Abstract: A combination spray and cold plate thermal management system for effectively thermally managing a heat producing device during startup. The combination spray and cold plate thermal management system includes a spray unit thermally managing a heat producing device and a coolant reservoir thermally connected to the heat producing device. The coolant reservoir includes a porous media with coolant channels for storing a volume of the waste coolant after spraying of coolant has terminated. The coolant reservoir is fluidly connected to the spray chamber within the spray unit to receive the waste coolant.