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51.
Experiments have been carried out to determine heat transfer rates from a continuously moving belt to an air jet impinging normally. The parameters that were varied included the jet velocity (4 < VN < 40 m/s), the jet width (4.8 < B < 19 mm), the nozzle-to-plate distance (3 < H/2B < 11) and the belt speed (0. 15 < VB < 5. 5 m/s). An infrared thermometer was used for the measurement of temperature of the moving belt. The average heat transfer coefficients increase with belt speed steeply initially to a maximum value and then remain almost constant for all higher belt speeds. The maximum heat transfer coefficients are about 1.5 to 2.0 times higher than those predicted for the stationary surface. The present data on continuously surface in still air and in impinging jet flow are well compared with the data on rotating cylinders reported in the literature.
Nomenclature A Heat transfer area - B Width of the nozzle - D Diameter of the cylinder or equivalent diameter of the flat surface (D=L/) - k Thermal conductivity - Gr Grashof number - h Heat transfer coefficient - H Height of the nozzle from the surface - i Number of nozzles - L Heat transfer length of a flat surface - NuD Nusselt number hD/k - ReDB Belt Reynoldsnumber, DVB/ - ReDN Nozzle Reynolds number, DVN/ - ReSN Nozzle Reynolds number, SVN/ - S Hydraulic diameter of the nozzle, 2B - VB Belt velocity or circumferential velocity of a cylinder - VN Nozzle celocity - Kinematic viscosity 相似文献
Wärmeübergang zwischen einem senkrecht auftreffenden Strahl und einer bewegten Oberfläche
Zusammenfassung Experimentell bestimmte Wärmeübergangskoeffizienten für Düsengeschwindigkeiten zwischen 4 m/s und 40 m/s, sowie Düsenbreiten zwischen 4,8 mm und 19 mm lagen bei Bandgeschwindigkeiten zwischen 0, 15 m/s bis 5, 5 m/s ca. 50 % bis 100 % höher als bei unbewegtem Band. Die gemessenen Daten bei bewegtem wie bei unbewegtem Band schließen gut an bekannte Werte aus der Literatur an.
Nomenclature A Heat transfer area - B Width of the nozzle - D Diameter of the cylinder or equivalent diameter of the flat surface (D=L/) - k Thermal conductivity - Gr Grashof number - h Heat transfer coefficient - H Height of the nozzle from the surface - i Number of nozzles - L Heat transfer length of a flat surface - NuD Nusselt number hD/k - ReDB Belt Reynoldsnumber, DVB/ - ReDN Nozzle Reynolds number, DVN/ - ReSN Nozzle Reynolds number, SVN/ - S Hydraulic diameter of the nozzle, 2B - VB Belt velocity or circumferential velocity of a cylinder - VN Nozzle celocity - Kinematic viscosity 相似文献
52.
Ahyi AC Cao H Raju PK Uberall H 《The Journal of the Acoustical Society of America》2005,118(1):124-128
We consider evacuated thin semi-infinite shells immersed in a fluid, which may be either of cylindrical shape with a hemispherical shell endcap, or formed two-dimensionally by semi-infinite parallel plates joined together by a semi-cylinder. The connected shell portions are joined in a manner to satisfy continuity but with a discontinuous radius of curvature. Acoustic waves are considered incident along the axis of symmetry (say the z axis) onto the curved portion of the shell, where they, at the critical angle of coincidence, generate Lamb and Stoneley-type waves in the shell. Computations were carried out using a code developed by Cao et al. [Chinese J. Acoust. 14, 317 (1995)] and was used in order to computationally visualize the waves in the fluid that have been re-radiated by the shell waves a the critical angle. The frequency range was below that of the lowest Lamb wave, and only the A0 wave (and partly the S0 wave) was observed to re-radiate into the fluid under our assumptions. The results will be compared to experimental results in which the re-radiated waves are optically visualized by the Schardin-Cranz schlieren method. 相似文献
53.
54.
An effort has been made for obtaining the anharmonic properties of rocksalt structure solids starting from primary physical parameters viz. nearest-neighbor distance and hardness parameter assuming long- and short-range potentials at elevated temperatures. The elastic energy density for a deformed crystal can be expanded as power series of strains for obtaining coefficients of quadratic, cubic and quartic terms which are known as the second-, third- and fourth-order elastic constants, respectively. When the values of the higher-order elastic constants are known for a crystal, many of the anharmonic properties of the crystal can be treated within the limit of the continuum approximation in a quantitative manner. In this study, higher-order elastic constants are computed up to their melting temperature for rocksalt structure solids, which are alkali cyanides, sodium and potassium halides. The first order pressure derivatives of second- and third-order elastic constants, the second-order pressure derivatives of second-order elastic constants and partial contractions are also evaluated at different temperatures for these substances. The results thus obtained are compared with experimental data and found in well agreement with present values. 相似文献
55.
