Search

The characteristics of flow boiling heat transfer and pressure drop of organic fluid with high saturation temperature in a vertical porous coated tube are experimentally studied in this paper. The experiments are performed at evaporation pressure of 0.16-0.31MPa, mass flux of 390-790kg/m2s, and vapor quality of 0.06-0.58. The variations of heat transfer coefficient and pressure drop with vapor quality are measured and compared to the results of smooth tube. Boiling curves are generated at mass flux of 482 and 675kg/m2s. The experimental results indicate that the heat transfer coefficients of the porous tube are 1.8-3.5 times those of smooth tube, and that the frictional pressure drops of the porous tube are 1.1-2.9 times those of smooth tube. The correlations for heat transfer coefficient and frictional pressure drop are derived, in which the effect of fluid molecular weight is included. The experiments show that significant heat transfer enhancement is accompanied by a little pressure drop penalty, the application of the porous coated tube is promising in the process industries. [ABSTRACT FROM AUTHOR]

In this paper, the spiral water wall system of a 1000MW ultra supercritical tower boiler is simplified as a network system, consisting of circuits, pressure grids and connecting tubes. The establishment of the mathematical model for calculating the mass flux distribution and metal temperature in water wall is based on the mass, momentum and energy conservation equations. The water wall flow distribution and temperature profile of the boiler were computed. The result shows that the differences of outlet temperature and mass flux are small in spiral tube water wall at BMCR, 75%BMCR load and 40%BMCR load. The metal temperatures are all in the allowable ranger. [ABSTRACT FROM AUTHOR]

The shielded slot plate, a repeated structure of high sheared protrusions, is a major component of metallic bipolar plates for the molten carbonate fuel cell (MCFC). In order to increase the efficiency of the MCFC and long-term operation capability, the sheared protrusion should have a relatively large flat contact area. In addition, defects from the forming process such as local thinning should be minimized. In this work, the preform shape in the three-stage forming process that integrates the slitting process, the preforming process, and the final forming process was optimized to minimize the effective plastic strain. In the simulation of the forming process, the ductile fracture criterion was employed to the user material subroutine VUMAT in ABAQUS/Explicit. Steepest descent method was utilized in the design of the forming process to minimize equivalent plastic strain. High sheared protrusions were manufactured without defects from the three-stage forming process using the optimized preform shape. The minimum thickness of one sheared protrusion was increased by 25% over that of the two-stage forming process. The three-stage forming process using the optimized preform shape enables more uniformly distributed deformation and reduces localized deformation. [ABSTRACT FROM AUTHOR]

The rapid change in customer needs and industrial environment has demanded innovations in the manufacturing sector. Metal forming industries have been confronted with new challenges of innovations in products, processes, machines, materials and production systems. From the viewpoints of competitiveness of products, new paradigms are required for innovation in manufacturing, especially in net shape manufacturing. Product innovations are increasingly put under emphasis beyond manufacturing innovations based on the holistic concurrent engineering approach. The presentation covers not only the innovation methodologies, but also the innovation directions in net shape manufacturing. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Inverse problem solving computation was performed for solving PDF (pair distribution function) from simulated data EXAFS based on data FEFF. For a realistic comparison with experimental data, we chose a model of the first sub-shell Mn-0 pair showing the Jahn Teller distortion in crystalline LaMnO3. To restore the Fourier filtering signal distortion, involved in the first sub-shell information isolated from higher shell contents, relevant distortion matching function was computed initially from the proximity model, and iteratively from the prior-guess during consecutive regularization computation. Adaptive computation of EXAFS background correction is an issue of algorithm development, but our preliminary test was performed under the simulated background correction perfectly excluding the higher shell interference. In our numerical result, efficient convergence of iterative solution indicates a self-consistent tendency that a true PDF solution is convinced as a counterpart of genuine chi-data, provided that a background correction function is iteratively solved using an extended algorithm of MEPP (Matched EXAFS PDF Projection) under development. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

Through numerical simulation of inverse problem computation, our new method of EXAFS analysis was tested for a simple structure of copper metal. For a simulation test, we constructed a structural model with all possible paths of single and multiple scattering within 6 Å. Typically, the first-shell PDF (pair distribution function) is computed according to an algebraic equation describing the temperature dependence of specific anharmonic distribution. Through the MEPP (matched EXAFS PDF projection) method — combing iterative regularization and matched correction of Fourier filtering distortion, it is shown that the original function of anharmonic PDF is iteratively solved from the initial proximity model, even approximated in terms of non-realistic sub-shell mixture of anharmonic distribution feature. To remove the problem of extraneous pattern at intermediate PDF solution, we also tested a proper pattern fit on the anharmonic curve formula, resulting in significantly suitable convergence to the true PDF solution. Our simulation results indicate that the projection to true PDF solution is only reachable when the perfect background correction is selected. Our precision EXAFS analysis performance requires manipulating the apparent correlation between the first and second shells using a typical numerical process of first-shell matching Fourier filtering. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

Fe60Ni40 alloys were fabricated by the mechanical alloying process with process periods of 1, 2, 4, 6, 12 and 24 hours, respectively. The formation of alloy and the structural evolution of the alloy were examined by X-ray diffraction and extended X-ray absorption fine structure methods. With increase of alloying time the BCC phase of iron was changed significantly during the mechanical alloying process. The alloying was activated in about 6 hours and completed in about 24 hours. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

In this work we analyzed the local structure of GexSi1-x (x = 0.5 and 0.8) ultra thin film alloys deposited on silicon substrate. The local structural parameters for the thin films were compared to the values for a bulk sample. The coordination numbers for the thin films were similar to the value of a bulk sample but the interatomic distances were different. Also, the use of a germanium solid state detector was important for EXAFS analysis of ultra thin film alloys. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]