Kinetics of melt crystallization of organic eutectic forming binary mixtures in non-flow systems

doi:10.1016/S0255-2701(00)00113-6

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Kinetics of melt crystallization of organic eutectic forming binary mixtures in non-flow systems

Journal Article•DOI•

Kinetics of melt crystallization of organic eutectic forming binary mixtures in non-flow systems

K.B Radhakrishnan, A.R. Balakrishnan¹•Institutions (1)

Indian Institute of Technology Madras¹

01 Jan 2001-Chemical Engineering and Processing (Elsevier)-Vol. 40, Iss: 1, pp 71-81

TL;DR: In this paper, the effect of subcooling, superheating and the initial concentration of the melt on the crystallization kinetics of binary eutectic forming organic mixtures in non-flow systems with cooling from below for the preferential crystallization of one component alone was studied experimentally.

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Abstract: The kinetics of melt crystallization of binary eutectic forming organic mixtures in non-flow systems with cooling from below for the preferential crystallization of one component alone have been studied experimentally. The effect of subcooling, superheating and the initial concentration of the melt on the crystallization kinetics have been studied. Based on the experimental data, a correlation for the instantaneous height of the crystal (volume fraction of the solidified mass) has been proposed. The experimental results were also analyzed based on a model from the literature, which considered simultaneous heat and mass transport. The analysis shows that in the present experiments, the melt crystal interface was very close to the initial melt composition, i.e. concentration equilibrium was maintained. This is attributed to the very low cooling rates used, even though the thermal diffusivity is much greater than the mass diffusivity of the melt.

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Journal Article•DOI•

Broadband dielectric spectroscopy of a nematic liquid crystal in benzene.

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Shyamal Kumar Kundu¹, Shun Okudaira, Masanori Kosuge, Naoki Shinyashiki, Shin Yagihara - Show less +1 more•Institutions (1)

Tokai University¹

27 Oct 2008-Journal of Chemical Physics

TL;DR: For the first time, the molecular mechanism and structure of liquid crystalline materials as a function of concentration, temperature, and frequency is explained.

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Abstract: Broadband dielectric spectroscopy has been used to analyze the temperature, frequency, and concentration dependences of the molecular dynamics of a nematic liquid crystal (5CB) mixed with the nonpolar solvent benzene. Differential scanning calorimetry measurement has been also performed to confirm the phase transitions of 5CB/benzene mixtures. The phase transition temperatures (crystalline to isotropic phases) thus obtained have been described very accurately from the temperature-dependent relaxation strength, the relaxation time, and the symmetric shape parameter of the relaxation function obtained from the fitting procedure. Two relaxation processes reflecting overall rotations around the short and long molecular axes are observed in both the nematic and isotropic phases. In the crystalline phase, the former process with the longer relaxation time disappeared, and latter process with shorter relaxation time shows a discontinuity at the freezing temperature. The relaxation process with shorter relaxation time obtained in the crystalline phase is larger than that obtained in the nematic phase because of the large restrictions in the crystalline phase. For the first time, we have precisely explained the molecular mechanism and structure of liquid crystalline materials as a function of concentration, temperature, and frequency.

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19 citations

Journal Article•DOI•

A new melt crystallization process for efficient purification of chlorobromobenzene

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Liu Qiong¹, Zhengjie Li¹, Baoshu Liu¹, Hua Sun¹•Institutions (1)

Hebei University of Science and Technology¹

15 Nov 2020-Separation and Purification Technology

TL;DR: In this article, a melt crystallization was carried out to explore the separation and purification process of chlorobromobenzene, and the influences of the cooling rate, final crystallization temperature, and crystal growth time were examined systemically based on the following criteria: the distribution coefficient, crystallization yield and purity.

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7 citations

Journal Article•DOI•

Phase transition and abnormal behavior of a nematic liquid crystal in benzene.

