Sublimation Of Naphthalene Research Articles

Mass Transfer Technique for Investigation of Heat Transfer by Jet-Impingement Systems

The technique of using mass transfer measurements (by sublimation of naphthalene) together with the Chilton–Colburn analogy is shown to be feasible for evaluation of heat transfers from impinging jets. The method is then used to determine heat transfer coefficients at the burner walls in models of jet–impingement furnaces.

The standard enthalpy of sublimation of naphthalene

The standard enthalpy of sublimation of naphthalene has been determined calorimetrically at 298.15 K. The value obtained, (73.00 ± 0.25) kJ mol −1 is in agreement with the accepted value derived from vapour pressure measurements.

Studies on Heat Transfer to Turbulent Jets with Adjacent Boundaries : 1st Report, Flow Development and Mass Transfer in Plane Turbulent Wall Jet

In order to make clear heat transfer to curved turbulent jets by adjacent boundaries, at first the mass transfer of a turbulent wall jet without deflection of the jet center line has been experimentally studied by the following programs using the technique of the sublimation of the sublimation of naphthalene. (a) Mass transfer at the developed region of a wall jet. (b) Mass transfer at the initial region of a wall jet. (c) Mass transfer from the discontinuous naphthalene surface to the developed wall jet. The experimental results are compared with an approximate analytical treatment, generalized to apply for the reattached wall jets to adjacent boundaries.

Studies on Heat Transfer to Turbulent Jets with Adjacent Boundaries : 2nd Report, Mass Transfer to Plane Turbulent Jet Reattached on an Inclined Flat Plate

Heat transfer to plane jet reattached on a flat plate, having an inclination for the plane nozzle, has been studied by the law of analogy from mass transfer, using the technique of sublimation of naphthalene. The flow development on an inclined flat plate depends on shapes of bubble induced due to separation and reattachment. The change of bubble shape occurs roughly at an inclined angle of 30°. Considering such flow field, empirical formulas were derived for the following items. (1) Maximum Sherwood number in reattachment region (2) Mean Sherwood number in separated bubble region (3) Local Sherwood number over the region of reattached wall jet (4) The effect of reattachment by the curved jet on distribution of the local Sherwood numbers.

Stoffübergang und druckverlust an parallel angeströmten stabbündeln in einem grossen bereich von reynolds-zahlen und teilungsverhältnissen

An experimental investigation is reported for smooth rod clusters in parallel flow to the axis in nearly infinite triangular lattice. The ratios of centre-to-centre spacing (pitch) to rod diameter were: 1, 1.02, 1.05, 1.2 and 1.67. For isothermal conditions and constant partial pressure on the wall, the mass transfer by sublimation of Naphthalene, Camphor, Paradichlorbenzene and Thymol in air flow is measured, friction factors are measured, too. The measurements are varied in the ranges 200 < Re < 200000 and 2.2 < Sc < 2·6. The influence of the ratios pitch to rod diameter and the Reynolds-number of the friction coefficient, the average Sherwood-number and the distribution of the local Sherwood-number around the rod circumference is specified. The course of the local Sherwood-number in the mass transfer entrance region with fully developed velocity profile is investigated. A comparison was made both, between the theories of Deissler/Taylor for turbulent flow and Sparrow-Loeffler for laminar flow and with qualified experimental results of other authors. The results are: 1. (1) The friction coefficient in turbulent flow can be presented in form of the Prandtl-Kármán relation and in laminar flow as the Hagen-Poiseuille relation. The empirical coefficients depending on ratio of pitch to rod diameter. 2. (2) The critical Reynolds-number is lower than in tube flow. 3. (3) The analogy based on the Prandtl-Kármán theory between mass and momentum transfer in turbulent and laminar flow is valid for all ratios of pitch to rod diameter. 4. (4) For ratios of pitch to rod diameter between 1 to 1.05 a strong variation, and from 1.05 to 2 a less strong variation of the average Sherwood-number, of the local Sherwood-number around the rod circumference and of friction coefficient can be observed. In greater ratios of pitch to rod diameter, the corresponding sizes do not depend on the ratios of pitch to rod diameter. 5. (5) In turbulent flow the hydraulic entrance length amounts to 20 equivalent diameters, the mass-transfer entrance length with fully developed velocity-profiles takes a dimensionless distance in stream direction of about 5000.

