Advanced Materials Research Vols. 614-615

Abstract: MAN Diesel’s 6S50MC-C disel is a two-stroke marine diesel engine. As the boundary conditions of temperature field distribution, the mean temperature and mean heat transfer coefficient are calculated firstly. The coupled heat transfer of piston crown, piston rings and cylinder liner are analyzed. The steady temperature field and the transient heat transfer under starting condition of diesel engine are obtained in ANSYS. Maximum temperature is 413.55°C in the top surface edge of the piston crown. 59.5% of the total heat from high-temperature fuel gas heat is absorbed by the cooling oil. The temperature of piston crown is effectively reduced by shaker cooling. The load of diesel engine should be increased slowly to prevent stress concentration. To reduce the destructive effect, enhancing cooling and warming up the main engine are requested.

Abstract: The temperature distribution of the cyclone was analyzed in the presented work, which was imitated by using RSM turbulence model of software FLUENT. Temperature difference in different regions is less than one centigrade degree with the maximum temperature in the cone part and the minimum temperature in inlet tube and cylinder part of the cyclone, what’s more, the temperature is relatively higher near the wall. The air compression can lead the higher temperature in the lower part, so the cone part has the maximum temperature. The higher temperature near the wall is caused by the friction between the wall and flow.

Abstract: The condenser vacuum influences the steam turbine’s safety and economy. The dirty level of the water side tube and the air accumulation of the steam side affect overall heat transfer coefficient .That make the condenser vacuum low and terminal temperature difference increase. It is a generally interested problem that making a distinction between fouling loss and air accumulation loss for the operating personnel and maintenance person. In this article, we judged the vacuum system work normal or not by comprehensive cleaning curve, and further calculation and curve analysis were done so as to distinguish the affection of the dirty level of the water side tube and the air accumulation of the steam side to overall heat transfer coefficient and terminal temperature difference.

Abstract: A numerical simulation was conducted to investigate the flow characteristics, film cooling effectiveness and aerodynamics loss over flat plate. Three types of shaped holes, separately, cylindrical hole, laterally diffused hole and converging-expanding hole were studied with 35°inclination angle and 0°compound angle. The inlet diameter of the hole in this paper is 12.7 mm, giving a L/D ratio of 3.5 at a mainstream velocity of 20m/s, turbulence intensity 2%, and temperature ratio to cooling jet 1.97, with blowing ratio M equaling to 0.5. Realizable k-ε turbulence model, standard wall function and SIMPLE method for pressure-velocity coupling were used .The coefficients η and ξ were calculated to analyze cooling effectiveness and aerodynamics loss. Both high film cooling effectiveness and low loss are found with laterally diffused hole. While optimizing the hole geometry in film cooling, cooling effectiveness and aerodynamics loss should been considered simultaneously.

Abstract: An asperity model between piston head and cylinder liner had been contained in the simulation of piston secondary motion. A prediction of wear of piston head has been made from the simulation which shows that the contact force of piston head is abnormal. The later engine installed experiment shows that the piston head is worn, which has confirmed this prediction.

Abstract: Free-piston Stirling engine is considered to be the most novel and revolutionary Stirling configuration. Schmidt analysis is used to describe the physical model of free-piston Stirling engine and to drive the formulation about thermodynamic parameters. The performance of free-piston Stirling engine has been analyzed. Finally it made a comparison between analysis calculation, experimental and numerical results.

Abstract: An improved random walk mode is proposed based on fractal geometry and random walk theory to characterize the features of porous channels quantitatively. Three different types of fractal Sierpinski carpet structures are obtained by iterative method. The effective thermal conductivities and fractal dimensions are calculated by finite volume method and statistical fractal algorithm respectively. The influences of porosity and pore distribution on effective thermal conductivity are investigated. Results indicate that, the effective thermal conductivity may be different for various structures with the same porosity, and the direction of porous channels formed by connected pores is the critical factor. The spectral fractal dimension of porous channels dD in the direction of temperature gradient coincides with the effective thermal conductivity of Sierpinski carpet.

Abstract: The numerical simulation for radiant tube heat transferring process of the gas-infrared heated room was finished. By means of numerical calculation, the influences of radiant tube installation height to the indoor temperature and workspace air temperature as well as the heat radiation flux were studied. The results show: The greater of radiant tube surface installation height, The lower of the workspace average temperature, average radiation temperature and radiant tube total heat flux.

Abstract: In view of the highly heat exchanger efficient of heat pipe, two vacuum heat pipes of water and Fe3O4-water were prepared and test system was designed to test the heat transfer efficiency of them when they are within and without magnetic field. The experimental results showed that the heat exchange of heat pipe with magnetic fluid was more efficient than the other one. According to the results and combine the physical properties of two kinds of refrigerant, analyze the heat transfer characteristics of the magnetic fluid in magnetic field.

Abstract: In order to explore the condensed phase whether may promote abnormal heating phenomenon and nuclear reactions occur, as well as how to construct and characterization of condensed phase structure filled with deuterium and the use of exogenous trigger transient change. Some deuterium atoms were charged into metal palladium lattice and reached a certain ratio in a D-Pd gas-solid system under the pressure of PD26J heat energy were released in 8 hours, when loading ratio of deuterium x was 0.12, current 8A, pressure 9×10⁴Pa. Improvement of experiment, that excess heat power 41W and 79.58MJ heat energy, which was corresponding to 1.8×10⁴eV for each palladium atom were released in 83 hours and 17 minutes, when current 7.25A, pressure 9×10⁴Pa. An energy dispersive spectrometer (EDS) revealed that new surface topographical features with concentrations of unexpected elements Ag were detected, which implied that the excess heat might come from a nuclear transmutation reaction.