Crystallization of ethylene–octene copolymers at high cooling rates

The modelling of the correlation between pressure, specific volume and temperature (pvT) of polymers is highly important for applications in the polymer processing of semi-crystalline thermoplastics, especially in injection moulding. In injection moulding, the polymer experiences a wide range of cooling rates, for example, 60 °C/min near the centre of the part and up to 3000 °C/min near the mould walls. The cooling rate has a high influence on the pvT behaviour, as was shown in the continuous two-domain pvT model (CTD). This work examined the Hoffman–Lauritzen nucleation and growth theory used in the modified Hammami model for extremely high cooling rates (up to 300,000 °C/min) by means of Flash differential scanning calorimeter (DSC) measurements. The results were compared to those of the empirical continuous two-domain pvT model. It is shown that the Hammami model is not suitable to predict the crystallisation kinetics of polypropylene at cooling rates above 600 °C/min, but that the continuous two-domain pvT model is well able to predict crystallisation temperatures at high cooling rates.

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Intentionally Deadheading SAGD ESPs - An Unconventional Approach to Improve Run Life

10.2118/204521-ms ◽

2021 ◽

Author(s):

J. Daine Studer ◽

Jesus E. Chacin ◽

Roger Walters ◽

Hoai Ann Nguyen

Keyword(s):

Fiber Optics ◽

Field Tests ◽

Field Trials ◽

Base Line ◽

Cooling Rates ◽

Temperature Changes ◽

Plant Maintenance ◽

High Cooling Rates ◽

Log Normal ◽

Log Normal Distribution

Abstract SAGD ESPs run at the highest motor temperatures current technology allows. However, they cool very rapidly when shutdown. High cooling rates promote motor oil volumetric contraction, eventually leading to wellbore fluid ingress and short-circuited motors. The Paper presents successful field tests designed to decrease ESP cooling rates by inducing controlled deadheads, rather than shutting down ESPs. Various extended deadhead field trials (up to 70+ days duration) validated the approach, while confirming that no deadhead related ESP damage was induced. ESP temperature changes were measured using fiber optics strings installed as part of the usual completion in 60+ wells, during a four week-long field-wide plant maintenance turn-around. While cooling rates varied somewhat from well to well, they all showed very similar behavior and were very well fitted with a log-normal distribution, R2factor > 95%. Most ESP temperatures decreased between 50°C to 120°C in a week. This data was used as a general baseline to support the deadheading field trials. An ESP was fitted internally with an RTD at the base of the motor and externally with a clamped fiber optics string. This ESP was operated normally at 55 Hz for a few months. An 8-hour shut down test established an initial base line cooling rate of 6.6°C/hour. Subsequent 6-hour deadhead tests at 30Hz and 45 Hz showed decreased cooling rates of 4.0°C/hour and 2.2°C/hour, respectively. This result clearly established the potential to deadhead at different frequencies to obtain different lower cooling rates. Finally, two extended deadhead tests (3 and 10 weeks in duration) were executed to help determine if it was possible to induce damage in SAGD ESPs by deadheading, as is usually the case in most non-thermal applications. These ESPs operated normally after the extended tests and one was dismantled upon failure, looking for any signs of deadhead damage. Results presented show that deadheading SAGD ESPs provides the opportunity to safely minimize ESP thermal cycles, which could lead to a significant improvement in ESP run life.

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Atomic-scale simulations of strain localization in a single-component three-dimensional model amorphous solid

MRS Proceedings ◽

10.1557/proc-0903-z16-05 ◽

2005 ◽

Vol 903 ◽

Author(s):

Yunfeng Shi ◽

Michael L Falk

Keyword(s):

Shear Bands ◽

Three Dimensional ◽

Amorphous Solid ◽

Single Component ◽

Atomic Scale ◽

Dimensional Model ◽

Three Dimensional Model ◽

Localized Deformation ◽

Cooling Rates ◽

High Cooling Rates

AbstractMolecular dynamics is used to simulate model non-crystalline solids described by a single-component Dzugutov system. The solids are produced by quenching equilibrium liquids at different cooling rates. These are then tested in uniaxial compression. Samples produced at high cooling rates exhibit homogenous deformation while samples quenched at low cooling rates exhibit localized deformation. Shear bands are shown to correspond to regions of depleted short-range order as determined by a Frank-Kasper criterion.

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The Origin of High Ice Crystal Number Densities in Cirrus Clouds

Journal of the Atmospheric Sciences ◽

10.1175/jas3487.1 ◽

2005 ◽

Vol 62 (7) ◽

pp. 2568-2579 ◽

Cited By ~ 97

Author(s):

C. R. Hoyle ◽

B. P. Luo ◽

T. Peter

Keyword(s):

Cirrus Clouds ◽

Small Scale ◽

Ice Crystal ◽

Cooling Rates ◽

Density Distributions ◽

In Situ Forming ◽

Independent Particle ◽

Scale Temperature ◽

High Cooling Rates ◽

Homogeneous Freezing

Abstract Recent measurements with four independent particle instruments in cirrus clouds, which formed without convective or orographic influence, report high number densities of ice particles (as high as nice = 50 cm−3) embedded in broad density distributions (nice = 0.1–50 cm−3). It is shown here that small-scale temperature fluctuations related to gravity waves, mechanical turbulence, or other small-scale air motions are required to explain these observations. These waves have typical peak-to-peak amplitudes of 1–2 K and frequencies of up to 10 h−1, corresponding to instantaneous cooling rates of up to 60 K h−1. Such waves remain unresolved in even the most advanced state-of-the-art global atmospheric models. Given the ubiquitous nature of these fluctuations, it is suggested that the character of young in situ forming cirrus clouds is mostly determined by homogeneous freezing of ice in solution droplets, driven by a broad range of small-scale fluctuations (period ∼a few minutes) with moderate to high cooling rates (1–100 K h−1).

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