The intrinsic viscosities and the slopes of qBP/C against C were estimated for natural rubber, polystyrene, and polyisobutene in hydrocarbon and high mol.wt. alkyl ester solvents. Whereas no correlation could be established between slopes and c.e.d. (cohesiveenergy-densities) balance of the systems, the plot of [?] versus 8, the solubility parameters of the solvents, yielded smooth curve8 similar to those obtained by plotting swelling coefficients against 6. GEE'S method of estimating aP from swelling coefficients, was therefore extended to estimate 6, from viscosity measurements. The present values of 6, are in good agreement with those obtained by swelling measurements. Z US AMM E N F A S S U N G :Die STAUDINGER-Indices (Intrinsic-Viskositaten) und die Neigungen der Kurven der Funktion qep/c = f(c) von natiirlichem Kautschuk, Polystyrol und Polyisobutylen in Kohlenwasserstoffen und hohermolekularen Alkylestern als Losungsmittel wurden bestimmt. Falls keine Beziehung zwischen den Neigungen und dem Kohiisionsenergiedichte-Gleichgewicht der Systeme gefunden wurde, gab die Auftragung von [q] gegen 6, den Loslichkeitsparametern der Losungsmittel, glatte Kurven. Diese sind iihnlich jenen, die man beim Auftragen der Quellungskoeffizienten gegen 6 erhiilt. Deshalb wurde GEES Methode der Bestimmung von 6, aus den Quellungskoeffizienten zur Bestimmung von 8 , aus Viskositltsmessungen erweitert. Die gefuudenen Werte von 6, stimmen gut mit jenen aus Quellungsmessungen erhaltenen uberein.

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Natural convection heat transfer from horizontal solid cylinders has been studied numerically by varying the Rayleigh number in the range of (104≤Ra≤108) and (1010≤Ra≤1013) for both laminar and turbulent flows, respectively. The computations were carried out for three different geometries of three, six, and ten cylinders in a stack arranged in a triangular manner having same characteristic length scale. The present numerical investigation on natural convention is able to capture a very interesting flow pattern and temperature field over the stack of horizontal cylinders which has never been reported in the literature so far. Visualization of plume structure over the horizontal cylinders has also been obtained pictorially in the present work. From the numerical results, it has been observed that the total heat transfer is marginally higher for three-cylinder stack in the laminar range. In contrast, for turbulent flow, starting from Ra = 1010, heat transfer for six-cylinder case is higher but when Ra exceeds 5 × 1011, heat transfer for ten cylinders stack is marginally higher. The average surface Nusselt number is higher for the stack of three cylinders compared to six- and ten-cylinder cases for all range of Ra in both laminar and turbulent regimes. A correlation for the average Nusselt number has also been developed as a function of Rayleigh number which may be useful for researchers and industrial purposes.

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The solubility parameters of polymethyl, -ethyl, -propyl, and -butyl acrylates were estimated by measuring their solution viscosities in a series of alkyl ester solvents. The results agreed well with those obtained by swelling measurements and it was observed that in the homologous series, c.e.d decrease with increase in the alcoholi chain length. ZUS AMME N F ASSU NG:Die Loslichkeitsparameter von Polyacrylsauremethyl-, -athyl-, -propyl-und -butylester wurden mittels Messungen ihrer Losungsviskositaten in einer Reihe von Alkylestern als Losungsmittel bestimmt. Die Ergebnisse stimmen gut mit jenen uberein, die man uber Quellungsmessungen erhielt. Es wurde beobachtet, da13 in einer homologen Reihe die Kohasionsenergiedichten mit zunehmender Kettenlange des Alkohols abnehmen.