An especial snake SiC pipe was designed for collecting losing heat from furnaces. The three-dimensions thermal, fluid and thermal stress coupled field of heat exchanger was analyzed by using the commercial engineering...An especial snake SiC pipe was designed for collecting losing heat from furnaces. The three-dimensions thermal, fluid and thermal stress coupled field of heat exchanger was analyzed by using the commercial engineering computer package ANSYS. The structural and operational parameters of heat exchanger, the junction between standpipe and snake pipe, the diameter of snake pipe, ratio of thickness to diameter of pipe, velocity of inlet air were optimized for thermal stress. The computed results show that the large thermal stress exits in the SiC, and the stand pipe should be ellipse for the least thermal stress; the optimal ratio of thickness to diameter of pipe is 6, the velocity of inlet air is 25 m/s. The most thermal stress is in inverse proportion to diameter of pipe and velocity of inlet air.展开更多
Multiphase composition design is a strategy for optimizing the microstructures and properties of ceramic materials through mutual inhibition of grain growth, complementary property improvement, or even mutually reinfo...Multiphase composition design is a strategy for optimizing the microstructures and properties of ceramic materials through mutual inhibition of grain growth, complementary property improvement, or even mutually reinforcing effects. More interesting phenomena can be expected if chemical interactions between the constituent phases exist. In this study, spark plasma sintering was used to prepare fully dense dual-phase (Zr,Hf,Ta)B_(2)–(Zr,Hf,Ta)C ceramics from self-synthesized equimolar medium-entropy diboride and carbide powders. The obtained ceramics were composed of two distinct solid solution phases, the Zr-rich diboride phase and the Ta-rich carbide phase, indicating that metal element exchange occurred between the starting equimolar medium-entropy diboride and carbide phases during sintering. Owing to the mutual grain-boundary pinning effect, fine-grained dual-phase ceramics were obtained. The chemical driving force originating from metal element exchange during the sintering process is considered to promote the densification process of the ceramics. The metal element exchange between the medium-entropy diboride and carbide phases significantly increased the Young’s modulus of the dual-phase ceramics. The dual-phase medium-entropy 50 vol% (Zr,Hf,Ta)B_(2)–50 vol% (Zr,Hf,Ta)C ceramics with the smallest grain size exhibited the highest hardness of 22.4±0.2 GPa. It is inferred that optimized comprehensive properties or performance of dual-phase high-entropy or medium-entropy ceramics of diborides and carbides can be achieved by adjusting both the volume content and the metal element composition of the corresponding starting powders of diborides and carbides.展开更多
The CFD-DEM model was developed to simulate solid exchange behavior between two half beds in a bench-scale two-dimensional dual-leg fluidized bed （DL-FB）. Power spectrum density （PSD） analysis was applied to obtai...The CFD-DEM model was developed to simulate solid exchange behavior between two half beds in a bench-scale two-dimensional dual-leg fluidized bed （DL-FB）. Power spectrum density （PSD） analysis was applied to obtain the dominant frequency （F） of the simulated differential particle number （APLR） between the two half beds. Effects of fluidization velocity （u） and bed material inventory （H） on the solid exchange behavior were studied using the CFD-DEM model. Not only snapshots of the simulated particle flow patterns using the OpenGL code but also the dominant frequency of APLR was similar to the experimental results. The simulation results show that higher fluidization velocity assists the exchange of more particles between the two half beds, but the dispersion of clusters on the bed surface into single particles decreases the cluster exchange frequency. A greater bed material inventory results in more intense cluster exchange. The cluster exchange frequency decreases with an increase of the bed material inventory.展开更多
文摘An especial snake SiC pipe was designed for collecting losing heat from furnaces. The three-dimensions thermal, fluid and thermal stress coupled field of heat exchanger was analyzed by using the commercial engineering computer package ANSYS. The structural and operational parameters of heat exchanger, the junction between standpipe and snake pipe, the diameter of snake pipe, ratio of thickness to diameter of pipe, velocity of inlet air were optimized for thermal stress. The computed results show that the large thermal stress exits in the SiC, and the stand pipe should be ellipse for the least thermal stress; the optimal ratio of thickness to diameter of pipe is 6, the velocity of inlet air is 25 m/s. The most thermal stress is in inverse proportion to diameter of pipe and velocity of inlet air.
基金financially supported by the National Natural Science Foundation of China(Nos.52032001,52371023,52332003,and 52211540004)the Fundamental Research Funds for the Central Universities(No.2232024G-07).
文摘Multiphase composition design is a strategy for optimizing the microstructures and properties of ceramic materials through mutual inhibition of grain growth, complementary property improvement, or even mutually reinforcing effects. More interesting phenomena can be expected if chemical interactions between the constituent phases exist. In this study, spark plasma sintering was used to prepare fully dense dual-phase (Zr,Hf,Ta)B_(2)–(Zr,Hf,Ta)C ceramics from self-synthesized equimolar medium-entropy diboride and carbide powders. The obtained ceramics were composed of two distinct solid solution phases, the Zr-rich diboride phase and the Ta-rich carbide phase, indicating that metal element exchange occurred between the starting equimolar medium-entropy diboride and carbide phases during sintering. Owing to the mutual grain-boundary pinning effect, fine-grained dual-phase ceramics were obtained. The chemical driving force originating from metal element exchange during the sintering process is considered to promote the densification process of the ceramics. The metal element exchange between the medium-entropy diboride and carbide phases significantly increased the Young’s modulus of the dual-phase ceramics. The dual-phase medium-entropy 50 vol% (Zr,Hf,Ta)B_(2)–50 vol% (Zr,Hf,Ta)C ceramics with the smallest grain size exhibited the highest hardness of 22.4±0.2 GPa. It is inferred that optimized comprehensive properties or performance of dual-phase high-entropy or medium-entropy ceramics of diborides and carbides can be achieved by adjusting both the volume content and the metal element composition of the corresponding starting powders of diborides and carbides.
基金the support provided by the National Science and Technology Support Program of China(No.2012BAA02B00)
文摘The CFD-DEM model was developed to simulate solid exchange behavior between two half beds in a bench-scale two-dimensional dual-leg fluidized bed （DL-FB）. Power spectrum density （PSD） analysis was applied to obtain the dominant frequency （F） of the simulated differential particle number （APLR） between the two half beds. Effects of fluidization velocity （u） and bed material inventory （H） on the solid exchange behavior were studied using the CFD-DEM model. Not only snapshots of the simulated particle flow patterns using the OpenGL code but also the dominant frequency of APLR was similar to the experimental results. The simulation results show that higher fluidization velocity assists the exchange of more particles between the two half beds, but the dispersion of clusters on the bed surface into single particles decreases the cluster exchange frequency. A greater bed material inventory results in more intense cluster exchange. The cluster exchange frequency decreases with an increase of the bed material inventory.
