Development and performance test of a cryoprobe with heat transfer enhancement configuration

In the present study, a cryoprobe with heat transfer enhancement configuration (HTEC) is developed and its freezing performance is evaluated experimentally. Two kinds of heat transfer enhancement configurations, i.e., coiled wire insert and helical mesh insert, are proposed and used in the cryoprobe. Furthermore, in order to ensure that vapor can be discharged freely and only liquid nitrogen reaches the cryogenic section of the cryoprobe, a vapor-liquid separator is employed upstream of the cryoprobe. It is found that the precooling time of the cryoprobe is significantly shortened with the vapor-liquid separator. The enhancement of the freezing capacity with the helical mesh insert is slightly superior to that with the coiled wire insert. With the helical mesh insert, the freezing capacity of the cryoprobe can be enhanced by 41%, and the wall temperature can reach 111.3 K in about 10 min. Significant temperature oscillations are observed in the precooling stage of the cryoprobe with HTEC, while only slight temperature oscillations can be found without HTEC.