Raju Suresh Kumar Stephen Michael Rajesh Subbu Perumal Perumal Yogeeswari Dharmarajan Sriram 《Tetrahedron: Asymmetry》2010,21(11-12):1315-1327
Enantiomerically pure (R)-(1-phenylethyl)-3,5-bis[(E)-arylmethylidene]tetrahydro-4(1H)-pyridinones were synthesized for the first time, and their 1,3-dipolar cycloaddition with nitrile oxides affording di- and trispiroheterocycles regio- and stereoselectively in moderate yields was investigated. These compounds were evaluated against Mycobacterium tuberculosis H37Rv (MTB) and multi-drug-resistant M. tuberculosis (MDR-TB). Among the compounds screened, the dispiroheterocycle, namely, (5R,6R,10S)-3,9-bis(4-chlorophenyl)-10-(2,4-dichlorophenyl)-14-[(E)-(2,4-dichlorophenyl)methylidene]-12-[(R)-1-phenylethyl]-1,4,7-trioxa-2,8,12-tri-azadispiro[4.0.4.4]tetradeca-2,8-diene 5m was found to possess the maximum activity with MIC of 0.49 μM against MTB, being 9.6 and 15.6 times more potent than ciprofloxacin and ethambutol, respectively. Against MDR-TB, 5m displayed maximum activity with an MIC of 0.49 μM, with it thus being more active than rifampicin, isoniazid, ciprofloxacin and ethambutol by 7.8, 23, 77 and 124 times, respectively. 相似文献
56.
C. Yohannan Panicker Hema Tresa Varghese K. Madhusoodanan Pillai Y. Sheena Mary K. Raju T.K. Manojkumar Anna Bielenica Christian Van Alsenoy 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2010,75(5):1559-1565
Fourier-transform-Raman and infrared spectrum of 4-azatricyclo [5.2.2.02,6] undecane-3,5,8-trione were recorded and analyzed. The vibrational wavenumbers were examined theoretically using the Gaussian03 set of quantum chemistry codes, and the normal modes were assigned by potential energy distribution (PED) calculations. The first hyperpolarizability, predicted infrared intensities and Raman activities are reported. The calculated first hyperpolarizability is comparable with reported values of similar structures which makes this compound an attractive object for future studies of nonlinear optics. Optimized geometrical parameters of the compound are in agreement with similar reported structures. The red shift of the NH stretching wavenumber in the infrared spectrum from the computational wavenumber indicates the weakening of NH bond. 相似文献
57.
R Srinivasan V Sankaranarayanan N P Raju S Natarajan U V Varadaraju G V Subba Rao 《Pramana》1987,29(2):L225-L230
The absolute thermopower of single phase YBa2Cu3O7 and Y0.8Er0.2Ba2Cu3O7 has been measured in the range 250 K to the superconducting transition temperature. It is found that these compounds show
a large enhancement of thermopower in the range 150 K down toT
c. This enhancement shows a steep exponential drop as the temperature increases from the transition temperature. The temperature
variation of the enhancement is too steep to be accounted for by electron-phonon or electron-local structural excitation mechanisms. 相似文献
58.
An efficient synthesis of the title compound by Diels-Alder cycloaddition of spiro(4.2) heptadiene with p-benzoquinone followed by photochemical ring closure is described. 相似文献
59.
G K Raju K Venkataramaniah M S Prasad K Narasimhamurty V A Narasimhamurty 《Pramana》1986,26(4):327-335
Differential incoherent scattering cross-section ratios of 279.2 keV photons by zirconium, tin, tantalum, lead and uranium
elements are experimentally determined by comparing the peak areas under the degraded photon energy with that of an equivalent
aluminium foil employing a high resolution 35 c.c. coaxial Ge(Li) detector. Studies have been made in single configuration
in an angular range of 20° to 115°. The results are compared with theoretical values obtained from the non-relativistichfs model of Hubbell and co-workers. The cross-section ratios decrease as the atomic number increases for a given scattering
angle. 相似文献
60.
J.S. Yadav B.V. Subba Reddy T. Srinivasa Rao K. Bhavani A. Raju 《Tetrahedron letters》2010,51(19):2622-4577
The vinyl arenes undergo smooth hydroalkylation with 1,3-diketones in the presence of 10 mol % of iodine to afford phenethyl diketones and ketoesters in good yields in short reaction times. The use of inexpensive and readily available molecular iodine makes this method quite simple, more convenient and practical. 相似文献