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Shyamal Kumar Kundu¹, Shun Okudaira¹, Masanori Kosuge¹, Naoki Shinyashiki¹, Shin Yagihara¹ - Show less +1 more•Institutions (1)

Tokai University¹

13 Aug 2009-Journal of Physical Chemistry B

TL;DR: Surprisingly, the abnormal behavior of the isotropic phase was observed in LC/benzene mixtures that suggested the presence of local structure in the mixture, which set off the dipole moments along the long axis.

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Abstract: Differential scanning calorimetry and broadband dielectric spectroscopy measurements were performed to investigate the phase transitions in nematic liquid crystal (LC)/benzene mixtures. Noticeable changes of the crystal-isotropic phase transition and the phase transition enthalpy were observed. We also estimated the number of unfreezable benzene molecules from the LC/benzene mixtures. The crystal-isotropic phase transition temperature was described very accurately from the temperature-dependent relaxation strength, the relaxation time, and the symmetric shape parameter obtained from the fitting procedure. Surprisingly, the abnormal behavior of the isotropic phase was observed in LC/benzene mixtures that suggested the presence of local structure in the mixture, which set off the dipole moments along the long axis. The interaction between the LC molecules was also discussed from the tau-beta diagram.

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7 citations

Journal Article•DOI•

Revamping an Existing Aromatics Complex with Simulated Moving-Bed Reactor for p-Xylene Production

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Jonathan C. Gonçalves¹, Alírio E. Rodrigues¹•Institutions (1)

University of Porto¹

01 Dec 2015-Chemical Engineering & Technology

TL;DR: In this article, a simulated moving-bed reactor (SMBR) for the production of p-xylene is studied as part of a proposal to modify an existing aromatics complex in order to increase the output of benzene and xylene.

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Abstract: A simulated moving-bed reactor (SMBR) for the production of p-xylene is studied as part of a proposal to modify an existing aromatics complex in order to increase the production of benzene and p-xylene. The proposed complex includes a single-stage crystallization unit to further purify high p-xylene streams from a selective toluene disproportionation and said SMBR units. Mass balances for two cases are estimated, namely, the current flow of reformate fed to the complex and a twofold flow. Results show significant increases of benzene and p-xylene for both cases compared to the current production of the complex.

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2 citations

Journal Article•DOI•

Behaviour of Ice Crystal Growth in a Vertical Finned Cylindrical Freeze Concentrator

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Amran Nurul Aini¹, Samsuri Shafirah¹, Norzita Ngadi¹, Zaki Yamani Zakaria¹, Jusoh Mazura¹ - Show less +1 more•Institutions (1)

Universiti Teknologi Malaysia¹

01 Nov 2014-Applied Mechanics and Materials

TL;DR: In this article, the authors investigated the behavior of ice crystal growth at two different operating parameters (coolant temperature and circulation time) for progressive freeze concentration (PFC) of glucose solution through a vertical finned crystallizer (VFC).

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Abstract: Behaviours of ice crystal growth at two different operating parameters namely coolant temperature and circulation time were investigated for progressive freeze concentration (PFC) of glucose solution through a vertical finned crystallizer (VFC). Two determinant parameters which are ice production rate (mu), and water recovery (WR) were used to illustrate the behaviours of ice crystal growth in this study. From the result, higher ice production rate (mu) and water recovery (WR) were achieved at lower coolant temperature. On the other hand, longer circulation time resulted in lower ice production rate (mu), but at the same time increased the water recovery (WR). The maximum ice production rate (mu) and water recovery (WR) attained through this study were 1.522 gm-2s-1 and 51.131 %, respectively.

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2 citations

Cites background from "Kinetics of melt crystallization of..."

...According to Radhakrishnan and Balakrishnan [3], the basic characteristic of PFC process is normally described by the rate of crystal growth, in which this rate is mainly determined by heat and mass transfer at solid-liquid interface....
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References

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Journal Article•DOI•

Melting and Solidification of a Pure Metal on a Vertical Wall

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Chie Gau¹, R. Viskanta¹•Institutions (1)

Purdue University¹

01 Feb 1986-Journal of Heat Transfer-transactions of The Asme

TL;DR: Etude experimentale de l'ecoulement de convection naturelle dans la phase liquide and de son influence on le mouvement of l'interface liquide-solide et sur le transfert de chaleur au cours de la fusion and de la solidification de gallium a haute purete sur une paroi verticale as mentioned in this paper.

