ChemInform Abstract: The Estimation of Melting Points and Fusion Enthalpies Using Experimental Solubilities, Estimated Total Phase Change Entropies, and Mobile Order and Disorder Theory.

A one-dimensional heat transfer problem in the phase-change slab, one side of which is isothermal while the other is insulated, is considered. Both cases—fusion and solidification—are treated. Slab temperature at the intitial moment is assumed constant and not critical. The main goal of this paper is to find the additional time required for a total phase change, compared with the case of the critical initial temperature. By analogy with perturbation problems in hydrodynamics, an appropriate solution is constructed consisting of an inner and an outer solution. The evaluation of the maximum error of the integral heat balance equation of the slab is treated as an indirect evaluation of the accuracy of the solution obtained. This evaluation shows that the solution can provide sufficient accuracy only in cases in which at least one of the three nondimensional parameters of the problem is small.

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Total phase change entropies and enthalpies

Thermochimica Acta ◽

10.1016/s0040-6031(02)00213-7 ◽

2002 ◽

Vol 395 (1-2) ◽

pp. 59-113 ◽

Cited By ~ 28

Author(s):

James S Chickos ◽

William E Acree

Keyword(s):

Phase Change ◽

Total Phase

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Segregation of molecules in binary solvent mixtures without H bonds. A quantitative treatment based on the theory of mobile order and disorder

Journal of the Chemical Society Faraday Transactions ◽

10.1039/a806626d ◽

1998 ◽

Vol 94 (24) ◽

pp. 3587-3594 ◽

Cited By ~ 1

Author(s):

Pierre L. Huyskens ◽

Marie-Claire Haulait-Pirson ◽

Peter Vandevyvere ◽

Katarine Seghers ◽

The´rèse Zeegers-Huyskens

Keyword(s):

Binary Solvent ◽

Solvent Mixtures ◽

Binary Solvent Mixtures ◽

Order And Disorder ◽

Mobile Order ◽

Quantitative Treatment

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Prediction of Partition Coefficients of Fluorous and Nonfluorous Solutes in Fluorous Biphasic Solvent Systems by Mobile Order and Disorder Theory

The Journal of Physical Chemistry B ◽

10.1021/jp036751f ◽

2004 ◽

Vol 108 (4) ◽

pp. 1458-1466 ◽

Cited By ~ 23

Author(s):

Elwin de Wolf ◽

Paul Ruelle ◽

Joep van den Broeke ◽

Berth-Jan Deelman ◽

Gerard van Koten

Keyword(s):

Partition Coefficients ◽

Order And Disorder ◽

Solvent Systems ◽

Mobile Order

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Calculation of Five Thermodynamic Molecular Descriptors by Means of a General Computer Algorithm Based on the Group-Additivity Method: Standard Enthalpies of Vaporization, Sublimation and Solvation, and Entropy of Fusion of ordinary Organic Molecules and Total Phase-Change Entropy of Liquid Crystals

10.20944/preprints201705.0169.v1 ◽

2017 ◽

Author(s):

Rudolf Naef ◽

William E. Acree Jr.

Keyword(s):

Liquid Crystals ◽

Phase Change ◽

Goodness Of Fit ◽

Cross Validation ◽

Organic Molecules ◽

Enthalpy Of Fusion ◽

Computer Algorithm ◽

Group Additivity ◽

Entropy Of Fusion ◽

Total Phase

The calculation of the standard enthalpies of vaporization, sublimation and solvation of organic molecules is presented using a common computer algorithm on the basis of a group-additivity method. The same algorithm is also shown to enable the calculation of their entropy of fusion as well as the total phase-change entropy of liquid crystals. The present method is based on the complete break-down of the molecules into their constituting atoms and their immediate neighbourhood; the respective calculations of the contribution of the atomic groups by means of the Gauss-Seidel fitting method is based on experimental data collected from literature. The feasibility of the calculations for each of the mentioned descriptors was verified by means of a 10-fold cross-validation procedure proving the good to high quality of the predicted values for the three mentioned enthalpies and for the entropy of fusion, whereas the predictive quality for the total phase-change entropy of liquid crystals was poor. The goodness of fit (Q2) and the standard deviation (σ) of the cross-validation calculations for the five descriptors was as follows: 0.9641 and 4.56 kJ/mol (N=3386 test molecules) for the enthalpy of vaporization, 0.8657 and 11.39 kJ/mol (N=1791) for the enthalpy of sublimation, 0.9546 and 4.34 kJ/mol (N=373) for the enthalpy of solvation, 0.8727 and 17.93 J/mol/K (N=2637) for the entropy of fusion and 0.5804 and 32.79 J/mol/K (N=2643) for the total phase-change entropy of liquid crystals. The large discrepancy between the results of the two closely related entropies is discussed in detail. Molecules, for which both the standard enthalpies of vaporization and sublimation were calculable, enabled the estimation of their standard enthalpy of fusion by simple subtraction of the former from the latter enthalpy. For 990 of them the experimental enthalpy-of-fusion values are also known, allowing their comparison with predictions, yielding a correlation coefficient R2 of 0.6066.

