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Selected AbstractsErrors of kinematic wave and diffusion wave approximations for time-independent flows with infiltration and momentum exchange includedHYDROLOGICAL PROCESSES, Issue 9 2005V. P. Singh Abstract Error equations for kinematic wave and diffusion wave approximations were derived for time-independent flows on infiltrating planes and channels under one upstream boundary and two downstream boundary conditions: zero flow at the upstream boundary, and critical flow depth and zero depth gradient at the downstream boundary. These equations specify error in the flow hydrograph as a function of space. The diffusion wave approximation was found to be in excellent agreement with the dynamic wave approximation, with errors below 2% for values of KF (e.g. KF , 7·5), where K is the kinematic wave number and F is the Froude number. Even for small values of KF (e.g. KF = 2·5), the errors were typically less than 3%. The accuracy of the diffusive approximation was greatly influenced by the downstream boundary condition. For critical flow depth downstream boundary condition, the error of the kinematic wave approximation was found to be less than 10% for KF , 7·5 and greater than 20% for smaller values of KF. This error increased with strong downstream boundary control. The analytical solution of the diffusion wave approximation is adequate only for small values of K. Copyright © 2005 John Wiley & Sons, Ltd. [source] Computational study of a novel continuous solar adsorption chiller: performance prediction and adsorbent selectionINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 10 2007Evan Voyiatzis Abstract A novel solar adsorption chiller intended for domestic use is presented. The chiller can be integrated with existing solar systems based on flat plate collectors, and, contrary to commercial chillers, it operates continuously. A detailed analysis of both the simple and the heat-integrated cycle is carried out so as to select the optimal adsorbent and operating conditions. The employed integral thermodynamic model takes into account the inert masses that limit the performance of the chiller, such as the metal frame, the thermo-fluid, and the non-adsorbed steam, by introducing heat capacity effects. Given the adsorption equilibrium data, the energy balances, the performance, and the useful thermal loads of the system can be calculated at any operating conditions. The results indicate that silica gel Type A is a more efficient adsorbent compared to silica gel Type RD or Type 3A. Furthermore, the total porosity has a slight effect on system performance, while optimal operation can be achieved when the condenser temperature is less than 326 K and the evaporator temperature greater than 280 K. Copyright © 2006 John Wiley & Sons, Ltd. [source] In situ Raman and optical microscopy of the relaxation behavior of amorphous ices under pressureJOURNAL OF RAMAN SPECTROSCOPY, Issue 6 2010Yukihiro Yoshimura Abstract The transformation of low-density amorphous (LDA) ice produced from high-density amorphous (HDA) ice was studied up to 400 MPa as a function of temperature by in situ Raman spectroscopy and optical microscopy. Changes in these amorphous states of H2O were directly tracked without using emulsions to just above the crystallization temperature Tx. The spectra show significant changes occurring above ,125 K. The results are compared with data reported for the relaxation behavior of HDA, to form what we call relaxed HDA, or rHDA. We find a close connection with expanded HDA (eHDA), which is reported to exist as another metastable form in this P,T region. The observation of this temperature-induced LDA transition under pressure complements the previously observed pressure-induced reversible transition between LDA and HDA at 120,140 K. Copyright © 2009 John Wiley & Sons, Ltd. [source] Raman spectroscopy of dimethyl sulphoxide and deuterated dimethyl sulphoxide at 298 and 77 KJOURNAL OF RAMAN SPECTROSCOPY, Issue 2 2002Wayde N. Martens Raman spectroscopy was used to determine the molecular behaviour of DMSO and DMSO- d6, and to compare it with that of DMSO in DMSO-intercalated kaolinites. For DMSO at 298 K two bands are observed at 2994 and 2913 cm,1 and are assigned to the antisymmetric and symmetric CH stretching modes. At 77 K the degeneracy of these bands is lost. Bands are now observed as antisymmetric bands at 3001, 2995 and 2988 cm,1 and symmetric bands at 2923, 2909 and 2885 cm,1, respectively. For the DMSO-intercalated low-defect kaolinite, the 2913 cm,1 band resolves into five component bands at 2882, 2907, 2917, 2920 and 2937 cm,1. The CD antisymmetric and symmetric stretching modes in the 298 K spectrum are found at 2250 and 2125 cm,1, respectively. Both bands show some asymmetry and further bands may be resolved at 2256 and 2244 cm,1 in the antisymmetric stretching region and at 2118 cm,1 in the symmetric stretching region. The spectra of the SO stretching region of DMSO and DMSO- d6 are complex with a band profile centred at 1050 cm,1. Three bands are curve resolved at 1058, 1042 and 1026 cm,1 attributed to the unassociated monomer and the out-of-phase and the in-phase vibrations of the dimer, respectively. Upon cooling to liquid nitrogen temperature, these three bands are observed at 1057, 1038 and 1019 cm,1. The spectra of the SO stretching region of DMSO- d6 are more complex because of the overlap of the DCD deformation modes with the SO stretching modes. The antisymmetric and symmetric stretching CS modes of DMSO are observed at 698 and 667 cm,1, shifting at 77 K to 705 and 672 cm,1. It is concluded that the structure of DMSO in DMSO-intercalated kaolinite is different from those of both liquid DMSO at 298 K and solid DMSO measured at 77 K. Copyright © 2002 John Wiley & Sons, Ltd. [source] Experimental study on gasification characteristics and slagging behavior of Chinese typical high ash fusion temperature coal in lab scale downflow gasifierASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2010Xiaojiang Wu Abstract In order to extend the applicability of entrained flow gasification technology by using Chinese high ash fusion temperature (AFT) coal with dry ash extraction, gasification characteristics and slagging behavior of Chinese high AFT coal were studied in a lab scale downflow gasifier. The results showed that under this experimental condition, the optimum temperature window which is suitable for dry ash extraction with high AFT coal ranges from 1573 to 1623 K, as well as the corresponding optimum O2/coal mass ratio ranges from 0.93 to 1.13. The cold gas efficiency and carbon conversion are around 42 and 90%, respectively in this experiment. The slag on the bottom of the gasifier and in the cyclone existed, on the whole, as solid except that some small parts were melted with several micrometers in diameter, while the slag in the bag filter had remained unmelted when continue operating at an optimum condition for 1.5 h. Due to the small percentage of melted parts in the slag, the tendency of plugging is small and the problems of plugging can be avoided at the exit of gasifier by gasifying Chinese high AFT coal at around 1623 K. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] | |||||||||||||