Bao Dong Shao

Multi-Objective Optimization Design of Multi-Layer Rectangle Micro-Channel Heat Sink for Single-Phase Flow and Heat Transfer

The purpose of this paper is to optimize the structural sizes of multi-layer rectangle micro-channel heat sink, which has been widely used to cool electronic chip for its high heat transfer coefficient and compact structure. Taking the thermal resistance and the pressure drop as goal functions, a binary-objective optimization model was proposed for the multi-layer rectangle micro-channel heat sink based on Sequential Quadratic Programming (SQP) method. The number of optimized micro-channel in width n1 and that in height n2 are 21 and 7, the width of optimized micro-channel Wc and fin Wf are 340 and 130μm, the height of optimized micro-channel Hc is 415μm, and the corresponding total thermal resistance of the whole micro-channel heat sink is 1.3354 °C/W. The corresponding pressure drop is about 1.3377 Pa. When the velocity of liquid is larger than 0.3 m/s, the effect of change of velocity of liquid on the thermal resistance and pressure drop can be neglected.

Numerical Simulation of Multi-Layer Rectangle Micro-Channel Heat Sink for Single-Phase Flow and Heat Transfer

The single-phase flow and heat transfer for multi-layer rectangle micro-channel heat sink are numerically simulated. During the simulation, Finite Volume Method (FVM) was used to solve Computational Fluid Dynamics (CFD) problem. First order upwind scheme was used to discrete control equations, and semi-implicit method for pressure-linked equations was used to solve discretization equations. The maximum temperature difference is 76.2362 °C, and the total thermal resistance is 0.4765 °C/W, which agrees well with the result of analysis result 0.5145 °C/W. The corresponding pressure drop is about 54.1360 N/m2.

The Numerical Analysis of Ultimate Efficiency for Vertically Loaded Anchors

The purpose of this article is to deepen the understanding and knowing for the limited efficiency of bearing of plate anchors by means of the calculation of the ultimate holding capacity (UPC) of plate anchors with different shapes. In the process of calculation of UPC, the commercial software MARC is employed. The soil is assumed to be elastic-perfect plastic with yield determined by the VON MISES condition. And displacement constraints are imposed and the corresponding ultimate anti-force can be determined. Then the ultimate bearing efficiency of anchor plates with different shapes can be obtained.

Optimization Design the Configuration Sizes of Multi-Layer Rectangle Micro-Channel Heat Sink

The configuration sizes of multi-layer rectangle micro-channel heat sink are optimized, which has been widely used to cool electronic chip for its high heat transfer coefficient and compact structure. Taking the thermal resistance and the pressure drop as goal functions, a binary-objective optimization model was proposed for the multi-layer rectangle micro-channel heat sink based on Sequential Quadratic Programming (SQP) method. The number of optimized micro-channel in width n1 and that in height n2 are 24 and 3, the width of optimized micro-channel Wc and fin Wf are 360 and 55μm, the height of optimized micro-channel Hc is 1000μm, and the corresponding total thermal resistance of the whole micro-channel heat sink is 1.5429 °C/W. The corresponding pressure drop is about 2.3454 Pa. When the velocity of liquid is larger than 0.3 m/s, the effect of change of velocity of liquid on the thermal resistance and pressure drop can be neglected.

Comparison of Surface Heat-Transfer Coefficient of GCr15 Steel Quenched by Clear Water and Nitrogen-Spray Water

In order to simulate the thermal stresses, thermal strains and residual stresses of steel during quenching by numerical means, it is necessary to obtain an accurate boundary condition of temperature field. The explicit finite difference method, nonlinear estimate method and the experimental relation between temperature and time during water and nitrogen-spray water quenching have been used to solve the inverse problem of heat conduction. The relations between surface heat-transfer coefficient in water and nitrogen-spray water quenching and surface temperature of cylinder have been given. In numerical calculation, the thermal physical properties of material were treated as the function of temperature. The results show that the relations between surface heat-transfer coefficient and surface temperature are non-linear during water and nitrogen-spray water quenching, the heat-transfer coefficient is bigger when water quenching than when nitrogen-spray water before 580°C, the heat-transfer coefficient is smaller when water quenching than when nitrogen-spray water after 400°C. The results of calculation coincided with the results of experiment. This method can effectively determine the surface heat-transfer coefficient during water and nitrogen-spray water quenching.