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Abstract: Etude experimentale de l'ecoulement de convection naturelle dans la phase liquide et de son influence sur le mouvement de l'interface liquide-solide et sur le transfert de chaleur au cours de la fusion et de la solidification de gallium a haute purete sur une paroi verticale

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518 citations

"Kinetics of melt crystallization of..." refers background or methods in this paper

...The correlation has also been compared with the data of Hale and Viskanta [4], who studied the freezing and melting of n-octodecane in a rectangular enclosure (again with Ste*=0 and C0%=0) with slightly better agreement than with the data of Gau and Viskanta [7]....
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...Gau and Viskanta’s [8] experimental data on the solidification of pure gallium on a vertical wall with initial superheat is also shown in Fig....
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...In using the data of Gau and Viskanta [8] with the present...
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...In using the data of Gau and Viskanta [8] with the present correlation, C0% is set equal to 0 (pure substance)....
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...Gau and Viskanta’s [7] experimental data on the solidification of Lipowitz metal (an alloy of Bi, Pb, Sn and Cd) in a rectangular enclosure with no initial superheat and at its eutectic composition (Ste*=0 and Co%=0) is shown in Fig....
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Journal Article•DOI•

Solidification of an alloy from a cooled boundary

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M. Grae Worster¹•Institutions (1)

Massachusetts Institute of Technology¹

01 Jun 1986-Journal of Fluid Mechanics

TL;DR: In this article, a mathematical model for the region of dendritic or cellular growth which often forms during the solidification of alloys is presented, where the model treats the mixed phase (solid and liquid) as a continuum whose properties vary with the local volume fraction of solid.

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Abstract: We Present a mathematical model for the region of dendritic or cellular growth which often forms during the solidification of alloys. The model treats the region of mixed phase (solid and liquid) as a continuum whose properties vary with the local volume fraction of solid. It is assumed that transports of heat and of solute are by diffusion alone, and the model is closed by a condition of marginal equilibrium. Results are obtained for the unidirectional solidification of an alloy from a plane wall. The spatial variations of solid fraction are highly suggestive of the types of morphology that can occur, and a wealth of different structures are found as the physical parameters are varied. Although the model ignores gravity entirely, the results can be applied to the solidification from below of an alloy which is initially less dense than its eutectic. Predictions for the growth rate of the mixed-phase region agree well with existing experimental measurements of ice growing from aqueous salt solutions.

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295 citations

"Kinetics of melt crystallization of..." refers background in this paper

...Huppert and Worster [9] stated that the crystal layer height varied with the square root of the growth time....
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...The parameter g is given by Huppert and Worster [9] as cC0 F(g) 1−F(g) n rmCpm F(emg) + rsCps G(esg) n = rsCps(Tl(C0)−Tw) G(esg) − rmCpm(T0−Tl(C0)) F(emg) (24) where, F(x)=P1/2xex2erfc(x) (25) and G(x)=P1/2xex2erfc(x) (26) The interface concentration is obtained from the following equation F(g)= Ci−C0 C0 (27) and subsequently the interface temperature is obtained from the phase diagram....
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...Worster [5] defined a criterion to avoid supercooling and subsequent linear instabilities at the interface (i.e. non-flat and non-planar interface) ks\ km 1− [1− (l/jCps)(D/as)(1/C0)] (2) where, j is the slope of the liquidus line and C0 is the initial composition of the melt....
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...Furthermore, Worster [5] has pointed out that the bulk temperature and the solute fields are statistically stable to convective motion if the system is cooled at the lower horizontal boundary and if the less dense component is crystallized....
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...In order to use the above solutions due to Huppert and Worster [9], the parameter g was determined from Eq....
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Journal Article•DOI•

Dynamic solidification of a binary melt

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Herbert E. Huppert¹, M. G. Worster²•Institutions (2)

University of Cambridge¹, Massachusetts Institute of Technology²

01 Apr 1985-Nature

TL;DR: The fundamental physics and fluid dynamics of a solidifying two-component system cooled from below is analyzed quantitatively in this paper, where theoretical results for the rate of growth of the solid are in good agreement with experimental measurements on crystallizing aqueous solutions.

