This paper experimentally studied the performance of exhaust steam reclaim device with a swirling flow vane at different inlet water pressures, temperatures, different inlet steam pressures and different distances bet...
This paper experimentally studied the performance of exhaust steam reclaim device with a swirling flow vane at different inlet water pressures, temperatures, different inlet steam pressures and different distances between the throat and spout. The results indicated that the injection coefficient decreased as the inlet water pressure and temperature increased, respectively. There is a best distance between the throat and spout which makes the injection coefficient reached to its maximal value at the same experimental pressure and temperature, and the value equals to 130 mm in our experimental system. The resistance coefficient has a minimum value which makes the device have the highest outlet water pressure. Compared with the device without a swirling flow vane, it improves the heating performance for higher injection coefficient and exergy efficiency.
Concentrating PV systems usually use Fresnel lens as radiation concentrator. In this paper, in order to study the concentrating performance of the Fresnel lens, modular Fresnel lens mode was developed and its optical ...
Concentrating PV systems usually use Fresnel lens as radiation concentrator. In this paper, in order to study the concentrating performance of the Fresnel lens, modular Fresnel lens mode was developed and its optical performance was analyzed by the ray tracing method. The imaging characteristic of Fresnel was studied and the optimal imaging location and the size of dispersion spot with different inlet angle were figured out. Flux distribution of the different imaging plane were also examined and compared. The results show that the dispersion spot deviates from the focus and the size of the dispersion spot is enlarged as the incidence angle increase, especially at the high geometric concentration ratio. Then in order to solve the problem, a flat light pipe was applied to reflect sun light onto the absorber plane. The simulation results show that with the new design, sun lights with large inlet angle could also be casted on the absorber.
On the basis of a 350 MW supercritical pressure OTSC boiler, established the mathematical model for the circulation loop flow and grid pressure in a complex flow network system, and an iteration method was used to sol...
On the basis of a 350 MW supercritical pressure OTSC boiler, established the mathematical model for the circulation loop flow and grid pressure in a complex flow network system, and an iteration method was used to solve the nonlinear equations. The water wall flow distribution and temperature profile of the boiler were computed. The results show that the flow difference and heat difference are small in spiral tube water wall at BMCR, 75%BMCR load and 30%BMCR load. The metal temperatures are all in the range of allowable range, and the operation of boil is safe and reliable.
In an attempt to understand the problem of severe slagging in biomass-fired boilers, slags formed on the fourth-, second-, and first-stage superheaters in a 12 MW biomass-fired grate furnace have been collected, sampl...
详细信息
Aeration is an important factor affecting the biological aeration *** a set of experiment device specially designed for the purpose,and the particle image velocimetry technique,the velocity field of the gas-liquid two...
详细信息
Aeration is an important factor affecting the biological aeration *** a set of experiment device specially designed for the purpose,and the particle image velocimetry technique,the velocity field of the gas-liquid two-phase flow is studied under different *** various simulated aeration states were actually applied to the experimental device of sewage treatment,and the results of the numerical simulation were *** final experimental results indicate that the most efficient state occurs when the ratio of water in aeration tank h / w =1,the diameter of capillary tubes d=0.6mm and the velocity of bubbles v=0.3m/s.
Exergy analysis of solar dynamic closed Brayton cycle (SDCBC) for space applications was presented in this paper. An integrated model for the system and specific models for its components were proposed. Influence of m...
详细信息
Exergy analysis of solar dynamic closed Brayton cycle (SDCBC) for space applications was presented in this paper. An integrated model for the system and specific models for its components were proposed. Influence of main parameters on system exergy efficiency was discussed. The results shown the efficiencies of expander, compressor, and regenerating temperature of the regenerator have significant influence on the exergy efficiency of SDCBC system. Therefore, besides the enhancement of component efficiencies, the matching among components of SDCBC system should be also taken into account. Moreover, it would be always desirable to enhance the effectiveness of recuperator within the requirements of flow resistance and system weight.
