Various heat transfer mechanisms which have been previously proposed are analyzed in the light of recent experiments. Evidence is presented in favor of a liquid-vapor exchange mechanism and against the widely accepted "micro-convection" mechanism. The vapor-liquid exchange rnechanism is shown to explain the insensltivity of boiling heat flux to the level of subcooling. A "Reynolds Analogy" for nucleate boiling is presented in some detail. A procedure is given for calculating the superheat at which the liquid bulk velocity ceases to contribute to the heat flux. An expression for the growth of a vapor bubble in a highly superheated liquid is deduced. A method is presented which allows the deduction of correlations for nucleate boiling which give the dependence of heat flux on superheat and system pressure. Two such correlations are presented and results are compared with experiment. It is shown that one correlation yields the heat flux for different liquids varying from water to mercury, without necessitating any change in constant or exponent of the correlation. (auth)

An investigation of trim from the HRP Dump Valve Test Loop revealed that performance improved with increasing poppet hardness. From this it was hypothesized that deformation of softer poppets increased the poppet-seat contact area, thus reducing the closing pressure. The deformation areas of a number of poppets were measured and the closing pressures calculated. A plot of closing pressure against leak rate showed a fair correlation and tends to support the hypothesis. (auth)

A three-stage mass spectrometer that utilizes two consecutive magnetic focusing;lenses of 20-in. radii followed by a 20-in. radius-of-curvature electrostatic analyzer is described. An abundance sensitivity of 1010 was measurcd for this instrument in the low mass region. Application of this instrument to analytical and research problems in the field of mass spectrometry and the results obtained are discussed. (auth)