Numerical Simulation and Size Optimization of the Flow Channel of Rectangular Micro-Channel Heat Sink

Because micro-channel has the advantages of small volume, low flow velocity and high efficiency, with the rapid development of miniaturization industry, micro heat sink is widely used. Previous studies have shown that the micro-channel heat transfer performance is mainly determined on its geometric and flow condition, and compared with triangle and trapezoid shape, rectangle structure has better heat transfer performance.Based on the finite element software ANSYS Workbench, micro-channel heat sink with the length of 40mm and different cross-sectional dimension are analyzed numerically, the dimension of micro-channel with smaller pressure drop and high heat transfer is gained. For the optimized model, when a given initial temperature 298K, flow rate of 1.5×10-4kg/s, the substrate give heat flux as 187500 W/m2. The heat flux of 5532W/m2 can be dissipated, the pressure drop is reduced to 230.2Pa, and the heat transfer rate is 5.254W, so this micro-channel heat sink has good working performance.

Martensite Phase Transform during Nitrogen-Spray Water Jet Quenching

Nitrogen-spray water jet quenching is a new kind of quenching, whose cooling velocity can be controlled. Thus different phase can be achieved according requirement, which can improve the characteristic of material. 9SiCr alloy steel was tested during Nitrogen-spray water jet quenching. The continuous cooling curves of 9SiCr under mixture of Nitrogen-spray water quenching for different pressure and mixture ratio of Nitrogen and spray water are obtained. After quenching, the metallographic structures were investigated, in which the uniform martensite was obtained after quenching.

The Investigation of Performance of Gas-Spray Water Quenching

In order to study the performance of gas-spray water quenching, the gas-spray water quenching test to 9SiCr alloy steel was conducted. After quenching , the hardness and metallographic structures were investigated. The results show that the hardness of the specimen was greatly improved, and the inner hardness was a little higher than the outer. Besides, the uniform martensite was obtained after quenching.

Experimental Study on Nitrogen-Spray Water Quenching for 9SiCr

Alloy steel 9SiCr is quenched by a certain proportion of mixture gas of nitrogen and spray water at atmosphere, and the continual cooling curve during quenching is determined, the rigidity of quenched workpiece is measured and the metallographic map is captured. The results show that it can improve the cooling effect of quenching medium on the one hand; on the other hand, it can decrease the deformation and residual stress of workpieces. The results show that the rigidity of quenched workpiece is about 62 (HRC), which is corresponding with the rigidity after oil quenching. Martensite phase transformation occurs at the end of quenching that can be seen from the metallographic map.

Study on Cooling Performance of Eject Quenching by Mixture of Nitrogen-Spray Water

Though gas quenching has several advantages, such as minimal environmental impact, little deformation, low energy cost, clean products, and ability to control the cooling locally and temporally for best product properties, its cooling performance is less than that of oil and water. If gas is mixed with spray water, the mixture will has favorable cooling performance. The cooling performance of eject quenching by mixture of Nitrogen-spray water is studied experimentally. Alloy steel 9SiCr is specimen, and it is quenched by a certain proportion of mixture gas of Nitrogen and spray water under normal pressure and high velocity, and the continual cooling curve is determined. The experimental results show that it can improve the cooling effect of quenching medium on the one hand; on the other hand, it can decrease the deformation and residual stress of specimen. The results also show that cooling performance of the mixture and cooling velocity can be enhanced by increasing gas pressure when the mixture ratio is fixed, and it takes short time to cool to room temperature. The cooling performance of the mixture and cooling velocity can be enhanced by increasing the mixture ratio under same pressure, and it also takes short time to cool to the room temperature. The continual cooling curve is determined, which gives the information of cooling performance of eject quenching by mixture of Nitrogen-spray water under Normal pressure changed with the pressure and the mixture ratio of Nitrogen and spray water.