U.S. patent application 20190053330 (Watlow Electric Manufacturing Co., St. Lous, Mo.):
"An exhaust system is provided that includes an exhaust aftertreatment unit, first and second exhaust pathway in communication with and upstream of the exhaust aftertreatment unit, a thermally activated flow control device operable in a first and second mode, and a thermal storage device. ... The thermal storage device or thermal flywheel may also include a phase change material, an in one form a phase change material that changes phase at a temperature between 180° C. and 45° C."