Cryogen spray cooling (CSC) can be used in laser dermatology to prevent burning injury of skin during *** uses a short spurt of (40 ~100 ms) on the skin surface before laser irradiation, leading to quick reduction in ...
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Cryogen spray cooling (CSC) can be used in laser dermatology to prevent burning injury of skin during *** uses a short spurt of (40 ~100 ms) on the skin surface before laser irradiation, leading to quick reduction in the skin *** this work, a systematic experimental study was presented to investigate the spray behavior of R134a.
Great quantities of experiments were performed to study the effects of two-phase spray cooling with high heat flux used R22 as refrigerant. A detailed research of the performance of spray cooling at different subcooli...
Great quantities of experiments were performed to study the effects of two-phase spray cooling with high heat flux used R22 as refrigerant. A detailed research of the performance of spray cooling at different subcooling temperature was conducted. The experimental results show that the critical heat flux can reach 272.04W⋅cm−2 with R22 as the working medium, and the corresponding surface temperature is 21.11°C These figures prove that the spray cooling has the advantages of high heat flux as well as lower surface temperature. With increasing overcooling degree of refrigerant at the entrance of nozzle, CHF rises at first and goes to stable then. Which means the CHF can be developed by adding the overcooling of refrigerant. However, the development is limited to a certain degree according to the characteristics of the system; namely, the overmuch increment plays a little role to improve CHF value.
In present work,the gas-solid two-phase flow in a flat-bottom multiple-spouted bed is simulated by the Eulerian-Eulerian *** kinetic theory of granular flow is used to close the equations,and the Johnson & Jac...
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In present work,the gas-solid two-phase flow in a flat-bottom multiple-spouted bed is simulated by the Eulerian-Eulerian *** kinetic theory of granular flow is used to close the equations,and the Johnson & Jackson boundary condition is defined for the solid phase at the wall.
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...
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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...
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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...
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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.
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...
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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.
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...
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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.
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.
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