Study of the insulation effect of freezing apparatuses

In-situ tests and numerical manipulations were conducted for comparison of superior/inferior quality of casing-tube-vacuumized insulation and polyurethane insulation of freezing apparatuses in relation to non-uniform cold distribution in the multi-coil freezing layout and the contradiction between large-coil diameter layout of the freezing holes and stability of the headframe base. Tests show that: (1) under current technology, vacuumized insulation is of short duration due to lack of appropriate applied vacuum; (2) after the freezing pipe is insulated with polyurethane, the temperature gradient is less than no insulation, and the temperature difference between insulated and non-insulated apparatuses is stable as the freezing period increases. Finally, it is pointed out that polyurethane insulation is quite efficient in present technical freezing construction.