Mathematical prediction of freezing times of bovine semen in straws placed in static vapor over liquid nitrogen

It was observed both the external heat transfer coefficient in stagnant nitrogen vapor and its temperature (controlled by the distance from the surface of liquid nitrogen to the straw) affected freezing times. The accuracy of the model to estimate freezing times of the straws was further confirmed by comparing with experimental literature data. Results of this study will be useful to select “safe” holding times of bull semen in plastic straws placed N2V/LN2 to ensure that complete freezing of the sample has occurred in the nitrogen vapor and avoid cryodamage when plunging in LN2. Freezing times predicted by the numerical model can be applied to optimize freezing protocols of bull semen in straws.