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Abstract: The fundamental physics and fluid dynamics of a solidifying two-component system cooled from below is analysed quantitatively Theoretical results for the rate of growth of the solid are in good agreement with experimental measurements on crystallizing aqueous solutions The results are applicable to the solidification of a wide variety of binary alloys

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189 citations

"Kinetics of melt crystallization of..." refers background or methods in this paper

...Huppert and Worster [9] stated that the crystal layer height varied with the square root of the growth time....
[...]
...The interface concentration is obtained from an equation due to Huppert and Worster [9] for (D/a) 1 and is given by 1+ cC0 (Tl(C0)− Tw) n−1 = Ci−C0 C0 (10)...
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...The parameter g is given by Huppert and Worster [9] as cC0 F(g)...
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...In order to use the above solutions due to Huppert and Worster [9], the parameter g was determined from Eq....
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...Huppert and Worster [9] solved these equations and the results are...
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Journal Article•DOI•

Melting and solidification of a metal system in a rectangular cavity

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Chie Gau¹, R. Viskanta¹•Institutions (1)

Purdue University¹

01 Jan 1984-International Journal of Heat and Mass Transfer

TL;DR: In this article, the role of natural convection on solid-liquid interface motion during melting and solidification of Lipowitz metal in a rectangular cavity was studied, and measurements of both temperature distributions and temperature fluctuations were used as a qualitative indication of the natural convective flow regimes and structures of melt during phase transformation.

...read moreread less

112 citations

"Kinetics of melt crystallization of..." refers background or result in this paper

...The correlation has also been compared with the data of Hale and Viskanta [4], who studied the freezing and melting of n-octodecane in a rectangular enclosure (again with Ste*=0 and C0%=0) with slightly better agreement than with the data of Gau and Viskanta [7]....
[...]
...4 between the present data and the data of Hale and Viskanta [4]....
[...]
...Gau and Viskanta’s [8] experimental data on the solidification of pure gallium on a vertical wall with initial superheat is also shown in Fig....
[...]
...The correlation has also been compared with the data of Hale and Viskanta [4], who studied the freezing and melting of n-octodecane in a rectangular enclosure (again with Ste*=0 and C0 %=0) with slightly better agreement than with the data of Gau and Viskanta [7]....
[...]
...In using the data of Gau and Viskanta [8] with the present correlation, C0% is set equal to 0 (pure substance)....
[...]

Journal Article•DOI•

Solid-liquid phase-change heat transfer and interface motion in materials cooled or heated from above or below

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N.W. Hale¹, R. Viskanta¹•Institutions (1)

Purdue University¹

01 Mar 1980-International Journal of Heat and Mass Transfer

TL;DR: In this paper, the phase-change boundary motion of n-octadecane has been studied experimentally and analytically in a rectangular test cell suitable for photographic observations.

...read moreread less

105 citations

"Kinetics of melt crystallization of..." refers result in this paper

...These were compared with the data of Hale and Viskanta [ 4 ], whose experiments were conducted using n-octadecane....
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...Good agreement can be observed in Fig. 4 between the present data and the data of Hale and Viskanta [ 4 ]....
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...The correlation has also been compared with the data of Hale and Viskanta [ 4 ], who studied the freezing and melting of n-octodecane in a rectangular enclosure (again with Ste* 0 and C 0% 0) with slightly better agreement than with the data of Gau and Viskanta [7]....
[...]