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Numerical study of conduction and radiation heat losses from vacuum annulus in parabolic trough receivers

Dongqiang LEI, Yucong REN, Zhifeng WANG

《能源前沿（英文）》 2022年 第16卷 第6期   页码 1048-1059 doi: 10.1007/s11708-020-0670-7

摘要： Parabolic trough receiver is a key component to convert solar energy into thermal energy in the parabolic trough solar system. The heat loss of the receiver has an important influence on the thermal efficiency and the operating cost of the power station. In this paper, conduction and radiation heat losses are analyzed respectively to identify the heat loss mechanism of the receiver. A 2-D heat transfer model is established by using the direct simulation Monte Carlo method for rarefied gas flow and heat transfer within the annulus of the receiver to predict the conduction heat loss caused by residual gases. The numerical results conform to the experimental results, and show the temperature of the glass envelope and heat loss for various conditions in detail. The effects of annulus pressure, gas species, temperature of heat transfer fluid, and annulus size on the conduction and radiation heat losses are systematically analyzed. Besides, the main factors that cause heat loss are analyzed, providing a theoretical basis for guiding the improvement of receiver, as well as the operation and maintenance strategy to reduce heat loss.

关键词： parabolic trough receiver     vacuum annulus     rarefied gas     DSMC (direct simulation Monte Carlo)     heat loss    

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Numerical simulation of two-dimensional spouted bed with draft plates by discrete element method

ZHAO Yongzhi, JIANG Maoqiang, CHENG Yi, JIN Yong

《化学科学与工程前沿（英文）》 2008年 第2卷 第1期   页码 5-9 doi: 10.1007/s11705-008-0009-0

摘要： A discrete element method (DEM)-computational fluid dynamics (CFD) two-way coupling method was employed to simulate the hydrodynamics in a two-dimensional spouted bed with draft plates. The motion of particles was modeled by the DEM and the gas flow was modeled by the Navier-Stokes equation. The interactions between gas and particles were considered using a two-way coupling method. The motion of particles in the spouted bed with complex geometry was solved by combining DEM and boundary element method (BEM). The minimal spouted velocity was obtained by the BEM-DEM-CFD simulation and the variation of the flow pattern in the bed with different superficial gas velocity was studied. The relationship between the pressure drop of the spouted bed and the superficial gas velocity was achieved from the simulations. The radial profile of the averaged vertical velocities of particles and the profile of the averaged void fraction in the spout and the annulus were statistically analyzed. The flow characteristics of the gas-solid system in the two-dimensional spouted bed were clearly described by the simulation results.

关键词： annulus     BEM-DEM-CFD simulation     gas-solid     two-dimensional     relationship    

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Experimental investigation of multiphase flow behavior in drilling annuli using high speed visualization technique

Alap Ali ZAHID, Syed Raza ur REHMAN, Anwarul HASAN, S. RUSHD, Mohammad Azizur RAHMAN

《能源前沿（英文）》 2020年 第14卷 第3期   页码 635-643 doi: 10.1007/s11708-018-0582-y

摘要： Imaging with high definition video camera is an important technique to visualize the drilling conditions and to study the physics of complex multiphase flow associated with the hole cleaning process. The main advantage of visualizing multiphase flow in a drilling annulus is that the viewer can easily distinguish fluid phases, flow patterns and thicknesses of cutting beds. In this paper the hole cleaning process which involves the transportation of cuttings through a horizontal annulus was studied. The two-phase (solid-liquid) and the three-phase (solid-liquid-gas) flow conditions involved in this kind of annular transportation were experimentally simulated and images were taken using a high definition camera. Analyzing the captured images, a number of important parameters like velocities of different phases, heights of solid beds and sizes of gas bubbles were determined. Two different techniques based on an image analysis software and MATLAB coding were used for the determinations. The results were compared to validate the image analyzing methodology. The visualization technique developed in this paper has a direct application in investigating the critical conditions required for efficient hole cleaning as well as in optimizing the mud program during both planning and operational phases of drilling. Particularly, it would be useful in predicting the cuttings transport performance, estimating solid bed height, gas bubble size, and mean velocities of bubbles/particles.

关键词： visualization     horizontal annulus     hole cleaning     multiphase flow     image analysis     flow regime    

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标题 作者 时间 类型 操作

Numerical study of conduction and radiation heat losses from vacuum annulus in parabolic trough receivers

Dongqiang LEI, Yucong REN, Zhifeng WANG

期刊论文

Numerical simulation of two-dimensional spouted bed with draft plates by discrete element method

ZHAO Yongzhi, JIANG Maoqiang, CHENG Yi, JIN Yong

期刊论文

Experimental investigation of multiphase flow behavior in drilling annuli using high speed visualization technique

Alap Ali ZAHID, Syed Raza ur REHMAN, Anwarul HASAN, S. RUSHD, Mohammad Azizur RAHMAN

期刊论文