scholarly journals Broadband acoustic focusing effect based on temperature gradient distribution

2016 ◽  
Vol 65 (4) ◽  
pp. 044303
Author(s):  
Liu Chen ◽  
Sun Hong-Xiang ◽  
Yuan Shou-Qi ◽  
Xia Jian-Ping
Keyword(s):  
Temperature Gradient ◽  
Gradient Distribution ◽  
Focusing Effect ◽  
Acoustic Focusing

scholarly journals Research on the Processing Method of Acoustic Focusing Cavities Based on the Temperature Gradient

2021 ◽  
Vol 11 (12) ◽  
pp. 5737
Author(s):  
Liqun Wu ◽  
Yafei Fan ◽  
Hongcheng Wang ◽  
Linan Zhang ◽  
Yizheng Sheng ◽  
...  
Keyword(s):  
Temperature Gradient ◽  
Theoretical Basis ◽  
Acoustic Pressure ◽  
High Energy ◽  
Processing Method ◽  
Key Factors ◽  
Factors Affecting ◽  
Focusing Effect ◽  
Acoustic Focusing ◽  
Transmission And Reflection

Aiming at the key factors affecting the quality and efficiency of high-energy in-beam machining, this paper studies the broadband acoustic focusing effect based on a discrete temperature gradient. Firstly, the basic theory and mathematical model of temperature-controlled acoustic focusing are established. Secondly, the acoustic focusing effect is achieved by combining the design of metasurfaces and discrete temperature. Then, the acoustic pressure and intensity distribution of acoustic focusing under a discrete temperature gradient are simulated and experimentally studied. The results show that the phase delay of transmission and reflection of acoustic wave covers the 2π interval by changing the temperature in different transmission units, which provides a theoretical basis for the processing of the acoustic focusing cavity.

Optimization of Process Parameters for Unidirectional Solidification of Magnesium Alloy

2013 ◽  
Vol 750 ◽  
pp. 228-231
Author(s):  
Ming Chen ◽  
Xiao Dong Hu ◽  
Hong Yang Zhao ◽  
Dong Ying Ju
Keyword(s):  
Magnesium Alloy ◽  
Temperature Gradient ◽  
Process Parameters ◽  
Solidification Process ◽  
Optical Microscope ◽  
Field Method ◽  
Unidirectional Solidification ◽  
Grain Structure ◽  
Phase Field Method ◽  
Gradient Distribution

The unidirectional solidification process of magnesium alloy needs to establish a specific temperature gradient in casting mold, the direction of crystal growth and heat flow are in the opposite direction in the unidirectional solidification. The process can better control the grain orientation, and eliminate the horizontal grain boundary, so to attain columnar grain structure and excellent performance of magnesium alloy. In this paper, Numerical simulation is carried out by orthogonal experiments in order to obtain the optimal process parameters according to the actual experimental device. Different process parameters are taken into account, including pulling speed, cooling time and cooling intensity. FEM (finite element method) is employed to calculate the temperature field and reached a straight shape of temperature gradient distribution which is conductive to achieve unidirectional solidification microstructure. PFM(phase field method) is adopted into the microstructure calculation. The microstructure obtained by PFM is in agreement with the actual pattern by the optical microscope observation.

scholarly journals Numerical Simulation of Microstructure Evolution in Solidification Process of Ferritic Stainless Steel with Cellular Automaton

Crystals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 309
Author(s):  
Wenli Wang ◽  
Qin Shi ◽  
Xu Zhu ◽  
Yinhua Liu
Keyword(s):  
Temperature Gradient ◽  
Cellular Automaton ◽  
Vibration Frequency ◽  
Coupled Model ◽  
Solidification Process ◽  
Solute Diffusion ◽  
Large Temperature ◽  
Gradient Distribution ◽  
Crystal Nucleus ◽  
Curvature Effects

