CRYOGENIC HEAT EXCHANGE SYSTEM AND FREEZE DRYER - Patent Articles

(12) Patent: (11) CA 2117858
ABSTRACT:
A cryogenic heat exchange system and freeze dryer incorporating the same. The cryogenic heat exchange system has a heat exchanger provided with at least one pass for receiving a cryogenic heat exchange fluid. A reversing circuit is provided to reverse the flow direction of the cryogenic heat transfer fluid in the at least one pass to help prevent asymmetric ice buildup on the heat exchanger. Additionally, a portion of the spent cryogenic heat transfer fluid after having passed through the at least one pass is recirculated. During the recirculation, the spent cryogenic heat transfer fluid is mixed with incoming cryogen to produce the cryogenic heat transfer fluid. Such cryogenic heat transfer fluid after creation is then introduced into the flow reversing circuit and the one or more passes of the heat exchanger. A remaining portion of the cryogenic heat transfer fluid is vented. The recirculation raises the temperature of the heat transfer in the heat exchanger to also promote uniform ice buildup. The heat exchanger can be a condenser used in a freeze drier for freezing water vapor sublimated during the freeze drying process. Additionally, in a proper application of the present invention, the reversal coupled with the recirculation and mixing can be used to provide the cryogenic heat exchange system with a self-defrost capability.
(72) Inventors (Country): LEE, RON C. (United States)
(73) Owners (Country): THE BOC GROUP, INC. (United States)
(71) Applicants (Country):
(74) Agent: GOWLING LAFLEUR HENDERSON LLP
(45) Issued: Dec. 9 , 1997
(22) Filed: Oct. 11, 1994
(41) Open to Public Inspection: May 2 , 1995
Examination requested: Oct. 11, 1994
(51) International Class (IPC): F28F 17/00
F26B 5/06
Patent Cooperation Treaty (PCT): No
(30) Application priority data: Application No. Country Date
08/143,723 United States Nov. 1 , 1993
Availability of licence: N/A
Language of filing: English