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排序方式: 共有223条查询结果,搜索用时 75 毫秒
41.
太阳能光伏光热一体化系统运行实验研究 总被引:2,自引:1,他引:1
太阳能光伏光热一体化系统(hybrid photovoltaic-thermal solar system—PVT系统)作为一种利用太阳能同时获得电收益和热收益的新型能源利用方式,近年来受到学者的广泛关注。本文搭建了PVT系统电、热性能综合实验台,通过全天实验,分别研究和分析了系统的温度特性与相对电效率的关系。结果袁明,在日照条件较好,系统循环水温较低的情况下,PVT系统的电效率与普通光伏电池相比可以提高约7%。同时,文章还分析了PVT系统内水的温度一天内的变化情况,提出了在午后太阳辐射强度逐渐减弱,环境温度逐渐升高时如何保持PVT系统较高电效率的方法。 相似文献
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43.
Yung-Hsiang Chang Tzu-Hsiang Wei Shia-Chung Chen Ying-Fan Lou 《Polymer Engineering and Science》2020,60(11):2895-2907
Injection molding is one of the commonly used processes for plastic part production due to numerous advantages, such as rapid production, complex shape modability, and material selectivity. However, highly experience-based conventional production restrains the industry development. Company know-how loses with the experienced operator's left. On the other hand, molded part quality was only based on the operator check. There is without an effective solution to maintain its stability and defect-free adjustment. How to establish a scientific injection molding setup and quality control method is an urgent topic. This study established a practical method for quality monitoring based on the pressure-volume-temperature (PVT) property. The PVT processing path control for scientific molding parameter setup was investigated. This is not only the method for parameter optimization but also the molded part quality control. Three major qualities were discussed in this study, including product weight, shrinkage, and warpage. By the molding condition optimization, three qualities improved up to 1%, 41.9%, and 9.2%, respectively. 相似文献
44.
《International Journal of Hydrogen Energy》2020,45(13):7498-7507
This study aims to investigate the performance of the Photovoltaic Thermal (PVT) collector based hydrogen production system. For this purpose, a solar assisted water splitting system is fabricated. This system comprises the array of photovoltaic (PV) cells with 0.303 m2 surface area, a spiral flow thermal collector with 12.7 mm outer diameter, 10.26 mm internal diameter, 10 m length copper tube and Hoffman voltameter. The results have been taken for three different mass flow rates (0.008, 0.01 and 0.011 kg/s) and compared with the reference PV module. This study results clearly show that the collector outlet temperature, output voltage and output power increase as the flow rate increases and the PV module temperature decreases with an increase of flow rate. The maximum thermal and electrical efficiency of 33.8% and 8.5% are observed for water based PVT solar collector with 0.011 kg/s flow rate at 12.00. It is also noted that the hydrogen yield rate increases significantly with an increase in flow rate. The highest hydrogen yields of 17.1 ml/min are obtained at a fluid flow rate of 0.011 kg/sec at 12.00. 相似文献
45.
G. C. Straty A. M. F. Palavra T. J. Bruno 《International Journal of Thermophysics》1986,7(5):1077-1089
Measurements of the PVT behavior of compressed gas and liquid methanol are reported. Pressure versus temperature observations were made along paths of very nearly constant density (pseudoisochores) in the temperature range from about 100 to 300°C and at pressures to about 35 MPa. Eighteen pseudoisochores were determined, ranging in density from about 2 to 22 mol · dm–3. 相似文献
46.
MOS capacitors have been fabricated on 4H–SiC epilayers grown by physical vapor transport (PVT) epitaxy. The properties were compared with those on similar structures based on chemical vapor deposition (CVD) layers. Capacitance–voltage (C–V) and conductance measurements (G–V) were performed in the frequency range of 1 kHz to 1 MHz and also at temperatures up to 475 K. Detailed investigations of the PVT structures indicate a stable behaviour of the interface traps from room temperature up to 475 K. The amount of positive oxide charge QO is 6.83 × 109 cm−2 at room temperature and decreases with temperature increase. This suggests that the processed devices are temperature stable. The density of interface states Dit obtained by Nicollian–Brews conductance method is lower in the structure based on the PVT grown sample. 相似文献
47.
This paper presents models for predicting the bubble-point pressure (Pb) and oil formation-volume-factor at bubble-point (Bob) for crude oil samples collected from several regions around the world. The regions include major producing oil fields in North and South America, North Sea, South East Asia, Middle East, and Africa. The model was developed using artificial neural networks with 5200 experimentally obtained PVT data sets. This represents the largest data set ever collected to be used in developing Pb and Bob models. An additional 234 PVT data sets were used to investigate the effectiveness of the neural network models to predict outputs from inputs that were not used during the training process. The network model is able to predict the bubble-point pressure and the oil formation-volume-factor as a function of the solution gas-oil ratio, the gas relative density, the oil specific gravity, and the reservoir temperature. In order to obtain a generalized accurate model, back propagation with momentum for error minimization was used. The accuracy of the models developed in this study was compared in details with several published correlations. This study shows that if artificial neural networks are successfully trained, they can be excellent reliable predictive tools to estimate crude oil properties better than available correlations. The network models can be easily incorporated into any reservoir simulators and/or production optimization software. 相似文献
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49.
In this paper, a novel hybrid digital-controlled oscillator (DCO) is proposed, which is used to improve the accuracy of the all-digital clock generator without reference source. The DCO with hybrid architecture consists of two parts: DCO_high and DCO_low. The DCO_high decides the coarse output frequency of DCO, and adopts the cascade structure to decrease the area. The DCO_low adopts the chain structure with three-state buffer, and decides the fine output frequency of DCO. Compared with traditional cascade DCO, the proposed hybrid DCO features higher precision with less inherent delay. Therefore the clock generator can tolerate process, voltage and temperature (PVT) variation and meet the needs of different conditions. The DCO is designed in SMIC 180 nm CMOS process with 0.021 mm2 chip area. The output frequency is adjusted from 15-120 MHz. The frequency error is less than 0.83% at 25 MHz with 1.6-1.8 V supply voltage and 0-80 ℃ temperature variations in TT, FF, SS corners. 相似文献
50.
J. M. H. Levelt Sengers 《International Journal of Thermophysics》2001,22(1):3-22
During the past century, the Van der Waals Laboratory at the University of Amsterdam has been the principal provider of reliable fluid property data over large ranges of pressure and temperature. This paper describes the history of the laboratory, starting in 1898 when funding for it was obtained. In the early period, under Van der Waals and Kohnstamm, the high-pressure direction was chosen, and the first PVT and phase equilibria data were published. The main focus of this paper is the Michels period, from 1921 to 1960. In this period, the laboratory acquired its own building and assumed a unique position in the world because of its highly accurate thermodynamic, transport, and other property measurements in fluids at high pressures. In the 1950s, a second laboratory was built by Michels at the University of Maryland, per request of the U.S. Navy. Under Trappeniers, 1961–1987, the laboratory incorporated new techniques, such as NMR, undertook a major expansion of the pressure range, and extended its interest to phase transitions in molecular solids. The position of the Van der Waals Laboratory in the world of high-pressure science is highlighted. 相似文献