scholarly journals Kinetics of Nonisothermal Phase Change with Arbitrary Temperature-Time History and Initial Transformed Phase Distributions

2021 ◽  
Author(s):  
Joseph Kangas ◽  
John C. Bischof ◽  
Christopher J. Hogan
Keyword(s):  
Phase Change ◽  
Time History ◽  
Arbitrary Temperature ◽  
Kinetics Of ◽  
Temperature Time

Temperature Effect on the Two-Dimensional Phase Transition Kinetics of Adenine Adsorbed at the Hg Electrode/Aqueous Solution Interface

2003 ◽  
Vol 68 (8) ◽  
pp. 1407-1419 ◽  
Author(s):  
Claudio Fontanesi ◽  
Roberto Andreoli ◽  
Luca Benedetti ◽  
Roberto Giovanardi ◽  
Paolo Ferrarini
Keyword(s):  
Phase Transition ◽  
Aqueous Solution ◽  
Phase Change ◽  
Temperature Effect ◽  
Transition Rate ◽  
Effect Of Temperature ◽  
Two Dimensional ◽  
Solution Interface ◽  
Phase Transition Kinetics ◽  
Kinetics Of

The kinetics of the liquid-like → solid-like 2D phase transition of adenine adsorbed at the Hg/aqueous solution interface is studied. Attention is focused on the effect of temperature on the rate of phase change; an increase in temperature is found to cause a decrease of transition rate.

scholarly journals Thermodynamics and kinetics of glassy and liquid phase-change materials

2021 ◽  
Vol 135 ◽  
pp. 106094
Author(s):  
Narges Amini ◽  
Julian Pries ◽  
Yudong Cheng ◽  
Christoph Persch ◽  
Matthias Wuttig ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Phase Change ◽  
Phase Change Materials ◽  
Thermodynamics And Kinetics ◽  
Kinetics Of

scholarly journals Cement-Based Renders Manufactured with Phase-Change Materials: Applications and Feasibility

2016 ◽  
Vol 2016 ◽  
pp. 1-6 ◽  
Author(s):  
Luigi Coppola ◽  
Denny Coffetti ◽  
Sergio Lorenzi
Keyword(s):  
Compressive Strength ◽  
Phase Change ◽  
Phase Change Materials ◽  
Residential Buildings ◽  
Setting Time ◽  
Drying Shrinkage ◽  
Hydration Kinetics ◽  
Mechanical Performances ◽  
Entrapped Air ◽  
Kinetics Of

The paper focuses on the evaluation of the rheological and mechanical performances of cement-based renders manufactured with phase-change materials (PCM) in form of microencapsulated paraffin for innovative and ecofriendly residential buildings. Specifically, cement-based renders were manufactured by incorporating different amount of paraffin microcapsules—ranging from 5% to 20% by weight with respect to binder. Specific mass, entrained or entrapped air, and setting time were evaluated on fresh mortars. Compressive strength was measured over time to evaluate the effect of the PCM addition on the hydration kinetics of cement. Drying shrinkage was also evaluated. Experimental results confirmed that the compressive strength decreases as the amount of PCM increases. Furthermore, the higher the PCM content, the higher the drying shrinkage. The results confirm the possibility of manufacturing cement-based renders containing up to 20% by weight of PCM microcapsules with respect to binder.

Phase Change Materials - From Structures to Kinetics

2006 ◽  
Vol 918 ◽  
Author(s):  
Matthias Wuttig ◽  
Wojciech Welnic ◽  
Ralf Detemple ◽  
Henning Dieker ◽  
Johannes Kalb ◽  
...  
Keyword(s):  
Phase Change ◽  
Crystalline State ◽  
Phase Change Materials ◽  
Amorphous State ◽  
Structural Difference ◽  
Fast Time ◽  
Optical Contrast ◽  
Fast Time Scale ◽  
Kinetics Of ◽  
Structure Properties

AbstractPhase change materials possess a unique combination of properties which include a pronounced property contrast between the amorphous and crystalline state, i.e. a high electrical and optical contrast. In particular the latter observation is indicative for a considerable structural difference between the amorphous and crystalline state. At the same time the crystallization of the amorphous state proceeds on a fast time scale. This raises the question how structure, properties and kinetics are related in phase change alloys. It will be demonstrated that only a small group of covalent semiconductors with octahedral-like coordination has the required property combination. This is related to their thermodynamic properties which govern the kinetics of crystallization.

