The soot raise great environmental and health problems. Conventional methods don ' t have such low measurement limits. So in this paper soot's component and size information will be studied in theory and exper...
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Aim: The article presents an analysis of the feasibility of R1234yf and R448A, two new low GWP refrigerants, as alternatives to R404A in the refrigeration system of small high and low-temperature test equipment. Metho...
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Source term identification is very important for the contaminant gas emission event. Thus, it is necessary to study the source parameter estimation method with high computation efficiency, high estimation accuracy and...
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Source term identification is very important for the contaminant gas emission event. Thus, it is necessary to study the source parameter estimation method with high computation efficiency, high estimation accuracy and reasonable confidence interval. Tikhonov regularization method is a potential good tool to identify the source parameters. However, it is invalid for nonlinear inverse problem like gas emission process. 2-step nonlinear and linear PSO （partial swarm optimization）-Tikhonov regularization method proposed previously have estimated the emission source parameters successfully. But there are still some problems in computation efficiency and confidence interval. Hence, a new 1-step nonlinear method combined Tikhonov regularizafion and PSO algorithm with nonlinear forward dispersion model was proposed. First, the method was tested with simulation and experiment cases. The test results showed that 1-step nonlinear hybrid method is able to estimate multiple source parameters with reasonable confidence interval. Then, the estimation performances of different methods were compared with different cases. The estimation values with 1-step nonlinear method were close to that with 2-step nonlinear and linear PSO-Tikhonov regularization method, 1-step nonlinear method even performs better than other two methods in some cases, especially for source strength and downwind distance estimation. Compared with 2-step nonlinear method, 1-step method has higher computation efficiency. On the other hand, the confidence intervals with the method proposed in this paper seem more reasonable than that with other two methods. Finally, single PSO algorithm was compared with 1-step nonlinear PSO-Tikhonov hybrid regularization method. The results showed that the skill scores of 1-step nonlinear hybrid method to estimate source parameters were close to that of single PSO method and even better in some cases. One more important property of 1-step nonlinear PSO-Tikhonov regularization metho
Three-dimensional numerical simulation results are presented for a fin-and-tube heat transfer surface with vortex *** effects of the Reynolds number (from 800 to 2 000) and the attack angle (30° and 45°) of ...
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Three-dimensional numerical simulation results are presented for a fin-and-tube heat transfer surface with vortex *** effects of the Reynolds number (from 800 to 2 000) and the attack angle (30° and 45°) of a delta winglet vortex generator are *** numerical results are analyzed on the basis of the field synergy principle to explain the inherent mechanism of heat transfer enhancement by longitudinal *** secondary flow generated by the vortex generators causes the reduction of the intersection angle between the velocity and fluid temperature *** addition,the computational evaluations indicate that the heat transfer enhancement of delta winglet pairs for an aligned tube bank fin-and-tube surface is more significant than that for a staggered tube bank fin-and-tube *** heat transfer enhancement of the delta winglet pairs with an attack angle of 45° is larger than that with an angle of 30°.The delta winglet pair with an attack angle of 45° leads to an increase in pressure drop,while the delta winglet pair with the 30°angle results in a slight *** heat transfer enhancement under identical pumping power condition for the attack angle of 30° is larger than that for the attack angle of 45°either for staggered or for aligned tube bank arrangement.
The method of characteristic(MOC) was adopted to analyze the check valve-induced water hammer behaviors for a Parallel Pumps Feedwater System(PPFS) during the alternate startup *** motion of check valve disc was simul...
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The method of characteristic(MOC) was adopted to analyze the check valve-induced water hammer behaviors for a Parallel Pumps Feedwater System(PPFS) during the alternate startup *** motion of check valve disc was simulated using inertial valve *** parameters including the pressure oscillation,local flow velocity and slamming of the check valve disc *** been *** results showed that severe slamming between the valve disc and valve seat occurred during the alternate startup of parallel *** induced maximum pressure vibration amplitude is up to 5.0 *** scheme of appending a damping torque to slow down the check valve closing speed was also performed to mitigate of water *** has been numerically approved to be an effective approach.
