Nam and Song's model, which describes the first stage of vacuum freeze drying, is adapted to atmospheric pressure conditions in a pulsating fluidized bed, discretizing the differential equations by finite-difference according to the implicit scheme. The generated algebraic systems of equations are solved by the tridiagonal matrix algorithm (TDMA). The effect of the variable time step on computation time is analyzed. The effect of particle size reduction, bed temperature increase, and the incorporation of infrared radiation made it possible to reduce drying times. Comparison with experimental values of the first stage of the freeze drying of carrot slices and the values calculated from the model showed a maximum mean quadratic error of 0.09.