In one embodiment of the disclosure, an apparatus is provided for fueling a device using a cryogenic fluid. The apparatus may comprise: a cryogenic fluid supply container; a vessel connected to the supply container with an entrance valve to regulate flow of cryogenic fluid from the supply container; a heat transfer system capable of transferring heat from a device to the vessel to heat gas in the vessel; and an accumulator connected to the vessel with an exit valve to regulate flow of gas from the vessel to the accumulator. The accumulator may be capable of being connected to a device. In other embodiments, methods are provided of controllably mixing at least one fluid within a fluid mixing device.