4 Matching Results

Search Results

Advanced search parameters have been applied.

Computer modeling of the Morgantown Energy Research Center's fixed bed gasifier. [Theory and development]

Description: This report describes the modeling of a fixed bed stirred gasifier operated by the Morgantown Energy Research Center. One objective of this project was to increase the fundamental understanding of existing gasification processes with mathematical modeling, and thereby assist the Department of Energy in its overall project planning. Models are used for scale-up and optimization purposes and also for extrapolation beyond the normal operating conditions. However, very often, due to the complexity of the real system and the mathematical limitations, certain simplifying assumptions are made. Therefore, before using any model, its assumptions and hence its limitations should be examined and clearly understood. The theory and the development of the model are described. Background information about the MERC's and similar commercial gasifiers is provided.
Date: March 1, 1978
Creator: DeSai, P.R. & Wen, C.Y.
Partner: UNT Libraries Government Documents Department

User's manual for computer simulation and design of the moving-bed coal gasifier. Final report

Description: A computer model of countercurrent moving-bed coal gasifier developed previously has been updated. This manual presents in detail how the computer program developed is used. The unique feature of the present gasifier model is the treatment of the pyrolysis of coal. A semi-empirical approach is taken in the present model to represent the pyrolysis zone of the bed. The pyrolysis reactions are represented by three simple chemical reactions: devolatilization, cracking and carbon deposition with empirically estimated reaction rate constants. The gasification reactions are assumed to be heterogeneous reactions. For fast reactions, diffusion is the rate controlling step while for slow reactions, the surface reactions within the pores of particles is the rate controlling step. Therefore, the rates of gasification reactions used in the model are composed of two terms,the reaction term and the diffusion term. The computer program developed can be used for both simulation and design. It can be used to simulate a gasifier to obtain the gas product distributions and coal conversion and calculate the required bed height for a given carbon conversion. A map of feasible operation ranges can then be constructed for the optimum design of a gasifier. Kinetic parameters for three different kinds of coal are specified in the program. However, the program users may change these parameters according to the guides listed in the manual if the coal used is different. In addition, the reaction rate equations may be replaced if better rate expressions become available. It is important that the user checks the assumptions, the simplifications and the limitations of this computer program before applying in order to assure that the applicability of the model is within the range specified. The scale-up and extrapolation from normal operating conditions should be done with caution and, if possible, verified through additional experimentations.
Date: January 1, 1982
Creator: Wen, C.Y.; Chen, H. & Onozaki, M.
Partner: UNT Libraries Government Documents Department

The Early Optical Brightening in the GRB 071010B

Description: We report the detection of early (60-230 s) optical emission of the gamma-ray burst afterglow of GRB071010B. No significant correlation with the prompt {gamma}-ray emission was found. Our high time-resolution data combining with other measurements within 2 days after the burst indicate that GRB071010B is composed of a weak early brightening ({alpha} {approx} 0.6), probably caused by the peak frequency passing through the optical wavelengths, followed by a decay ({alpha} {approx} -0.51), attributed to continuous energy injection by patchy jets.
Date: April 8, 2008
Creator: Wang, J H; Schwamb, M E; Huang, K Y; Wen, C Y; Zhang, Z W; Wang, S Y et al.
Partner: UNT Libraries Government Documents Department

The TAOS Project Stellar Variability II. Detection of 15 Variable Stars

Description: The Taiwanese-American Occultation Survey (TAOS) project has collected more than a billion photometric measurements since 2005 January. These sky survey data - covering timescales from a fraction of a second to a few hundred days - are a useful source to study stellar variability. A total of 167 star fields, mostly along the ecliptic plane, have been selected for photometric monitoring with the TAOS telescopes. This paper presents our initial analysis of a search for periodic variable stars from the time-series TAOS data on one particular TAOS field, No. 151 (RA = 17{sup h} 30{sup m} 6.67{sup s}, Dec = 27 degrees, 17 minutes, 30 seconds, J2000), which had been observed over 47 epochs in 2005. A total of 81 candidate variables are identified in the 3 square degree field, with magnitudes in the range 8 < R < 16. On the basis of the periodicity and shape of the lightcurves, 32 variables, 18 of which were previously unknown, are classified as RR Lyrae, Cepheid, {delta} Scuti, SX Phonencis, semi-regular and eclipsing binaries.
Date: January 28, 2010
Creator: Mondal, S; Lin, C C; Zhang, Z W; Alcock, C; Axelrod, T; Bianco, F B et al.
Partner: UNT Libraries Government Documents Department