The evaporation and condensation phenomena of alkali metals are not co
rrectly described by the analysis using the continuum equations, becau
se discontinuity of physical quantities such as temperature at the vap
or-liquid interface occurs in the phase change process. The authors ap
ply the direct simulation Monte Carlo (DSMC) method, which is based on
the molecular gas dynamics, to the problem of potassium condensation.
The simulation results are found to be in excellent agreement with th
e experimental results previously reported by two of the authors, when
the condensation and evaporation coefficients are set to unity. It is
also confirmed that a slight shift of evaporation and condensation co
efficients from unity considerably changes the simulation result so th
at it disagrees with the experimental data. The authors conclude from
these results that the direct simulation Monte Carlo method is very us
eful to predict the phase change problems of alkali metals.