Improved Study On A Cryosurgery Apparatus

Cryosurgery employs low temperature to destroy diseased tissues. This technology has been developed as part of modern medicine. It is an alternative of traditional surgery and has advantages of easy operation, no bleeding, low side effect and high security. So far, cryosurgery can be applied to many clinical departments including general surgery, neurosurgery, urology, bone, chest heart surgery, dermatology and oncology.An auto-cascade refrigeration system utilizes only one compressor with zeotropic refrigerant as the working fluid. It can reach temperature of below -100℃.The system is simple, compact and reliable. As a cooling source for cryosurgery apparatus, the auto-cascade refrigeration system can bring about many benefits.In this thesis, improved experimental studies were carried out on an existing apparatus, and simulation was done with the cryoprobe. The main contents were as follows:(1) The connecting tube was replaced to offer better thermal insulation and flexibility. A new cryoprobe was designed. Through test it was found that the freezing capacity of the cryoprobe was obviously improved.(2) After choosing appropriate ratio of a quaternary refrigerant mixture, the lowest temperature at the cryoprobe could reach as low as-130℃, and 18W refrigeration capacity could be obtained at-90℃.The impacts of the fluid composition on the system performance were studied.(3) The influences of the ambient temperature on the operation parameters of the system, such as the cryoprobe temperature, suction and discharge pressure, exhaust temperature, were investigated.(4) Numerical simulations on the heat transfer and fluid flow around the cryoprobe were done with Fluent software. How the freezing capacity and the refrigerant pressure drop were affected by the inlet state of the refrigerant was discussed.