1. Kendra Passow M.S. Graduate Student Mechanical Engineering
Room: 1327 ERB
Home Town:
Maple Plain, Minnesota
Thesis: Experimental modeling of a surgical cryoprobe

2. Cryosurgery
A technique for destroying undesirable tissue such as cancers using a freezing process
Used to ablate prostate and liver cancer tumors
Also used in a variety of procedures in dermatology, gynecology, and cardiology
Relies on cryosurgical probe that is inserted into the body in order to create the necessary cryogenic temperatures (~ K)
The cryolesion that is formed is typically on the order of tens of millimeters in diameter and the lethal zone extends outward into the tissue from the cryoprobe tip approximately to the location where the tissue is about 240 K

3. Project Goals
Develop a modeling tool for optimizing gas mixtures and operating conditions for a precooled mixed gas JT cycle used for cryosurgery.
1. Improvement of model used to optimize performance and design of a cryosurgical probe
Verify accuracy of mixture property data used in the model at cryogenic temperatures
Develop empirically tuned heat exchanger models for the multi-phase, multi-component mixtures
Improve system level refrigeration performance predictive capability
2. Experimental data
Measure relevant system thermodynamic states
Quantify performance over a range of mixtures and operating conditions
Compute component- and system-level performance and compare with modeled predictions
Schematic of 2-stage mixed gas Joule-Thompson cryosurgical probe system
recuperator

4. Experimental Setup
The test facility was built to simulate cryoprobe performance during surgery
Pressure, temperature, and mass flow measurements quantify thermodynamic states and heat transfers
Thermal load of warm tissue simulated using a heater
Interchangeable jewel orifice used to modify the pressure and mass flow applied to the cycle
Jewel orifice piece for Joule-Thompson expansion
Cold components of experimental test facility enclosed in vacuum chamber