Advanced Materials Research Vols. 383-390

Abstract: Heat transfer and fluid flow on the air side for heat exchanger in the air conditioning system are numerically simulated by FLUENT commercial software. Numerical analysis is conducted on the plate louver fin, the sinusoid louver fin and the leaf louver fin when the inlet velocity rang is from 2m/s to 7m/s. Heat transfer factor and friction coefficient are respectively fitted with the Reynolds number by the correlation. The sinusoid louver fin is found to have the best comprehensive heat transfer performance. Not only the leaf louver fin’s comprehensive heat transfer performance is good, but also its pressure drop loss is 28.1%~38.8% lower than that of plate louver fin

Abstract: Wind turbine towers are belonging to towering cylinder shell structures, which are easy to appear buckling instability under wind or other complicated loads, and on which integral elastic-plastic buckling analyses have great theoretical and practical significances. This paper used large deflection nonlinear pre-buckling and Koiter initial post-buckling theories, and adopted the finite element scheme of updated integration algorithm and LDC nonlinear solution method, then analyzed the linear buckling, elastic-plastic static buckling, and post-buckling response of the towers with initial imperfections in different location and size. It has obtained that: 1) the critical load of towers with elastic-plastic buckling is much smaller than it with elastic buckling; 2) gravity has certain influence on the critical buckling load; 3) the critical buckling load is insensitive to initial imperfections, meanwhile the imperfections which located on the top or the bottom of the tower are inferior for the stability of tower.

Abstract: Based on the existing quality problems of external wall insulation system, a new external wall insulation system was developed through the rational use of closed air layer’s thermal insulation performance. Considering three kinds of ways of heat transfer-- convection, conduction and radiation and using the coefficient of air equivalent thermal conductivity to obtain the thermal resistance in the air layer, compared with the thermal resistance at different thicknesses in the new system using polyurethane and polystyrene board of insulation material with two different thicknesses, the authors can get the most optimal model. This paper takes the extreme value of indoor and outdoor temperature in summer as the temperature loads of this model and uses ANSYS simulation to obtain its heat flow density, gradient and temperature field, and in the meanwhile, undertakes a comparison with the present form of external wall insulation in the new code. Data indicates that in the same index of energy saving, this system can not only meet the needs of the code, but also reduce the requirement of heat insulator, as well as greatly improve anti-cracking and waterproofing ability. Thus, the new system follows the direction of the development in this field.

Abstract: To achieve the operational efficiency maximization of ultrasonic motor system, this paper analyzes optimum control of the ultrasonic motor system’s efficiency including driving circuit, while the speed closed-loop control performance is ensured. Based on regulating characteristics of open-loop speed control and fuzzy control, two optimum control methods for regulating the changing step-length of driving voltage amplitude, to shorten the elapsed time of efficiency optimization process and to improve the general operational efficiency of motor system and the speed closed-loop control performance, are also analyzed. The effectiveness of the methods mentioned in this paper are reflected using experiments.

Abstract: A laboratory water medium fluidized separator (WMFS), which is 0.06 m in diameter and 1.5 m high, was designed based on fluidization technique and the principle of hindered settling in hydrodynamics. Then the separation principle of WMFS and the construction of the separation system were introduced. The coarse slime as feed is fluidized by upstream, and is separated according to the different settling velocities (terminal velocities) of the coarse slime in WMFS. The water flow pattern in WMFS was simulated by using CFD software, and the data were analyzed in theory. Finally, the experiment results show that the fluidization technology can be efficiently used in beneficiating coarse slime of -1mm+0.25mm with an Ep value of 0.074.

Abstract: This paper presents a new intelligent control method which can lower the energy consumption and the pollution risk of electric bicycles. Lowering the energy consumption depends on improving the efficiency of energy transformation, and lowering the pollution risk depends on prolonging the service life of battery. Firstly, we organizes the acceleration model, then quantitative analysis are given to show the relationship between transient current and acceleration time, and the method of lowering the transient current during acceleration is given. Secondly, we determine the speed of motor when it is working at peak efficiency, at which speed the PID control algorithm is used to make the electric bicycles working. This method has been carried out on ARM processor.

Abstract: Based on the method of CFD, a study on the structure parameters that affect the performance of chevron-type corrugated plate were carried out by simulating with the CFD software Fluent. The impact on flow and heat transfer performance were compared in different plate arrangement forms, different corrugation angles, corrugation depths and corrugation spacing for periodic boundary condition. The results show that heat transfer can be enhanced by staggering the plates. Heat transfer performance is about 1.444 times as corrugation angel is 60° to that of 30° while friction factor is 6.97 times as the angel is 70° to that of 30°. Comprehensive performance is higher at a small corrugation angel. When the ratio of corrugation length to depth is less than 3.0, skin friction factor increases with the increasing of depth, the dimple corrugated plate is about 59.2% and 58.7% higher than the common one on heat transfer and friction factor respectively.

Abstract: Based on the theory analysis of electromagnetic shielding mechanism and structure design, a woven fabric with stainless steel core-spun yarns is selected. Several sets of shielding clothes with variable structure parameters are designed and manufactured through orthogonal experiment method. An experimental platform has been set up to measure the shielding efficiency of the shielding clothes in key parts. With direct and variance analysis identify the significant structure parameters which influence the shielding performance, so as to provide a theory basis for the optimization structure design of electromagnetic shielding clothes.

Abstract: Pure heat conversion coefficient, which is one important parameter for the advance boiling water reactor nuclear power unit, is defined, and the coefficient reflects energy grade values of heaters. According to the structural characteristics of the thermodynamic system of the advanced boiling water reactor nuclear power plant, four sorts of auxiliary steam-water components are categorized. Via strict deduction and demonstration, the general matrix of the coefficient is deduced, so the thermal economic analysis of advance boiling water reactor nuclear power unit can be done with one of extraction steam efficiency. In this way, a new method of thermal economic quantitative analysis for this unit is offered.

Abstract: Loading rate has an effect on the low-cycle fatigue of the stud shear connector. A reasonable test have been used for the study, the results show that, number of cycle and the maximum slip are obviously different at the rate of 1Hz, 3Hz, 5Hz, but the difference are not in linear with the rate. Moreover, the fitting parameters of the Load-Slip curves follow certain laws.