Abstract Some of the same characteristics of open cycle Joule Thompson (JT) cryostats that have made them attractive for military applications also make them attractive for cryosurgical applications. These include their small size, ability to cool fast, long term storage, and potentially small and flexible connecting lines. One characteristic that is different is the nature of the heat load. Cooling tissue requires a high initial cooling rate but the load decreases as the ice ball grows because of the low thermal conductivity of tissue. Characteristics of ice ball formation in tissue including temperature distribution, heat flux, and fraction cooled below −20°C have been calculated for different size cylindrical and spherical cryoprobes and different probe temperatures. Cooling characteristics of different gases are discussed including gas-cooling effects in bottles, flow rates and cooling rates. Maximum refrigeration rates at 40 MPa, are presented for Ar and kr in finned-tube and matrix-tube heat exchangers in the size range of interest for cryoprobes. The relative merits of finned-tube and matrix-tube heat exchangers are discussed. Test data is presented for ice ball formation in beefliver using a 3.45 mm diameter by 19 mm long cold tip probe cooled by 2.5 L Ar at an initial pressure of 42 MPa using a finned-tube JT heat exchanger.


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    Title :

    Considerations in Applying Open Cycle J-T Cryostats to Cryosurgery


    Contributors:

    Published in:

    Publication date :

    2002-01-01


    Size :

    10 pages




    Type of media :

    Article/Chapter (Book)


    Type of material :

    Electronic Resource


    Language :

    English