| CPC F25D 11/04 (2013.01) [F25B 9/14 (2013.01); F25B 9/145 (2013.01); F25D 3/105 (2013.01); F25D 17/06 (2013.01); F25D 19/006 (2013.01); F25D 19/02 (2013.01); F25D 23/003 (2013.01); F25D 29/008 (2013.01); F25D 2201/14 (2013.01); F25D 2600/04 (2013.01); F25D 2700/12 (2013.01); F25D 2700/121 (2013.01)] | 18 Claims |

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1. A cryogenic freezer comprising:
a container defining a storage space;
a reservoir vessel positioned within the storage space and configured to contain a cryogenic liquid with a headspace above the cryogenic liquid in a reservoir interior space that is sealed with respect to the storage space by a wall of the reservoir vessel;
a refrigeration module that is in a heat exchange relationship with a vapor in the headspace of the reservoir above the cryogenic liquid,
wherein the refrigeration module includes a cold tip that is in the heat exchange relationship with the vapor in the headspace of the reservoir and that is positioned in an upper end of a reservoir neck;
a sensor configured to determine a pressure within the reservoir interior space; and
a system controller connected to the sensor and the refrigeration module and configured to control an amount of cooling by the refrigeration module to the cold tip in the headspace of the reservoir when a pressure or temperature of the vapor within the headspace increases,
wherein the wall of the reservoir vessel cools the storage space by heat transfer through the wall of the reservoir vessel and prevents fluid communication between the storage space and the reservoir interior space.
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