Analogie entre le transfert de chaleur et le transfert de masse par sublimation d'un dépôt de naphtalène

A heat and mass transfer analogy is frequently very useful for the investigation of local exchange Coefficient distributions. Forced sublimation of naphthalene in air is the technicque used here in studying convection phenomena in a bundle of rods lying parallel to the flow. Although this method undoubtedly offers material advantages over heated models it also suffers from the limitation that it cannot represent absolutely similar boundary conditions to those associated with thermal problems ; experience has shown, however, that in the simple case of a circular tube the results obtained are to within 5 per cent of the thermal data, with the mass transfer number D = (h/u) instead of the Margoulis number and the Schmidt number S = (u/rD)) instead of the Prandtl number. Experimental data on the relative variation of mass transfer, coefficients for a bundle of nineteen rods in a circular section duct are discussed and it is found that the transfer coefficients vary very much as the frictional velocities, though generally with slightly greater amplitudes. These results are then used for the boundary conditions in a heat calculation in which the fluid temperatures in each sub-channel are calculated with allowance for heat exchanges taking place throughout the cross-section. Considering the approximations involved and the amount of scatter in the measured comparative heat data this calculation method seems quite satisfactory.

Detection of Molecular Beams by Meams of Electron Bombardment

The most universal detector for molecular beams is an electron bombardment detector But, usually, in this detector molecular beam signal is obscured by the background and noise from the residual gas. By means of beam modulation and lock-in amplification the beam signal can be separated from the background and amplified with the improvement in signal to noise ratio. A detector of this type was constructed in our laboratory and its performance was studied with a molecular beam of naphthalene. The detector is a kind of an ionization gauge. Sensitivity of the detector as a ' vacuum gauge was 2×10-2 A/torr · mA for the residual gas. Beam signal of about 10-2 of the residual background gas signal was measured with S/N ratio of 2-3×102. Ionization efficiency of beam molecules was the order of 10-5 with electron current of 0.1 mA and a signal of 10-12A could be measured with the S/N ratio. of 1. This ion current corresponds to the beam intensity of 1012molecules/ sec.Beam profiles and the dependence of the beam intensity upon the oven temperature were measured. From the latter measurement heat of sublimation of naphthalene was estimated as 18. 6 kcal/mole and 19.8 kcal/mole for two different runs. The values are reasonable compared with the value 18. 8, 18. 9 kcal/mole calculated from the vapor pressure of naphthalene.

MASS TRANSFER THROUGH RAREFIED GAS BETWEEN CONCENTRIC SPHERES

A theoretical analysis of mass transfer under a reduced pressure, especially the transition regime was made on the basis of the gas kinetic theory. Maxwell moment method utilizing the two-sided Maxwellian distribution function proposed by Lees et al. was applied to the mass transfer between two concentric spheres, and the accomodation coefficient was taken into account. The analytical solution with the evaluated accomodation coefficient O.9 agreed well with the experimental results of sublimation of naphthalene performed by the authors.

A profilometric technique for determining local mass-transfer rates: Application to the estimation of local heat-transfer coefficients in a nuclear reactor

A technique is described for determining local mass-transfer rates at a solid boundary by measurements of local changes in the thickness of a volatile (or soluble) surface coating. A probe comprising electromagnetic and pneumatic proximity gauges allows the changes of coating thickness to be measured with an accuracy of ± 6 × 10 −5 in., and it is shown that this permits the accurate measurement of configurational changes small enough to have no significant influence on the motion of the fluid in many flow situations. The technique has been applied to the measurement of local rates of sublimation of naphthalene into an air stream from the surfaces of naphthalene-coated rods incorporated in a replica of the fuel-rod cluster of a gas-cooled nuclear reactor. A comparison of the results with local heat-transfer measurements indicates that the accuracy of the method is at present limited by the difficulty of preparing adherent coatings.

ナフタリン昇華法による熱伝達率の測定

ナフタリン昇華法による熱伝達率の測定

The fine structure of endothelium of large arteries.

Endothelium of large arteries from several species was studied in thin sections with the electron microscope. Before sacrifice, some animals received an intravenous injection of colloidal thorium dioxide which was visualized in the sections. Surface replicas were prepared by carbon evaporation on either frozen-dried endothelium or on endothelium dried by sublimation of naphthalene with which the tissue had been impregnated. Cell boundaries, stained with silver, were observed in sections and also from the surface by stripping off the inner part of the endothelium. In addition to the usual cytoplasmic organelles, the endothelial cells showed certain characteristic features, namely, large invaginated pockets communicating with the arterial lumen, numerous much smaller vesicular structures immediately under the plasma membrane and apparently also communicating with the lumen, and inclusions, into which injected thorium particles were incorporated. Intercellular boundaries appeared as regular double membranes in thin sections, and they were outlined by a double row of silver granules after silver staining. No evidence was obtained of permeation of intracellular spaces by colloidal thorium.