摘要 |
A controlled rate freezer for the controlled freezing of biological material, the freezer comprising a first chamber which can hold biological material to be frozen, a second chamber which can hold a cryogenic material, forced convection apparatus which lowers the temperature of the first chamber by forcibly moving air present in the first chamber towards the second chamber whereby heat transfer occurs at the second chamber, and control apparatus which monitors the temperature of the first chamber and which controls the forced convection apparatus based on the monitored temperature, so that the lowering of the temperature of the first chamber, and thus the freezing of the biological material, follows a material-dependent predetermined optimum or substantially optimum freezing profile. The forced convection apparatus includes two recirculating flow paths along which air in the first chamber is movable at a rate controlled by the control apparatus. The first flow path is solely located in the first chamber and spaced from the second chamber, so that air travelling on the first flow path is not subjected to direct cooling at the second chamber, and the second flow path meets the first flow path and extends to the second chamber, so that air travelling on the second flow path is subjected to cooling at the second chamber and, once cooled, is fed onto the first flow path.
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