LV-11-C043 -- Experimental Apparatus for Measuring the Performance of a Precooled Mixed Gas Joule Thomson Cryoprobe ✓ Most Recent

Cryosurgery is a technique for destroying undesirable tissue such as cancers using a freezing process. A previous ASHRAE paper describes the development of a thermodynamic modeling tool for a precooled Mixed Gas Joule-Thomson (MGJT) cryoprobe used for cryosurgery. An experimental test facility has been constructed to measure the performance of a precooled MGJT cryoprobe; the experimental data will be used to tune and verify the model, and to demonstrate additional cooling capacity available with the optimal mixture compositions and operating parameters selected by the model.

A commercially available cryoprobe system has been modified to integrate measurement instrumentation that is sufficient to characterize the performance of the individual components as well as the overall system. Measurements include temperature and pressure sensors to resolve thermodynamic states, and flow meters to calculate heat and work transfer rates. A thermal load is applied using an electric heater to characterize the refrigeration performance. Temperature measurements located inside of the recuperator are used to capture the heat transfer performance of the two-phase, multi-component mixture. An uncertainty analysis for the experiment is presented which shows that the performance targets can be computed from the measurements with an uncertainty of less than 10% under nominal operating conditions using both a synthetic refrigerant and hydrocarbon based gas mixture. Preliminary data for a mixture of R23, R14 and argon are reduced and presented in order to demonstrate the computation of various performance metrics. See more