Applied Mechanics and Materials Vols. 448-453

Abstract: The selection of the cutting wavenumbers within the line-by-line model and the integral method within the narrow band k-distribution model has been discussed. By conducting numbers of computational calculations and contrasting the related results, the fitting formula used to select the cutting wavenumbers of the line-by-line model is obtained. For the k-distribution model, in order to improve computational accuracy when applying the model to various computational conditions, especially when the optical path length is thin, we divide the curve of the reordered absorption coefficient into two parts according to the point where the cumulative distribution function g (k) =0.95 within the narrow band and integrate the curve separately, thus the computational accuracy is significantly improved.

Abstract: Seawater desalination system has been established based on the ocean thermal energy conversion in this paper. Through compared finned tube heat exchanger with round tube heat exchanger obtained the fresh water output at different temperature and flow velocity of the warm and cold sea water. In this system the energy of the warm and cold sea water has been fully utilized, and so improved the economic benefits of the ocean thermal energy conversion.

Abstract: The characteristics of the external heat exchanger (EHE) for a 4 MWth circulation fluidized bed combustor were studied in the present paper. The length, width and height of EHE were 1.5 m, 0.8 m and 9 m, respectively. The circulating ash flow passing the heating surface bed could be controlled by adjusting the fluidizing air flow and the heating transferred from the circulating ash to the cooling water. The ash flow rate passing through the heat transfer bed was from 0.4 to 2.2 kg/s. The ash average temperature was from 500 to 750 °C. And the heat transfer rate between the ash and the cooling water was between 150 and 300 W/(m²·°C). The relationships among the circulating ash temperature, the heat transfer, heat transfer rate, the heat transfer coefficient and the circulating ash flow passing through the heating exchange cell were also presented and could be used for further commercial EHE design.

Abstract: In this paper, three typical working fluids were selected for the near-critical ORC and subcritical ORC. The difference of performance between the near-critical ORC and subcritical ORC was analyzed by establishing the thermodynamic model. The reason for difference was analyzed in terms of the thermophysical properties. The results indicate that the performance of the near-critical ORC is better than the subcritical ORC. The net absorbed heat, net power and efficiency of the near-critical ORC vary slowly with the vapor generation temperature, which means that the near-critical ORC has good off-design performance. The dry working fluid R236fa is best adapted for the near-critical ORC among the three working fluids. The singular performance of the near-critical ORC depends on the properties of latent heat and type of working fluid in near-critical region.

Abstract: Delayed coking coke drum is the core equipment of delayed coking technology, which experiences almost all the thermal and mechanical loadings during operation. In this study, two coke drum finite element models have been created with four material models and the thermal boundary conditions are determined based on the temperature measurement data. Finite element analysis methods known as function loading and multiple steps analysis are used through the simulation. Temperature distributions and temperature variation curves of different nodes are then obtained by finite element heat transfer analysis. Numerical results show that temperature distribution is complex in the transition section and the water cooling stage has the highest temperature change rate.

Abstract: Cooler is an essential part of closed cycle diesel (CCD) system. Based on the main principle of mass and heat transfer of water-air system, the thesis create the cooler model and discretize the calculation domain. The kinematic, heat and mass transfer process is studied based on similarity theory. Experiments on spraying cooler under different working parameters are carried out to verify the model. The result shows that the model can describe the heat and mass transfer process in the cooler and predict the cooling effect.

Abstract: In order to obtain the concentration, temperature and size variations of a bicomponent moving droplet during evaporation process, a mathematic based on multicomponent droplet evaporation model and droplet motion equation was developed to simulate the evaporation characteristic of a binary decane-ethanol droplet at high temperature nitrogen environment. By numerical calculations, the time evolution of internal concentration distribution within droplet was obtained, and the variations of droplet temperature and dimensionless size were analyzed. The numerical results show that: the droplet temperature variation includes transient heating and equilibrium evaporation at atmospheric pressure; while at high pressure environment, the droplet temperature increases gradually till reaches to ambient temperature. The variations of dimensionless droplet size are deviated from the d² law due to the concentration variation during evaporation.

Abstract: Flow and heat transfer characteristics in the microchannel cooling passages with three different types of the MTPV systems are numerically investigated. Reynolds ranged from 100 to 1000 and hydraulic diameter from 0.4mm to 0.8mm. The steady, laminar flow and heat transfer equations are solved in a finite-volume method. The local heat transfer characteristics, thermal resistance, Nusselt numbers, friction factor and pressure losses of the different types are analyzed. A comparison of the heat transfer coefficient, pressure losses and friction factor of the different microchannels are also presented. The heat transfer performance of the rob bundles microchannel is found to be much better than others. However, the rectangular passage has the lowest thermal resistance than the other types of microchannels.

Abstract: To meet different DCS training requirements of thermal staff, while addressing the high cost of purchasing several sets of DCS, this paper presents the general DCS configuration training platform, which is based on Ovation system, could simulate the Symphony, XDPS and other DCS training environments, and complete basic operations such as configuration, compilation, downloading and debugging. This platform gets significant savings in expenses, and provides a new idea for thermal training.

Abstract: Pulverizing system equipped by fan mills uses three medium (ie. low-temperature furnace smoke, high-temperature furnace smoke, hot air) for drying coal, especially in large-scale plants burning lignite. A constantly increasing unit capacity leads to a more complicated design for pulverizing system, with a heavier weight of furnace smoke tube. This paper focuses on a research of water-cooled membrane flue tube instead of traditional inner and outer insulation tube through experiments like changing water side parameters to replace the low-temperature flue pipe from three medium to two medium (ie. adjustable-temperature furnace smoke, hot air). This paper studies heat transfer coefficient of water-cooled furnace smoke pipe at different flow rate and flue gas temperature though a established water-cooled furnace smoke pipe test bed. It is using a certain mathematic method to obtain dimensionless relationship among Nu, Re, Pr and obtain the dimensionless rule equation of water-cooled furnace smoke tube.