Zhongliang Liu

Studies of Static and Dynamic Characteristics of the EDM Machine Based on the ANSYS Workbench

The static and dynamic characteristics of the EDM machine as the main machining unit directly influence the machining accuracy and stability. For a particular type of the EDM machine, the three-dimensional model was built with SolidWorks and the finite element method was employed with the ANSYS workbench to analyze the static and dynamic characteristics of the machine. The results show that the stiffness of the ram and vertical guide (Z-axis) in the Y and Z directions is the weak side of the machine. The analytical method is proved to be effective for the optimization of the machine design.

Study on Optimal Operating Mode of a Thermosyphon Heat Exchanger Unit in a Shopping Center

AbstractIn order to meet the operating requirements during both winter and summer, a thermosyphon heat exchanger unit used to recover energy from the exhaust air needs to be adjusted for its inclination angle by a regulation mechanism. In this paper, the factors that affect the heat transfer efficiency of the thermosyphon heat exchanger was analyzed and the unit practical operating data in a shopping center was studied. The unit optimal operating mode was acquired due to the influence of the unit inclination angle on the temperature effectiveness under a wide temperature change of the outdoor air. In addition, the inclination angle regulation mechanism uses a programmable logic controller (PLC) to control the unit to work at the optimal operating mode. The unit charged with R410A working fluid worked well and was highly effective.

NUMERICAL SIMULATION AND AUXILIARY ENTRAIMENT OF STEAM EJECTORS

The numerical results disclose that there are several locally low-pressure areas inside a well-designed steam ejector. Based on this finding, a so-called auxiliary entrainment technology is proposed to entrain extra entrained steam by connecting these locally low-pressure areas to the suction chamber of the entrained steam. Then numerical simulations are carried out of different auxiliary entrainment schemes. The results reveal that although the auxiliary entraining entrance of the mixing chamber auxiliary entrainment can entrain some low-pressure steam into the ejector, the auxiliary entrainment results in a decrease in the entrained steam mass flow rate of the main entrained steam entrance that is greater than the auxiliary entrainment steam mass flow rate. However, it is also disclosed that the throat auxiliary entrainment does increase the entrainment ratio of the steam ejector. The best result obtained in our simulation is that the ejector entrainment ratio is increased by 3.68%. Therefore, it may be concluded that auxiliary entrainment may be an effective way for improving the performance of steam ejectors, although its feasibility needs proving experimentally.

Numerical Investigation of a Novel Grooved Vapor Chamber

An effective thermal spreader can achieve more uniform heat flux distribution and thus enhance heat dissipation of heat sinks. Vapor chamber is one of highly effective thermal spreaders. In this paper, a novel grooved vapor chamber was designed. The grooved structure of the vapor chamber can improve its axial and radial heat transfer and also can form the capillary loop between condensation and evaporation surfaces. A two dimensional heat and mass transfer model for the grooved vapor chamber is developed. The numerical simulation results show the thickness distribution of liquid film in the grooves is not uniform. The temperature and velocity field in vapor chamber are obtained. The thickness of the liquid film in groove is mainly influenced by pressure of vapor and liquid beside liquid-vapor interface. The thin liquid film in heat source region can enhance the performance of vapor chamber, but if the starting point of liquid film is backward beyond the heat source region, the vapor chamber will dry out easily. The optimal filling ratio should maintain steady thin liquid film in heat source region of vapor chamber. The vapor condenses on whole condensation surface, so the condensation surface achieves great uniform temperature distribution. By comparing the experimental results with numerical simulation results, the reliability of the numerical model can be verified.Copyright