distribution but also enhance the heat transfer of the salt, where the heat transfer coefficient increases with the Reynolds number and heat flux. Moreover, the enhanced effect of the corrugated tube depends on both the pitch and the height of ridges. It is found that the heat transfer coefficient of the salt gets a maximum when the ratio of the height of ridge to the pitch is 0.2. The research presented here may provide guidelines for design optimization of receiver tube in CSP system.
关键词： heat transfer,FLiNaK,non-uniform heat flux,corrugated tube,Concentrated Solar Power
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE International Conference on Imaging Systems and Techniques (IST) - Krakow, Poland (2018.10.16-2018.10.18)] 2018 IEEE International Conference on Imaging Systems and Techniques (IST) - Measurement of External-Solids Circulation Flux in a Circulating Fluidized Bed by Electrical Capacitance Tomography and Microwave Doppler Radar
摘要： In a gas-solids circulating fluidized bed (CFB), the external-solids circulating flux (Gs) has important effect on the mass and heat transfer inside the CFB system. To improve the process operation efficiency and reduce the emission of pollution, it is important to accurately measure Gs. In this paper, the authors proposed a new approach to measuring Gs using electrical capacitance tomography (ECT) and microwave Doppler radar (MDR) velocity meter based on a lab-scale CFB system with multi-cyclone separators. The ECT sensor is used to get the solids volume fraction in the cross section of the standpipe and MDR is used to measure the averaged solids velocity along the standpipes. Based on those two values, Gs can be addressed. Meanwhile, computation particle fluid dynamic (CPFD) is used to investigated the gas-solids flow hydrodynamic characteristics and verified the measurement results.
关键词： CPFD simulation,Microwave Doppler radar,External-Solids Circulating flux,Electrical capacitance tomography
更新于2025-09-04 15:30:14