Numerical simulation of single bubble pool boiling process including transient thermal response of solid wall is performed using the ghost fluid method and the level set method for the sharp interface representation. ...
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Numerical simulation of single bubble pool boiling process including transient thermal response of solid wall is performed using the ghost fluid method and the level set method for the sharp interface representation. The results show that non-physical initial condition in the numerical simulation deeply affects the process of bubble growth, and then multi-cycle simulation is necessary to eliminate its influence. It is shown by the present results that two nucleate criteria, i.e. constant waiting time and constant nucleate superheat, for determining the appearance time for the subsequent bubble lead to the same quasi-steady process of bubble growth if they are matched with each other. A periodically expanding and receding thermal "hollow" can be observed inside solid wall underneath the growing bubble. The recovery of the temperature on the nucleate site and the thermal boundary layer near the heating surface is influenced by transient heat conduction inside solid wall, which can affect evidently bubble thermal dynamics and heat transfer.
Recently, nanotechnology attracts more and more attention in heat transfer system. Many studies have shown that using nanofluid as the working fluid can improve the thermal performance of the heat pipe. In this paper,...
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With the PDPA(Phase Doppler Particle Analyzer) measurement technology,the probability distributions of particle impact and lift-off velocities on bed surface and the particle velocity distributions at different height...
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With the PDPA(Phase Doppler Particle Analyzer) measurement technology,the probability distributions of particle impact and lift-off velocities on bed surface and the particle velocity distributions at different heights are detected in a wind tunnel. The results show that the probability distribution of impact and lift-off velocities of sand grains can be expressed by a log-normal function,and that of impact and lift-off angles complies with an exponential function. The mean impact angle is between 28° and 39°,and the mean lift-off angle ranges from 30° to 44°. The mean lift-off velocity is 0.81-0.9 times the mean impact velocity. The proportion of backward-impacting particles is 0.05-0.11,and that of backward-entrained particles ranges from 0.04 to 0.13. The probability distribution of particle horizontal velocity at 4 mm height is positive skew,the horizontal velocity of particles at 20 mm height varies widely,and the variation of the particle horizontal velocity at 80 mm height is less than that at 20 mm height. The probability distribution of particle vertical velocity at different heights can be described as a normal function.
Solar-driven CO_(2)conversion to chemical fuels in an aqueous solution is restricted not only by photocatalysts but also by mass ***,a regulatable three-phase interface on a porous fixed-bed is constructed for efficie...
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Solar-driven CO_(2)conversion to chemical fuels in an aqueous solution is restricted not only by photocatalysts but also by mass ***,a regulatable three-phase interface on a porous fixed-bed is constructed for efficient C-C coupling in photocatalytic CO_(2)*** photocatalytic results show that∼90%selectivity towards C^(2+)products is obtained by a Cu/Cd_(0.5)Zn_(0.5)S photocatalyst,with a yield of 6.54μmol/h(an irradiation area of 0.785 cm^(2)),while only 0.94μmol/h(an irradiation area of 19.625 cm^(2))is achieved with a commonly used suspension photocatalytic *** find that under the same CO_(2)feed rate,the local CO_(2)concentration in this porous fixed-bed photoreactor is obviously higher than in the suspension *** larger local CO_(2)coverage derived from a higher CO_(2)supply and aggregation enhances the C-C coupling,thereby generating more C^(2+).Even an observable three-phase interface on the porous fixed-bed can be regulated by adjusting the CO_(2)supply,for which the optimal gas inlet rate is 5-10 sccm.
In this study, based on the modification of the pellet cladding mechanical interaction, gap closure process, and the cladding water corrosion model, Fuel Rod Behavior Analysis-ANNULAR (FROBA-ANNULAR) was uprated. The ...
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