Experiments on the condensation of steam jet submerged in the subcooled water were carried out. The water temperature and the inlet steam pressure were in the range of 293 K–343 K and 0.2–0.6 MPa, respectively. Four...
Experiments on the condensation of steam jet submerged in the subcooled water were carried out. The water temperature and the inlet steam pressure were in the range of 293 K–343 K and 0.2–0.6 MPa, respectively. Four essential shapes of steam plume were enumerated. According to the comparisons of the pictures of steam plume with the graphs in the same size, the pressure came to maximum value in the contraction spots, except for the double expansion‐emanative shape. Moreover, pressure distributions of the flow field were characterized by means of drawing isobar. Comparison and discussions on the relationship between steam plume and pressure distributions were given. With the increase of temperature, pressure distributions within steam plume became more complex. Radial pressure distributions were classified according to different regions. Comparisons of the pressure distributions at different water temperature and inlet steam pressure were obtained.
This paper proposes an improved lattice Boltzmann scheme for incompressible axisymmetric flows. The scheme has the following features. First, it is still within the framework of the standard lattice Boltzmann method u...
详细信息
This paper proposes an improved lattice Boltzmann scheme for incompressible axisymmetric flows. The scheme has the following features. First, it is still within the framework of the standard lattice Boltzmann method using the single-particle density distribution function and consistent with the philosophy of the lattice Boltzmann method. Second, the source term of the scheme is simple and contains no velocity gradient terms. Owing to this feature, the scheme is easy to implement. In addition, the singularity problem at the axis can be appropriately handled without affecting an important advantage of the lattice Boltzmann method: the easy treatment of boundary conditions. The scheme is tested by simulating Hagen-Poiseuille flow, three-dimensional Womersley flow, Wheeler benchmark problem in crystal growth, and lid-driven rotational flow in cylindrical cavities. It is found that the numerical results agree well with the analytical solutions and/or the results reported in previous studies.
In this paper, a numerical simulation is performed in order to reveal the evaporation heating transfer mechanism of the falling‐film of water on the outer wall of horizontal tubes, and the influence of gas‐water‐so...
In this paper, a numerical simulation is performed in order to reveal the evaporation heating transfer mechanism of the falling‐film of water on the outer wall of horizontal tubes, and the influence of gas‐water‐solid contact angles on the film distribution on the tube is mainly addressed. The simulation is performed by solving the motion equation of the fluid on fixed three‐dimensional (3D) grid systems, and the so‐called volume of fluid (VOF) method is employed to handle the movement of interface between the liquid and the vapor phase. The numerical results are compared with that of a simplified model and also with the experimental recordings obtained in visualization experiments conducted with tubes made of different materials, and it is shown that the numerical results are in very good agreement with the experimental observation of the falling films, indicating that the numerical methods applied in the present study is correct and accurate. Based on the numerical results, effects of the contact angle, the flow rate, the tube diameter and the liquid feeder height on the falling film behavior are discussed. Generally, the film width increases along with the increase of flow rate or the liquid feeder height, while variation of the film thickness exhibits different features at different conditions, and the contact angle is one of the major factors governing the behavior of the falling films.
In this paper a mathematical model is built for a buried hot crude oil pipeline during shutdown, and an unstructured grid and polar coordinate grid are respectively applied to generating grids for the soil region and ...
详细信息
In this paper a mathematical model is built for a buried hot crude oil pipeline during shutdown, and an unstructured grid and polar coordinate grid are respectively applied to generating grids for the soil region and the three layers in the pipe （wax layer, pipe wall, and corrosion-inhibiting coating）. The governing equations are discretized using the finite volume method. The variations in temperatures of static oil and soil were investigated during pipeline shutdown in both summer and winter, in which some important parameters of the soil and crude oils of a Northeast pipeline are employed.
暂无评论