Numerical solution of the second-order partial differential equation describing the evolution of temperature of a tungsten filament in time allows the simulation of some effects that occur in the case of heating thp filament by a series of pulses. Namely, the phenomena investigated are (1) phase shifts between heating current and filament temperature, (2) amplitude of temperature modulation due to variation of supply voltage and (3) the temperature dependence of the time constant of temperature changes. The method presented here may be used for any filament working in vacuo. It may be applied in mass spectrometry, vacuum measurements, thin films deposition by hot filaments and other applications.