| 摘要 |
A refrigeration system (12) comprising three expansion units (19A, 19B, 19C) connectable in parallel via respective conduits (30) to a supply (16) of compressed refrigerant. Each expansion unit comprises an expansion chamber (22) and three series connected secondary chambers (24, 26 and 28). The expansion chamber (22) and secondary chambers (24, 26 and 28) are formed with progressively reducing volumetric capacity. The end of each of the third secondary chambers (28), distant from their respective second secondary chambers (26) is connected to a common bleed tube (29) having a bleed hole (34) for venting the refrigerant. The bleed hole (34) opens on the outside of a housing (15) which houses the expansion units (19A, 19B, 19C). The interior of the housing (15) is filled with a gel which a changes state from a liquid to a solid at a predetermined temperature. A valving arrangement (32) connects the expansion units (19A, 19B and 19C) to a supply of compressed refrigerant. The housing (15) together with a connected supply (16) refrigerant can be installed into a cooling box for cooling the space within, and thus any contents of, the cooling box. This is achieved by the valve mechanism (32) periodically admitting a volume of compressed refrigerant into the expansion units (19A, 19B and 19C). Upon such admittance, the compressed refrigerant initially expands in the expansion chambers (22). This is accompanied by an absorption of heat from the surrounding gel which in turn absorbs heat from the space within the colling box. The flow of expanded refrigerant through the secondary chambers is retarded by back pressure produced by having the secondary chambers of progressively reducing volumetric capacity. This allows the gel to be maintained at a frozen state for a long period of time while consuming only small volumes of compressed refrigerant.
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