Performance evaluation of liquid nitrogen-cooled cryoprobes using a combined numerical and experimental approach

•Performance evaluation of liquid nitrogen-cooled cryoprobes.•Cryoprobe-based freezing phenomena.•Effect of insertion depth and operating pressures.•Lens-less Fourier transform-based digital holography interferometry.•Real time tracking of freezing front and whole field temperature distribution. In this study, the effect of the operating pressure and insertion depth is investigated on the cooling performance of cryoprobes. Two cryoprobes having different diameters are used. Experiments are performed with each cryoprobe for operating pressure ranging from 2.2 to 4 atm and insertion depths ranging from 2 to 15 mm. The temperature of the cryoprobe tip is measured by three thermocouples, and the recorded temperature is used as a boundary condition in the numerical simulations. The optics-based experimental setup, comprising digital holographic interferometry (DHI), is implemented to accurately track the freezing interface for all the experimental cases. The tracked interface using DHI-based intensity maps and the thermocouples placed inside the freezing front provided the means to ascertain the accuracy of the results obtained using numerical simulations. For both cryoprobes, the cooldown time is reduced by a factor of 2 to 3 when higher operating pressure is used. The higher operating pressure resulted in accelerated cooling for both cryoprobes. For the smaller-sized cryoprobe, i.e., Cryoprobe-1, the higher operating pressure is necessary if it needs to be operated for an insertion depth of 6 mm or more. However, for the larger-sized cryoprobe, i.e., Cryoprobe-2, the higher operating pressure only resulted in reduced cooldown time. The temperature data predicted by the numerical simulations are used to quantify the cooling performance of the cryoprobes. The average cooling power for Cryoprobe-1 ranges from 8 to 12 W, while for Cryoprobe-2, it ranges from 10 to 30 W depending on the insertion depth.