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- Havlicek, Jaroslav, et al.
(författare)
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Partition chromatography and mass spectrometry of tetrulose and pentuloses
- 1972
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Ingår i: Acta Chemica Scandinavica. ; 26, s. 2205-2215
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Tidskriftsartikel (refereegranskat)abstract
- Partition chromatography on ion exchange resins in aqueous ethanol is an excellent tool for the separation of tetrulose and pentuloses for both analytical and preparative purposes. The analysis of complex mixtures is facilitated by the fact that the ketoses are recorded by both the orcinol and periodate-formaldehyde methods whereas under proper conditions aldoses are only recorded in the orcinol channel. In gas chromatography the trimethylsilylated 3-pentuloses gave rise to only one prominent peak which as revealed by mass spectrometry corresponded to the keto form. Tetrulose and the 2-pentuloses gave two or more peaks. The 1,2-enediol derivative obtained from tetrulose was identical with that recorded for threose.
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- Leckner, Bo G, 1936
(författare)
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Heat transfer in the entrance region with fully develped turbulent flow between parallel plates
- 1972
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Ingår i: International Journal of Heat and Mass Transfer. - 0017-9310. ; 15, s. 35-42
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Tidskriftsartikel (refereegranskat)abstract
- An analysis is made of local heat transfer in a thermal entrance region with a fully developedturbulent velocity profile for various Reynolds and Prandtl numbers. Difference methods are used tosolve the energy equation. The velocity and eddy diffusivities are described by semi-empirical relationships.The geometrical picture is simple: flow between parallel plates, one of which is thermally insulated, theother transmits a known heat flux. Certain comparisons with calculations on laminar flow are made as acheck on the reliability of the numerical method. This also provides an estimate of the influence of turbulencein the various cases and gives a possibility of judging the validity of approximations. Finally a comparisonwith available empirical expressions for fully developed heat transfer is shown
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- Leckner, Bo G, 1936
(författare)
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Spectral and total emissivity of water vapor and carbon dioxide
- 1972
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Ingår i: Combustion and Flame. - 1556-2921 .- 0010-2180. ; 19:1, s. 33-48
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Tidskriftsartikel (refereegranskat)abstract
- Data on the infrared radiation characteristics of carbon dioxide and water vapor in the form of absorption coefficients and line spacings averaged over narrow spectral intervals have been compiled from various sources. These data are to be used in heat transfer calculations from hot gases. In order to investigate the accuracy of the data, the simplest case possible is chosen: a comparison with the total emissivity charts of water vapor and carbon dioxide. It appears however that the charts are not entirely reliable as standards for comparison: it seems probable that Hottel's chart for water vapor gives too low values at temperatures above 900°C and that the partial pressure correction is temperature dependent. With the exception of some regions where judgment is difficult, the calculations using spectral data seem to represent total emissivities with a maximum error which is estimated to around 10%. Sources of error in the spectral data and in Hottel's total emissivity charts are discussed. Total emissivity charts, pressure and overlap corrections based on calculations with spectral data are presented.
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