For various chemical processes, heat and mass evaporative flows are generated through vacuum control in order to ensure isothermal operations or flexible tracking of temperature trajectories. To study such processes, a 5-liter bench-scale evaporative calorimeter is presented in this paper. As an example, the application of this microcomputer-controlled calorimeter to the on-line identification of the differential heat evolution during batch evaporative crystallizations is reported. It is shown that satisfactory estimated results are obtained by means of a recursive least-squares policy. These results could allow an extension of diagnostic and control possibilities for many common processes which operate in vacuum conditions.