No abstract available

[en] We describe measurements on a-Si films made by adding atomic hydrogen during evaporation of silicon. The material has conductivity comparable to that formed by silane decomposition and is also photoconducting. The photocurrent in these initial experiments is smaller than in the bes silane-produced films

[en] Measurements have been made of the behaviour of the helium film when it is isolated from the bath. The film is measured optically (using an automatic ellipsometer) on a magnetically leviated substrate. Spontaneous evaporation is observed due to the extreme sensitivity of the film to small changes in thermal equilibrium. However, contrary to expectations the evaporation rate is observed to increase as the film thickness decreases. (Auth.)

[en] The condensate-film heat-transfer coefficients on the exterior of a tube under conditions of inundation, vapour shear and the presence of non-condensing gas may be estimated from the equations which are reviewed in the paper, assuming that the conditions surrounding the tube are known. Estimating these conditions in a large condenser is a problem of some complexity and computer programs for determining these conditions are discussed. Methods for estimating rates of condensing inside tubes with stratified or annular flow are reviewed and the changes in pressure drop resulting from condensation are examined. Surfaces for enhanced condensation include those treated or designed to give drop-wise condensation and those shaped to give locally-thin films under the influence of surface tension. The theories underlying both of those methods of enhancement are discussed and the results which can be achieved are reviewed

No abstract available

[en] The problems of heat transmission in laminar film condensation, has been solved by Palacios' theory of dimensional analysis and by using the enlarged dimensional base proposed by us, obtaining in all cases studied condensation on a vertical flat plates, on a vertical cylinder, on a horizontal cylinder and on an inclined flat plate a more precise solution than that obtained by classical dismensional analysis. (Author)

[en] Investigation of heat transfer and friction characteristics had been conducted at atmosphere pressure on B30 horizontal circularly-grooved tube. The experimental result indicates that the circularly-grooved tube can effectively enhance the heat transfer. Within the experimental scope, the total heat transfer coefficient of the circularly-grooved tube can be increased more than 48% compared with that of the smooth tube. Through regression analysis on the experimental data, the experimental correlations for the inside heat transfer coefficient, the condensation heat transfer coefficient on film condensation and the friction coefficient were achieved. (authors)

[en] In the past several decades, experimentalists have proposed a large number of correlations to estimate steam condensation rates in the presence of noncondensable gases in free convection regimes. These correlations are largely empirical, and usually of limited scope, which often leads to their use outside their range of validity, thus incurring the risk of significant errors. In this investigation, we disregard the correlations altogether, and instead go back to their underlying original data, consolidate them in a single set, and propose a generalized correlation that is compatible with the heat and mass transfer analogy. This best-estimate correlation for steam-air mixtures, based on six different investigations and 350 data points, covers two orders of magnitude in the heat transfer coefficient, and is valid for pressures up to 20 bars and steam mass fraction from 0.1 to 0.95. The consolidated raw data are self-consistent and collapse around a curve with a standard deviation of 16 %, thus well within typical experimental error bands. This demonstrates that there is no physical justification for the large deviations (factor 2 or more) observed sometimes when one compares the heat transfer coefficients predicted by different empirical correlations. (author)

[en] An intermittent (periodic) liquid flow rate is examined as a means to enhance local condensation rates in a vertical column where quasi-stagnant vapor-gas mixtures come in direct contact with falling wavy liquid layers. The gas mixture being effectively stagnant is responsible for the major resistance to heat transfer due to its relatively large concentration of noncondensables. Flow intermittency is found to improve heat transfer rates by as much as an order of magnitude. The local condensation heat transfer coefficients depend greatly on both liquid flow mode and liquid flow rate. For the range of frequencies encountered here, the flow cycling frequency seems to have only a minor effect on the transport process, whereas the asymmetry in the intermittency (flow/pause time periods) appears to be more significant. Statistical analysis of the measured local fluctuations of film thickness reveals that condensation is responsible only for slight modifications of the isothermal liquid surface morphology. There is also evidence that the interfacial transport process is aided by increased liquid wave velocities. (author)

[en] In our present work, cBN films were deposited on Si wafers by dc plasma CVD. Experimental results have shown a high growth rate, and the obtained films consisted of almost single cBN under some deposition conditions. (orig.)