The synthesis and properties of metal chalcogenides have been extensively researched because of their useful and novel *** of them have been synthesized by traditional high-temperature calcination ***, other preparati...
详细信息
The synthesis and properties of metal chalcogenides have been extensively researched because of their useful and novel *** of them have been synthesized by traditional high-temperature calcination ***, other preparation methods have also been investigated such as solvothermal synthesis method.
For the investigation on deflagration of oil/natural gas boiler and its prevention, an experimental system was designed and built to measure deflagration characteristics of combustible gas. The explosion limits of met...
详细信息
For the investigation on deflagration of oil/natural gas boiler and its prevention, an experimental system was designed and built to measure deflagration characteristics of combustible gas. The explosion limits of methane and its mixture of CO were measured at different temperature. The results matched the theoretical values well. It was also found that the range of explosion limit widens with an increase of initial temperature or a rise of CO rate, which indicates that incompletely burned methane causes high risk of deflagration. The possibility of deflagration, which may happen during purging, was numerically analyzed. Igniting without purging after flameout increases the possibility of deflagration. The result of unsteady numerical modeling on purging shows that ignition should be done rapidly within 5 minutes and purging is necessary before sparking again. The amount of purging air to ensure safety is 4 times of the furnace volume.
For high-efficiently solving the power dissipation problem of electronic components on the spacecraft, experiments were performed using micro-pin-finned structure as heater surface in subcooled nucleate pool boiling o...
详细信息
For high-efficiently solving the power dissipation problem of electronic components on the spacecraft, experiments were performed using micro-pin-finned structure as heater surface in subcooled nucleate pool boiling of FC-72 under microgravity condition utilizing the drop tower Beijing. Micro-pin-fins with the dimensions of 50 μm×120 μm (thickness × height) were fabricated on the surface of square silicon by using the dry etching technique. The micro-pin-finned silicon chip was heated by means of controlling heating voltage for the desired heat flux. At the same time, video of the bubble behavior was obtained by using high speed camera. The results showed that micro-pin-fins can increase the effective nucleate boiling sites number and the heat transfer performance efficiently, which stems from the sufficient supply of fresh liquid to the heater surface due to the capillary force independent of gravity. The steady nucleate pool boiling heat transfer on micro-pin-finned surface can be obtained at high heat fluxes and is greatly enhanced compared with smooth surface in microgravity.
Flashing spray is a common phenomenon which finds many applications in the industry, such as flash-spray internal combustion engine, distillation of salt water by flashing evaporation, cryogen spray cooling in dermato...
详细信息
Flashing spray is a common phenomenon which finds many applications in the industry, such as flash-spray internal combustion engine, distillation of salt water by flashing evaporation, cryogen spray cooling in dermatology. In order to improve the understanding of atomization mechanism, this paper presents an experimental investigation to the droplets dynamics in the R134a flashing spray including the variations of droplets diameter and velocities. The droplets diameter, droplets axial velocity and radial velocity at different locations are simultaneously measured by the PDPA system. The PDPA measurements data find that both the non-dimensional velocities show self-similar profile. Two empirical equations have been proposed to describe the non-dimensional velocities.
A modularized code based on the Finite Element QZ (FEQZ) method is developed, for a better estimate of the critical speed and a more convenient method of rotor-dynamic stability analysis for a gas bearing high speed...
详细信息
A modularized code based on the Finite Element QZ (FEQZ) method is developed, for a better estimate of the critical speed and a more convenient method of rotor-dynamic stability analysis for a gas bearing high speed turboexpander rotor system with actual structure and application of a cryogenic turboexpander. This code is then validated by the experimental data of a gas bearing turboexpander, with a rotor diameter of 25 mm and a rated speed of 106,400 rpm. With this code, four rotors with different structures, available to the turboexpander, are parametrically analyzed by the available speed range, vibration modes and logarithmic attenuation rate. The results suggest that the rotor with a structure of two thrust collars on the system exhibits a better performance in the designed conditions.
<正>Introduction Liver cirrhosis generally occurs with the hemodynamic changes during the portal vein hypertension and finally leads to the atrophy of the right lobe of the liver and hepatic *** to the hemodynamic c...
<正>Introduction Liver cirrhosis generally occurs with the hemodynamic changes during the portal vein hypertension and finally leads to the atrophy of the right lobe of the liver and hepatic *** to the hemodynamic changes,a hypothesis has been proposed that the liver volume is related to the istribution of blood from the splenic vein(SV) that involves nutrition from spleen and pancreas The objective of the present paper is to simulate the blood flow in real models of portal vein hypertension and validate the hypothesis using computational fluid dynamics (CFD) method.
The characteristics of flow boiling heat transfer and pressure drop of organic fluid with high saturation temperature in a vertical porous coated tube are experimentally studied in this paper. The experiments are perf...
The characteristics of flow boiling heat transfer and pressure drop of organic fluid with high saturation temperature in a vertical porous coated tube are experimentally studied in this paper. The experiments are performed at evaporation pressure of 0.16-0.31MPa, mass flux of 390-790kg/m2s, and vapor quality of 0.06-0.58. The variations of heat transfer coefficient and pressure drop with vapor quality are measured and compared to the results of smooth tube. Boiling curves are generated at mass flux of 482 and 675kg/m2s. The experimental results indicate that the heat transfer coefficients of the porous tube are 1.8-3.5 times those of smooth tube, and that the frictional pressure drops of the porous tube are 1.1-2.9 times those of smooth tube. The correlations for heat transfer coefficient and frictional pressure drop are derived, in which the effect of fluid molecular weight is included. The experiments show that significant heat transfer enhancement is accompanied by a little pressure drop penalty, the application of the porous coated tube is promising in the process industries.
Bubble dynamics is quite complicated in the field of two-phase hydrodynamics because the interfacial heat and mass transfer is comprehensively affected by various influencing factors. Bubble condensation can be either...
Bubble dynamics is quite complicated in the field of two-phase hydrodynamics because the interfacial heat and mass transfer is comprehensively affected by various influencing factors. Bubble condensation can be either thermally controlled or inertia controlled. Inertia controlled bubble condensation indicates that considerable pressure difference exists between the steam bubble and ambient liquid. In this paper, the inertia controlled steam bubble condensation was simulated using moving particle semi-implicit (MPS) method. The spherical bubble is located in the center of the cylindrical pool which makes the possibility of 2-D axisymmetric computation. The lateral and bottom wall are set to be rigid insulated boundaries and the top is free surface boundary. The pool volume must be large enough to eliminate the effects by pool wall. The initial bubble pressure ranges from 0.48 MPa to 3.98 MPa, and the initial bubble diameter ranges from 2 mm to 5 mm, and the ambient water pressure and temperature is 0.1 MPa and 70 °C, respectively. The bubble dynamics during condensation was investigated and the influences of initial bubble pressure and diameter were obtained. The bubble deformation during condensation is shown in figure 1, and the variations of bubble diameters and pressures during condensation are shown in figures 2 and 3, respectively.
From the analytical model derived earlier [17], analytical expressions for the relative thickness ratio rs of a bi-layer electrolyte and the maximum power density of a fuel cell are developed. Using these expressions,...
详细信息
The solar chimney power plant (SCPP) has been accepted as one of the most promising approaches for future large-scale solar energy applications. This paper reports on a heat transfer model that is used to compare the ...
详细信息
暂无评论