The subject of present work was to predict internal temperature gradients developed during freezing of bovine sperm diluted in extender, packaged in 0.5 ml French plastic straws and suspended in static liquid nitrogen vapor at -100°C. For this purpose, a mathematical heat transfer
model previously developed to predict freezing times (phase change was considered) of semen/extender packaged in straw was extended to predict internal temperature gradients during the cooling/freezing process. Results showed maximum temperature differences between the centre and the periphery
of semen/extender "liquid" column was 1.5°C for an external heat transfer coefficient, h = 15 W/(m2 K), and only 0.5°C for h = 5 W/(m2 K). It is concluded that if a thermocouple wire were inserted in a 0.5 ml plastic straw to monitor the freezing process in nitrogen
vapor, its radial position would have little importance since expected internal gradients may be safely neglected. This finding facilitates the interpretation of freezing rates in 0.5 ml plastic straws immersed in nitrogen vapor over liquid nitrogen, a widely used method for cryopreservation
of bovine spermatozoa.
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FINITE ELEMENT METHOD;
FRENCH PLASTIC STRAWS;
HEAT TRANSFER COEFFICIENT;
TEMPERATURE GRADIENTS NITROGEN VAPOR
Document Type: Research Article
Publication date: March 1, 2013
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CryoLetters is a bimonthly international journal for low temperature sciences, including cryobiology, cryopreservation or vitrification of cells and tissues, chemical and physical aspects of freezing and drying, and studies involving ecology of cold environments, and cold adaptation
The journal publishes original research reports, authoritative reviews, technical developments and commissioned book reviews of studies of the effects produced by low temperatures on a wide variety of scientific and technical processes, or those involving low temperature techniques in the investigation of physical, chemical, biological and ecological problems.