In order to study the basic principles of vibration-excited liquid metal nucleation technology, a coupled model to connect the temperature field calculated by ANSYS Fluent and the dendritic growth simulated by cellular automaton (CA) algorithm was proposed. A two-dimensional CA model for dendrite growth controlled by solute diffusion and local curvature effects with random zigzag capture rule was developed. The proposed model was applied to simulate the temporal evolution of solidification microstructures under different degrees of surface undercooling and vibration frequency of the crystal nucleus generator conditions. The simulation results showed that the predicted columnar dendrites regions were more developed, the ratio of interior equiaxed dendrite reduced and the size of dendrites increased with the increase of the surface undercooling degrees on the crystal nucleus generator. It was caused by a large temperature gradient formed in the melt. The columnar-to-equiaxed transition (CET) was promoted, and the refined grains and homogenized microstructure were also achieved at the high vibration frequency of the crystal nucleus generator. The influences of the different process parameters on the temperature gradient and cooling rates in the mushy zone were investigated in detail. A lower cooling intensity and a uniform temperature gradient distribution could promote nucleation and refine grains. The present research has guiding significance for the process parameter selection in the actual experimental.

A Preliminary Study for 3D Numerical Simulation of a Through-Plane Temperature Profile in a PEMFC Incorporating Coolant Channels

2012 ◽  
Author(s):  
Mustafa Koz ◽  
Satish G. Kandlikar
Keyword(s):  
Temperature Gradient ◽  
Heat Pipe ◽  
Proton Exchange Membrane ◽  
Numerical Approach ◽  
Gas Diffusion ◽  
Proton Exchange ◽  
Operating Conditions ◽  
Gradient Distribution ◽  
Vapor Flux ◽  
Plane Temperature

In a proton exchange membrane fuel cell (PEMFC), the water removal from the cathode to reactant flow channels is a critical aspect of cell operation. This is an active area of research to understand the transport mechanisms of water. In the available literature, it has been shown that a significant portion of the product water is removed in vapor form by the heat pipe effect through the gas diffusion layer (GDL). The intensity of the heat pipe effect is dependent on the local mean temperature and the through-plane temperature gradient across the GDL. This gradient is spatially affected by the reactant channel-land patterns of the bipolar plate (BPP) and the coolant plate operation. Therefore, the heat pipe effect can have spatial variances depending on the BPP design and cooling method. In order to show the local temperature and through-plane temperature gradient distribution in a GDL, a numerical approach was taken in this work using a commercially available software package, COMSOL Multiphysics® 4.2a. A repetitive cathode section of the PEMFC was modeled in 3D with domains of a GDL and BPP. In-plane thermal conductivity of the GDL was incorporated by using experimentally obtained values from the available literature. By changing the design and operating conditions of the coolant system, the thermal profile and so, the vapor flux across the GDL were investigated. It was found that the increasing temperature non-uniformity on coolant plates leads to less uniform distribution of vapor flux. This is expected to lead to more condensation of water vapor under the lands.

scholarly journals Thermal and Hydrodynamic Characteristics Research of a Tree-Shaped Microchannel Network Thermal Exchanger on the High-Speed Motorized Spindle

2020 ◽  
Author(s):  
Song-Hua Li ◽  
Zi-Chen Zhao ◽  
Yong-Hua Wang ◽  
Wei-Nan Wang
Keyword(s):  
Temperature Gradient ◽  
High Speed ◽  
Cooling Water ◽  
Thermal Dissipation ◽  
Coefficient Of Performance ◽  
Hydrodynamic Characteristics ◽  
Motorized Spindle ◽  
Gradient Distribution ◽  
Wide Range ◽  
Thermal Exchanger

Abstract To improve the thermal dissipation of high-speed motorized spindle, core component of machine tool, according to the construction theory of mammalian circulation and respiratory system, this paper optimizes the distribution of the existing tree-shaped microchannel network structure, changes the thermal exchanger assembly mode, directly as the spindle shell, and make it possible in engineering applications. Considered the conjugate heat transfer between the spindle stator, thermal exchanger, and cooling water, a three-dimensional (3D) fluid thermodynamic model of a tree-shaped microchannel network thermal exchanger and a conventional spiral thermal exchanger are established. Both have the identical heat exchange area and inlet size. The hydrodynamic characteristics, pressure loss, temperature gradient distribution, and coefficient of performance (COP) are compared. The results indicate that the new structure proposed in this paper has more excellent hydrodynamic characteristics, smaller pressure changes, more uniform temperature gradient distribution, and greater COP. The experiment results verify the correctness of the theoretical calculation. It has a wide range of application prospects in thermal problems of high-speed spindle.

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