Heat transfer devices and systems are provided for the rapid cooling of pulsed high-powered, high-flux devices using flash boiling. Such devices comprise at least two fluidly connected chambers and a heat exchanger in thermal communication with a heat source. A flash boiling event is actively triggered at a location close to the heat source by rapid depressurization of the chamber containing a multi-phase coolant. This boiling process allows for high heat transfer rates from the heat source into the chambers due to the latent heat of vaporization, which results in the rapid cooling of the heat source. A porous medium may also be positioned within a chamber of the device to enhance boiling nucleation and extended surface heat transfer. Methods of rapidly cooling pulsed heat sources are also provided using the devices and systems hereof.