Transient responses of the closed loop MHD experimental facility from non-power generation to power generation have been investigated by means of time-dependent quasi-one-dimensional numerical simulations. For the long-time continuous power generation experiment, the time required to obtain the steady state for the power generation is estimated to be approximately 20 hours. By increasing the electrical input power to the heater as an exponential function of time, the temperature increase of the ceramics can be moderated. When the duration of the experiment is around 10 minutes, argon gas temperature at the exit of the heater hardly changes because of the large heat capacity of the structure materials. It is found that the fluid disturbances are induced at the instant of the power generation and propagate as it reflects at the sudden change of the duct shape. Since the disturbances disappear taking approximately 0.4 second, the time scale that the disturbances exist in the facility can be 1 second at largest.