Run-on in Gasoline Engines

1968 ◽  
Vol 183 (1) ◽  
pp. 21-51 ◽  
Author(s):  
W. S. Affleck
Keyword(s):  
Combustion Chamber ◽  
Time History ◽  
Spontaneous Ignition ◽  
Research Octane Number ◽  
Gasoline Engines ◽  
Engine Cooling ◽  
History Of ◽  
Valve Overlap ◽  
Temperature Time ◽  
Small Valve

When the ignition of a car engine is switched off, the engine normally comes to rest within a few revolutions but, occasionally, it may continue to fire erratically for a few seconds or longer. This phenomenon is known as run-on and, for the majority of European engines, is the result of spontaneous ignition of the fuel-air mixture in the combustion chamber. Part 1 of this paper describes experiments in a single-cylinder research engine which have been made to establish the principles controlling run-on. In particular the effects of air/fuel ratio, the nature of the fuel and the pressure-temperature-time history of the fuel-air mixture in the combustion chamber have been studied, as it is known that these factors play an important part in spontaneous ignition in experiments in laboratory vessels. From these observations it has been possible to formulate a theoretical model of the run-on process which explains the salient features of the phenomenon. In particular, it shows how the gradual cooling of the engine limits the duration of run-on and also how the duration of run-on may be considered as a measure of the extent to which fuel or engine factors must be altered to eliminate run-on. Part 2 describes the application of these principles to car engines using normal commercial-type fuels. It is concluded that the following are important features in the control of run-on: the use of fuel of sufficiently high Research octane number, minimum opening of throttle at idle, sufficient time for cooling of the combustion chamber before the ignition is switched off, efficient engine cooling, and small valve overlap. Current devices for reducing exhaust emissions are likely, through their effects on these features, to increase the tendency of an engine run-on. Combustion chamber deposits, though, appear to have little influence.

Thermal history and subsidence of rifted continental margins—evidence from wells on the Nova Scotian and Labrador Shelves

1979 ◽  
Vol 16 (3) ◽  
pp. 505-522 ◽  
Author(s):  
C. E. Keen
Keyword(s):  
Nova Scotia ◽  
Time History ◽  
The United States ◽  
Tectonic Subsidence ◽  
Continental Margins ◽  
Thermal Cooling ◽  
Nova Scotian ◽  
Temperature Time ◽  
Good Agreement ◽  
Cooling Model

The subsidence histories of the Labrador and Nova Scotian rifted continental margins have been determined from biostratigraphic data for 11 deep exploratory wells off Nova Scotia, for five wells off Labrador, for three wells northeast of Newfoundland, and for one well off the northeast coast of the United States of America. The components of subsidence, due to sediment loading, and when possible due to loading by changes in eustatic sea level, were removed, leaving that part of the subsidence, the tectonic subsidence, caused by cooling of the lithosphere or by other deep seated processes. The thermal cooling model theoretically predicts a linear relationship between tectonic subsidence and t½, where t is the time since subsidence began. This relationship should be obeyed during the first tens of Ma of subsidence. The slope of this curve depends upon the temperature to which the crust and upper mantle were heated during the initial rifting stage and can be used to derive the temperature–time history within the sediments, the present temperature distribution, and geothermal gradient. The data show that the observed subsidence curves behave in accordance with the thermal cooling model, at least during the first 80 Ma after subsidence began and obey the equation y = 300(± 80)t1/2 m, where y is the tectonic subsidence. The slopes of the subsidence curves are similar for the Labrador Shelf, the Nova Scotian Shelf, and the shelf off the northeastern U.S.A. More rapid and variable subsidence occurs northeast of Newfoundland and this may be associated, in a way yet to be established, with the anomalous foundered continental crust near the Orphan Knoll and Flemish Cap micro-continents which lie close to this area. After about 80 Ma, the subsidence appears to depart from the linear t1/2 law in a manner similar to the subsidence curves for oceanic crust, but this is not well established by the data. The present temperatures and temperature gradients computed using the slope of the subsidence curves show good agreement with measured values; geothermal gradients of 17.5 °C km−1 and 26 °C km−1 are calculated off Nova Scotia and Labrador respectively, and mean values of about 23 °C km−1 are observed. The computed temperature–time history within the sediments was used to estimate values of vitrinite reflectance, an indicator of the degree of organic metamorphism. These values show reasonable agreement with the measured values and suggest that only the Upper Jurassic and Lower Cretaceous sediments off Nova Scotia and the Paleocene sediments off Labrador are sufficiently mature to be good sources of petroleum. The linear t1/2 behaviour of the subsidence, and the good agreement between predicted and observed temperatures support the contention that cooling is largely responsible for the observed tectonic subsidence. The similarity of results from different areas suggests that the usefulness of the method is not restricted to a particular geographical area and may be applied to other rifted continental margins. Comparisons between the subsidence rates, thermal histories, and crustal structure at rifted margins on a worldwide scale may provide insights concerning the processes controlling their development. The temperature–time histories of the sediments estimated from the subsidence may be useful in establishing the potential of a rifted margin area for petroleum generation when little other information is available.

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