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Multi-stage chemical heating for instrument-free biosensing

10.1101/367029 ◽

2018 ◽

Author(s):

John P. Goertz ◽

Kenya M. Colvin ◽

Andrew B. Lippe ◽

John L. Daristotle ◽

Peter Kofinas ◽

...

Keyword(s):

Phase Change ◽

Rolling Circle Amplification ◽

Melting Points ◽

Rolling Circle ◽

Reaction Field ◽

Diagnostic Assays ◽

Multi Stage ◽

Automation Systems ◽

Chemical Heating ◽

Global Access

AbstractImproving the portability of diagnostic medicine is crucial to alleviating global access-to-care deficiencies. This requires not only designing devices that are small and lightweight but also autonomous and independent of electricity. Here, we present a strategy for conducting automated multi-step diagnostic assays using chemically generated, passively regulated heat. Ligation and polymerization reagents for Rolling Circle Amplification of nucleic acids are separated by melt-able phase-change partitions, thus replacing precise manual reagent additions with automated partition melting. To actuate these barriers and individually initiate the various steps of the reaction, field ration heaters exothermically generate heat in a thermos while fatty acids embedded in a carbonaceous matrix passively buffer the temperature around their melting points. Achieving multi-stage temperature profiles extends the capability of instrument-free diagnostic devices and improves the portability of reaction automation systems built around phase-change partitions.

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Experiment Study for Evaluation of Phase Change Material Cooling Vest’s Effectiveness at Two Melting Points Used by People With Paraplegia During Exercise

Volume 11: Heat Transfer and Thermal Engineering ◽

10.1115/imece2020-23083 ◽

2020 ◽

Author(s):

Farah Mneimneh ◽

Nesreen Ghaddar ◽

Kamel Ghali ◽

Charbel Moussalem ◽

Ibrahim Omeis

Keyword(s):

Thermal Comfort ◽

Phase Change ◽

Phase Change Material ◽

Core Temperature ◽

Perceived Exertion ◽

Ambient Conditions ◽

Melting Points ◽

Cord Injury ◽

Change Material ◽

Skin Temperatures

Abstract Phase change material (PCM) cooling vests were tested on people with thoracic (T1-T12) spinal cord injury (SCI), also called people with paraplegia (PA), during exercise in heat. The purpose was to reduce heat stress, limit the increase in core temperature, and improve thermal comfort for PA under high metabolic rates and hot ambient conditions. This health risk was a result of thoracic SCI and disruption of thermoregulatory responses in PA. The current study aims to evaluate the efficacy of cooling vest on PA during arm-crank exercise at two melting points, 20°C (V20) and 14°C (V14) compared to no vest test (NV). Eleven participants with high- (T1-T3) and mid-thoracic SCI (T4-T8) were selected to participate in three tests. Core and skin temperatures and heart rate values were measured during 15-min precondition, 30-min exercise and 15-min recovery. Subjective voting of thermal comfort, sensation, skin wettedness and perceived exertion were recorded during exercise only. The main findings revealed significant reduction in change in core temperature (0.42±0.3°C;0.38±0.2°C) in V20 and V14 compared to NV tests for mid-thoracic group. For high-thoracic group, V20 and V14 were least effective in reducing core temperature (p > 0.05). Improvements in thermal comfort was established when using V14 and V20 compared to NV by 85% and 30% for high-thoracic group and by 72% and 53% for mid-thoracic group.

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