Isotope effects in aqueous systems. VI. partial molal free energies in NaCl−H2O−D2O by freezing-point measurements. The heat of fusion of D2O

1975 ◽  
Vol 4 (11) ◽  
pp. 923-947 ◽  
Author(s):  
Quentin D. Craft ◽  
W. Alexander Van Hook
Keyword(s):  
Freezing Point ◽  
Isotope Effects ◽  
Heat Of Fusion ◽  
Aqueous Systems ◽  
Free Energies

Measurement and Modeling of Latent Heat Release During Freezing of Aqueous Solutions in a Small Container

2000 ◽  
Author(s):  
Ramachandra V. Devireddy ◽  
John C. Bischof ◽  
Perry H. Leo ◽  
John S. Lowengrub
Keyword(s):  
Mass Transport ◽  
Heat Release ◽  
Latent Heat ◽  
Pure Water ◽  
Heat Of Fusion ◽  
Freezing Process ◽  
Latent Heat Release ◽  
Aqueous Systems ◽  
Heat And Mass Transport ◽  
Latent Heat Of Fusion

Abstract The latent heat of fusion, ΔHf of a cryobiological medium (a solute laden aqueous solution) is a crucial parameter in the cryopreservation process. The latent heat has often been approximated by that of pure water (∼ 335 mJ/mg). However, recent calorimetric (DSC - Pyris 1) measurements suggest that the actual magnitude of latent heat of fusion during freezing of solute laden aqueous systems is far less. Fourteen different pre-nucleated solute laden aqueous systems (NaCl-H2O, Phosphate Buffered Saline or PBS, serum free RPMI, cell culture medium, glycerol and Anti Freeze Protein solutions) were found to have significantly lower ΔHf than that of pure water (Devireddy and Bischof, 1998). In the present study additional calorimetric experiments are performed at 1, 5 and 20 °C/min in five representative cryobiological media (isotonic or 1× NaCl-H2O, 10× NaCl-H2O, 1× PBS, 5× PBS and 10× PBS) to determine the kinetics of ice crystallization. The temperature (T) and time (t) dependence of the latent heat release is measured. The experimental data shows that at a fixed temperature, the fraction of heat released at higher cooling rates (5 and 20 °C/min) is lower than at 1 °C/min for all the solutions studied. We then sought a simple model that could predict the experimentally measured behavior and examined the full set of heat and mass transport equations during the freezing process in a DSC sample pan. The model neglects the interaction between the growing ice crystals and is most appropriate during the early stages of the freezing process. An examination of the coefficients in the heat and mass transport equations shows that heat transport occurs much more rapidly than solute transport. Hence, the full model reduces to one in which the temperature profile is constant in space while the solute concentration profile obeys the full time and space dependent diffusion equation. The model reveals the important physical parameters controlling the mass transport at the freezing interface and further elucidates the experimental results, i.e. the temperature and time dependence of the latent heat release.

scholarly journals Effects of Egg Yolk, Glycerol and the Freezing Rate on the Viability and Acrosomal Structures of Frozen Ram Spermatozoa

1975 ◽  
Vol 28 (2) ◽  
pp. 153 ◽  
Author(s):  
PF Watson ◽  
ICA Martin
Keyword(s):  
Latent Heat ◽  
Significant Interaction ◽  
Freezing Point ◽  
Egg Yolk ◽  
Freezing Rate ◽  
Heat Of Fusion ◽  
Significant Deterioration ◽  
Cooling Rates ◽  
Latent Heat Of Fusion ◽  
Cooling Phase

The influence of egg yolk, glycerol and the freezing rate on the survival of ram spermatozoa and on the structure of their acrosomes after freezing was investigated. Egg yolk was shown to be beneficial not only during chilling but also during freezing; of the levels examined, 1� 5 % gave the greatest protection. Although the presence of glycerol in the diluent improved the survival of spermatozoa, increasing concentrations produced significant deterioration of the acrosomes. With closely controlled linear cooling rates, no overall difference was detected in the survival of spermatozoa frozen at rates between 6 and 24�C per min. However, a significant interaction between freezing rate and the inclusion of glycerol in the diluent showed that glycerol was less important at the highest freezing rate. A sudden cooling phase near to the freezing point following the release of the latent heat of fusion was not detrimental to spermatozoa.

STUDY ON NEW ICE SLURRY GENERATOR USING NaCl AQUEOUS SOLUTION AT LOW CONCENTRATION

2013 ◽  
Vol 21 (01) ◽  
pp. 1350004 ◽  
Author(s):  
KOJI FUMOTO ◽  
TSUYOSHI KAWANAMI ◽  
TAKAO INAMURA
Keyword(s):  
Aqueous Solution ◽  
High Pressure ◽  
Test Section ◽  
Freezing Point ◽  
New Method ◽  
Heat Of Fusion ◽  
Test Fluid ◽  
Ice Slurry ◽  
Slurry Ice ◽  
Experimental Apparatus

A cold thermal energy storage system has been developed for HVAC. There are many ice-based cooling systems operating around the world. Ice slurry, which is a mixture of fine ice crystals and liquid water, is utilized in ice storage systems owing to its good flowability and large latent heat of fusion. For slurry ice production techniques, there are presently a number of commercially available ice slurry generators (e.g., Supercooled slurry ice generator, Scraper type generator, and Vacuum type generator, etc.). In the present study, a new method was developed to generate ice slurry without the deposition of an ice layer on a cooled surface. The basic components of the experimental apparatus is a cooling brine circulating loop, a high pressure pump, a valve, an aqueous solution flow loop containing the test section, which is made of transparent acrylic, and the associated instrumentation. This new method is based on freezing-point depression of the aqueous solution, which is maintained under high-pressure conditions. To control the timing for solidification and to generate ice slurry, we investigated the relationships among the pressure and temperature of the aqueous solution. The freezing phenomenon of the aqueous solution in the test section was observed in detail. As a result, we developed a new ice slurry generator based on the new method that controls the pressure and temperature of the aqueous solution. Experimental results showed that the characteristics of the ice slurry generation were closely related to the pressure and initial stage temperature of the test fluid. Finally, the optimum operation condition of the ice slurry generator based on visualization experiment was discussed.

Zn:Tl PHASE DIAGRAM AT VERY LOW THALLIUM CONCENTRATIONS

1961 ◽  
Vol 39 (4) ◽  
pp. 588-595 ◽  
Author(s):  
E. H. McLaren ◽  
F. Weinberg
Keyword(s):  
Phase Diagram ◽  
Freezing Point ◽  
Solubility Limit ◽  
Heat Of Fusion ◽  
Kcal Mole ◽  
Solid Solubility Limit ◽  
Pure Zinc ◽  
Latent Heat Of Fusion ◽  
A Value ◽  
Resistance Thermometry

The Zn:Tl liquidus has been accurately determined from pure Zn (419.505 °C) to the monotectic transition temperature (416.926 °C at 0.42 at.% Tl) using precision resistance thermometry. The upper solidus was determined approximately from measurements of the distribution coefficient (~0.01) and the solid solubility limit (~0.004 at.% Tl) of thallium in zinc. A value 1.53 ± 0.1 kcal/mole for the latent heat of fusion of pure zinc was calculated from the freezing point depressions.

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