To accurately forecast freeze-drying time

COMSOL software was used to simulate the sublimation drying process of pitaya slices based on the theory of heat and mass transfer in this study. The thickness of the red pitaya slices was 12 mm

and the radius was 4 cm. By simulating the water vapor flow coupled with the heat and mass transfer of the sublimation drying stage

the temperature distribution characteristics of pitaya slices

the movement of the sublimation interface

and the condition of ice sublimation

the sublimation cycle was forecast. Experiments were conducted to validate the model. The results show that the errors are low: the absolute error between the simulated and measured pitaya center temperatures is 0.9 ℃

the comparative error between the forecast and measured moisture ratios is only 1.2%

and the relative error between the simulated and measured dehydration rates is 6.63%. It can be concluded that the model can accurately simulate the dynamic changes in heat and mass transfer during the sublimation drying process. By comparing the simulated sublimation cycle of pitaya slices with different thicknesses

and considering the quality and production of freeze-drying products

it is concluded that 12 mm is the best thickness of red pitaya slices for freeze-drying.